Significance of progesterone receptor-A and -B expressions in endometrial adenocarcinoma

The progesterone receptor (PR) has two isoforms, A and B, among which PR-B is mainly involved in regulating proliferation of the uterine endometrium. In this study, immunohistochemical analysis was carried out to investigate the correlation of PR-A and -B expressions with cell cycle-regulatory proteins and clinicopathological parameters in endometrial adenocarcinoma. One hundred and forty-one endometrioid adenocarcinomas 76 with well-differentiated (G1), 35 with moderately differentiated (G2) and 30 with poorly differentiated (G3)] were used. Specimens of formalin-fixed and paraffin-embedded tissue were immunohistochemically stained using the high polymer method (HISTOFINE, NICHIREI). The percentage of positive nuclei of tumor cells observed in three high power fields was expressed as a labeling index (LI). PR-B expression significantly occurred more frequently in G1. It was inversely correlated with p53 gene mutation and p53 over expression, and also with clinicopathological variables, including myometrial and lymph-vascular space invasion and the FIGO stage. Patients with negative PR-B had a poorer prognosis than positive cases. PR-A expression was also significantly higher in G1 and was inversely correlated with Ki-67 expression and myometrial invasion, but not with prognosis. PR-A and -B expressions were significantly correlated with biologically malignant potential. Especially, PR-B expression is useful as a prognostic indicator of endometrial adenocarcinoma.