Evaluation of estrogen receptor α and β and progesterone receptor expression and correlation with clinicopathologic factors and proliferative marker Ki-67 in breast cancers

SummaryTo elucidate the molecular profile of hormonal steroid receptor status, we analyzed ER-α, ER-β, and PGR mRNA and protein expression in 80 breast carcinomas using reverse transcriptase polymerase chain reaction (RT-PCR), quantitative RT-PCR, and immunohistochemical analysis. Qualitative analysis revealed positive expression of ER-α, ER-β, and PGR mRNA in 48%, 59%, and 48% of the breast carcinomas, respectively. ER-α, ER-β, and PGR transcript overexpression was observed in 51%, 0%, and 12% of the cases, respectively, whereas moderate or strong protein expression was detected in 68%, 78%, and 49% of the cases, respectively. Tumor grade was negatively correlated with transcript and protein levels of ER-α (P = .0169 and P = .0006, respectively) and PGR (P = .0034 and P = .0005, respectively). Similarly, proliferative index Ki-67 was negatively associated with transcript and protein levels of ER-α (P = .0006 and P < .0001, respectively) and PGR (P = .0258 and P = .0005, respectively). These findings suggest that ER-α and PGR expression are associated with well-differentiated breast tumors and less directly related to cell proliferation. A significant statistical difference was observed between lymph node status and ER-β protein expression (P = .0208). In ER-α–negative tumors, we detected a correlation between ER-β protein expression and high levels of Ki-67. These data suggest that ER-β could be a prognostic marker in human breast cancer.