Abstract 2020: Adipocytes up-regulates CD36 expression, fatty acid uptake and oxidation enhancing breast cancer cell progression

The role of the tumor microenvironment in tumor progression has recently gained enormous attention, with studies reporting heterogeneous interactions between tumor cells and tumor stroma cells driving tumor progression. The breast cancer microenvironment is unique since the breast tissue within which the tumor originates comprises predominantly of adipocytes. This makes adipocytes a unique component in the breast cancer microenvironment. Adipocytes secrete various growth factors and cytokines that influence tumor progression by induction of epithelial-mesenchymal transition (EMT) which enhances cancer cell migration, invasion and metastasis. This study presents an alternative approach by which adipocytes may enhance cancer progression via the transfer of free-fatty acids from tumor-associated adipocytes to breast cancer cells. The uptake of free fatty acid subsequently serves as a secondary source of energy to drive breast cancer progression. The study aimed to provide an in-depth understanding of the molecular mechanism by which free fatty acid are imported and metabolized in cancer cells in an adipocyte-rich microenvironment. Human adipocytes were co-cultured with cancer cells and the fatty acid (FA) translocase (CD36) activity was inhibited by the chemical inhibitor sulfosuccinimidyl oleate (SSO). Silencing RNA and expression plasmids were used to evaluate CD36 activity in cancer cells. Expression levels of key genes and proteins involved in lipid transfer and metabolism were evaluated by qtPCR and western blot. Inhibition of CD36 reduces free fatty acid uptake and induces intracellular lipogenesis with upregulation of fatty acid synthase (FASN). Breast cancer cells co-cultured with human adipocytes express high levels of the CD36 facilitating free fatty acid uptake from adipocytes. Co-cultured cells had increased levels of fatty acid oxidation (FAO) and oxygen consumption, with increased migration and invasion characteristics. We also observed a significant increase in the expression of CPT1A required for mitochondrial fatty acid import and ATGL required for triglyceride metabolism. Our findings indicate an enhanced dependence on FAO in co-cultured cancer cell. Indicating a potential bioenergetic adaptation of breast cancer cells to the adipocyte-rich microenvironment. Inhibition of CD36 and CPT1 significantly decreased breast cancer cell migration and invasion. These results suggest that cancer-associated adipocytes induce free fatty acid uptake via upregulation of CD36 and reprogram breast cancer cell metabolism. Thus, targeting CD36 may have a potential targeted therapy. Citation Format: Junjeong Choi, Jones Gyamfi. Adipocytes up-regulates CD36 expression, fatty acid uptake and oxidation enhancing breast cancer cell progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2020.