FAS and neoplasm: Considering the clinical response of immunotherapy is highly dependent on increased infiltration of immune effector T lymphocytes in solid tumors [13, 14], and the CAR-T efficacy being highly reliant on bystander FasL: Fas (CAR-T cell: Tumor cell) signaling and killing [15–17], it is highly imperative to uncover the most critical and regulatory targeting epitope of Fas receptor for the next generation of immunotherapeutic capable of selectively targeting tumors.