A frequent activated smoothened mutation in sporadic basal cell carcinomas Oncogene. 1999 Jan 21;18(3):833-6. Related Articles, Links

Lam CW, Xie J, To KF, Ng HK, Lee KC, Yuen NW, Lim PL, Chan LY, Tong SF, McCormick F.

Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital.

Basal-cell carcinomas (BCCs) are the most common cancer in Caucasians. It has been reported that the patched gene is inactivated in 30-40% sporadic BCCs and 20% sporadic medulloblastomas via loss of heterozygosity and nonsense mutations. Recently, two activating smoothened mutations have been found in the sporadic basal cell carcinomas. One, at base pair 1604 (G-to-T transversion) of exon 9, changes codon 535 from tryptophan to leucine, and the other, at base pair 1685 (G-to-A transition) of exon 10, changes codon 562 from arginine to glutamine (Xie et al., 1998). In our study, 1604G-->T was found in 20 out of 97 (20.6%) sporadic BCCs. The high prevalence indicates that 1604G is the mutation hot spot in our tumor samples. This mutation was detected in all three histological subtypes of BCCs, suggesting that smoothened mutation is an early event during the development of the tumor. Our finding of a high smoothened mutation rate, together with high frequent patched gene mutations reported recently, indicates that activation of the hedgehog signal transduction pathway is the most common and early event in the development of sporadic BCCs. Additionally, to determine whether smoothened, like patched, is also involved in the carcinogenesis of medulloblastomas, we screened medulloblastoma samples for these two mutations by restriction analysis. We have found the 1604G-->T mutation in 1 out of 21 medulloblastomas. This result confirmed smoothened gene involvement in the carcinogenesis of medulloblastoma.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9989836&query_hl=1


A role of PDGFRalpha in basal cell carcinoma proliferation
Proc Natl Acad Sci U S A. 2001 Jul 31;98(16):9255-9. Related Articles, Links
Xie J, Aszterbaum M, Zhang X, Bonifas JM, Zachary C, Epstein E, McCormick F.

Cancer Research Institute, and Department of Dermatology, University of California, San Francisco, CA 94115, USA. jinxie@utmb.edu

Activation of the hedgehog pathway, through the loss of patched (PTC) or the activation of smoothened (SMO), occurs frequently in basal cell carcinoma (BCC), the most common human cancer. However, the molecular basis of this neoplastic effect is not understood. The downstream molecule Gli1 is known to mediate the biological effect of the pathway and is itself up-regulated in all BCCs. Gli1 can drive the production of BCCs in the mouse when overexpressed in the epidermis. Here we show that Gli1 can activate platelet-derived growth factor receptor alpha (PDGFRalpha) in C3H10T(1/2) cells. Functional up-regulation of PDGFRalpha by Gli1 is accompanied by activation of the ras-ERK pathway, a pathway associated with cell proliferation. The relevance of this mechanism in vivo is supported by a high level expression of PDGFRalpha in BCCs of mice and humans. In the murine BCC cell line ASZ001, in which both copies of the PTC gene are inactivated, DNA synthesis and cell proliferation can be slowed by re-expression of PTC, which down-regulates PDGFRalpha expression, or by downstream inhibition of PDGFRalpha with neutralizing antibodies. Therefore, we conclude that increased expression of PDGFRalpha may be an important mechanism by which mutations in the hedgehog pathway cause BCCs.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11481486&query_hl=1

Absence of detectable alterations in the putative tumor suppressor gene BTRC in cerebellar medulloblastomas and cutaneous basal cell carcinomas
Acta Neuropathol (Berl). 2003 Oct;106(4):287-90. Epub 2003 Jul 24. Related Articles, Links

Wolter M, Scharwachter C, Reifenberger J, Koch A, Pietsch T, Reifenberger G.

Department of Neuropathology, Heinrich-Heine-University, Moorenstrasse 5, 40225 Dusseldorf, Germany.

The sonic hedgehog signal transduction pathway is aberrantly activated in the majority of cutaneous basal cell carcinomas and a subset of cerebellar medulloblastomas. The latter tumors may also show activation of the wingless (Wnt) signaling pathway. In Drosophila, the F-box/WD40-repeat containing protein Slimb has been shown to function as an intracellular negative regulator of both pathways. The BTRC gene (beta-transducin repeat-containing protein) is a human homolog of Slimb that is located at 10q24.3, a chromosome region frequently deleted in medulloblastomas. Here, we report on the mutational analysis of BTRC in 91 human tumors, including 66 primitive neuroectodermal tumors (PNETs) of the central nervous system (62 medulloblastomas and 4 supratentorial PNETs) and 25 cutaneous basal cell carcinomas (BCCs). These analyses revealed no tumor-associated BTRC mutations. BTRC transcripts were expressed in non-neoplastic brain tissue, normal skin, as well as in all PNETs and BCCs analyzed by real-time reverse transcription-PCR. Two novel BTRC transcript variants were expressed at higher levels in non-neoplastic brain tissue than in normal skin and the investigated tumors. Taken together, our results indicate that PNETs and BCCs neither show mutations nor loss of mRNA expression of BTRC. Therefore, BTRC alteration does not appear to be involved in the pathogenesis of these neoplasms.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12898158&query_hl=1

Activating Smoothened mutations in sporadic basal-cell carcinoma
Nature. 1998 Jan 1;391(6662):90-2. Related Articles, Links

Xie J, Murone M, Luoh SM, Ryan A, Gu Q, Zhang C, Bonifas JM, Lam CW, Hynes M, Goddard A, Rosenthal A, Epstein EH Jr, de Sauvage FJ.

Department of Dermatology, San Francisco General Hospital, University of California, 94110, USA.

Basal-cell carcinomas (BCCs) are the commonest human cancer. Insight into their genesis came from identification of mutations in the PATCHED gene (PTCH) in patients with the basal-cell nevus syndrome, a hereditary disease characterized by multiple BCCs and by developmental abnormalities. The binding of Sonic hedgehog (SHH) to its receptor, PTCH, is thought to prevent normal inhibition by PTCH of Smoothened (SMO), a seven-span transmembrane protein. According to this model, the inhibition of SMO signalling is relieved following mutational inactivation of PTCH in basal-cell nevus syndrome. We report here the identification of activating somatic missense mutations in the SMO gene itself in sporadic BCCs from three patients. Mutant SMO, unlike wild type, can cooperate with adenovirus E1A to transform rat embryonic fibroblast cells in culture. Furthermore, skin abnormalities similar to BCCs developed in transgenic murine skin overexpressing mutant SMO. These findings support the role of SMO as a signalling component of the SHH-receptor complex and provide direct evidence that mutated SMO can function as an oncogene in BCCs. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9422511&query_hl=1

Activation of expression of hedgehog target genes in basal cell carcinomas
J Invest Dermatol. 2001 May;116(5):739-42. Related Articles, Links
Bonifas JM, Pennypacker S, Chuang PT, McMahon AP, Williams M, Rosenthal A, De Sauvage FJ, Epstein EH Jr.

Department of Dermatology, San Francisco General Hospital, California, USA.

