Genetic profiling of basal cell carcinomas detects postzygotic mosaicism in basal cell naevus syndrome.

Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene. Postzygotic mosaicism can also cause BCNS. Here we describe two patients, one with multiple basal cell carcinomas (BCCs) and one with clinical BCNS, who had no PTCH1 mutation in DNA extracted from blood. In both patients, we performed genetic analysis on different BCCs, revealing the presence of a shared PTCH1 mutation in all tumours. Our findings show that in patients with symptoms of BCNS and initial absence of a PTCH1 mutation in blood, genetic profiling of BCCs can detect postzygotic mosaicism. What's already known about this topic? Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene, but it can also be caused by low-grade postzygotic mosaicism in PTCH1. What does this study add? In patients suspected of having BCNS or patients with multiple basal cell carcinomas (BCCs) with a special distribution on the body and no mutation detected in blood, it is worthwhile to search for a shared PTCH1 mutation in their BCCs as this can detect postzygotic mosaicism. This information is important to ensure proper surveillance programmes, choose the right therapy and provide adequate genetic counselling.

Frameshift mutation in the PTCH2 gene can cause nevoid basal cell carcinoma syndrome.

Nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by developmental defects and tumorigenesis. The gene responsible for NBCCS is PTCH1, encoding a receptor for the secreted protein, sonic hedgehog. Recently, a Chinese family with NBCCS carrying a missense mutation in PTCH2, a close homolog of PTCH1, was reported. However, the pathological significance of missense mutations should be discussed cautiously. Here, we report a 13-year-old girl diagnosed with NBCCS based on multiple keratocystic odontogenic tumors and rib anomalies carrying a frameshift mutation in the PTCH2 gene (c.1172_1173delCT). Considering the deleterious nature of the frameshift mutation, our study further confirmed a causative role for the PTCH2 mutation in NBCCS. The absence of typical phenotypes in this case such as palmar/plantar pits, macrocephaly, falx calcification, hypertelorism and coarse face, together with previously reported cases, suggested that individuals with NBCCS carrying a PTCH2 mutation may have a milder phenotype than those with a PTCH1 mutation.

High prevalence of vitamin D deficiency in patients with basal cell nevus syndrome.

OBJECTIVES: To evaluate vitamin D status in patients with basal cell nevus syndrome (BCNS) who practice photoprotection because of their genetic predisposition to skin cancer and to determine risk factors for deficiency. DESIGN: Retrospective cohort study. SETTING: Academic medical centers. PATIENTS: Forty-one ambulatory patients with BCNS who participated in a 2-year chemoprevention clinical trial. Population-based controls (n = 360) were selected and matched by age, sex, Fitzpatrick skin type, and season/geography. MAIN OUTCOME MEASURES: Levels of 25-hydroxyvitamin D (25[OH]D) and vitamin D deficiency (defined as a 25[OH]D level of ≤20 ng/mL). RESULTS: Twenty-three patients with BCNS (56%) were vitamin D deficient. Patients with BCNS had mean 25(OH)D levels below those of the general population (-3 ng/mL; P = .02) and were 3 times more likely to be vitamin D deficient (56% vs 18%; P < .001). Levels of 25(OH)D were lower in patients who were overweight (-3.0 ng/mL; P = .04) and who had blood collected in the winter compared with the summer (-7.1 ng/mL; P < .001). CONCLUSION: Patients with BCNS may be at increased risk for vitamin D deficiency, depending on their adherence to photoprotection practices.

Multiple keratocystic odontogenic tumors associated with nevoid basal cell carcinoma syndrome having distinct PTCH1 mutations: a case report.

Nevoid basal cell carcinoma syndrome (NBCCS) is a rare autosomal dominant disorder characterized by developmental abnormalities and a predisposition to cancers. Although multiple jaw tumors, such as keratocystic odontogenic tumors (KCOTs), are one of the most frequent complications in NBCCS, the molecular mechanism for how KCOTs develop in NBCCS is poorly understood. A 15-year-old girl with 2 jaw tumors was diagnosed as NBCCS according to the clinical criteria. The pathologic findings indicated that the 2 tumors were consistent with KCOTs. A PTCH1 mutation, c.1472delT, was detected in her peripheral blood as well as in the 2 tumors. Interestingly, an additional PTCH1 mutation, c.264_265insAATA, that was not present in the peripheral blood, was found in the maxillary tumor but not the mandibular tumor. The Ki-67 labeling index was significantly higher in the maxillary KCOT (17.7%) than in the mandibular KCOT (14.3%). These findings indicate distinct molecular mechanisms of tumorigenesis in these KCOTs.

A novel polymorphism in the PTC gene allows easy identification of allelic loss in basal cell nevus syndrome lesions.

