Figure 1.

Tuning of CD73 blockade is required to improve the response of low CD73-expressing MC38 tumors to IR. (A) MC38 tumor cells were injected subcutaneously in C57BL/6 mice and when tumors reached 80–100 mm³, tumor were irradiated at 12 Gy, and mice were treated with anti-CD73 commencing 1 day before IR then 2, 6 and 9 day post-IR. (B) Tumor growth was monitored in treated mice. (C) The Kaplan-Meier survival curves for the treated mice are shown. Data were obtained from two independent experiments and are represented as the mean±SEM. n=11–12, *p<0.05 ****p<0.0001 (two-way ANOVA). (D, right panel) Representative histograms of CD73 expression in MC38 and TS/A cells 24-hour post-IR at 6 and 12 Gy compared with non-irradiated (NIR) cells. (D, left panel) cultured cells were analyzed by flow cytometry for their CD73 expression, which is represented as the mean fluorescence intensity (∆MFI=MFI of the isotype control - MFI of stained cells). Data were obtained from two independent experiments and are represented as the mean±SEM. n=6, **p<0.01, ***p<0.001, ****p<0.0001 (two-way ANOVA). (E) TS/A tumor cells were injected subcutaneously in BALB/c mice and when tumors reached 60–70 mm³, tumor were irradiated at 12 Gy, and mice were treated with anti-CD73 commencing 1 day before IR then 2, 6 and 9 days post-IR. (F) Tumor growth was monitored in treated mice. (G) The Kaplan-Meier survival curves for the treated mice are shown. (I) Tumor growth is shown for individual mice in each treatment group. Data were obtained from two independent experiments and are represented as the mean±SEM. n=12–13, **p<0.01 (two-way ANOVA). ANOVA, analysis of variance; IgG, immunoglobulin G; IR, irradiation.