S100P enhances the chemosensitivity of human gastric cancer cell lines.

BACKGROUND: The effect of the protein S100P on biological characteristics of cancer is not clear, especially in gastric cancer. We previously showed that S100P positive gastric cancer patients have a better cumulative survival than S100P negative patients. OBJECTIVE: To study the possible mechanisms of S100P enhanced the chemosensitivity to oxaliplatin in gastric cancer cell lines. METHODS: S100P was overexpressed in vitro by plasmid transfection and downregulated by siRNA transfection in the BGC823 and SGC7901 gastric cancer cell lines. Cell survival rate, changes in the chemoresistance gene, such as GST-π, MDR1, MRP1, Topo-II, MVP and BCRP, intake of anticancer drug were measured after oxaliplatin treatment. RESULTS: In SGC7901 cells, MTT assay indicated that increased S100P expression levels decreased the survival rate and decreased S100P expression levels increased the survival rate. In BGC823 and SGC7901 cell lines, mRNA of MDR1, a chemoresistance genes, was decreased in cells that overexpressed S100P, and increased in cells with downregulation of S100P. Intracellular accumulation of platinum increased in cells with overexpressed S100P, and decreased in cells with S100P downregulation. CONCLUSIONS: S100P contributes to oxaliplatin chemosensitivity in gastric cell lines by increasing drug inflow. It might also be a novel independent prognostic factor in gastric cancer patients who receive adjuvant chemotherapy with oxaliplatin.

[Impact of S100P expression on clinical outcomes of gastric cancer patients with adjuvant chemotherapy of oxaliplatin and its mechanisms].

OBJECTIVE: To investigate the impact of the expression of S100P on the prognosis and tumor chemosensitivity in patients with resectable gastric cancer and its mechanisms. METHODS: The expression of S100P was analyzed in 121 resected primary gastric cancer tissues by using tissue array of immunohistochemistry excised from January 2003 to December 2007. The patients received adjuvant chemotherapy with oxaliplatin. The pEGFP-S100P plasmid was constructed and was transfected into BGC823 cell line to establish gastric cancer cell line with over-expression of human S100P, BGC823-S100P. The expression level of S100P was determined by real-time PCR and Western blot assay. The chemosensitivity of BGC823-S100P cell line to oxaliplatin was detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. RESULTS: The S100P was positively expressed in 64 tumors (52.9%, 64/121). Although there was no significant relation between the expression of S100P and tumor T staging (P = 0.683), N staging (P = 0.472), M staging (P = 0.770) and differentiation (P = 0.553), Wilcoxon test showed that the 5-year cumulative survival rate of patients with positive S100P expression was significantly higher than that of patients with negative expression (20.3% vs. 3.5%, P = 0.034). Furthermore, overexpressed of S100P was found in the BGC823 cell line, BGC823-S100P. The mRNA and protein level of S100P in pEGFP transfected BGC823-S100P cell lines were significantly higher than those in control group (8.42 ± 1.38 vs. 0.83 ± 0.11 and 3.52 ± 0.48 vs. 0.97 ± 0.19, all P < 0.05). It indicated with MTT assay that the half-inhibitory concentration (IC(50)) to oxaliplatin decreased in BGC823-S100P cells, and was significantly lower than that in vector-only transfected cells [(142 ± 16) mg/L vs. (266 ± 11) mg/L, P = 0.032]. CONCLUSIONS: S100P may also be a potentially novel independent prognostic factor in gastric cancer patients following curative resection. And it could improve the cumulative survival of the patients through enhancing the chemosensitivity of tumor cell line to oxaliplatin.