Fig 1: Genetic ablation of HCK reduces tumor immunosuppression and augments antitumor responses to αPD1 immunotherapy.(A) Mass of individual subcutaneous MC38 tumors from WT and HckKO hosts. Where indicated, mice were treated with αPD1 (200 μg, once every 3 days) or an isotype-matched IgG control for 10 days. Representative tumors are depicted above the graphs. Scale bar, 1 cm. Each symbol represents an individual mouse. (B) Flow cytometry quantification of the indicated myeloid cell populations from subcutaneous MC38 tumors of WT and HckKO hosts treated as described in (A). Each symbol represents an individual mouse. (C) Quantitative polymerase chain reaction (qPCR) analysis on fluorescence-activated cell sorter (FACS)–purified CD45+CD11b+F4/80HighLy6C−Ly6G− TAMs and CD45+CD11c+F4/80−MHCII+ dendritic cells for markers associated with immune cell activation. Cells were isolated from subcutaneous MC38 tumors of WT and HckKO hosts treated as described in (A). n = 4 mice per group. (D) Mass of individual subcutaneous MC38 tumors from WT and HckKO hosts. Where indicated, mice were treated with αIL-12, αCXCR3, or an isotype-matched IgG control once every 3 days (total of three treatments) before subcutaneous MC38 tumor cell injection and continued until the experimental end point. Once palpable tumors formed, mice were treated with αPD1 for 10 days. Each symbol represents an individual mouse. (E) Mass of individual subcutaneous MC38 tumors from WT bone marrow chimeras reconstituted with cDC1-deficient (cDC1KO) or cDC1-proficient (WT) bone marrow. To deplete TAMs, half of each cohort were treated with αCSF1R before MC38 tumor cell injection and continued until the experimental end point. Once palpable tumors formed, all hosts were treated with αPD1 in the presence or absence of the small-molecule HCK inhibitor RK20449 for 20 days. Each symbol represents an individual mouse. Data represent mean ± SEM; *P < 0.05, **P < 0.01, and ***P < 0.001, with statistical significance determined by one-way ANOVA followed by Tukey’s multiple comparison test.