Parkin gene alterations in ovarian carcinoma from northern Indian population

Parkin, a tumor suppressor gene located on chromosome 6q25-27, has been identified as a target for mutation in many human malignancies like breast, ovaries, cervical and lungs etc. After a preliminary report on the loss of heterozygosity and altered Parkin expression in breast and ovarian tumors, we aimed to study loss of heterozygosity in the Parkin gene associated microsatellite markers and its expression in human ovarian cancer patients from Indian population. We examined 102 paired normal and ovarian cancer samples for allelic loss in Parkin gene locus using Parkin gene associated microsatellite markers through loss of heterozygosity and changes in its expression through semiquantitative RT-PCR. Loss of heterozygosity identified common region of loss in Parkin locus with highest frequency for the intragenic marker D6S1599 (53%) whereas, 49 of 102 (48%) specimens showed decreased or no expression of Parkin in ovarian tumors. The study revealed that presence of loss of heterozygosity was significantly higher in both the intragenic markers (D6S1599 and D6S305) as compared with the locus of flanking region (D6S1008) with their p value 0.000001 and 0.00008, respectively. It also revealed that Parkin inactivation is probably a combination of loss of heterozygosity coupled with downregulation of Parkin gene through an alternative means like epigenetic mechanism. These data strongly supports the previous study and argue that Parkin is a tumor suppressor gene whose inactivation may play an important role in ovarian carcinoma.