CD80 and neoplasm: Biology and therapeutic potential of the immunoglobulin (Ig) superfamily (IgSF) members, including LAG-3, TIM-3, TIGIT, CD47/SIRPα, B7 family members, and others such as leukocyte Ig-like receptor family, butyrophilin family, and sialic acid-binding Ig-type lectins, are increasingly found to be important in T cell-mediated anti-tumor immunity.