By targeting key signaling pathways—PD-1/PD-L1, CTLA-4/CD28, JAK/STAT, PI3K/AKT/mTOR, and MAPK/ERK—it enhances T-cell activation and proliferation and regulates immune checkpoint expression, such as PD-L1 on tumor cells. The gene discussed is CTLA4; the disease is neoplasm.