Genetic Analysis of Cancer-implicated MicroRNA in Ovarian Cancer

Purpose: There is accumulating evidence that microRNAs may function like classic tumor suppressor genes but little is known about their mechanism of inactivation in cancer cells. We investigated whether somatic mutations are a common mechanism of inactivation of microRNA genes in ovarian cancer. Experimental Design: Ten cancer-implicated microRNA genes were analyzed for somatic mutations in 90 ovarian epithelial cancers and matching normal DNA. High-resolution melt analysis and bidirectional sequencing was used to detect sequence variations. Results: High-resolution melt analysis and direct sequencing did not identify any somatic mutations but did reveal numerous novel and previously reported germ line base substitutions, deletions, and insertions surrounding the mature microRNA sequences. The majority of variants were detected in the same proportion of non-cancer control individuals suggesting that they do not represent ovarian cancer-predisposing alleles. Conclusion: The absence of somatic mutations in any of the 10 cancer-implicated microRNAs in our large cohort of ovarian tumors suggests that this may be an uncommon mechanism of inactivation of microRNAs in ovarian cancer.