RESUMEN

In mammalian epidermis, the level of beta-catenin signaling regulates lineage selection by stem cell progeny. High levels of beta-catenin stimulate formation of hair follicles, whereas low levels favor differentiation into interfollicular epidermis and sebocytes. In transgenic mouse epidermis, overexpression of beta-catenin leads to formation of hair follicle tumors, whereas overexpression of N-terminally truncated Lef1, which blocks beta-catenin signaling, results in spontaneous sebaceous tumors. Accompanying overexpression of beta-catenin is up-regulation of Sonic hedgehog (SHH) and its receptor, Patched (PTCH/Ptch). In DeltaNLef1 tumors Ptch mRNA is up-regulated in the absence of SHH. We now show that PTCH is up-regulated in both human and mouse sebaceous tumors and is accompanied by overexpression of Indian hedgehog (IHH). In normal sebaceous glands IHH is expressed in differentiated sebocytes and the transcription factor GLI1 is activated in sebocyte progenitors, suggesting a paracrine signaling mechanism. PTCH1 and IHH are up-regulated during human sebocyte differentiation in vitro and inhibition of hedgehog signaling inhibits growth and stimulates differentiation. Overexpression of DeltaNLef1 up-regulates IHH and stimulates proliferation of undifferentiated sebocytes. We present a model of the interactions between beta-catenin and hedgehog signaling in the epidermis in which SHH promotes proliferation of progenitors of the hair lineages whereas IHH stimulates proliferation of sebocyte precursors.

Asunto(s)

Proteínas del Citoesqueleto/metabolismo , Neoplasias de las Glándulas Sebáceas/metabolismo , Neoplasias de las Glándulas Sebáceas/patología , Glándulas Sebáceas/citología , Glándulas Sebáceas/metabolismo , Transactivadores/metabolismo , Animales , Diferenciación Celular , Línea Celular , Folículo Piloso/citología , Folículo Piloso/metabolismo , Proteínas Hedgehog , Humanos , Técnicas In Vitro , Péptidos y Proteínas de Señalización Intracelular , Proteínas de la Membrana/metabolismo , Ratones , Ratones Transgénicos , Modelos Biológicos , Receptores Patched , Receptor Patched-1 , Receptores de Superficie Celular , Transducción de Señal , Células Madre/citología , Células Madre/metabolismo , beta Catenina

RESUMEN

It is widely accepted that disruption of the hedgehog-patched pathway is a key event in development of basal cell cancer. In addition to patched gene alterations, p53 gene mutations are also frequent in basal cell cancer. We determined loss of heterozygosity in the patched and p53 loci as well as sequencing the p53 gene in tumors both from sporadic and hereditary cases. A total of 70 microdissected samples from tumor and adjacent skin were subjected to PCR followed by fragment analysis and DNA sequencing. We found allelic loss in the patched locus in 6/8 sporadic basal cell cancer and 17/19 hereditary tumors. All sporadic and 7/20 hereditary tumors showed p53 gene mutations. Loss of heterozygosity in the p53 locus was rare in both groups. The p53 mutations detected in hereditary tumors included rare single nucleotide deletions and unusual double-base substitutions compared to the typical ultraviolet light induced missense mutations found in sporadic tumors. Careful microdissection of individual tumors revealed genetically linked subclones with different p53 and/or patched genotype providing an insight on time sequence of genetic events. The high frequency and co-existence of genetic alterations in the patched and p53 genes suggest that both these genes are important in the development of basal cell cancer.

Asunto(s)

Síndrome del Nevo Basocelular/genética , Proteínas de la Membrana/genética , Mutación/genética , Neoplasias Basocelulares/genética , Proteína p53 Supresora de Tumor/genética , Adulto , Anciano , Anciano de 80 o más Años , Síndrome del Nevo Basocelular/patología , Femenino , Humanos , Inmunohistoquímica , Hibridación in Situ , Pérdida de Heterocigocidad/genética , Masculino , Persona de Mediana Edad , Mutación Missense/genética , Neoplasias Basocelulares/patología , Receptores Patched , Reacción en Cadena de la Polimerasa , ARN Mensajero/análisis , ARN Mensajero/genética , ARN Neoplásico/análisis , ARN Neoplásico/genética , Receptores de Superficie Celular

RESUMEN

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.

