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-P) in addition to a classical ER-a. ER-P mRNA expression has yet to be studied in pancreatic cancers. Thus, we studied the expression of ER-a and ER-P 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-alpha mRNA levels were significantly (P < 0.01) higher in ER-positive (679.4 +/- 74.7 fmol/mug RNA) than ER-negative (159.7 +/- 33.4) breast cancers, and pancreatic cancers showed significantly (P < 0.01) lower ER-a mRNA levels (17.5 +/- 10.0) than ER-negative breast cancers. On the other hand, ER-P 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-P mRNA levels (28.1 +/- 5.1) than ER-negative breast cancers. Accordingly, ER-alpha /ER-beta 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-beta2 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-P I 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-beta (ER-beta2) plays a more important role than ER-alpha in pancreatic cancers. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.