CTLA4 and neoplasm: When malignant cells continue to metastasize, they overly express immune checkpoint inhibition (CPI) signals, resulting in stimulation of inhibitory co-stimulatory molecules (PD1/PD-L1/LAG-3, CTLA4) and anti-apoptotic signaling pathways, causing tumor cells to deactivate immune activation and immune detection; hence, the tumor cells escape and progress to cancerous form [17].