CTLA4 and neoplasm: Interestingly, while subcutaneous tumors exhibited higher levels of immune-inhibiting checkpoint cytotoxic T-lymphocyte associated protein 4 (CTLA-4) and PD-1 on T cells as compared to orthotopic tumors, these tumors persisted post α-PD-1 and α-CTLA-4 treatment while orthotopic tumor growth ceased [39].