(A) Quantification of flow cytometry showing the absolute number of the indicated immune cell populations in subcutaneous (s.c.) tumors derived from Myc-CaP cells with or without Cdk12/13 depletion (sgCdk12/13). DCs, dendritic cells; PMN-MDSCs, polymorphonuclear myeloid-derived suppressor cells; M-MDSCs, monocytic myeloid-derived suppressor cells. (B) Quantification of flow cytometry showing the absolute number of IFN-γ⁺ or TNF-α⁺ CD8⁺ T cells in tumors from A. (C) Representative images (left) or quantification (right) of flow cytometry measuring the proportion of IFN-γ⁺ and TNF-α⁺ CD8⁺ T cells in the indicated tumor models treated with vehicle, α-PD-1, YJ1206, or the combination (combo) of α-PD-1 and YJ1206 (n = 5–9 mice per group). (D) Left: Gating strategy for CD8⁺ T cells specific to TRP2 in flow cytometry. Right: Quantification of flow cytometry measuring the absolute number of CD8⁺ T cells specific to TRP2 in the indicated tumor models treated as in C (n = 6–7 mice per group). (E) Growth curves of s.c. tumors derived from Myc-CaP cells in FVB mice treated with the combination (combo) of α-PD-1 and YJ1206, following CD8⁺ T cell depletion by anti-CD8 antibody treatment (α-CD8a). Mice without CD8⁺ T cell depletion (IgG treated) were used as control (n = 5–10 mice per group). YJ1206 (100 mg/kg) was given orally 3 times per week, and α-PD-1 (200 μg/mouse) was administered intraperitoneally every 3 days. Data in A and E are displayed as mean ± SEM. Data in B–D are presented as box-and-whisker plots, with the median (center line), 25th–75th percentiles (box), and minimum to maximum values (whiskers). Significance in A–D was determined by 2-tailed t test and by 2-way ANOVA in E. NS, not significant. Bonferroni’s correction was applied for multiple comparisons.