PIIO-1 promotes antitumor activity that is dependent on CD8+ T cells and CXCR3. (A, B) CD8-dependence of antitumor activity. (A) Experimental scheme. (B) Tumor growth curve of mice treated with indicated conditions (ISO, n=5; PIIO-1, n=5; anti-CD8, n=3; Combo, n=5). (C–F) Antitumor activity of PIIO-1 depends on active egress of lymphocytes from the secondary lymphoid tissues. (C) Experimental scheme. (D) Tumor growth curve of mice treated with indicated conditions (ISO, n=4; PIIO-1, n=4; FTY720, n=6; combo, n=6). (E) The frequencies of CD8+ and CD4+ T cells in the peripheral blood of indicated groups of mice. (F) Absolute number of CD8+ T cells in the tumors. (G) Impact of PIIO-1 on CXCR3+ CD8+ T cells in the dLNs. MB-49 bearing hLRRC32KI mice were treated with 2 courses of PIIO-1or ISO, followed by analysis of CXCR3 expression on CD8+ T cells in the dLN. (H–L) Antitumor effect of PIIO-1 requires CXCR3. (H) Experimental scheme. (I) Tumor growth curve of mice treated with indicated conditions (ISO, n=5; PIIO-1, n=5; FTY720, n=7; combo, n=7). (J) Tumor weight on day 17. (K) Absolute number of CD8+ T cells in the dLN. (L) Absolute number of CD8+ T cells in tumors. Tumor growth analysis was performed using repeated measures two-way analysis of variance. Other data were compared using two-tailed Student’s t-test. (B, D, I) were corrected for multiple testing using the Sidak procedure. Quantitative data are presented as mean±SEM. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001.