Abstract 417: Chromosomal instability leads to durable tumor suppression upon macrophage-checkpoint disruption, with induction of anti-tumor IgG

Abstract

Abstract Solid tumors generally exhibit chromosome copy number variation caused by chromosomal instability (CIN) in mitosis, and the resulting aneuploidy associates with poor prognosis in various cancer types and poor Tcell checkpoint blockade response in melanoma. In such contexts, however, macrophages and the SIRPa-CD47 checkpoint are understudied. Here, CIN is induced pharmacologically in poorly immunogenic B16F10 mouse melanoma cells, generating micronuclei plus diverse aneuploidy and skewing macrophages towards an anti-cancer phenotype based on markers and short-term tumor studies. Mice bearing CIN-afflicted tumors with wild-type CD47 levels survive only slightly longer compared to chromosomally stable controls, but long-term survival can be maximized when anti-tumor IgG opsonization is combined with adoptive transfer of macrophages with SIRPa blockade or with CD47 knockout of the B16F10. Multi-epitope, de novo anti-cancer IgG in survivors promote phagocytosis of CD47 knockout B16F10 cells by macrophages and suppress tumoroids in vitro and growth of tumors in vivo. An unexpected benefit of pairing CIN with maximal macrophage anti-cancer activity is thus an anti-cancer vaccination-like response that can lead to durable cures and potentiate cell-mediated acquired immunity. Citation Format: Dennis E. Discher. Chromosomal instability leads to durable tumor suppression upon macrophage-checkpoint disruption, with induction of anti-tumor IgG [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 417.