Abstract 2499: Complement activation at the interface between cancer cells and adipocytes
Authors: Valdivia Andres Felipe , Huang Hao , Cardenas Horacio , Klingelhutz Aloysius , Matei Daniela 
Published: April 2023

Abstract
Introduction: Ovarian cancer (OC) preferred site of metastasis is the fat-rich omentum. The interaction between cancer cells and adipocytes induces genotypical and phenotypical changes favoring increased invasiveness and metastatic potential of OC cells. In this study we stablish a novel in-vitro direct co-culture model by using immortalized human visceral pre-adipocytes and OC cells to understand the genotypical and phenotypical changes that adipocytes coculture generates over OC cells.
Materials and Methods: OVCAR5 or OVCAR8 OC cells expressing either GFP or RFP were co-cultured with matured primary immortalized human visceral pre-adipocyte (VNPAD). The cells were seeded together in direct monolayer co-culture. After co-culture, OC cells were sorted by FACS and used to evaluate cell proliferation, resistance to cisplatin and transcriptomic changes.
Results: Direct co-culture (3 days) of adipocytes and OC cells increased proliferation (p &lt; 0.001), invasiveness (p &lt; 0.005), and induced epithelial to mesenchymal transition (EMT) of OC cells relative to cells cultured alone. Co-culture with adipocytes also increased resistance to platinum (cisplatin IC50 from 3.90 µM to 7.07 µM for OVCAR5, and from 7.54 µM to 9.35 µM for OVCAR8 cells). RNAseq of co-cultured OVCAR5 cells detected 7783 differentially expressed genes (FDR&lt;0.05, fold change &gt;2). The most affected pathways included the PI3K/AKT pathway, inflammatory response, complement activation, and lipid localization. Activation of the complement (C) system in cells co-cultured with adipocytes was associated with upregulation of both C3 and C5 which was confirmed by quantitative RT-PCR, western blot and ELISA. Treatment of primary OC cells with media conditioned by adipocytes increased the expression of C3 and C5 (P&lt;0.05). Similarly, treatment of OVCAR5 cells with a lipid mixture increased expression of C3 and C5 (mRNA and protein). The co-culture of OC cells with adipocytes and the treatment with lipids activated the PI3K pathway and the integrated stress response (ISR) pathway mediated by ATF4. shRNA knockdown of C3 and a chemical inhibitor for the C3 and C5 receptor (sb290157) reverted the increased proliferative phenotype and activation of PI3K in cocultured OC cells. Stable knockdown of C3 with shRNA in OVCAR5 cells reduced tumor volume and tumor weight in an intraperitoneal OC xenograft model (p&lt;0.05). IHC of paired primary tumors and metastatic implants in the omentum showed increased C3 expression adjacent to fat (p&lt;0.05).
Conclusion: Co-culture of adipocytes and cancer cells drives changes in proliferation and cisplatin responsiveness in OC cells. These changes are induced by transfer of lipids from adipocytes to cancer cells and subsequent activation of the complement proteins C3 and C5 through the ISR pathway and ATF4.
Citation Format: Andres Felipe Valdivia, Hao Huang, Horacio Cardenas, Aloysius Klingelhutz, Daniela Matei. Complement activation at the interface between cancer cells and adipocytes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2499.