Chimeric antigen receptor dendritic cells targeted delivery of a single tumoricidal factor for cancer immunotherapy
**Background:** Chimeric antigen receptor T cells (CAR-T cells) have been utilized to treat hematologic malignancies by producing a broad spectrum of cytokines. However, while effective against blood cancers, CAR-T cells are not successful in treating solid tumors and can cause severe side effects like cytokine release syndrome. Tumor necrosis factor-alpha (TNFα) is a tumoricidal cytokine but significantly elevates the protein levels of cIAP1 and cIAP2—members of the inhibitor of apoptosis protein (IAP) family of E3 ubiquitin ligases that limit caspase-induced apoptosis. Although degrading IAP proteins with an IAP antagonist does not effectively kill cancer cells alone, it enables TNFα to strongly induce apoptosis in these cells. Therefore, the targeted delivery of TNFα through an inactive adoptive cell, combined with an IAP antagonist, presents a promising approach for cancer treatment.
**Methods:** We engineered human dendritic cells (DCs) to express a single tumoricidal factor, TNFα, along with a membrane-anchored Mucin1 antibody single-chain variable fragment (scFv), creating Mucin1-directed DCs expressing TNFα (M-DCs^TNF). The efficacy of M-DCs^TNF in recognizing and treating breast cancer was evaluated both in vitro and in vivo.
**Results:** Mucin1 was found to be highly expressed on the surface of various human breast cancer cell lines. In NSG mice, M-DCs^TNF directly associated with MDA-MB-231 cells in the bone. The combination of M-DCs^TNF and an IAP antagonist, SM-164—but neither agent alone—significantly induced apoptosis in MDA-MB-231 breast cancer cells; this effect was blocked by a TNFα antibody. Importantly, M-DCs^TNF combined with SM-164, but not SM-164 alone, inhibited the growth of patient-derived breast cancer in NSG mice.
**Conclusion:** Targeted delivery of TNFα via adoptive cells, in combination with an IAP antagonist, represents a novel and effective approach to treat breast cancer and could potentially be expanded to other solid tumors. Unlike CAR-T cells, this novel adoptive cell therapy is not activated to produce a wide variety of cytokines—only the overexpressed TNFα—and thus may avoid severe side effects such as cytokine release syndrome.