Mutations in hedgehog signaling pathway genes, especially PTC1 and SMO, are pivotal to the development of basal cell carcinomas. The study of basal cell carcinoma gene expression not only may elucidate mechanisms by which hedgehog signaling abnormalities produce aberrant tumor cell behavior but also can provide data on in vivo hedgehog target gene control in humans. We have found, in comparison with normal skin, that basal cell carcinomas have increased levels of mRNA for PTC1, GLI1, HIP, WNT2B, and WNT5a; decreased levels of mRNA for c-MYC, c-FOS, and WNT4; and unchanged levels of mRNA for PTC2, GLI2, WNT7B, and BMP2 and 4. These findings suggest that mutations in hedgehog signaling pathway genes may exert both cell autonomous and indirect effects and indicate that basal cell carcinoma tumor cells have a phenotype that at least in some aspects resembles that of epidermal stem cells. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11348463&query_hl=1

Activation of the transcription factor Gli1 and the Sonic hedgehog signalling pathway in skin tumours
Nature. 1997 Oct 23;389(6653):876-81. Related Articles, Links

Erratum in:
Nature 1997 Dec 4;390(6659):536.
Dahmane N, Lee J, Robins P, Heller P, Ruiz i Altaba A.

The Skirball Institute, Department of Cell Biology, New York University Medical Center, New York 10016, USA.

Sporadic basal cell carcinoma (BCC) is the most common type of malignant cancer in fair-skinned adults. Familial BCCs and a fraction of sporadic BCCs have lost the function of Patched (Ptc), a Sonic hedgehog (Shh) receptor that acts negatively on this signalling pathway. Overexpression of Shh can induce BCCs in mice. Here we show that ectopic expression of the zinc-finger transcription factor Gli1 in the embryonic frog epidermis results in the development of tumours that express endogenous Gli1. We also show that Shh and the Gli genes are normally expressed in hair follicles, and that human sporadic BCCs consistently express Gli1 but not Shh or Gli3. Because Gli1, but not Gli3, acts as a target and mediator of Shh signalling, our results suggest that expression of Gli1 in basal cells induces BCC formation. Moreover, loss of Ptc or overexpression of Shh cannot be the sole causes of Gli1 induction and sporadic BCC formation, as they do not occur consistently. Thus any mutations leading to the expression of Gli1 in basal cells are predicted to induce BCC formation.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9349822&query_hl=1
Basal cell carcinoma and its development: insights from radiation-induced tumors in Ptch1-deficient mice
Cancer Res. 2004 Feb 1;64(3):934-41. Related Articles, Links

Mancuso M, Pazzaglia S, Tanori M, Hahn H, Merola P, Rebessi S, Atkinson MJ, Di Majo V, Covelli V, Saran A.

Biotechnology Unit and Radiation Protection Unit, ENEA-Ente per le Nuove Tecnologie, l'Energia e l'Ambiente, Centro Ricerche, Casaccia, Rome, Italy.

Loss-of-function mutations in Patched (Ptch1) are implicated in constitutive activation of the Sonic hedgehog pathway in human basal cell carcinomas (BCCs), and inherited Ptch1 mutations underlie basal cell nevus syndrome in which a typical feature is multiple BCC occurring with greater incidence in portals of radiotherapy. Mice in which one copy of Ptch1 is inactivated show increased susceptibility to spontaneous tumor development and hypersensitivity to radiation-induced tumorigenesis, providing an ideal in vivo model to study the typical pathologies associated with basal cell nevus syndrome. We therefore examined BCC development in control and irradiated Ptch1(neo67/+) mice. We show that unirradiated mice develop putative BCC precursor lesions, i.e., basaloid hyperproliferation areas arising from both follicular and interfollicular epithelium, and that these lesions progress to nodular and infiltrative BCCs only in irradiated mice. Data of BCC incidence, multiplicity, and latency support the notion of epidermal hyperproliferations, nodular and infiltrative BCC-like tumors representing different stages of tumor development. This is additionally supported by the pattern of p53 protein expression observed in BCC subtypes and by the finding of retention of the normal remaining Ptch1 allele in all nodular, circumscribed BCCs analyzed compared with its constant loss in infiltrative BCCs. Our data suggest chronological tumor progression from basaloid hyperproliferations to nodular and then infiltrative BCC occurring in a stepwise fashion through the accumulation of sequential genetic alterations.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14871823&query_hl=1
Basal cell carcinoma development is associated with induction of the expression of the transcription factor Gli-1. Br J Dermatol. 1998 Nov;139(5):911-5. Related Articles, Links
Green J, Leigh IM, Poulsom R, Quinn AG.

Centre for Cutaneous Research, St Bartholomew's and The Royal London Hospital School of Medicine and Dentistry, 2 Newark Street, Whitechapel, London E1 2AT, U.K.

Recent work has established that activation of Hedgehog/patched signalling plays a key role in the development of basal cell carcinomas (BCCs). In Drosophila the effects of hedgehog signalling are mediated by the transcription factor Cubitus interruptus, which is homologous to the mammalian Gli family of transcription factors. In order to investigate the downstream consequences of patched gene inactivation in BCCs, we have investigated the expression of Gli-1 and Gli-3 in normal skin and BCCs by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. Gli-3 was found to be expressed in both normal skin and BCCs by both RT-PCR and in situ hybridization using a Gli-3-specific probe. Using a sensitive RT-PCR assay we were unable to detect Gli-1 transcripts in normal skin. Gli-1 was expressed in 13 of 14 BCCs examined, and in situ hybridization confirmed that the transcripts were localized to the epithelial component of the tumours. Our results demonstrate that inactivation of the patched gene BCCs is associated with the accumulation of Gli-1 transcripts. These findings suggest that the Gli-1 transcription factor plays a key role in BCC development. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9892966&query_hl=2

Basal cell carcinoma: a dermatopathological and molecular biological update. Br J Dermatol. 2003 Feb;148(2):195-202. Related Articles, Links
Saldanha G, Fletcher A, Slater DN.

