FAS and neoplasm: CRISPR/Cas9 knock-in genetic modification of T cells with a pooled library demonstrated that a synthetic Fas-4-1BB fusion protein improved T cell fitness during in vitro expansion,26 and we previously demonstrated that T cells expressing a Fas-4-1BB fusion protein improved tumor cell killing in vitro and in vivo.13 Following transfer into ID8VEGF tumor-bearing mice, we have now shown that T cells engineered to express both TCR1045 and a Fas-4-1BB IFP persist better in the ovarian TME than T cells modified with only TCR1045, and significantly further prolong host survival.