SLC16A1 and neoplasm: Short-term exposure to tumor-derived lactic acid rapidly impairs CD8+ cytotoxic T lymphocytes by reducing their proliferation, suppressing cytokine production (IL-2 and interferon gamma (IFN-γ)), and decreasing cytolytic ability through the loss of perforin and granzyme B. This immunosuppressive effect is driven not just by acidic pH in the TME, but by a combined lactate–proton mechanism mediated through MCT1 transporters (65).