Abstract B038: CD4Th1 cytokine interferon gamma regulates genome profiles and inhibits tumorigenesis of disseminated cancer cells in breast cancer
Authors: Ramamoorthi Ganesan , Lee Marie Catherine , Kodumudi Krithika , Snyder Colin , Gautam Namrata , Garg Saurabh K. , Pilon-Thomas Shari , Czerniecki Brian 
Published: February 2024

Abstract
Detection and persistence of disseminated cancer cells (DCCs) in the bone marrow (BM) of breast cancer (BC) patients has been identified as a primary source for late recurrence and distant metastasis in multiple organs and the central nervous system. Selective targeting and eradication of DCCs in BM can be of a significant advantage to prevent future recurrence and enhance disease-free survival in BC patients. Unfortunately, no such targeted therapy presently exists. Instead, intense chemotherapy in the adjuvant or neoadjuvant setting are given with the ultimate goal to prevent DCC-driven metastasis in these patients. Clinical studies have confirmed that DCCs have not been effectively eradicated by conventional chemotherapies. DCCs express unique gene signatures that differ from circulating tumor cells (CTC) in BC, but only limited knowledge is available for the genome profiles of DCCs compared to primary and metastatic lesions in BC patients. Here we investigated the detailed gene expression profiles of DCCs compared to primary and metastatic lesions from a murine spontaneous metastasis model and BC patients. Using a two-step immunomagnetic enrichment assay, we were able to successfully isolate highly enriched EpCAM+ DCCs from both the BM aspirates of HER2+ early BC patients and BALB-HER2/neu transgenic (BALB-neuT) spontaneous metastasis mice. RNA sequencing revealed that DCCs from HER2+ BC patients and BALB-neuT mice displayed remarkably similar genomic expression profiles, but both had substantially different profiles when comparing to primary and metastatic lesions. We identified highly enriched signatures in DCCs associated with cancer stemness, epithelial to mesenchymal transition (EMT), cell cycle, cell adhesion, progesterone signaling and cholesterol biosynthesis. Notably, these DCCs showed loss of MHC class I, MHC class II, and CD1d expression leading to a defect in antigen presentation machinery and their subsequent escape from CD4 T, CD8 T, B and NKT-cell mediated clearance. Interestingly, we observed for the first time that anti-tumor CD4Th1 cells, through interferon gamma (IFN-γ) production, upregulated CD1d, MHC class I and II expressions in DCCs leading to high infiltration of CD4Th1, NKT and B cells into the BM to selectively target and eliminate DCC burden. IFN-γ remarkably downregulated stemness, EMT, self-renewing potential and their genome signatures and induced apoptosis and irreversible senescence in DCCs of HER2+ BC patients. Notably, these IFN-γ treated patient DCCs lost their ability to grow into tumors in an immunodeficient NSG mouse model. Collectively, these results provide a detailed genome profile of DCCs from HER2+ BC patients and a novel role for anti-tumor CD4Th1 response in inhibiting DCC-driven tumorigenesis and metastasis.
Citation Format: Ganesan Ramamoorthi, Marie Catherine Lee, Krithika Kodumudi, Colin Snyder, Namrata Gautam, Saurabh K. Garg, Shari Pilon-Thomas, Brian Czerniecki. CD4Th1 cytokine interferon gamma regulates genome profiles and inhibits tumorigenesis of disseminated cancer cells in breast cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B038.