VTCN1 and neoplasm: Moreover, the ligation of immune checkpoint molecules (as programmed death-ligand-1—PD-L1; cytotoxic T-lymphocyte antigen-4-CTLA-4; B7 homolog 3—B7-H3 known as CD276; B7 homolog 4—B7-H4 also known as V-set domain containing T cell activation inhibitor-1—VTCN1) expressed on the surface of CSCs to their respective receptors on T lymphocytes results in a decrease in T cell proliferative and secretory abilities followed by the inhibition of IFN- γ-mediated anti-tumor activity and T cell apoptosis [367].