STUDY OF MIR-200C AND MIR-9 METHYLATION ON PATIENTS WITH BREAST CANCER

Breast cancer is one of the most common causes of death among women worldwide. DNA methylation is essential for normal development and it is associated with a number of key processes including genomic imprinting, X- chromosome inactivation, carcinogenesis. We determined promoter methylation status of miR-9 and miR-200c on DNA obtained from 30 breast cancer cases (mean age of 57±14). DNA was extracted from fresh frozen specimens, after ensuring that tumour samples contained more than 70% cancer cell, treated with sodium bisulphite and amplified by using Methylation Specific PCR (MSP). As control four normal breast tissue from healthy women were also analyzed. Methylation at the miR-9 promoter region was detected in 20 out of 31 cases (64%) and none of the normal breast tissues (P=0.026, X-square. Whereas, miR-200c promoter region showed methylation in 25 out of 31 tumours (80%) and all four normal tissues (P=NS C- square test). A trend towards an association was seen between miR-9 methylation status and patient’s age, and Ki67 expression (Mann Whitney U Test). Our results suggest a possible role of miR9 methylation and breast cancer carcinogenesis. We are currently validating these results on an extended data sample of 72 breast cancer cases.