Department of Pathology, University of Leicester, Leicester, UK. gss4@le.ac.uk

The ideal classification of basal cell carcinoma (BCC) should be able to identify subtypes which correlate with clinical behaviour and treatment requirements. Unfortunately, however, such a classification has yet to be defined. In the interim, the currently most favoured classification is one based predominantly on histological growth pattern. This classification contributes to the useful concept of low- and high-risk histological subtypes of BCC. The latter are characterized by an increased probability of subclinical extension and/or incomplete excision and/or aggressive local invasive behaviour and/or local recurrence. The Royal College of Pathologists has published a minimum dataset for the histopathological reporting of BCC and this has been written to be compatible with the British Association of Dermatologists' management guidelines. Growth patterns to be reported include nodular, superficial, infiltrative/morphoeic and micronodular types, together with differentiation when of severely atypical or malignant squamous type (basosquamous carcinoma). Deep and peripheral excision margins will be reported to be either involved or clear. The latter will include a comment of a clearance of less than 1 mm for close margins and a measured distance in whole millimetres for other excisions. Clinical assessment and histology remain the 'gold standard' for evaluating BCC and cancers in general. However, in the postgenomic era emphasis is changing from the gathering and archiving of genomic data to its analysis and use in guiding clinical practice. In this context, a current goal is to define cancer phenotype in terms of molecular abnormalities and use this as a new gold standard. One way to assess whether this goal is being achieved for BCC is to determine whether our knowledge of its molecular pathology has any relevance to the minimum dataset for histological reporting. Knowledge of BCC molecular pathology has been fuelled by the recent discovery that deregulation of the Hedgehog (Hh) signalling pathway, a key player in embryonic patterning, appears to be fundamental to tumour growth. But despite accrual of a large amount of data concerning Hh pathway molecular alterations in neoplasia, little is known about the functional consequences of these changes in BCC, how they lead to tumour development, or how they relate to non-Hh pathway alterations such as TP53 mutation. Recent work suggests that the cellular localization of beta-catenin gives a degree of credence to the growth pattern classification of BCC. Furthermore, it is possible that beta-catenin may have a pathogenetic role in the invasive behaviour of BCC. This review draws on current evidence to discuss these issues and assess whether they are relevant to the minimum dataset.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12588368&query_hl=8
Basal cell carcinomas in mice overexpressing Gli2 in skin.
Nat Genet. 2000 Mar;24(3):216-7. Related Articles, Links

Grachtchouk M, Mo R, Yu S, Zhang X, Sasaki H, Hui CC, Dlugosz AA.

University of Michigan Comprehensive Cancer Center and Department of Dermatology, Ann Arbor, Michigan, USA.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10700170&query_hl=1
Basal cell carcinomas in mice overexpressing sonic hedgehog
Science. 1997 May 2;276(5313):817-21. Related Articles, Links

Basal cell carcinomas in mice overexpressing sonic hedgehog.

Oro AE, Higgins KM, Hu Z, Bonifas JM, Epstein EH Jr, Scott MP.

Howard Hughes Medical Institute, Department of Dermatology, Stanford University School of Medicine, Stanford, CA 94305-5427, USA.

Mutations in the tumor suppressor gene PATCHED (PTC) are found in human patients with the basal cell nevus syndrome, a disease causing developmental defects and tumors, including basal cell carcinomas. Gene regulatory relationships defined in the fruit fly Drosophila suggest that overproduction of Sonic hedgehog (SHH), the ligand for PTC, will mimic loss of ptc function. It is shown here that transgenic mice overexpressing SHH in the skin develop many features of basal cell nevus syndrome, demonstrating that SHH is sufficient to induce basal cell carcinomas in mice. These data suggest that SHH may have a role in human tumorigenesis. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9115210&query_hl=1

Developmental genes and cancer: role of patched in basal cell carcinoma of the skin
J Natl Cancer Inst. 1997 Aug 6;89(15):1103-9. Related Articles, Links Gailani MR, Bale AE.

Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06520, USA. mae_gailani@yale.edu

Many genes originally identified because of their role in embryonic development are also important in postnatal control of cell growth and differentiation. Mutations in some of these genes have been shown to cause cancer. Basal cell carcinoma (BCC) of the skin is the most common cancer in humans. More than 750000 new cases are diagnosed annually, and the incidence is rising. BCCs are slow-growing, locally invasive tumors that rarely metastasize but can result in extensive morbidity through local recurrence and tissue destruction. Epidemiologic studies suggest that sunlight (particularly UVB radiation) is a strong risk factor for BCC formation, although other factors are also involved. The nevoid basal cell carcinoma syndrome (NBCCS), a rare genetic disorder, is characterized by predisposition to BCCs and other tumors as well as to a wide range of developmental defects. NBCCS maps to chromosome 9q22.3, and loss of heterozygosity at this site in both sporadic and hereditary BCCs suggests that it functions as a tumor suppressor. The gene for NBCCS was recently cloned and is the human homologue of the Drosophila gene "patched." Genetic studies in Drosophila show that patched is part of the hedgehog signaling pathway, which is important in determining embryonic patterning and cell fate in multiple structures of the developing embryo. Human patched is mutated in both hereditary and sporadic BCCs, and inactivation of this gene is probably a necessary, if not sufficient, step for BCC formation. Delineation of the biochemical pathway in which patched functions may lead to rational medical therapy for BCCs and possibly for other tumors associated with NBCCS. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9262247&query_hl=1
Dissecting the oncogenic potential of Gli2: deletion of an NH(2)-terminal fragment alters skin tumor phenotype Cancer Res. 2002 Sep 15;62(18):5308-16. Related Articles, Links

Sheng H, Goich S, Wang A, Grachtchouk M, Lowe L, Mo R, Lin K, de Sauvage FJ, Sasaki H, Hui CC, Dlugosz AA.

Comprehensive Cancer Center, Department of Dermatology, University of Michigan, 1500 E Medical Center Drive, Ann Arbor, MI 48109, USA.

Development of basal cell carcinomas (BCCs) in skin is associated with uncontrolled Sonic hedgehog (Shh) signaling, which operates primarily through the Gli family of transcription factors. Gli2 is a mediator of physiological Shh signaling in skin and is sufficient to produce BCCs when overexpressed by use of a Keratin 5 (K5) promoter. Analysis of Gli protein deletion mutants has identified an NH(2)-terminal transcription repressor domain in Gli2 but not Gli1. To assess the potential involvement of the Gli2 repressor domain in skin tumor development, we overexpressed the Gli2DeltaN2 mutant in transgenic mice by use of the K5 promoter. K5-Gli2DeltaN2 mice developed a variety of skin tumors resembling human trichoblastomas, cylindromas, basaloid follicular hamartomas, and rarely, BCCs. In striking contrast, K5-Gli2 mice overexpressing wild-type Gli2 developed only BCCs. Other differences between tumors arising in these two sets of transgenic mice included their gross appearance, growth rate, and predilection for specific body sites. However, the expression levels of Shh target genes, which reflect the magnitude of Shh pathway activation, were not dramatically different. Tumors from K5-Gli2DeltaN2 mice, unlike human or mouse BCCs, gave rise to cell lines that constitutively expressed Shh target genes in vitro and were tumorigenic in nude mice. Interestingly, the phenotype of K5-Gli2DeltaN2 mice was strikingly similar to that reported after K5 promoter-driven overexpression of GLI1, which lacks an NH(2)-terminal region homologous to the Gli2 repressor domain. These results underscore the qualitative difference in oncogenicity of GLI1 and Gli2 when overexpressed in skin, and reveal a previously unanticipated role for the Gli2 NH(2) terminus in defining tumor phenotype.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12235001&query_hl=1
Expression of a sonic hedgehog signal transducer, hedgehog-interacting protein, by human basal cell carcinoma Br J Dermatol. 2002 Jan;146(1):69-73. Related Articles, Links

Tojo M, Kiyosawa H, Iwatsuki K, Kaneko F.

