Response to irinotecan in patient-derived gastric cancer xenografts with different three-gene signature. A, chemosensitivity of mice model with sensitive-signature (Index = 0.95, gene expression level: APTX = 1.01, BRCA1 = 2.78 and Topo1 = 33.96). B, chemosensitivity of mice model with resistant-signature (Index = 0.28, gene expression level: APTX = 8.33, BRCA1 = 6.87 and Topo1 = 2.09). Twelve mice per cohort were treated with the irinotecan or no administration in control as described in Materials and Methods. The black arrow stood for administration time. Tumor growth was measured every other day, and relative tumor volume (Y-axis) was plotted against time. C, in the second generation, the subsequent tumor size in sensitive-signature mice kept exhibiting a reduced tumor size compared with the tumor size in resistant-signature and control groups. Tumor growth was measured every day, and tumor volumes (Y-axis) were plotted against time. SDs were not shown because of better clarity. Asterisks (★), significance compared with control.