Abstract 3473: iPS-derived MSC secreting IL7 and IL15 exert immune mediated anti-tumor activities

Abstract We previously discovered that BM-derived Mesenchymal stromal cells (BM-MSCs) are migrating to the stroma of numerous cancers and their metastasis, forming TAFs and secrete proteins intra-tumorally. MSCs have not been used in cancer therapy because of their immune suppressive properties, limited replicative capacity, source dependent quality and controversial roles in cancer biology. Here, we report the characterization of novel MSCs (iMSCs), which were generated from adult skin fibroblast-derived induced pluripotent stem cells (iPSC). These iPSCs were generated via a unique, transient mRNA transfection technique and subsequently differentiated into iMSCs. Notably, iMSCs displayed contact inhibition and significantly enhanced proliferative capacity under both normoxic and hypoxic conditions, outperforming bone marrow-derived MSCs (BM-MSCs) while fully retaining trilineage differentiation potential. Comprehensive molecular profiling, including RNA sequencing, single-cell mass cytometry (CyTOF), and Luminex assays, revealed strong phenotypic and functional resemblance between iMSCs and BM-MSCs. Crucially, no sarcoma formation was detected in NSGS mice following intraperitoneal, subcutaneous, or intravenous administration of iMSCs, underscoring their safety profile. We further engineered a DNA cassette into these cells to enable IL-7 and IL-15 cytokine production, expressed as either individual molecules (P2A) or a single fused molecule (FUS). Both P2A and FUS cells demonstrated the capacity to drive T cell proliferation autonomously in co-culture. Cytokine secretion from these modified iMSCs enhanced tumor cell death in a triple co-culture system comprising iMSCs, the ovarian cancer cell line ID8, and human PBMCs. In a syngeneic mouse model of ovarian cancer (ID8 in C57BL/6 mice), administration of P2A or FUS MSCs resulted in reduced tumor growth and extended survival. Immunohistochemical and flow cytometric analyses revealed massive infiltration of T cells, macrophages, NK cells, and other immune cells into the tumor microenvironment (TME) in both FUS or P2A groups, but not in control, unmodified MSC, or PBS injected animals. Moreover, the TME in P2A- and FUS-treated mice showed enrichment in M1-type macrophages, with no detection of any of the T cell exhaustion markers tested, in contrast to the control groups (PBS or GFP-iMSC). In conclusion, our findings indicate that IL7-IL15-secreting iMSCs migrate into solid tumors, induce massive immune cell infiltration into the TME and enhance antitumor immunity in a syngeneic mouse model of cancer. These cytokine-producing iMSCs represent a promising therapeutic strategy for modulating the immune response against tumors and advancing anticancer immunotherapy by converting “cold” into “hot” tumor microenvironments. Citation Format: Sandeep Singh, Andrea Bedoy, Dipmoy Nath, Kyung Hee Chang, Lauren B. Ostermann, Ivo Veletic, Christopher D. Pacheco, Po Yee Mak, Edward Ayoub, Muharrem Muftuoglu, Mahesh Basyal, Taeyun Kim, Raven Dance Hinkel, Kyle M. Garland, Matthew Angel, Sanjeev Luther, Christopher B. Rohde, Michael Andreeff. iPS-derived MSC secreting IL7 and IL15 exert immune mediated anti-tumor activities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3473.