Asunto(s)

Carcinoma Basocelular/genética , Neoplasias Cutáneas/genética , Factores de Transcripción/genética , Animales , Secuencia de Bases , Cartilla de ADN , Genes p53 , Genes ras , Humanos , Factores de Transcripción de Tipo Kruppel , Ratones , Ratones Transgénicos , Piel/metabolismo , Proteína con Dedos de Zinc GLI1

RESUMEN

Sonic hedgehog, Patched and Gli are components of a mammalian signalling pathway that has been conserved during evolution and which has a central role in the control of pattern formation and cellular proliferation during development. Here we identify the human Suppressor-of-Fused (SUFUH) complementary DNA and show that the gene product interacts physically with the transcriptional effector GLI-1, can sequester GLI-1 in the cytoplasm, but can also interact with GLI-1 on DNA. Functionally, SUFUH inhibits transcriptional activation by GLI-1, as well as osteogenic differentiation in response to signalling from Sonic hedgehog. Localization of GLI-1 is influenced by the presence of a nuclear-export signal, and GLI-1 becomes constitutively nuclear when this signal is mutated or nuclear export is inhibited. These results show that SUFUH is a conserved negative regulator of GLI-1 signalling that may affect nuclear-cytoplasmic shuttling of GLI-1 or the activity of GLI-1 in the nucleus and thereby modulate cellular responses.

Asunto(s)

Núcleo Celular/metabolismo , Proteínas de Drosophila , Proteínas Oncogénicas/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Factores de Transcripción/metabolismo , Transcripción Genética , Adulto , Secuencia de Aminoácidos , Animales , Diferenciación Celular , Línea Celular , Pollos , Citoplasma/metabolismo , Drosophila melanogaster/genética , Embrión de Mamíferos , Embrión no Mamífero , Regulación del Desarrollo de la Expresión Génica , Humanos , Mamíferos , Ratones , Datos de Secuencia Molecular , Osteoblastos/metabolismo , Osteogénesis , Proteínas Recombinantes/metabolismo , Proteínas Represoras/química , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Transactivadores , Transfección , Proteína con Dedos de Zinc GLI1

RESUMEN

By a combination of cDNA library screening, rapid amplification of cDNA ends analysis, and BAC sequencing, a novel human patched-like gene (PTCH2) has been cloned and sequenced. The genomic organization is similar to PTCH1 with 22 exons and, by radiation hybrid mapping, PTCH2 has been localized to chromosome 1p33-34, a region often lost in a variety of tumors. Several alternatively spliced mRNA forms of PTCH2 were identified, including transcripts lacking segments thought to be involved in sonic hedgehog binding and mRNAs with differentially defined 3' terminal exons. In situ hybridization revealed high expression of PTCH2 transcripts in both familial and sporadic basal cell carcinomas in similarity to what has been observed for PTCH1, suggesting a negative regulation of PTCH2 by PTCH1. This finding tightly links PTCH2 with the sonic hedgehog/PTCH signaling pathway, implying that PTCH2 has related, but yet distinct, functions than PTCH1.

Asunto(s)

Empalme Alternativo , Carcinoma Basocelular/genética , Proteínas de la Membrana/genética , Secuencia de Aminoácidos , Secuencia de Bases , Mapeo Cromosómico , Humanos , Datos de Secuencia Molecular , Receptores Patched , Receptor Patched-1 , Receptor Patched-2 , Receptores de Superficie Celular , Regulación hacia Arriba

RESUMEN

The human homologue of Drosophila patched (PTCH), located at chromosome 9q22.3, was recently identified as a candidate tumor suppressor gene for familial and sporadic basal cell carcinomas. Squamous cell carcinomas (SCCs) of the skin display allelic loss in this chromosomal region, which, in addition to the PTCH gene, contains the DNA repair gene xeroderma pigmentosum complementation group A (XPA). Patients with xeroderma pigmentosum are predisposed to non-melanoma skin tumors because of deficient excision repair of ultraviolet-induced DNA damage. Mutation analysis by single-strand conformation analysis and direct DNA sequencing of all 23 exons of the PTCH gene and all six exons of the XPA gene in 14 SCCs did not reveal structural alterations in any of these genes. Additionally, analysis of PTCH expression by in situ hybridization in SCCs revealed no evidence of upregulation of PTCH mRNA, confirming the lack of mutations in this gene. These findings suggest that another, yet to be identified gene or genes on chromosome 9q are involved in SCC tumorigenesis.

