Aberration of FHIT gene is associated with increased tumor proliferation and decreased apoptosis-clinical evidence in lung and head and neck carcinomas.

BACKGROUND: Human FHIT (fragile histidine triad) gene is highly conserved gene homologous to a group of genes identified in prokaryotes and eukaryotes. Loss of FHIT function may be important in the development and/or progression of various types of cancer. MATERIALS AND METHODS: We undertook a clinical study to analyze the relation between aberrant function of FHIT gene, tumor cell proliferation, and intensity of apoptosis as well as prognostic output in lung and squamous cell head and neck carcinoma (HNSCC). Status of FHIT gene, expression of p21waf1, intensity of apoptosis, and cell proliferation were analyzed in HNSCC and lung carcinoma tissues by molecular genetic methods, immunohistochemistry, [3H]-thymidine labeling method, and FACScan analysis in frozen and paraffin-embedded tissue sections. RESULTS: The majority of the malignant lung and HNSCC lesions displayed aberrant expression of FHIT gene, followed by low or negative expression of p21waf1, and increased intensity of cell proliferation. Similar results were obtained on synchronous combinations of normal, precancerous, and cancerous head and neck tissues. The observed changes increased with progression of these lesions. We examined tumor and corresponding normal tissue samples for microsatellite markers D3S1300 and D3S4103 to evaluate the loss of heterozygosity (LOH) at the FHIT gene loci. We found high percentage of LOH in both lung tumors and HNSCC (75% for D3S1300 and 79% for D3S4103 in lung cancer, and 87% for D3S1300 and 78% for D3S4103 in HNSCC). The median survival time of the patients suffering from lung cancer without FHIT protein expression was 22.46 months and that of the patients with FHIT expression 36.04 months. FHIT-negative cases tended to correlate with a worse prognosis, but this was not statistically significant. Median survival time of HNSCC patients without FHIT protein expression was 30.86 months and that of the patients with FHIT expression was 64.04 months (p < 0.05). CONCLUSIONS: Our results show a correlation between aberrant FHIT expression, a low rate of apoptosis, and high tumor cell proliferation. Aberrant FHIT gene could be a prognostic marker in lung cancer.

PTCH gene altered in dentigerous cysts.

Motivated by the evidence that odontogenic keratocysts are associated with genetic alterations, we examined the possibility that development of other odontogenic cysts can be attributed to gene malfunctioning, in particular to the PTCH gene. Cyst epithelium was examined for polymorphism on chromosome 9q22.3, the region that contains the PTCH gene. Loss of heterozygosity (LOH) for the D9S287 marker and/or D9S180 marker was observed in about 50% of dentigerous cysts, whereas radicular cysts gave no indication of lesions in the PTCH region. As a more direct argument for PTCH involvement in cystic growth, we report evidence of PTCH expression in dentigerous cyst lining, which indicates malfunctioning of the relevant signaling pathway. While we found no reason to believe that PTCH should be associated with radicular cysts, other genes may be implicated in their development. We performed immunohistochemical comparisons of keratocysts, dentigerous and radicular cysts for the nonmetastatic marker Nm23. A graded response placed radicular cysts in between the other two types, suggesting a similar neoplastic character for their epithelial proliferation.

Involvement of PTCH gene in various noninflammatory cysts.

Constitutional hemizygous inactivation of PTCH, the Shh signaling pathway gene that moderates the signal, manifests itself as nevoid basal cell carcinoma syndrome or Gorlin syndrome, a condition variably characterized by a number of developmental disorders and malformations, and by predisposition to some malignancies, basal cell carcinoma in particular. Loss of heterozygosity for the PTCH region was found several years ago in the epithelial lining of odontogenic keratocysts, the cyst type with highly increased incidence in nevoid basal cell carcinoma syndrome. This finding confirmed the expectations that the gene responsible for the syndrome would have a decisive role in the genesis of these cysts even when they are not syndrome related. Suggestive temporal distribution of Shh signaling, recently observed during tooth development, lead us to investigate PTCH association with dentigerous cysts, the other major noninflammatory cyst of odontogenic origin. We report here that PTCH appears to be inactivated in dentigerous cysts, suggesting that it is responsible for their genesis as well. More generally, if our similar observations of incomplete heterozygosity in this region for dermoid cysts can be interpreted as loss of heterozygosity, PTCH alterations may prove to be a necessary, and perhaps the initiating event, in formation and growth of various noninflammatory cysts. This would be consistent with our view that local PTCH inactivation can, under favorable circumstances, lead to persistent though not by itself truly aggressive cell proliferation.

Variable expression of Gorlin syndrome may reflect complexity of the signalling pathway.

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) or Gorlin syndrome is an autosomal dominant disorder characterized by cancer predisposition and multiple developmental defects. Syndrome related disorders have been attributed to alterations of PTCH gene, which plays an important role in Shh signalling pathway. Unresolved complexities of the pathway impede understanding of mechanisms through which PTCH alterations lead to variable phenotype expression in Gorlin syndrome patients, while the role of chromosomal instability is not yet clear. To increase our understanding of NBCCS, every manifestation of the syndrome and associated genetic damage should be seriously considered. Therefore, several atypical NBCCS cases are presented in this paper.

Involvement of patched (PTCH) gene in Gorlin syndrome and related disorders: three family cases.

AIM: To find genetic alterations in PTC or other genes of the Shh/PTCH pathway in tumorous and non- tumorous samples from three families and to correlate them with the varying expression of disorders in presented nevoid basal cell carcinoma syndrome (NBCCS) phenotypes. METHOD: DNA was extracted from archival paraffin-embedded tissues, tumor tissue or peripheral blood leukocytes, and the loss of heterozygosity (LOH) and single strand conformational polymorphism analysis was performed using PCR with primers for polymorphic 9q22.3 markers (D9S196, D9S287, D9S180, D9S127); PTCH exons 3, 6, 8, 13, 15, 16; and smo (smoothened) exon 1. G-banding tecnique was used for cytogenetic analysis of the peripheral blood lymphocytes. RESULTS: We found a LOH for PTCH in several cases and variability in smo in one case. In one case NBCCS could reasonably be ascribed to hemizygous PTCH inactivation, while in other two families this typical correlation between the syndrome phenotype and the observed genetic alterations could not been established. CONCLUSIONS: Further analysis of relatively sparse cases of NBCCS is needed before the symptoms of the syndrome could be convincingly explained by genetic alterations in the Shh/PTCH signalling pathway.