Department of Dermatology, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan. tojo@fmu.ac.jp

BACKGROUND: Aberrant activation of the hedgehog pathway has been identified in various human tumours, including familial and sporadic basal cell carcinomas (BCCs). It has been postulated that binding of sonic hedgehog protein (SHH) to its receptor, patched protein (PTC), releases the inhibitory effect of PTC against smoothened protein (SMO), another protein of the SHH signalling pathway. The positive SMO signalling is not downregulated in BCCs because of the mutational inactivation of PTC. Recently, hedgehog-interacting protein (HIP) was found to bind to SHH directly and attenuate SHH signalling like PTC, while its expression was induced by SHH signals. OBJECTIVES: To examine the expression patterns of HIP, SHH and PTC gene mRNA by human BCCs, in comparison with those by normal human skin and various skin tumours. METHODS: We performed quantitative reverse transcriptase-polymerase chain reaction analyses with a series of samples from BCCs, other skin tumours and normal skin. RESULTS: We found that the mRNA expression of both HIP and PTC genes was enhanced in all samples of BCCs, whereas none of the other skin tumours tested exhibited an increased level of such mRNAs as compared with normal skin. The transcription of the SHH gene, however, was at a baseline level in most BCCs. CONCLUSIONS: These results indicate that both HIP and PTC gene expression are specifically involved in the development of BCCs, and that the production of HIP is linked with the expression of the PTC gene but not the SHH gene. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11841368&query_hl=1
Expression of sonic hedgehog signal transducers, patched and smoothened, in human basal cell carcinoma Pathol Int. 1999 Aug;49(8):687-94. Related Articles, Links

Tojo M, Mori T, Kiyosawa H, Honma Y, Tanno Y, Kanazawa KY, Yokoya S, Kaneko F, Wanaka A.

Department of Cell Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima City, Japan. tojo@cc.fmu.ac.jp

In basal cell nevus syndrome (BCNS) patients, mutations of a gene, patched (ptc), which encodes a putative signal transducer of sonic hedgehog protein (SHH), were found and are thought to be one of the major causes of BCNS. The SHH signaling pathway is an important developmental pathway, and ptc protein (PTC) is a suppressive component serving as a receptor for the secreted SHH. Another transmembrane protein, smoothened (SMO), forms a complex with PTC and regulates this signaling pathway. Recent transgenic studies have strengthened the importance of the SHH signaling system in the etiology of basal cell carcinoma (BCC). In this study, we examined the expression patterns of mRNA for ptc and smo in two different BCC subtypes and normal skin. We found that the expressions of ptc and smo mRNA were enhanced in the tumor nests of the nodular BCC, especially at the advancing portions, but were under the detectable level in the superficial BCC cases examined, indicating that ptc and smo mRNA expressions might be associated with BCC tumor progression and divide the BCC histologic types into two subtypes, superficial and nodular types. In addition, no obvious signals for ptc and smo mRNA were detected in the normal human epidermis, appendages, or seborrheic keratosis, indicating that the abnormal proliferation of follicular epithelial cells caused by ptc, smo and/or other genetic changes, which also cause ptc and smo overexpressions, might result in BCC tumor formation.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10504535&query_hl=1
Expression of the GLI2 oncogene and its isoforms in human basal cell carcinoma
Br J Dermatol. 2003 May;148(5):892-7. Related Articles, Links

Tojo M, Kiyosawa H, Iwatsuki K, Nakamura K, Kaneko F.

Department of Dermatology, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan.

BACKGROUND: Mutations of the patched (Ptc) gene, a developmental regulator implicated in the signalling pathway via sonic hedgehog (Shh) and smoothened (Smo), play an essential pathogenic role in the development of basal cell carcinomas (BCCs). We previously reported the upregulation of Shh signal transducers, including Ptc, Smo and hedgehog-interacting protein, in BCCs. In vertebrates, specific downstream effectors in the Shh signalling pathway include three zinc-finger transcription factors, Gli1, Gli2 and Gli3. Gli1 possesses only an activation domain, while Gli2 and Gli3 contain both activation and repression domains. It remains unclear which of these transcription factors are responsible for the development of BCCs. OBJECTIVES: To examine the expression pattern of Gli2 mRNA by human BCCs in comparison with those by normal human skin and various skin tumours. METHODS: We performed quantitative reverse transcriptase-polymerase chain reaction analyses with a series of samples from BCCs, other skin tumours and normal skin. RESULTS: We found that Gli2 mRNA expression was enhanced in the BCCs we examined, whereas there was no significant increase in other skin tumours or normal skin. Of four spliced Gli2 isoforms designated Gli2alpha, beta, gamma and delta, the expression of Gli2beta mRNA was increased the most in BCCs. CONCLUSIONS: As Gli2beta is an isoform spliced at the first splicing site containing a repression domain and consists of an intact activation domain, its overexpression may lead to the upregulation of the Shh signalling pathway, thereby inducing BCCs.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12786818&query_hl=1

Expression of the PTCH1 tumor suppressor gene is regulated by alternative promoters and a single functional Gli-binding site
Gene. 2004 Apr 14;330:101-14. Related Articles, Links

Agren M, Kogerman P, Kleman MI, Wessling M, Toftgard R.

Department of Bioscience at NOVUM, Center for Nutrition and Toxicology, Karolinska Institute, Huddinge 141 57, Sweden.

The PTCH1 tumor suppressor gene encodes a receptor for secreted hedgehog (HH) ligands and is important for proper proliferation, differentiation and patterning in almost every tissue and organ during embryogenesis. The PTCH1 protein works as a negative regulator of the HH-signaling pathway by repressing downstream signaling by the coreceptor smoothened (SMOH). Mutations in PTCH1 lead to constitutive expression of HH target genes and a relationship between mutated PTCH1 and the most common tumor form in the Western world, Basal Cell Carcinoma (BCC) has been clearly established. We here show that PTCH1 is transcriptionally regulated by three independent promoters generating transcripts with alternative first exons. We demonstrate that only one of two putative Gli-binding sites that were identified in the promoter region of PTCH1 is functional, and that the transactivating Gli proteins, GLI1, Gli2 and GLI3, bind and enhance transcription through this site. Moreover, a strong repression of both basal and induced PTCH1 transcription was observed following expression of a truncated version of GLI3. Most interestingly, the upstream components in the HH-signaling cascade, Sonic HH (SHH) and SMOH, solely operate through the functional Gli-binding site because mutation of the Gli-binding site resulted in the disappearance of the enhanced transcription induced by the Gli proteins, as well as by SHH or SMOH. This finding suggests that transcriptional activation of the PTCH1 gene mediated via the HH-signaling pathway is dependent on the single functional Gli-binding site.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15087129&query_hl=4

Expression of the Sonic Hedgehog receptor "PATCHED" in basal cell carcinomas and odontogenic keratocysts
J Pathol. 2001 Aug;194(4):473-7. Related Articles, Links

Zedan W, Robinson PA, Markham AF, High AS.

Molecular Medicine Unit, University of Leeds, Clinical Sciences Building, St James's University Hospital, Leeds, LS9 7TF, UK.

