Hyperactive Rac stimulates cannibalism of living target cells and enhances CAR-M-mediated cancer cell killing (BMDM RNA-seq)
The 21kD GTPase Rac is an evolutionarily ancient regulator of cell shape and behavior. Rac2 is predominantly expressed in hematopoietic cells where it is essential for survival and motility. The hyperactivating mutation Rac2E62K also causes human immunodeficiency, although the mechanism remains unexplained. Here we report that in Drosophila, hyperactivating Rac stimulates ovarian cells to cannibalize neighboring cells, destroying the tissue. We then show that hyperactive Rac2E62K stimulates human HL60-derived macrophage-like cells to engulf and kill living T cell leukemia cells. Primary mouse Rac2E62K/+ bone-marrow-derived macrophages also cannibalize primary Rac2E62K/+ T cells due to a combination of macrophage hyperactivity and T cell hypersensitivity to engulfment. Additionally, Rac2E62K/+ macrophages non-autonomously stimulate wild type macrophages to engulf T cells. Rac2E62K also enhances engulfment of target cancer cells by chimeric antigen receptor-expressing macrophages (CAR-M). We propose that Rac-mediated cell cannibalism may contribute to Rac2E62K/+ human immunodeficiency and enhance CAR-M cancer immunotherapy. Overall design: To investigate the differential gene expression and inflammatory  profiles of bone marrow derived macrophages (BMDM) from Rac2+/+ and Rac2E62K/+mice. To investigate the differential gene expression of bone marrow derived macrophages (BMDM), BMDMs from Rac2+/+ and Rac2E62K/+mice, and BMDMs from Rac2+/+ mice either stimulated to a classic M1 state or to a classic M2 state were compared. Samples were run in triplicate.