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Somatic mutations and deletions of PTCH gene in ovarian fibromas

We have been analyzing molecular genetic alterations of the Gorlin syndrome or Nevoid Basal Cell Carcinoma Syndrome (NBCCS) region, chromosome 9q22.3 in ovarian fibromas, the third tumor by incidence in the syndrome. Gorlin sindrome or Nevoid Basal Cell carcinoma (NBCCS) syndrome is an autosomal dominant disorder that predisposes to basal cell carcinomas of the skin, medulloblastomas and ovarian fibromas, as wide spread developmental defects. Syndrome related disorders have been atributted to alterations of PTCH gene, a human homologue of the drosophila segment polarity gene patched, which maps to chromosome 9q22.3. Loss of heterozygosity (LOH) at this site in both sporadic and hereditary basal cell carcinomas and medulloblastomas suggestss that it functions as a tumor suppressor. The aim is to confirm the tumor suppressor role of the Ptch in genesis of ovarian fibromas even when they are not syndrome related. DNA was isolated from fresh tissues and blood leukocytes. The DNA samples were typed for several short tandem repeat polymorphisms spanning chromosome 9p21-q31 in tumors (ovarian fibroma) and matched constitutional tissues. Polymorphic markers D9S287, D9S127, D9S180 and D9S196 and 20 PTCH exons were used. We screened for allelic loss and by SSCP analysis we have been analyzing variability in PTCH exons. PCR reactions were performed and products were fractionated on 6-12% polyacrylamide gels. We found LOH in 30% of sporadic ovarian fibromas. In about 70% ovarian fibromas variability in SSCP pattern was detected. LOH for the ptch region and aberrant SSCP pattern confirmed the expectations that the gene patched has a decisive role in the genesis of ovarian fibromas when they are not syndrome related.

somatic mutations; deletions; PTCH gene; LOH; SSCP

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