Associate Scientist Factor Bioscience Cambridge, Massachusetts, United States
Abstract: Immunotherapies, including immune checkpoint blockade (ICB), have demonstrated clinical success in certain solid tumor cancers such as melanoma. However, there are many cancers that immunotherapies have been unsuccessful in treating, including ovarian cancer. Ovarian cancers present immunosuppressive microenvironments, and ovarian cancer patients, particularly those with platinum-resistant tumors, respond poorly to ICB. Here we present engineered induced pluripotent stem cell (iPSC)-derived macrophages (iMacrophages) as a platform to repolarize the ovarian cancer tumor microenvironment. We generated an iPSC line with bi-allelic insertion of the human leukocyte antigen (HLA)-E transgene into the beta-2-microglobulin (B2M) gene. When co-cultured with PBMC T cells, B2M-HLA-E iMacrophages reduced the upregulation of the lymphocyte early activation marker CD69 in CD8+ T cells when compared to wildtype iMacrophages (1.72-fold versus 2.01-fold, p=0.02), suggesting that the B2M-HLA-E transgene mitigates cytotoxic T cell-mediated alloreactivity. B2M-HLA-E iPSCs were additionally engineered to express the potent immunostimulatory cytokine interleukin (IL)-12. The B2M-HLA-E/IL-12 iPSCs efficiently differentiated into iMacrophages that maintained expression of both transgenes throughout the differentiation, as measured by ELISA for IL-12 and flow cytometry for HLA-E. A feeder cell-free, xeno-free, bioreactor-based differentiation protocol amenable to clinical translation generated more than 500 million iPSC-derived macrophages in a 60mL working volume. B2M-HLA-E/IL-12 iMacrophages co-cultured with PBMC-derived T cells showed three-fold greater cell lysis of platinum-resistant SK-OV-3 ovarian adenocarcinoma cells (p=0.03) compared to B2M-HLA-E iMacrophages. In vivo, engineered iMacrophages injected intravenously trafficked to and infiltrated subcutaneous SK-OV-3 tumors while maintaining expression of the inserted transgene. These results suggest that iMacrophages could represent a novel treatment modality for immunosuppressive platinum-resistant ovarian cancer by repolarizing the tumor microenvironment via localized delivery of IL-12, while maintaining long-term persistence through hypoimmune modifications.