Basal cell carcinoma (BCC) is a common invasive skin lesion in Caucasians. Odontogenic keratocysts (OKs) are developmental, non-inflammatory oral cysts. They can be sporadic and/or multiple and are locally destructive. Basal cell naevus syndrome (BCNS) comprises both multiple BCCs and multiple OKs, in addition to several other systemic manifestations. The genetic defect underlying this autosomal dominant syndrome is a germ line mutation in the Sonic Hedgehog receptor PATCHED (PTCH) gene. For this study, a rabbit anti-peptide PTCH antiserum was produced. Immunohistochemistry procedures were performed using PTCH antibody and commercially produced GLI-1 antibody (downstream member in the hedgehog pathway) to stain 11 BCNS-OKs, eight sporadic OKs, two BCNS-BCCs, and six sporadic BCCs. Most of these lesions had been previously screened for PTCH mutation. Most BCCs (n=7) demonstrated moderate staining, with the heaviest staining in the outer palisading cell layer, except a BCNS-BCC which had mutation proximal to the sequence used for production of immunogenic peptide; this demonstrated only weak staining. Although moderate to heavy staining with PTCH antibody was demonstrated in the epithelium of both types of OK (n=19), a quite different pattern of staining of the basal cell layer was observed in the two patient groups. In BCNS, OK staining was heaviest in basal epithelial layers. In contrast, staining in non-BCNS odontogenic keratocysts was exclusively located in the superficial epithelial layers. Up-regulation of PTCH and GLI-1 protein was demonstrated in both BCCs and OKs. The pattern of PTCH expression matched the PTCH transcript pattern previously reported in BCCs and appeared sufficiently characteristic in OKs to allow differentiation between syndromic and non-syndromic cysts. Copyright 2001 John Wiley & Sons, Ltd.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11523056&query_hl=1

FOXE1, a new transcriptional target of GLI2 is expressed in human epidermis and basal cell carcinoma. J Invest Dermatol. 2004 May;122(5):1180-7. Related Articles, Links

Eichberger T, Regl G, Ikram MS, Neill GW, Philpott MP, Aberger F, Frischauf AM.

Department of Molecular Biology, University of Salzburg, Salzburg, Austria.

Sonic hedgehog (Hh) signaling plays a key role in epidermal development and skin cancer. Mutational inactivation of the tumor suppressor gene patched (PTCH) leads to constitutive activation of the Hh signaling pathway, resulting in activation of target gene transcription by the zinc finger transcription factors GLI1 and GLI2. Recent experiments in mice point to GLI2 as the key mediator of Hh signaling in skin. We have concentrated on the identification of candidate mediators of GLI2 function in the human epidermis. We show here that the forkhead/winged-helix domain transcription factor FOXE1 is likely to be a direct GLI2 target gene. The kinetics of FOXE1 induction are similar to the known direct target PTCH, and a 2.5 kb upstream fragment containing five GLI-binding sites activates transcription in a reporter assay. We show by in situ hybridization that FOXE1 is expressed in the outer root sheath of the hair follicle, where murine Gli2 is also expressed. FOXE1 expression is also found in basal keratinocytes of the human epidermis and basal cell carcinoma (BCC). These data point to a putative role of FOXE1 in mediating Hh signaling in the human epidermis downstream of GLI2.

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FOXM1 is a downstream target of Gli1 in basal cell carcinomas Cancer Res. 2002 Aug 15;62(16):4773-80. Related Articles, Links
Teh MT, Wong ST, Neill GW, Ghali LR, Philpott MP, Quinn AG.

Centre for Cutaneous Research, Barts & The London School of Medicine and Dentistry, Queen Mary, University of London, London E1 2AT, United Kingdom. m.t.teh@qmul.ac.uk

Forkhead box (FOX) proteins have been shown to play important roles in regulating the expression of genes involved in cell growth, proliferation, differentiation, longevity, and transformation. The functional importance of this gene family in normal human skin physiology and disease processes is not well understood. Activation of Sonic Hedgehog (Shh) signaling plays a key role in the development of basal cell carcinomas (BCCs) of the skin in humans. Recent studies have established that some FOX genes are downstream targets of Shh signaling. We have investigated the role of FOX proteins in transducing Shh effects in human skin by using degenerate PCR to identify FOX genes differentially expressed in BCCs. All three known FOXM1 isoforms (a, b, and c) were detected in human skin and cultured keratinocytes, and the transcriptionally active FOXM1b isoform was found to be up-regulated in BCCs. Real-time quantitative RT-PCR showed that the increase in FOXM1 mRNA levels was specific for BCCs and not a reflection of increased cell proliferation in that no up-regulation was seen in squamous cell carcinomas or proliferating primary human keratinocyte cultures. Immunostaining studies showed intense nuclear and cytoplasmic staining throughout BCC tumor islands and not confined to the periphery regions of the tumor where proliferating Ki-67-immunopositive cells are predominantly localized. Expression of the Shh target glioma transcription factor-1 (Gli1) in primary keratinocytes and other cell lines caused a significant elevation of FOXM1 mRNA level and transcriptional activity, indicating that FOXM1 is a downstream target of Gli1. Our data provide the first evidence that activation of Shh signaling via Gli1 is an important determinant of FOXM1 expression in mammalian cells. Given the role of FOXM1 in cell proliferation, the up-regulation of FOXM1 in BCCs may be one of the mechanisms whereby Shh signaling exerts its mitogenic effect on basal keratinocytes, leading to the development of this common human cancer.
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Functional analysis in Drosophila indicates that the NBCCS/PTCH1 mutation G509V results in activation of smoothened through a dominant-negative mechanism Dev Dyn. 2004 Apr;229(4):780-90. Related Articles, Links

Hime GR, Lada H, Fietz MJ, Gillies S, Passmore A, Wicking C, Wainwright BJ.

Department of Anatomy and Cell Biology, University of Melbourne, Australia. grhime@unimelb.edu.au

Mutations in the human homolog of the patched gene are associated with the developmental (and cancer predisposition) condition Nevoid Basal Cell Carcinoma Syndrome (NBCCS), as well as with sporadic basal cell carcinomas. Most mutations that have been identified in the germline of NBCCS patients are truncating or frameshift mutations, with amino acid substitutions rarely found. We show that a missense mutation in the sterol-sensing domain G509V acts as a dominant negative when assayed in vivo in Drosophila. Ectopic expression of a Drosophila patched transgene, carrying the analogous mutation to G509V, causes ectopic activation of Hedgehog target genes and ectopic membrane stabilisation of Smoothened. The G509V transgene behaves in a manner similar, except in its subcellular distribution, to a C-terminal truncation that has been characterised previously as a dominant-negative protein. G509V exhibits vesicular localisation identical to the wild-type protein, but the C-terminal truncated Patched molecule is localised predominantly to the plasma membrane. This finding suggests that dominant-negative function can be conferred by interruption of different aspects of Patched protein behaviour. Another mutation at the same residue, G509R, did not exhibit dominant-negative activity, suggesting that simple removal of the glycine at 509 is not sufficient to impart dominant-negative function. Copyright 2004 Wiley-Liss, Inc.
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Functional analysis of novel sonic hedgehog gene mutations identified in basal cell carcinomas from xeroderma pigmentosum patients Cancer Res. 2004 May 15;64(10):3559-65. Related Articles, Links

Couve-Privat S, Le Bret M, Traiffort E, Queille S, Coulombe J, Bouadjar B, Avril MF, Ruat M, Sarasin A, Daya-Grosjean L.

