These antigens may be cell surface proteins or may be intracellular proteins (eg, TAAs) that are expressed on the surface in combination with class I major histocompatibility complex (MHC) molecules. Tumor-specific CTLs have been found in Breast cancer Cervical cancer Colon cancer Endometrial cancer Kidney cancer Lung cancer Melanoma Nasopharyngeal cancer Neuroblastoma Sarcomas Ovarian cancer Testicular cancer Natural killer (NK) cells are another population of effector cells with anti-cancer activity.