Detection of methylation in the CpG islands of the RASSF1A and RAR2b gene promoters in breast cancer (BC)

Abstract

e14632 Background: Aberrant methylation of CpG islands of cancer-related genes has emerged as an important epigenetic mechanism during carcinogenesis. We examined the methylation of RASSF1A (Ras-association domain family 1, isoform A) and RAR2b (Retinoic Acid Receptor 2b) genes in BC. The knowledge of their role in BC is limited and confused to date. Methods: Promoter methylation was measured in 37 pts, 26 with BC and 11 with benign lesions. The specimens were obtained from archive formalin-fixed paraffin-embedded tumors. After DNA extraction, the methylation was determined by chemical modification of DNA with sodium bisulfite and subsequent double “hot start” Methylation-Specific PCR (MSP), followed by detection on agarose gel. Results: Methylation of at least one of the genes was observed in 18/26 pts (p<0.05). Methylation of RASSF1A gene was observed in 15/26 and RAR2b in 11/26 pts. Both genes were methylated in 8/26 pts. Correlation between methylation and clinicopathological features revealed an association of the RASSF1A gene with T2 tumors (12/15 pts, p<0.05) and ER (+) status (12/15 pts, p<0.05). T2 tumors and ER (+) status presented together in 9/15 pts. The methylation of RAR2b gene was not associated with any known clinicopathological features. In benign lesions methylation of at least one of the genes was observed in 8/11 pts (p<0.05). Methylation of RASSF1A gene was observed in 5/11 pts and RAR2b in 7/11 pts. Both genes were methylated in 4/11 pts. Conclusions: Both genes are frequently methylated in both benign and malignant breast lesions. The association of methylation of RASSF1A gene with tumor size and ER status is noteworthy. The small number of pts does not allow us to confirm the exact role of gene methylation in BC yet. Larger studies are required in order to assess if these epigenetic alterations point out new BC markers, which could be helpful for BC control. No significant financial relationships to disclose.