Gene signature in plasma and tumor to predict irinotecan chemosensitivity in gastric cancer.

e15098 Background: Personalized chemotherapy based on molecular biomarkers can maximize efficiency and reduce adverse effects. We investigated and validated predictive biomarkers for irinotecan and developed a gene signature that is closely associated with chemosensitivity to irinotecan in gastric cancer patients. Methods: We examined gene expression of APTX, BRCA1, ERCC1, ISG15 and Topo1 in plasma and paired formalin-fixed paraffin-embedded gastric cancer tissues from 175 patients and evaluated the association between gene expression levels and in vitro sensitivity to irinotecan. We used multiple linear regression analysis to develop a gene-expression model to predict irinotecan sensitivity in gastric cancer and validated this model in vitro and vivo. Results: The plasma gene expression levels of APTX (P= 0.006) and BRCA1 (P= 0.019) were significantly lower in irinotecan-sensitive gastric cancer samples, while ISG15 (P< 0.001) and Topo1 (P= 0.001) were significantly higher. The tumor gene expression leve...