Asunto(s)

Carcinoma de Células Escamosas/genética , Proteínas de Unión al ADN/genética , Proteínas de la Membrana/genética , Proteínas de Neoplasias/genética , Neoplasias Cutáneas/genética , Cromosomas Humanos Par 9 , Análisis Mutacional de ADN , Humanos , Hibridación in Situ , Pérdida de Heterocigocidad , Receptores Patched , Receptor Patched-1 , Polimorfismo Genético , Polimorfismo Conformacional Retorcido-Simple , ARN Mensajero/genética , ARN Neoplásico/genética , Receptores de Superficie Celular , Proteína de la Xerodermia Pigmentosa del Grupo A

RESUMEN

The nevoid basal cell carcinoma (Gorlin) syndrome (NBCCS) is an autosomal dominant disorder characterized by multiple developmental defects and cancer susceptibility. NBCCS is caused by mutations in the human homologue (PTCH) of the Drosophila patched gene, a developmental regulator implicated in signaling of hedgehog and smoothened. The PTCH gene was found to contain somatic mutations also in sporadic basal cell carcinomas and medulloblastomas, tumors seen in NBCCS, consistent with PTCH acting as a tumor suppressor. Because basal cell carcinomas have been observed to develop in association with benign trichoepitheliomas (TEs) in the same lesions, patients, and families and may share the same cell of origin, we have analyzed PTCH for mutations and expression in TEs. We report frameshift and in-frame somatic deletions in this gene and a consistent overexpression of PTCH mRNA in TEs. These findings provide the first evidence of a gene mutation in TEs and identify a common pathogenic pathway for histopathologically similar but prognostically distinct skin tumors. Moreover, these results support the presence of a gatekeeper mechanism in multistep skin tumorigenesis exerted by the altered PTCH signaling pathway.

Asunto(s)

Carcinoma Basocelular/genética , Genes Relacionados con las Neoplasias/genética , Genes Supresores de Tumor/genética , Mutación , Proteínas de Neoplasias/genética , Neoplasias Cutáneas/genética , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma Basocelular/metabolismo , Femenino , Mutación de Línea Germinal , Humanos , Masculino , Persona de Mediana Edad , Proteínas de Neoplasias/metabolismo , Neoplasias Cutáneas/metabolismo

RESUMEN

Recently, a human homologue of the Drosophila patched gene, PTCH, was identified as a putative tumor suppressor mutated in both hereditary and sporadic basal cell carcinomas. Because PTCH controls its own transcription, inactivating mutations in PTCH may lead to overexpression of mutant PTCH mRNA due to loss of autoregulation. The present study is aimed at evaluating whether deregulation of PTCH mRNA expression is a general feature of BCCs of varying histological growth pattern and malignant potential. Irrespective of histological subtype, PTCH mRNA was overexpressed consistently as determined by in situ hybridization in all of the sporadic (n = 16) and hereditary (n = 20) tumors examined. PTCH expression was found in all of the tumor cells but appeared stronger in the peripheral palisading cells. PTCH mRNA was not detected in adjacent nontumor epidermal cells or in other parts of the epidermis. In the majority of tumors (20 of 36), nuclear immunostaining for p53 was found in scattered cells, whereas seven tumors completely lacked p53 immunoreactivity. Our finding of an up-regulation of PTCH mRNA levels in all of the BCCs analyzed indicates that deregulation of the PTCH signaling pathway constitutes an early rate-limiting event in BCC development.

