Correlation between CpG methylation profiles and hormone receptor status in breast cancers

Introduction Aberrant DNA methylation has been found frequently in human breast cancers, associated with the loss of expression of a number of regulatory genes for growth and correlated to clinical outcomes. The present study was undertaken to determine whether methylation of a set of growth-suppressor genes would correlate to the expression of estrogen receptors ( ERs) and progesterone receptors (PRs). Methods We used a pyrosequencing methylation analysis to study the methylation of 12 known growth-suppressor genes in 90 pairs of malignant/normal breast tissues. We also examined the expression of ERs and PRs in those specimens by immunohistochemistry. Mutations of p53 in tumor cells were detected by direct sequencing. Results Twelve tumor-suppressor genes: ARHI, RASSF1A, HIN-1, RAR beta 2, hMLH1, 14-3-3 sigma, RIZ1, p16, E- cadherin, RIL, CDH13, and NKD2 were selected for this methylation study. Five of them ( RIL, HIN- 1, RASSF1A, CDH13, and RAR beta 2) were frequently methylated in breast cancers ( 57%, 49%, 58%, 44%, and 17%, respectively) but not the normal breast ( 0-4%). Two panels of methylation profiles were defined. The methylation of the HIN-1/RASSFIA panel strongly correlated to the expression of ERs, PRs, and hormone receptors ( HRs; which were defined as ' positive' if ERs and/or PRs were positive; p < 0.001). Conversely, the methylation of the RIL/CDH13 panel strongly correlated to negative ER, PR, and HR expression ( p = 0.001, 0.025, and 0.001, respectively). The subset of triple-negative breast cancers ( in other words, those with negative ER, PR, and HER-2/neu status) was positively associated with the methylation of the RIL/CDH13 panel and negatively associated with the HIN-1/RASSF1A panel. Mutations of p53 were found in nine breast tumors ( 11%), seven of which lacked methylation in both panels. Conclusion We have defined two panels ( HIN-1/RASSFIA, and RIL/CDH13) of methylation profiles, which correlated, either positively or negatively, to HR status.