Ablation of hematopoietic stem cell derived adipocytes reduces tumor burden in a syngeneic mouse model of high grade serous carcinoma

Introduction: The purpose of this study is to examine the influence of hematopoietic stem cell derived adipocytes (HSCDAs) on the proliferation and metastasis of high-grade serous carcinoma (HGSC), the most common and aggressive type of ovarian cancer. HSCDAs begin as myeloid cells that traffic to adipose tissue and differentiate a highly inflammatory subtype of adipocytes. HSCDAs accumulate within visceral adipose depots. HSCDA production is increased in ovariectomized mice, suggesting that HSCDAs are likely to extensively accrue in postmenopausal patients. We hypothesize that HSCDAs promote HGSC progression and establish a pro-tumoral niche within peritoneal adipose tissues such as the omentum. Methods: We sorted and differentiated primary human adipocyte precursors into HSCDAs and CMAs and examined cytokine secretion in adipocyte conditioned media by ELISA. We incubated human HGSC cells (PEO1, OVCAR4, and OVCAR8) in conditioned media and assayed proliferation. We incubated conditioned media on PEO1 ovarian cancer cells and analyzed protein expression and phosphorylation by reverse phase protein array (RPPA). Finally, we implanted mouse ID8 HGSC cells into syngeneic HSCDA Deficient (experimental) and Proficient (control) mice. We compared tumor size and intraperitoneal spread. We also measured the adipokine milieu of ascites fluid by ELISA, tumor transcription by RNA-Seq, and immune infiltration by IHC. Results: HSCDA cells secreted elevated amounts of IL-6 and IL-8. In proliferation assays, HGSC lines showed varying growth rates in HSCDA or CMA media. RPPA showed that PEO1 cells incubated in HSCDA media upregulated markers of epithelial to mesenchymal plasticity (EMP) and pro-survival phosphoprotein signaling. Conversely, PEO1 cells in HSCDA media downregulated multiple tumor suppressors. Finally, we observed that ablation of HSCDAs in mice reduced tumor burden. RNA-Seq of bulk omentum tumor from HSCDA Deficient mice had higher TLR and IFN signaling, and lower fatty acid oxidation pathway expression than Proficient mice. Densities of dendritic cells (DC) and natural killer (NK) cells was reduced in tumors in HSCDA Deficient mice, and spatial analysis showed fewer DCs, NKs, and B-cells near tumor cells in HSCDA Deficient mice. Conclusion: Our data suggest that HSCDAs can promote HGSC survival and plasticity while downregulating tumor suppressors, and also may alter the peritoneal adipose immune and metabolic environment to promote HGSC progression. To examine the effect of hematopoietic stem cell derived adipocytes (HSCDAs) on ovarian cancer progression and metastasis in vivo, we generated female mice that are Proficient (CONTROL GROUP) or Deficient (EXPERIMENTAL GROUP) for HSCDA production. The mice are generated by bone marrow transplant from DONOR mice that have an Adiponectin promoter with a reporter gene (for CONTROL Proficient) or an Adiponectin promoter with an Attenuated Diphtheria Toxin (DTA, for EXPERIMENTAL Deficient) into RECIPIENT C57BL6 mice that have had their bone marrow ablated by x-ray irradiation. The HSCDA Proficient mice can make both mesenchymal and HSC derived adipocytes. The HSCDA Deficient mice can only make mesenchymal adipocytes. We waited six weeks for the mice to recover from bone marrow transplant, and then implanted ovarian cancer cells by intraperitoneal injection. The cells are ID8 Tp53-/-, Brca2 -/-. After 39 days, all mice were sacrificed and tumor burden was assessed. Bulk omentum tumors were homogenized and RNA-Seq was performed on CONTROL/Proficient (N=4) and EXPERIMENTAL/Deficient (N=4) tumor RNA.