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Omental support of ovarian tumor cell growth is unabated in the absence of mature adipocytes

ABSTRACT: The omentum, a specialized adipose tissue arising off the stomach, is a key premetastatic niche for ovarian cancer metastasis and growth within the peritoneum. Why the omentum promotes optimal ovarian cancer growth remains unclear, but the prevailing concept is that omental adipocytes and the accompanying metabolic exchange of FABP4-binding fatty acids are critical. Here, we generated mice lacking mature adipocytes in all peritoneum tissues, including the omentum. ID8p53–/–Brca2–/– tumors retained a propensity to seed at regions typically associated with adipose depots, even without mature adipocytes. However, the lack of mature adipocytes did not suppress tumor expansion in the peritoneum, whereas removing the adipocyte-free omentum did. Single-cell RNA sequencing analysis revealed that endothelial FABP4 was especially high in the omentum, potentially accounting for the role of FABP4 in tumor growth rather than adipocyte FABP4, as previously thought. Thus, whether and how tumor cell-adjacent adipocytes impact tumor progression needs re-evaluation

ORGANISM(S): Mus musculus

PROVIDER: GSE281706 | GEO | 2026/06/13

REPOSITORIES: GEO

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Project description: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.

Project description:In this study we examined the influence of hematopoietic stem cell derived adipocytes (HSCDAs) on the proliferation and metastasis of high-grade serous carcinoma (HGSC), the most common type of ovarian cancer. HSCDAs are a subtype of adipocytes which begin as myeloid cells that traffic from bone marrow to adipose tissue, particularly visceral depots, and then differentiate and accumulate therein. We hypothesized that HSCDAs promote HGSC progression and establish a pro-tumoral niche within peritoneal adipose tissues such as the omentum. We took primary human adipose biopsies and flow sorted the myeloid and mesenchymal populations. We differentiated these adipose precursors in vitro into mature HSCDAs and CMAs, respectively. RNA-Seq analysis showed that HSCDAs have a distinct transcriptional profile from CMAs, including downregulation of cell cycle and upregulation of multiple metabolic and adipogenic pathways. Using ELISA, we found that HSCDAs secreted greater amounts of inflammatory cytokines IL-6 and IL-8 than CMAs. We incubated HGSC cell lines in conditioned media from HSCDAs and CMAs and performed reverse phase protein array (RPPA) and proliferation assays. HGSC cells in HSCDA media had elevated protein markers of epithelial to mesenchymal plasticity, including fibronectin, as well as increased serine phosphorylation of pro-survival AKT1/2. Conversely, HGSC cells in HSCDA media downregulated tumor suppressors including Wnt regulator GSK3β. Depending on the cell line and adipose donor, HGSC cells also showed altered growth rates in conditioned media. We next investigated the role of HSCDAs in HGSC progression and metastasis in vivo. We generated immunocompetent mice that were either HSCDA Proficient (can make both adipocyte subtypes) or Deficient (can only make CMAs). We performed two independent tumor studies using the ID8 (Tp53-/-, Brca2-/-) and SO (Tp53-/-, Brca1/2 wild-type, Hras and Myc amplified) syngeneic models. In both models, overall tumor burden was lower in HSCDA Deficient mice. In the ID8 model, omentum tumors from HSCDA Deficient mice, relative to those from Proficient mice, showed reduced proliferation (Ki67) and apoptosis (cleaved caspase 3). Analysis of bulk RNA-Seq of ID8 omentum tumors from HSCDA Deficient mice revealed downregulation of oxidative phosphorylation, adipogenesis, and fatty acid metabolism. These pathways were enriched in HSCDA cells in vitro, suggesting that ablation of HSCDAs had a significant influence on the tumor metabolic environment. We also observed reduced inflammatory pathways in ID8 tumors from HSCDA Deficient mice, so we interrogated immune cell infiltration into omentum tumors. Compared to HSCDA Proficient mice, tumors from HSCDA Deficient mice showed reduced densities of dendritic cells (DC) and natural killer (NK) cells. By spatial analysis we found fewer DCs, NKs, and B-cells near tumor cells. Overall, our data suggest that HSCDAs can promote HGSC survival and plasticity while downregulating tumor suppressors, and also alter the peritoneal immune and metabolic environment to promote HGSC progression.

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Omental support of ovarian tumor cell growth is unabated in the absence of mature adipocytes

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