Plasma TS mRNA expression as a potential predictive biomarker for pemetrexed and raltitrexed in gastric cancer.

Abstract

e21034 Background: Plasma mRNA opens up new investigational opportunities and has great potential for use in disease and treatment assessment. Pemetrexed and raltitrexed are novel water-soluble quinazoline folate analogues and act as direct and specific TS inhibitors. Although TS expression levels detected in tumor have shown potential in predicting sensitivity to those two chemotherapeutic agents, current knowledge is limited on the role of plasma TS mRNA as a predictive biomarker. The aim of this study was to investigate the association between plasma TS mRNA expression and in vitro chemosensitivity to pemetrexed and raltitrexed in gastric cancer. Methods: 150 freshly-removed gastric tumor specimens and corresponding blood samples before surgery were collected. Pemetrexed and raltitrexed sensitivity was determined by histoculture drug response assay (HDRA) procedures. Plasma and tumor TS mRNA expression level were determined by quantitative RT-PCR. Results: A significant correlation was observed between plasma and tumor TS mRNA expression levels (rho=0.665, P<0.001). Plasma TS expression level was negatively correlated with in vitro sensitivity to pemetrexed and raltitrexed in gastric cancer (pemetrexed-sensitive sub-group: 0.90, 95% CI: 0.66-1.16; pemetrexed-resistant sub-group: 1.82, 95% CI: 1.38-2.26, P<0.001; raltitrexed-sensitive sub-group: 0.91, 95% CI: 0.64-1.22; raltitrexed-resistant sub-group: 1.62, 95% CI: 1.06-2.17, P=0.013). There was no significant association between clinical characteristics and plasma TS mRNA levels or in vitro chemosensitivity. Conclusions: Our results indicated that plasma TS mRNA expression could be a prominent predictive biomarker for raltitrexed in gastric cancer, enabling the development of ‘‘real-time’’ individualized chemotherapy while tumor progression.