Integrating Fas-mediated apoptosis with IFNγ signaling to drive tumor regression in mRNA cancer therapeutics

For mRNA-based cancer gene therapy, we engineered a membrane-bound fusion protein combining interferon-{gamma} (IFN{gamma}) with the Fas intracellular domain (FasICD) to couple local IFN{gamma} signaling with Fas-driven apoptotic tumor cell death. IFN{gamma}-FasICD was robustly expressed on the plasma membrane after mRNA transfection. In murine cancer cell lines, IFN{gamma}-FasICD mRNA reduced viability within 24 h, resulting in [~]50% cell death in MC38 cells and [~]75% in B16OVA cells, exceeding the cytotoxicity of the FasICD-deleted control (IFN{gamma}-Fas{Delta}). Mechanistically, IFN{gamma}-FasICD induced predominantly apoptotic rather than necrotic cell death. IFN{gamma}-FasICD also activated IFN{gamma} receptor signaling in both cancer and the immune cells, inducing IFN{gamma}-responsive genes in IFN{gamma}R-high B16OVA cells and triggering STAT1 phosphorylation in co-cultured splenocytes. For in vivo delivery, IFN{gamma}-FasICD mRNA was formulated in lipid nanoparticles (LNPs), enabling strong intratumoral expression that peaked at [~]3 h and persisted for more than 48 h. Repeated intratumoral injections of LNP-formulated IFN{gamma}-FasICD mRNA suppressed the growth of established B16OVA and MC38 tumors and improved survival, with [~]40% and [~]20% of mice surviving beyond 30 days, respectively. IFN{gamma}-FasICD treatment remodeled the tumor microenvironment by increasing tumor-infiltrating CD45+ cells and CD8+ T cells, while further reducing FOXP3+ regulatory T cells. Moreover, NK/NKT cells and cDC1/cDC2 populations were increased, and their activation was enhanced. In tumor-draining lymph nodes, IFN{gamma}-FasICD mRNA promoted dendritic cell migration and increased priming and differentiation of CD8+ T cells toward effector and memory phenotypes, accompanied by enhanced functional activation of IFN{gamma}-producing CD8+ T cells and highly cytotoxic NK cells in peripheral blood. Overall, our findings provide a mechanistic foundation for cytokine-death receptor fusion proteins as an in vivo antitumor strategy that can reprogram tumor cells into localized sources of both apoptotic signals and immune-activating cues.