Objective: To investigate the role of human estrogen receptor-related receptor (ERR) alpha, a submember of orphan receptors, in the tumorigenesis of endometrial cancer.
Methods: Plasmid of pSG-ERRalpha was transfected into endometrial cancer cell lines HEC-1A, HEC-1B, and Ishikawa. Real-time quantitative RT-PCR and western blot were used to analyze the mRNA and protein expression of ERRalpha in endometrial cancer cell. Flow cytometry was used to analyze the cellular growth.
Results: Expressions of the ERRalpha were significantly increased in the endometrial cancer cells transfected with pSG-ERRalpha plasmid; expression of the ERRalpha mRNA in HEC-1A cell was 9644.4 copies/ng, HEC-1B: 9835.3 copies/ng, and Ishikawa: 8008.6 copies/ng (P < 0.01); expression of the ERRalpha protein in HEC-1A cell was 1.128, HEC-1B: 1.104, and Ishikawa: 1.008 (P < 0.05). Flow cytometry showed over-expression of ERRalpha was accompanied by increased HEC-1A and HEC-1B cells in S and G(2)/M phase (P < 0.01), while this could not be observed in the estrogen receptor (ER) positive endometrial cancer cell line Ishikawa. Furthermore, cellular growth analysis showed that over-expression of ERRalpha induced cell growth increase of the ER negative endometrial cancer cells HEC-1A and HEC-1B (P < 0.05).
Conclusion: Over-expression of ERRalpha could stimulate ER negative endometrial cancer cell proliferation independent of estrogen-ER pathway.