Background: Metabolic pathways are non-canonical targets of the EMT program. The relevance of re-programming metabolism during the metastasis cascade is underscored in ovarian cancer cells, which primarily metastasizes to the adipocyte-rich omentum. Ovarian cancer-adipocyte interaction has been shown to promote fatty acid (FA) uptake into the cancer cells. These FA are then catabolized via β-oxidation thus providing the energy required for rapid tumor growth. β-oxidation of FA requires efficient mitochondria and oxygen processing. The objective of this study is to determine if E/M status determine adaptation and survival in adipocyte-rich microenvironment.
Materials and Methods: RNA seq was performed in Ck18+/Twist- epithelial and Ck18-/Twist+ mesenchymal human ovarian cancer cells. Pathway and Gene Ontology analyses were performed on differentially expressed (DEX) genes (FC>2 and p<0.05) using iPathway Guide. Protein levels were determined by western blot. Oxygen consumption rate was measured using Seahorse XF Analyzer. Cell viability was quantified using CelltoxTM Green viability dye.
Results: Pathway analysis of DEX genes with focus on metabolic pathways showed the following DEX pathways: glycolysis/gluconeogenesis (p=0.008); pyruvate metabolism (0.019); fatty acid degradation (p=0.01); fatty acid elongation (0.008). Gene ontology analysis showed significant difference in GO:0006979: response to oxidative stress (p=0.007). Further analysis of DEX genes within these pathways showed upregulation in mesenchymal cancer cells of both pyruvate dehydrogenase subunits, PDHA1 (p = 0.011) and PDHB (p=0.014) and upregulation of carnitine palmitoyltransferase (CPT1; p=0.011), the rate limiting enzyme in FA β-oxidation. The upregulation of these genes was validated at the protein level by western blot analysis, which also showed increased levels of COX-IV in mesenchymal cancer cells compared to epithelial cancer cells. Moreover, mesenchymal cells exhibited enhanced maximal respiration and enhanced spare respiratory capacity. Finally, viability studies conclusively demonstrate the metabolic flexibility in mesenchymal cancer cells, which maintained viability upon nutrient deprivation suggesting metabolic plasticity. In contrast, cell death was observed epithelial cancer cells upon nutrient deprivation, which was rescued by the addition of glucose but not the FA, oleic acid.
Conclusion: Ovarian cancer cells acquire enhanced pyruvate shuttling to the TCA cycle, a more efficient FA β-oxidation machinery, as well as more efficient oxygen processing during EMT. These phenotypes are relevant in supporting survival in the adipocyte microenvironment. Further elucidation of EMT related pathways that re-program lipid metabolism may lead to better control of carcinomatosis in ovarian cancer patients.
Citation Format: Hussein Chehade, Alexandra Fox, Roslyn Tedja, Radhika Gogoi, Gil Mor, Ayesha B. Alvero. EMT programs ovarian cancer cells to survive the adipocyte-rich microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2333.