Basal cell nevus syndrome (BCNS; also nevoid basal cell carcinoma syndrome [NBCCS]; Gorlin's syndrome) is an autosomal dominant syndrome characterized by multiple basal cell carcinomas, keratocysts, and developmental skeletal defects. Mutation of the human homologue of Drosophila patched (PTC) gene is considered to be the molecular defect in BCNS. PTC mutations have been observed in sporadic tumors including basal cell and ovarian carcinomas and medulloblastoma. The authors report a novel C/T polymorphism in the PTC gene. Forty-eight normal blood samples were screened for the presence of the polymorphism using direct radioactive and automated sequencing of polymerase chain reaction (PCR) products and restriction enzyme digestion. Results demonstrated 20 homozygous T (43%), 11 homozygous C (23%), and 17 heterozygous C/T (35%). The presence of this polymorphism has permitted us to directly detect allelic loss in BCNS, sporadic keratocysts, and basal cell carcinoma (BCC). Further, four BCNS keratocysts and two BCNS-BCC and three non-BCNS keratocysts showed allelic loss of complementary DNA from lesions when compared with their corresponding blood genomic DNA.

Gamma-irradiation deregulates cell cycle control and apoptosis in nevoid basal cell carcinoma syndrome-derived cells.

The nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by nevi, palmar and plantar pits, falx calcification, vertebrate anomalies and basal cell carcinomas. It is well known in NBCCS that gamma-irradiation to the skin induces basal cell carcinomas or causes an enlargement of the tumor size, although the details of the mechanism remain unknown. We have established lymphoblastoid cell lines from three NBCCS patients, and we present here the first evidence of abnormal cell cycle and apoptosis regulations. A novel mutation (single nucleotide deletion) in the coding region of the human patched gene, PTCH, was identified in two sibling patients, but no apparent abnormalities were detected in the gene of the remaining patient. Nevertheless, the three established cell lines showed similar features in the following analyses. Flow cytometric analyses revealed that the NBCCS-derived cells were accumulated in the G2M phase after gamma-irradiation, whereas normal cells showed cell cycle arrest both in the G0G1 and G2M phases. The fraction of apoptotic cells after gamma-irradiation was smaller in the NBCCS cells. The level of p27 expression markedly decreased after gamma-irradiation in the NBCCS cells, although the effects of the irradiation on the expression profiles for p53, p21 and Rb did not differ in normal and NBCCS cells. These findings may provide a clue to the molecular mechanisms of tumorigenesis in NBCCS.

The nevoid basal cell carcinoma syndrome: sensitivity to ultraviolet and x-ray irradiation.

Demographic studies in patients with skin cancer have demonstrated the importance of exposure to ultraviolet and x-ray irradiation. This paper describes in vitro studies in peripheral lymphocytes from three patients with the nevoid basal cell carcinoma syndrome. Particular stress was placed on the following factors: (1) the distribution of the lymphocyte subsets, (2) the frequency of spontaneous sister chromatid exchange, (3) the effect of ultraviolet C (UVC) (254 nm) on deoxyribonucleic acid (DNA) synthesis, (4) the effect of UVC on the phytohemagglutinin-stimulated lymphocyte proliferation, and (5) the capacity to repair x-ray-induced DNA damage. Our data indicate that the distribution of the peripheral lymphocytes was normal, while the frequency of spontaneous sister chromatid exchange was high. The capacity of the lymphocytes to repair x-ray-induced DNA damage was low in all three patients. In two patients the UVC-induced DNA synthesis was reduced, while an increased UVC-induced inhibition of lymphocyte proliferation was observed. These cellular responses in vitro to ultraviolet and x-ray irradiation correspond to the clinical features of the nevoid basal cell carcinoma syndrome. A clearly defective in vitro cellular response to x-ray irradiation, reflecting the clinically evident x-ray sensitivity in the nevoid basal cell carcinoma syndrome, has not been reported previously.

Decreased UV-induced DNA repair synthesis in peripheral leukocytes from patients with the nevoid basal cell carcinoma syndrome.

The UV-induced DNA repair synthesis in peripheral leukocytes from 7 patients with the nevoid basal cell carcinoma syndrome was compared to that in peripheral leukocytes from 5 patients with basal cell carcinomas and 39 healthy subjects. A dose response curve was established for each individual, and maximum DNA repair synthesis was used as a measure of the capacity for DNA repair. The patients with the nevoid basal cell carcinoma syndrome had about 25% lower level of maximum DNA repair synthesis as compared to the patients with basal cell carcinomas and control individuals. The possibility that DNA repair mechanisms may be involved in the etiology to the nevoid basal cell carcinoma syndrome is discussed.

Multiple basal cell carcinomas and keratocysts - the Gorlin and Goltz syndrome.

This paper is based on our experience with the Gorlin-Goltz syndrome and on data from 14 patients of the Nordwestdeutsche Kieferklinik in whom this disorder was detected, treated and followed up. A clinical concept has been produced, with a diagnostic check list including a genetic and a dermatological routine work up as well as a radiological survey of the jaws and skeleton. Whenever multiple basal cell carcinomas plus the typical jaw lesions are found in a patient, the diagnosis is easy. A minimum diagnostic criterion is the combination of either the skin tumours or multiple odontogenic keratocysts plus a positive family history for this disorder, bifid ribs, lamellar calcification of the falx cerebri or any one of the skeletal abnormalities typical of this syndrome. All those in whom this disorder is diagnosed or suspected should be followed up for the rest of their lives. The family should be examined and genetic counselling should be offered.