E2F1 promotes proliferation and metastasis of clear cell renal cell carcinoma via activation of SREBP1-dependent fatty acid biosynthesis.

ABSTRACT

Enhanced synthesis or uptake of lipids contributes to rapid cancer cell proliferation and tumor progression. In recent years, cell cycle regulators have been shown to be involved in the control of lipid synthesis, in addition to their classical function of controlling the cell cycle. Clear cell renal cell carcinoma (ccRCC) is the most common subtype of kidney cancer and is characterized by lipid-rich cytoplasmic deposition. However, the relationship between altered lipid metabolism and tumor progression in ccRCC is poorly understood. Here, we demonstrated that E2F transcription factor 1 (E2F1), in addition to its key role in regulating the cell cycle, induces extensive lipid accumulation and elevated levels of lipogenic enzymes in ccRCC cells by upregulating sterol regulatory element-binding protein 1 (SREBP1). E2F1 knockdown or SREBP1 suppression attenuated fatty acid (FA) de novo synthesis, cell proliferation and epithelial-mesenchymal transition (EMT) in ccRCC cells. Furthermore, overexpression of E2F1 promoted lipid storage, tumor growth and metastasis in a mouse xenograft model, whereas E2F1 downregulation or SREBP1 inhibition reversed these effects. In ccRCC patients, high levels of E2F1 and SREBP1 were associated with increased lipid accumulation and correlated with poor prognosis. Our results demonstrate that E2F1 can increase proliferation and metastasis through SREBP1-induced aberrant lipid metabolism, which is a novel critical signaling mechanism driving human ccRCC progression.