Quantitative analysis of estrogen receptor-α and -β messenger RNA expression in human pancreatic cancers by real-time polymerase chain reaction

Recent studies have disclosed the presence of a second estrogen receptor (ER; ER-β) in addition to a classical ER-α. ER-β mRNA expression has yet to be studied in pancreatic cancers. Thus, we studied the expression of ER-α and ER-β mRNA in pancreatic cancers (n=29) by real-time quantitative reverse transcriptase-polymerase chain reaction, and compared the expression levels in pancreatic cancers with those in breast cancers (n=116) which are typical estrogen-dependent tumors. Breast cancers were divided into two groups, ER-positive and ER-negative, according to the ER status determined by enzyme immunoassay. ER-α mRNA levels were significantly (P<0.01) higher in ER-positive (679.4±74.7 fmol/μg RNA) than ER-negative (159.7±33.4) breast cancers, and pancreatic cancers showed significantly (P<0.01) lower ER-α mRNA levels (17.5±10.0) than ER-negative breast cancers. On the other hand, ER-β mRNA levels were significantly (P<0.01) higher in ER-negative (14.1±1.6) than ER-positive breast cancers (7.9±1.0), and pancreatic cancers showed significantly (P<0.01) higher ER-β mRNA levels (28.1±5.1) than ER-negative breast cancers. Accordingly, ER-α/ER-β mRNA ratios were significantly (P<0.01) lower in pancreatic cancers (0.94±053) than in ER-positive (203.9±34.5) and ER-negative (21.9±5.2) breast cancers. ER-β2 mRNA variant expression was significantly (P<0.05) higher in pancreatic cancers than in ER-positive and ER-negative breast cancers, and, on the contrary, ER-β1 mRNA variant expression was significantly (P<0.01) lower in pancreatic cancers than in ER-positive and ER-negative breast cancers. These results suggest a possibility that ER-β (ER-β2) plays a more important role than ER-α in pancreatic cancers.