Asunto(s)

Carcinoma Basocelular/metabolismo , Proteínas de Drosophila , Proteínas de Insectos/metabolismo , Proteínas de la Membrana/metabolismo , Neoplasias Cutáneas/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma Basocelular/genética , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Inmunohistoquímica , Hibridación in Situ , Masculino , Persona de Mediana Edad , ARN Mensajero/metabolismo , Receptores de Superficie Celular , Neoplasias Cutáneas/genética , Proteína p53 Supresora de Tumor/metabolismo

RESUMEN

The nevoid basal cell carcinoma syndrome is an autosomal dominant disorder, characterized by predisposition to multiple early basal cell carcinomas of the skin and several other tumours as well as frequent occurrence of developmental anomalies. The gene has previously been mapped to chromosome 9q22 and is believed to function as a tumour suppressor. We have applied linkage and haplotype analysis to four Swedish nevoid basal cell carcinoma syndrome families to refine the localization of the nevoid basal cell carcinoma syndrome gene. Information from critical recombinants localizes the gene proximal of marker D9S287, which in combination with analysis of loss of heterozygosity in a hereditary cardiac fibroma has allowed us to define a minimal candidate region of 1Mb or less for the nevoid basal cell carcinoma gene flanked by the markers D9S280 and D9S287 in the 9q22.3 area.

Asunto(s)

Síndrome del Nevo Basocelular/genética , Mapeo Cromosómico , Cromosomas Humanos Par 9 , Neoplasias Cutáneas/genética , Adolescente , Adulto , Anciano , Femenino , Ligamiento Genético , Humanos , Lactante , Masculino , Persona de Mediana Edad

RESUMEN

The nevoid basal cell carcinoma (Gorlin) syndrome (NBCCS) is an autosomal dominant disorder characterized by multiple developmental defects and cancer susceptibility, in particular to basal cell carcinoma. The human homologue of Drosophila patched (PTCH) was recently identified, mapped to the NBCCS locus on chromosome 9q22.3, and found mutated in patients with NBCCS and also in sporadic basal cell carcinomas. Here we show germ-line PTCH mutations in three families with NBCCS. We demonstrate that a germ-line PTCH frameshift deletion in one patient with NBCCS was accompanied by loss of the normal copy of PTCH in a tumor developed in the same patient. Another basal cell carcinoma from this patient did not show the loss of the normal copy of PTCH, instead a missense mutation in a highly conserved residue was identified in the nondeleted allele, illustrating two different mechanisms of PTCH inactivation in different tumors derived from the same NBCCS patient. We also show somatic PTCH mutations in 4 basal cell carcinomas identified by analyzing 18 non-NBCCS patients with sporadic tumors. These data provide further support for PTCH as an important tumor suppressor gene in the development of the most common human cancer.

Asunto(s)

Síndrome del Nevo Basocelular/genética , Proteínas de la Membrana/genética , Mutación Puntual/genética , Neoplasias Cutáneas/genética , Adulto , Anciano , Anciano de 80 o más Años , Salud de la Familia , Femenino , Mutación del Sistema de Lectura/genética , Humanos , Masculino , Persona de Mediana Edad , Receptores Patched , Receptor Patched-1 , Fenotipo , Reacción en Cadena de la Polimerasa , Polimorfismo Conformacional Retorcido-Simple , Receptores de Superficie Celular

RESUMEN

Basal cell carcinoma (BCC) is the most common cancer in humans. The majority of sporadic BCCs have allele loss on chromosome 9q22 implying that inactivation of a tumour suppressor in this region is an important step in BCC formation. The gene for nevoid basal cell carcinoma syndrome (NBCCS), an autosomal dominant disorder characterized by multiple BCCs, maps to the same region and is presumed to be the tumour suppressor inactivated at this site. NBCCS has been identified recently and encodes a protein with strong homology to the Drosophila segment polarity gene, patched. Analysis of Drosophila mutants indicates that patched interacts with the hedgehog signalling pathway, repressing the expression of various hedgehog target genes including wingless, decapentaplegic and patched itself. Using single strand conformational polymorphism (SSCP) to screen human patched in 37 sporadic BCCs, we detected mutations in one-third of the tumours. Direct sequencing of two BCCs without SSCP variants revealed mutations in those tumours as well suggesting that inactivation of patched is probably a necessary step in BCC development. Northern blots and RNA in situ hybridization showed that patched is expressed at high levels in tumour cells but not normal skin suggesting that mutational inactivation of the gene leads to overexpression of mutant transcript owing to failure of a negative feedback mechanism.

