S100P is a member of the S100 family of calcium-binding proteins. Our previous studies have demonstrated its significant downregulation in oxaliplatin-resistant colon cancer cell line. The present study investigated whether it plays a role in the regulation of chemosensitivity to anticancer drugs using human ovarian cancer cell line OVCAR3. We firstly overexpressed S100P in the OVCAR3 cell line, and evaluated the expression level of S100P by semiquantitative RT-PCR, Western blotting and immunofluorescence assay. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay indicated that overexpression of S100P sensitized OVCAR3 cells for chemotherapeutic drugs (paclitaxel, oxaliplatin, 5-fluorouracil, etoposide and epirubicin) induced cytotoxicity more than vector-only controls. Further studies showed that downregulation of S100P by RNA interference in OVCAR3 cells led to a significant increase of resistance to each of these anticancer drugs. Taken together, our results suggest that S100P plays an important role in regulation of chemosensitivity to anticancer drugs in ovarian cancer cells. Using S100P as a molecular biomarker may increase our ability to predict tumor drug response in ovarian cancer.

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