In summary, familial BFH can be distinguished from BCC based on clinical, histologic, and molecular features and is associated with deregulation of the PTCH pathway.
70-80% of XP skin cancers exhibit one or several mutations in the P53, PTCH-1, SMO or CDKN2A genes, the type and frequency of mutated genes being different between squamous cell (SCCs) and basal cell carcinomas (BCCs).
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).
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).
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.
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.
Loss of heterozygosity (LOH) for Patched 1 gene (PTCH) was demonstrated within two of the trichoepitheloma-like tumors and one tumor diagnosed as basal cell carcinoma, and the patient was show to have a PTCH gene deletion.
These pathways include (a) mutated PTCH (in the mitogenic Sonic Hedgehog pathway) and mutated p53 tumor-suppressor gene in basal cell carcinomas, (b) an activated mitogenic ras pathway and mutated p53 in squamous cell carcinomas, and (c) an activated ras pathway, inactive p16, and p53 tumor suppressors in melanomas.
Constitutive activation of hedgehog signaling, often caused by PTCH1 inactivation and leading to inappropriate activation of GLI target genes, is crucial for the development of several human tumors including basal cell carcinoma of the skin and medulloblastoma.
In 260 samples from 180 Swedish patients with NMSC and a control group of 96 healthy ethnically matched volunteers, no statistically significant pairwise differences between groups were detected in the PTCH codon 1315 allelic distribution, neither was a difference seen for multiple or early onset cases of BCC in the Swedish population.
Many of these mutations, including ptc1-Q688X, result in premature truncation of the ptc1 protein. ptc1-Q688X has been identified in patients with both BCC and nevoid basal cell carcinoma syndrome, an inheritable disorder causing a predisposition to cancer susceptibility.
Mutations in the human tumor suppressor gene, Patched-1, are associated with nevoid basal cell carcinoma syndrome characterized by developmental abnormalities and tumorigenesis, such as basal cell carcinoma and medulloblastoma.
None of the 13 pedigrees solely affected by multiple or early-onset basal cell carcinomas and none of the four pedigrees with jaw cysts alone had PTCH mutations.
The authors present the case of a 2.5-year-old African-American boy with desmoplastic medulloblastoma (MB) and nevoid basal cell carcinoma syndrome (NBCCS), also known as Gorlin syndrome, an autosomal dominant disorder resulting from mutations in the patched (PTCH) gene that predisposes to neoplasias (including basal cell carcinomas [BCCs] and MB) and to widespread congenital malformations.
Constitutional PTCH mutations are causative of the nevoid basal cell carcinoma syndrome, and somatic PTCH mutations are found in the vast majority of basal cell carcinomas.
These data suggest that a (UV-) mutated PTCH gene is important for sporadic BCC formation independent of clinical phenotype and that the IVS16-80G/C and/or IVS17+21G/A SNP site might be important for tumorigenesis in certain BCC patients.
Our results indicate that PTCH mutations are not mainly involved in the pathogenesis of sporadic trichoblastomas, in contrast to basal cell carcinomas and trichoepitheliomas.
The human Patched (PTCH) gene is a classical tumour suppressor gene for basal cell carcinomas and medulloblastomas, the loss of which causes increased signalling through the Sonic Hedgehog (SHH) pathway.
We describe a patient with Gorlin syndrome who had three molecular aberrations resulting in biallelic disruption of the PTCH gene, leading to abnormal protein expression and development of basal cell carcinoma.