Asunto(s)

Carcinoma Basocelular/genética , Genes Supresores de Tumor , Proteínas de la Membrana/genética , Neoplasias Cutáneas/genética , Animales , Carcinoma Basocelular/patología , Drosophila/genética , Drosophila/metabolismo , Expresión Génica , Variación Genética , Humanos , Mutación , Receptores Patched , Receptor Patched-1 , Polimorfismo Conformacional Retorcido-Simple , ARN Mensajero , Receptores de Superficie Celular , Neoplasias Cutáneas/patología

RESUMEN

Stromelysin-3 is produced in the stroma of various malignant tumors, and in breast carcinoma there seems to be a positive correlation between aggressive disease and intensity of stromelysin-3 expression, suggesting that stromelysin-3 participates in the tumor spread. In basal cell carcinoma, previous findings on stromelysin-3 have been inconclusive in this respect. Our study was undertaken to determine the pattern of stromelysin-3 production in relation to different histologic subtypes and stromal reactions in basal cell carcinoma. By in situ hybridization, stromelysin-3 mRNA was detected in stromal fibroblastic cells in 51/56 samples. Furthermore, there was a significant correlation between strong signal for stromelysin-3 mRNA and infiltrative tumor growth. In all tumors, there was ongoing collagen synthesis as shown by a signal for procollagen I mRNA; this signal co-localized with stromelysin-3 around tumor nests. Our findings suggest a link between stromelysin-3 and fibrotic stromal response, which prompted us to evaluate the expression of stromelysin-3 in other fibrotic skin tumors. Interestingly, stromelysin-3, co-localizing with procollagen I mRNA, was consistently expressed in lesional cells in dermatofibromas (19/19), but not in dermatofibrosarcomas (0/7). Thus, our results indicate that in addition to being a marker for malignant disease, stromelysin-3 is produced by fibroblastic cells associated with benign fibrosis. A subset of cells producing stromelysin-3 appears to be myofibroblasts as demonstrated by immunoreactivity for alpha smooth muscle actin in both basal cell carcinoma and dermatofibroma.

Asunto(s)

Carcinoma Basocelular/metabolismo , Dermatofibrosarcoma/metabolismo , Histiocitoma Fibroso Benigno/metabolismo , Metaloendopeptidasas/genética , Músculo Liso Vascular/metabolismo , ARN Mensajero/metabolismo , Neoplasias Cutáneas/metabolismo , Actinas/metabolismo , Carcinoma Basocelular/patología , Dermatofibrosarcoma/patología , Histiocitoma Fibroso Benigno/patología , Humanos , Metaloproteinasa 11 de la Matriz , Invasividad Neoplásica , Procolágeno/genética , Neoplasias Cutáneas/patología

RESUMEN

The nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by multiple basal cell carcinomas (BCCs), pits of the palms and soles, jaw keratocysts, a variety of other tumors, and developmental abnormalities. NBCCS maps to chromosome 9q22.3. Familial and sporadic BCCs display loss of heterozygosity in this region, consistent with the gene being a tumor suppressor. A human sequence (PTC) with strong homology to the Drosophila segment polarity gene, patched, was isolated from a YAC and cosmid contig of the NBCCS region. Mutation analysis revealed alterations of PTC in NBCCS patients and in related tumors. We propose that a reduction in expression of the patched gene can lead to the developmental abnormalities observed in the syndrome and that complete loss of patched function contributes to transformation of certain cell types.

Asunto(s)

Síndrome del Nevo Basocelular/genética , Proteínas de Drosophila , Genes Supresores de Tumor/genética , Hormonas de Insectos/genética , Proteínas de la Membrana/genética , Homología de Secuencia de Ácido Nucleico , Alelos , Animales , Secuencia de Bases , Mapeo Cromosómico , Cromosomas Humanos Par 9 , Clonación Molecular , ADN Complementario/genética , Drosophila/genética , Exones/genética , Femenino , Eliminación de Gen , Expresión Génica , Humanos , Técnicas In Vitro , Intrones/genética , Datos de Secuencia Molecular , Mutación/genética , Linaje , Receptores de Superficie Celular