Detection of Numerical Abnormalities of Chromosome 9 and p16/CDKN2A Gene Alterations in Ovarian Cancer with Fish Analysis

The molecular events leading to the development of ovarian cancer are not well-established. Defects of the retinoblastoma protein (pRb)/cyclin-D1/p16 pathway have been shown to play a critical role in the development of human malignancies. In particular, the p16/cyclin-dependent kinase inhibitor 2A (CDKN2A) gene located on chromosomal region 9p21 frequently is altered in several types of cancer. To investigate both the presence of numerical abnormalities of chromosome 9 and p16 gene alterations in ovarian cancer, we studied 28 cases by the fluorescence in situ hybridization (FISH) technique using a DNA p16 probe and an a-satellite probe specific for chromosome 9. Numerical abnormalities of chromosome 9 were found in all studied cases. Polysomy 9 was detected in 10 cases while monosomy 9 in seven cases. In 11 cases, there were two cell populations, one with polysomy 9 and the other with monosomy 9. In all cases, the p16 gene deletion was observed. Among them, 25 cases presented deletion of p16 gene in 21.43%-86.3% of the examined cells. Three cases carried deletion of the p16 gene in a lower proportion (12.04%-19.49%). In five cases with p16 gene deletion, homozygous deletion was detected. Numerical aberrations of chromosome 9 and p16 gene deletion are common findings in ovarian cancer. Data suggest that the p16 gene, located in the short arms of chromosome 9, may play a role in ovarian carcinogenesis. In addition, polysomy 9 could lead to activation of a number of oncogenes, thus participating in the neoplastic process in the ovaries.