Laboratoire Instabilite Genetique et Cancer, UPR2169 Centre National de la Recherche Scientifique, Institut Gustave Roussy, Villejuif Cedex, France.

Altered sonic hedgehog (SHH) signaling is crucial in the development of basal cell carcinomas (BCC), the most common human cancer. Mutations in SHH signal transducers, PATCHED and SMOOTHENED, have already been identified, but SHH mutations are extremely rare; only 1 was detected in 74 sporadic BCCs. We present data showing unique SHH mutations in BCCs from repair-deficient, skin cancer-prone xeroderma pigmentosum (XP) patients, which are characterized by high levels of UV-specific mutations in key genes involved in skin carcinogenesis, including PATCHED and SMOOTHENED. Thus, 6 UV-specific SHH mutations were detected in 5 of 33 XP BCCs. These missense SHH alterations are not activating mutations for its postulated proto-oncogene function, as the mutant SHH proteins do not show transforming activity and induce differentiation or stimulate proliferation to the same level as the wild-type protein. Structural modeling studies of the 4 proteins altered at the surface residues, G57S, G64K, D147N, and R155C, show that they do not effect the protein conformation. Interestingly, they are all located on one face of the compact SHH protein suggesting that they may have altered affinity for different partners, which may be important in altering other functions. Additional functional analysis of the SHH mutations found in vivo in XP BCCs will help shed light on the role of SHH in skin carcinogenesis. In conclusion, we report for the first time, significant levels of SHH mutations found only in XP BCCs and none in squamous cell carcinomas, indicating their importance in the specific development of BCCs.
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Gene linked to commonest cancer
Science. 1996 Jun 14;272(5268):1583-4.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8658128&query_hl=1
Genetic determinants of basal cell carcinoma risk. Med Pediatr Oncol. 2001 May;36(5):555-8. Related Articles, Links

Epstein E Jr.

Department of Dermatology, University of California, San Francisco, San Francisco, California, USA. ehepstein@orca.ucsf.edu

Basal cell carcinomas are can be induced by ionizing radiation, in particular in patients with the rare autosomal dominant basal cell nevus syndrome (BCNS). These patients also are prone to medulloblastomas, and curative ionizing radiation therapy for the latter is followed soon by the development of sheets of basal cell carcinomas in the overlying skin. Positional cloning of the gene mutant is BCNS patients has identified the hedgehog signaling pathway as crucial to the development of all basal cell carcinomas and presumably to this susceptibility to post-ionizing radiation carcinogenesis. Thus this pathway is a candidate for susceptibility to second, post-therapy cancers in the broader population. Copyright 2001 Wiley-Liss, Inc.
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GLI2 is expressed in normal human epidermis and BCC and induces GLI1 expression by binding to its promoter J Invest Dermatol. 2004 Jun;122(6):1503-9. Related Articles, Links

Ikram MS, Neill GW, Regl G, Eichberger T, Frischauf AM, Aberger F, Quinn A, Philpott M.

Center for Cutaneous Research, Barts and The London Queen Mary's School of Medicine & Dentistry, University of London, UK. m.s.ikram@qmul.ac.uk

Sonic hedgehog (Shh) binds to its receptor patched (PTCH), leading to the activation and repression of target genes via the GLI family of zinc-finger transcription factors. Deregulation of the Shh pathway is associated with basal cell carcinoma (BCC) due to upregulation of GLI1 and GLI2. We recently demonstrated a positive feedback loop between GLI1 and GLI2, which revealed that GLI1 may be a direct target of GLI2. Using band shift and luciferase reporter assays, we now show that GLI2 binds the GLI-binding consensus sequence in the GLI1 promoter. These data suggest that GLI2 directly activates GLI1 and that retrovirally expressed GLI2 induces expression of endogenous GLI1 in human primary keratinocytes. Finally, using in situ hybridization, we show that GLI2 is expressed in the interfollicular epidermis and the outer root sheath of hair follicles in normal skin as well as in BCC tumor islands. These results suggest an important role for GLI2 in regulating epidermal proliferation and skin tumorigenesis.
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Gorlin syndrome with ulcerative colitis in a Japanese girl.
Arch Dermatol Res. 2005 Jan;296(7):303-8. Epub 2004 Nov 23. Related Articles, Links

Tanioka M, Takahashi K, Kawabata T, Kosugi S, Murakami K, Miyachi Y, Nishigori C, Iizuka T.

Department of Dermatology, Graduate School of Medicine, Kobe University, 7 Kusunoki-cho, Shogoin, Chuo-ku, Kobe, 651-0017, Japan.

We identified seven novel germline mutations of the PTCH gene in eight unrelated Japanese patients with nevoid basal cell carcinoma syndrome (NBCCS). In order to ensure genetic diagnosis, all 23 coding exons of the PTCH gene were amplified from genomic DNA by polymerase chain reaction (PCR) and sequenced. Mutations were found in all eight patients with NBCCS. The mutations detected in this study include one insertion/deletion mutation, one 1-bp insertion, two 1-bp deletions, one nonsense mutation and two missense mutations. None of the mutations have been previously reported. Five mutations caused premature stop codons that are predicted to result in a truncated protein. In the two missense mutations, the strong basic residue arginine was substituted by serine or glycine in highly conserved components of the putative transmembrane domain of PTCH, and these mutations may therefore affect the conformation and function of the PTCH protein. No phenotype-genotype relationships were found in the Japanese NBCCS patients, consistent with results of previous studies on NBCCS in African-American and Caucasian patients.
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Human GLI2 and GLI1 are part of a positive feedback mechanism in Basal Cell Carcinoma
Oncogene. 2002 Aug 15;21(36):5529-39. Related Articles, Links
Regl G, Neill GW, Eichberger T, Kasper M, Ikram MS, Koller J, Hintner H, Quinn AG, Frischauf AM, Aberger F.

Institute of Genetics, University of Salzburg, A-5020 Salzburg, Austria.

Transgenic mouse models have provided evidence that activation of the zinc-finger transcription factor GLI1 by Hedgehog (Hh)-signalling is a key step in the initiation of the tumorigenic programme leading to Basal Cell Carcinoma (BCC). However, the downstream events underlying Hh/GLI-induced BCC development are still obscure. Using in vitro model systems to analyse the effect of Hh/GLI-signalling in human keratinocytes, we identified a positive feedback mechanism involving the zinc finger transcription factors GLI1 and GLI2. Expression of GLI1 in human keratinocytes induced the transcriptional activator isoforms GLI2alpha and GLI2beta. Both isoforms were also shown to be expressed at elevated levels in 21 BCCs compared to normal skin. Detailed time course experiments monitoring the transcriptional response of keratinocytes either to GLI1 or to GLI2 suggest that GLI1 is a direct target of GLI2, while activation of GLI2 by GLI1 is likely to be indirect. Furthermore, expression of either GLI2 or GLI1 led to an increase in DNA-synthesis in confluent human keratinocytes. Taken together, these results suggest an important role of the positive GLI1-GLI2 feedback loop in Hh-mediated epidermal cell proliferation.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12165851&query_hl=1

Human homolog of patched, a candidate gene for the basal cell nevus syndrome Science. 1996 Jun 14;272(5268):1668-71. Related Articles, Links
Johnson RL, Rothman AL, Xie J, Goodrich LV, Bare JW, Bonifas JM, Quinn AG, Myers RM, Cox DR, Epstein EH Jr, Scott MP.

