Mechanistically, SLC12A8 activated the TLR signaling pathway (upregulating TLR2, MyD88, IRAK1, TAK1 in CD8<sup>+</sup> T cells), leading to increased PD-1 expression on CD8<sup>+</sup> T cells, resulting in their functional exhaustion and enhanced invasive ability of Luminal B breast cancer cells. The gene discussed is CD8A; the disease is breast cancer.