CARS1 and neoplasm: The immune cells can be derived from one of two sources: (1) natural host T cells identified in the tumor mass—the autologous tumor infiltrating lymphocytes (TILs), (2) autologous T cells from patients’ peripheral blood that have been genetically engineered ex vivo to express specific antitumor T cell receptors (TCRs) or chimeric antigen receptors (CARs) [24, 25].