(A) 4TO7-Brca–KO cells stably expressing an empty vector (vector) or WT mouse Gsdmc (Gsdmc-WT) or the D263A mutant (Gsdmc-mut) were inoculated into the mammary fat pad of immunocompetent BALB/c mice (n = 10). Mice were administered olaparib. Percentage of tumor-infiltrating CD8⁺ T cells was analyzed. (B) Overexpression of eGFP in the stable cells as indicated in A. Then cells and mice were treated same as in A. Mean numbers of eGFP tetramer⁺ (eGFP tet⁺) CD8⁺ T cells per gram of tumor (left). Percentage of IFN-γ⁺ (middle) or TNF-α⁺ (right) CD8⁺ T cells activated by eGFP peptide. (C) Frequency of memory T cell subsets in lymph node (LN), spleen, and tumors of A. Tex, exhausted T cell. (D) Initial tumor challenge and mice treatment were same as in A. Tumors were removed on day 18. Then tumor rechallenge of 4TO7 parental cells was performed 60 days after tumor removal. Tumor growth was shown (n = 10). (E) Stable cells as indicated in A were inoculated into the mammary fat pad of immunocompetent BALB/c mice (n = 10). 4TO7 parental cells were simultaneously injected into contralateral mammary fat pad. Mice were administered olaparib. Tumor growth of 4TO7 parental cells was monitored. (F and G) 4TO7-Brca–KO Gsdmc-WT cells were inoculated into BALB/c mice (n = 10). Mice were administered olaparib. Depletion of CD8⁺ T cell with anti-CD8. Curves of tumor growth (F) and survival (G). (H) Growth curve of 4TO7-Gsdmc-WT and 4TO7-vector tumors in BALB/c mice (n = 10) treated with olaparib or PD-1 antibody or the combination. Data represent mean ± SD. 1-way ANOVA was used for A, B, D, E, and H. Unpaired 2-tailed t test was used for F. Log-rank test was used for G. **P < 0.01, ***P < 0.001.