CTLA-4 Blockade Combined with PD-1/PD-L1 Inhibition Enhances Cytokine Production and T-Cell Activation in Ex Vivo...

Immune checkpoint inhibitors (ICIs) show promise in cancer but have limited efficacy in ovarian cancer. This study compared combinations of the PD-1/PD-L1 inhibitor with anti-LAG-3, anti-TIM-3, or anti-CTLA-4 to identify the most effective regimen by assessing T-cell CD8/CD4 ratios and cytokine production. T cells isolated from ovarian cancer tissues (mean 3.8 × 10⁸ cells) were stimulated and treated with the PD-1/PD-L1 inhibitor alone or combined with anti-LAG-3, anti-TIM-3, or anti-CTLA-4. Flow cytometry measured CD8/CD4 expression; ELISAs quantified TNF-α, IL-6, and IFN-γ. Anti-PD-1 monotherapy produced no significant change in CD8/CD4 ratio (1.36 ± 0.43 vs. 1.41 ± 0.36) or cytokine levels. Combination therapy with PD-1/PD-L1 inhibitor + anti-CTLA-4 induced the largest increase in CD8/CD4 ratio (3.69 ± 1.33, p < 0.001) compared with PD-1/PD-L1 inhibitor alone; increases were smaller for PD-1/PD-L1 inhibitor + anti-LAG-3 (2.11 ± 0.63, p = 0.009) and PD-1/PD-L1 inhibitor + anti-TIM-3 (1.87 ± 0.48, p = 0.026). TNF-α rose significantly only with PD-1/PD-L1 inhibitor + anti-CTLA-4 (106.69 ± 45.42 pg/mL, p = 0.008), not with PD-1/PD-L1 inhibitor + anti-LAG-3 (72.46 ± 31.79 pg/mL, p = 0.231) or PD-1/PD-L1 inhibitor + anti-TIM-3 (82.06 ± 33.63 pg/mL, p = 0.074). IFN-γ increase was greater with PD-1/PD-L1 inhibitor + anti-CTLA-4 than with PD-1/PD-L1 inhibitor + anti-LAG-3 (p = 0.026). In conclusion, dual PD-1/PD-L1 and CTLA-4 blockade induced concomitant increases in T-cell CD8/CD4 proportions and cytokine levels compared to monotherapy or alternative ICI pairings. These descriptive ex vivo observations offer preliminary evidence of altered immune profiles, highlighting this combination as a candidate for further functional validation.