Expression of the ELAV-like protein HuR in the cytoplasm is associated with endometrial carcinoma progression

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Human antigen R (HuR) is an mRNA-binding factor that belongs to the embryonic lethal abnormal vision/Hu protein family which may function as a tumor maintenance gene in a variety of carcinomas. However, there is no study to analyze HuR expression in endometrial carcinoma. Here, we investigated the expression of HuR in endometrial carcinoma carcinogenesis and subsequent progression. The expression of HuR and estrogen receptor alpha (ER-α) protein was examined by immunohistochemistry on paraffin embedding specimens containing endometrial carcinoma and adjacent non-cancerous tissues. Short hairpin RNA against HuR was transfected to investigate the role of HuR in regulating the expression of ER-α and progression in endometrial carcinoma. Cell viability and cycle were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry, respectively. Apoptosis was examined by annexin V apoptosis assay. Our study result show that cytoplasmic HuR expression is more frequent in poorly differentiated carcinomas (p = 0.005), advanced stage (p = 0.020), and positive ER-α expression (p = 0.026). Three HuR short hairpin RNAs (shRNAs) were transfected into Ishikawa cells, and we selected the most effective shRNA for the following experiments. After the transfection, the ER-α protein level was decreased. Further, decreased expression of HuR resulted in the inhibition of proliferation and induced apoptosis in Ishikawa cells. Our results showed that HuR could be a causal factor of ER-α regulation in Ishikawa cells and thus may induce the hormone-dependent endometrial carcinoma.