Abstract 1525: Kaiso influences immune signaling of breast cancer exosomes

Abstract

Abstract Introduction: Exosomes are communication vesicles between tumor cells and immune cells. However, the mechanism underlining this cell-cell communication is not well understanding, particularly in African American (AA) breast cancer patients. Kaiso, a bi-modal transcription factor is highly expressed in AA patients and high Kaiso expression correlates with aggressiveness and the disparity in survival outcomes compared to European American (EA) patients. However, the biological consequences of Kaiso in immune signaling of breast cancer exosomes has not been studied. Herein we demonstrate the biological role of Kaiso in immune signaling in breast cancer exosomes. Methods: We utilized Nanostring immune profiling technology along with multiple in vitro and in vivo assays to study the role of Kaiso in breast cancer immune escape. Results: Nanostring pan cancer immune profiling showed that EA breast cancer exosomes exhibited higher expression of TILs markers, T cell activation markers and CD8+T Cells markers compared to AA, while we observed an increase in the expression of anti-phagocytic molecule CD47 in breast cancer patient exosomes of AA compared to EA. In addition to that CD47 and SIRP-α (Signal Regulatory Protein) are highly expressed in Kaiso-scrambled MDA-MB-231 cells (sh-SCR) and exosomes, whereas THBS1, which is a regulator of CD47 expression and is regarded as angiogenesis inhibitor is significantly increased in sh-Kaiso MDA-231 cells and exosomes. Additionally, we observed that Kaiso directly binds methylated sequences in the promoter region of CD47 and THBS1 by ChIP assay. Furthermore, in vivo sh-Kaiso cells injected into athymic mice exhibited delayed tumor formation after four weeks with smaller tumor size as compared to sh-SCR cells, and we observed higher expression of THBS1 with lower expression of CD47 and SIRP-α molecules by IHC and exosomes isolated from invivo tumors, indicating that Kaiso is associated with macrophage mediated immune escape. Conclusion: Our findings demonstrate the role of kaiso in immune signaling through exosomes which may be related with more aggressive cancer phenotype in breast cancer specially in African Americans. Citation Format: Md Shakir U. Ahmed, Brittany Jenkins, Benjamin Adu-Addai, Balasubramanyam Karanam, Melissa B. Davis, William E. Grizzle, Honghe Wang, Clayton C. Yates. Kaiso influences immune signaling of breast cancer exosomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1525.