Progesterone receptor isoform identification and subcellular localization in endometrial cancer.
OBJECTIVE
These studies were undertaken to characterize the subcellular localization of the two major isoforms of progesterone receptors (PR), PRA and PRB, in endometrial cancer.


METHODS
Immunohistochemistry, immunoprecipitation, and confocal microscopy were performed using Hec50co and KLE endometrial cancer cell models expressing PRA or PRB as a consequence of transduction. The location of PRB compared to PRA was determined, and antibodies were tested for specificity with respect to PR isoform recognition. Immunohistochemical analyses of PR expression and subcellular compartmentalization were also performed on 20 formalin-fixed endometrial cancer tumors.


RESULTS
Morphological and biochemical evaluations demonstrated that PRA is localized to the nucleus, even in the absence of progesterone. In contrast, a large proportion of PRB is cytoplasmic in the absence of ligand, but is rapidly translocated to the nucleus in the presence of progesterone. The differential distribution of PRA and PRB proved to be a hallmark of malignant and nonmalignant epithelia in 20 samples of archival endometrial tissue from women with the pre-operative diagnosis of endometrial cancer. All endometrial cancer specimens demonstrated cytoplasmic PRB in 50% or more of the cells, and five of the seven tumors that were moderately to poorly differentiated demonstrated no PRB staining in the nuclei. Nuclear PRB was significantly associated with increasing tumor differentiation (P = 0.031).


CONCLUSIONS
In the absence of ligand, PRA is nuclear and PRB is largely cytoplasmic. This suggests that PRA may exert ligand-independent nuclear effects, while PRB may have nongenomic cytoplasmic actions in endometrial cancer cells.
Leslie
Kimberly K
KK
Department of Obstetrics and Gynecology, The University of New Mexico Health Sciences Center, ACC-4, 211 Lomas Boulevard, NE, Albuquerque, NM 87131, USA.
Stein
Mary-Pat
MP
Kumar
Nirmala S
NS
Dai
Donghai
D
Stephens
Janet
J
Wandinger-Ness
Angela
A
Glueck
Deborah H
DH
D000911:Antibodies, Monoclonal / Q000737:chemistry; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D016889:Endometrial Neoplasms / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D011980:Receptors, Progesterone / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
D000911:Antibodies, Monoclonal; D011980:Receptors, Progesterone; C101118:progesterone receptor A; C097314:progesterone receptor B