Department of Developmental Biology, Howard Hughes Medical Institute, Stanford University School of Medicine, California 94305-5427, USA.

The basal cell nevus syndrome (BCNS) is characterized by developmental abnormalities and by the postnatal occurrence of cancers, especially basal cell carcinomas (BCCs), the most common human cancer. Heritable mutations in BCNS patients and a somatic mutation in a sporadic BCC were identified in a human homolog of the Drosophila patched (ptc) gene. The ptc gene encodes a transmembrane protein that in Drosophila acts in opposition to the Hedgehog signaling protein, controlling cell fates, patterning, and growth in numerous tissues. The human PTC gene appears to be crucial for proper embryonic development and for tumor suppression.
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Identification of a small molecule inhibitor of the hedgehog signaling pathway: effects on basal cell carcinoma-like lesions
Proc Natl Acad Sci U S A. 2003 Apr 15;100(8):4616-21. Epub 2003 Apr 4. Related Articles, Links
Erratum in:
Proc Natl Acad Sci U S A. 2003 Jul 8;100(14):8607.
Williams JA, Guicherit OM, Zaharian BI, Xu Y, Chai L, Wichterle H, Kon C, Gatchalian C, Porter JA, Rubin LL, Wang FY.

Curis Incorporated, 61 Moulton Street, Cambridge, MA 02138, USA.

The link between basal cell carcinoma (BCC) and aberrant activation of the Hedgehog (Hh) signaling pathway has been well established in humans and in mouse models. Here we report the development of assays, including two novel in vitro BCC models, which allowed us to screen for Hh inhibitors and test their validity as potential treatments for BCC. We identified a novel small molecule Hh inhibitor (CUR61414) that can block elevated Hh signaling activity resulting from oncogenic mutations in Patched-1. Moreover, CUR61414 can suppress proliferation and induce apoptosis of basaloid nests in the BCC model systems, whereas having no effect on normal skin cells. These findings directly demonstrate that the use of Hh inhibitors could be a valid therapeutic approach for treating BCC.
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IFNalpha induces Fas expression and apoptosis in hedgehog pathway activated BCC cells through inhibiting Ras-Erk signaling Oncogene. 2004 Feb 26;23(8):1608-17. Related Articles, Links

Li C, Chi S, He N, Zhang X, Guicherit O, Wagner R, Tyring S, Xie J.

Sealy Center for Cancer Cell Biology, Department of Pharmacology and Toxicology, University of Texas Medical Branch at Galveston, TX 77555, USA.

Basal cell carcinoma (BCC), the most common form of human cancer, is understood to be associated with activation of the sonic hedgehog pathway, through loss-of-function mutations of tumor suppressor PTCH1 or gain-of-function mutations of smoothened. Interferon (IFN)-based therapy is quite effective in BCC treatment, but the molecular basis is not well understood. Here we report a novel mechanism by which IFNalpha mediates apoptosis in BCCs. In the presence of IFNalpha, we observed increased apoptosis in a BCC cell line ASZ001, in which PTC is null, and therefore with constitutive activation of the sonic hedgehog pathway. We demonstrate that SMO agonist Ag-1.4 mediates activation of extracellular signal-regulated kinase (Erk) phosphorylation, which is abrogated by IFNalpha in sonic hedgehog responsive C3H10T1/2 cells. In transient transfection experiments, we demonstrate that IFNalpha inhibits Erk phosphorylation and serum response element activation induced by expression of SMO, Gli1, PDGFRalpha and activated Raf, but not activated mitogen-activated Erk-regulating kinase (Mek), suggesting that IFNalpha targets mainly on Mek function. We further show that IFNalpha induces expression of Fas in BCC cells through interfering with Mek function. The role of the Fas-L/Fas signaling axis in IFNalpha-mediated apoptosis is demonstrated by the fact that addition of Fas-L neutralizing antibodies, just as caspase-8 inhibitor Z-IETD-FMK, effectively prevents IFNalpha-mediated apoptosis. Thus, our data indicate that IFNalpha-based BCC therapy induces Fas expression and apoptosis through interfering with Mek function.
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Immunohistochemical detection for nuclear beta-catenin in sporadic basal cell carcinoma
Br J Dermatol. 2001 Nov;145(5):771-7. Related Articles, Links

Yamazaki F, Aragane Y, Kawada A, Tezuka T.

Department of Dermatology, Kinki University School of Medicine, 377-2 Ohnohigashi, Osakasayama-shi, 589-8511 Osaka, Japan.

BACKGROUND: Despite the increasing incidence of basal cell carcinoma (BCC), its pathogenesis has remained largely unknown. Recently, it was reported that genes involved in tissue morphogenesis, such as sonic hedgehog or patched, were found to be mutated in BCC, suggesting the involvement of those molecules in the pathogenesis of this tumour. Furthermore, there is evidence that the Wnt-mediated signalling pathway may be one of the downstream targets of sonic hedgehog-mediated signalling, which has led us to focus on molecular events on the Wnt pathway in BCC. Among the signal transducers involved in the Wnt pathway, it is clear that beta-catenin plays a pivotal role in the promotion of morphogenesis and cell growth. In respect to this, it has been reported that, in particular circumstances, as in colorectal cancers, beta-catenin migrates to the nuclei, where it exerts an ability to activate the transcription of various genes. OBJECTIVES: To investigate the cellular distribution of beta-catenin in skin tumours, in particular, in BCC. METHODS: Twenty skin biopsy specimens derived from BCC, 10 from inflammatory skin diseases and five from squamous cell carcinomas were immunostained with an antibody directed against beta-catenin. RESULTS: Fourteen of the 20 BCC samples tested showed nuclear localization of beta-catenin, while none of the other samples gave rise to positive nuclear staining. CONCLUSIONS: Nuclear localization of beta-catenin is a characteristic feature of BCC; this suggests its tumorigenic role in this tumour. This gives us a further insight into the molecular pathogenesis of BCC.
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Induction of basal cell carcinoma features in transgenic human skin expressing Sonic Hedgehog Nat Med. 1997 Jul;3(7):788-92. Related Articles, Links

Fan H, Oro AE, Scott MP, Khavari PA.

Veterans Affairs Palo Alto Health Care System, CA 94304, USA.

Hedgehog (HH) signaling proteins mediate inductive events during animal development. Mutation of the only known HH receptor gene, Patched (PTC), has recently been implicated in inherited and sporadic forms of the most common human cancer, basal cell carcinoma (BCC). In Drosophila, HH acts by inactivating PTC function, raising the possibility that overexpression of Sonic Hedgehog (SHH) in human epidermis might have a tumorigenic effect equivalent to loss of PTC function. We used retroviral transduction of normal human keratinocytes to constitutively express SHH. SHH-expressing cells demonstrated increased expression of both the known HH target, BMP-2B, as well as bcl-2, a protein prominently expressed by keratinocytes in BCCs. These keratinocytes were then used to regenerate human skin transgenic for long terminal repeat-driven SHH (LTR-SHH) on immune-deficient mice. LTR-SHH human skin consistently displays the abnormal specific histologic features seen in BCCs, including downgrowth of epithelial buds into the dermis, basal cell palisading and separation of epidermis from the underlying dermis. In addition, LTR-SHH skin displays the gene expression abnormalities previously described for human BCCs, including decreased BP180/BPAG2 and laminin 5 adhesion proteins and expression of basal epidermal keratins. These data indicate that expression of SHH in human skin recapitulates features of human BCC in vivo, suggest that activation of this conserved signaling pathway contributes to the development of epithelial neoplasia and describe a new transgenic human tissue model of neoplasia.
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Induction of basal cell carcinomas and trichoepitheliomas in mice overexpressing GLI-1 Proc Natl Acad Sci U S A. 2000 Mar 28;97(7):3438-43. Related Articles, Links

Nilsson M, Unden AB, Krause D, Malmqwist U, Raza K, Zaphiropoulos PG, Toftgard R.

Department of Biosciences at Novum, Karolinska Institutet, SE-141 57, Huddinge, Sweden.

Basal cell carcinoma is the most prevalent cancer in the western world, showing a rapid increase in incidence. Activation of the Sonic hedgehog/Patched (PTCH) signaling pathway because of PTCH1 inactivation is a key event in sporadic and familial basal cell carcinoma development in humans and is associated with transcriptional activation of specific target genes, including PTCH1 itself. These changes are analogous to the situation in Drosophila where hedgehog activates the zinc-finger transcription factor Cubitus interruptus, leading to increased transcription of target genes. In the present study, we show that mice ectopically expressing the human Cubitus interruptus homolog GLI-1 in the skin develop tumors closely resembling human BCCs as well as other hair follicle-derived neoplasias, such as trichoepitheliomas, cylindromas, and trichoblastomas. Furthermore, examination of the tumors revealed wild-type p53 and Ha ras genes. These findings firmly establish that increased GLI-1 expression is central and probably sufficient for tumor development and suggest that GLI-1-induced tumor development does not depend on additional p53 or Ha ras mutations.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10725363&query_hl=1

Induction of the differentiation and apoptosis of tumor cells in vivo with efficiency and selectivity Eur J Dermatol. 2004 Mar-Apr;14(2):96-102. Related Articles, Links Tabs S, Avci O.

Yasemin Sokak No. 6, Narlidere, Izmin 35320, Turkey. sinantas1@yahoo.com

Hedgehog/smoothened signaling is active in a variety of tumors and is also involved in the maintenance of normal stem cells in vivo. We evaluated the possibility of preferential affection of tumor versus normal cells following inhibition of this signaling. We applied a cream preparation of cyclopamine (an inhibitor of the hedgehog/smoothened signaling) onto skin tumors in patients who were scheduled for the excision of these tumors (four basal cell carcinomas and a trichoepithelioma in four unrelated patients). All of the cyclopamine-treated tumors regressed rapidly. Histological and immunohistochemical analyses showed inhibition of the proliferation and highly efficient induction of the differentiation and apoptosis of tumor cells by a non-genotoxic mechanism. No adverse effects were noted and normal skin tissue and putative stem cells that were exposed to cyclopamine together with tumors were well preserved under the conditions we describe. Our findings show selective and highly efficient induction of the differentiation and apoptosis of tumor cells in vivo by transient inhibition of the hedgehog/ smoothened signaling and provide a rational cancer therapy. Copyright John Libbey Eurotext 2003.
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Loss of protein kinase Calpha expression may enhance the tumorigenic potential of Gli1 in basal cell carcinoma Cancer Res. 2003 Aug 1;63(15):4692-7. Related Articles, Links
Neill GW, Ghali LR, Green JL, Ikram MS, Philpott MP, Quinn AG.

Centre for Cutaneous Research, Barts and the London, Queen Mary's School of Medicine and Dentistry, University of London, 2 Newark Street, Whitechapel, London E1 2AT, United Kingdom.

Activation of the Sonic hedgehog signaling pathway, primarily through mutational inactivation of the PTCH1 gene, is associated with the development of basal cell carcinoma (BCC). Gli1, a member of the Gli family of transcription factors, is expressed in BCC and in transgenic mice targeted expression of Gli1 in basal keratinocytes leads to BCC development. In addition to BCC, previous studies have shown that Gli1 is expressed in the outer root sheath (ORS) of the hair follicle but is absent in interfollicular epidermis. In this study, we have characterized the expression pattern of two protein kinase C (PKC) isoforms expressed in BCC and hair follicles. We have then used reporter assays to investigate the effects of these isoforms on Gli1 transcriptional activity. We report that in BCC sections, PKCalpha but not PKCdelta was weakly expressed in the epidermis, whereas in the hair follicle, PKCalpha was expressed in the ORS and PKCdelta in the inner root sheath. In contrast, neither PKCalpha nor PKCdelta was expressed in BCC tumor islands, although both isoforms were often expressed in the surrounding stroma. In mammalian 293T cells, coexpression of constitutively active PKCalpha reduced the activity of Gli1 in a dose-dependent manner, whereas constitutively active PKCdelta increased the activity of Gli1, although this required higher expression levels. Regulation of mutant Gli1 protein localized exclusively to the nucleus was similar to that of the wild-type protein, indicating that nuclear-cytoplasmic shuttling is not a determinant of Gli1 control by either PKC isoform. Furthermore, PKC regulation of Gli1 did not involve activation of mitogen-activated protein kinase signaling. Finally, we show that exogenous Gli1 does not alter the expression of PKCalpha in human primary keratinocytes, suggesting that loss of this isoform in BCC is not via Hedgehog signaling. As BCCs have been proposed to originate from the ORS, loss of PKCalpha expression may be relevant to tumor formation; this may, in part, be because of the predicted increase in Gli1 transcriptional activity.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12907651&query_hl=1

Molecular diagnosis of basal cell carcinoma and other basaloid cell neoplasms of the skin by the quantification of Gli1 transcript levels http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15606671&query_hl=2
Ornithine decarboxylase is a target for chemoprevention of basal and squamous cell carcinomas in Ptch1+/- mice http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15067319&query_hl=34
PATCHED and p53 gene alterations in sporadic and hereditary basal cell cancer http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11753655&query_hl=1
PTCH2, a novel human patched gene, undergoing alternative splicing and up-regulated in basal cell carcinomas http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10029063&query_hl=1
Significantly high levels of ultraviolet-specific mutations in the smoothened gene in basal cell carcinomas from DNA repair-deficient xeroderma pigmentosum patients http://www.ncbi.nlm.nih.g