SPP1 facilitates sorafenib resistance in hepatocellular carcinoma by upregulating aerobic glycolysis in endothelial cells

<p indent="0mm">The occurrence of resistance to sorafenib, a first-line treatment for hepatocellular carcinoma (HCC), significantly limits its clinical efficacy. Therefore, investigating the potential mechanism of sorafenib resistance in HCC is highly important for developing HCC treatment strategies. In the present study, we identify that SPP1 is significantly elevated in sorafenib-resistant HCC. Furthermore, the upregulation of SPP1 is related to vascular invasion, advanced disease stage and poor prognosis in HCC patients. As the IC50 of sorafenib increases in HepG2 cells, the SPP1 protein secreted by the cells is significantly upregulated, which subsequently facilitates the proliferation of human umbilical vein endothelial cells (HUVECs) and resistance to sorafenib. Further studies reveal that SPP1 induced resistance to sorafenib in HepG2 cells by upregulating glycolysis in HUVECs and further producing lactate. Mechanistically, SPP1 increases the expressions of the glucose transporter GLUT1 as well as the key glycolytic enzymes PFK1 and PKM2 in HUVECs, resulting in lactate accumulation, which in turn promotes the phosphorylation levels of BRAF and ERK as well as HIF-1α expression in HepG2 cells, leading to sorafenib resistance in HCC. Notably, <italic>SPP1</italic> silencing can inhibit the proliferation and invasion of sorafenib-resistant HepG2 cells both <italic>in vitro</italic> and <italic>in vivo</italic>. Importantly, lactate derived from HUVECs plays a more dominant role in sorafenib resistance than does SPP1 in HepG2 cells. In summary, SPP1 enhances sorafenib resistance in HepG2 cells through promoting aerobic glycolysis in HUVECs, suggesting that the SPP1-aerobic glycolysis axis might be a prognostic biomarker as well as a potential therapeutic target for sorafenib-resistant HCC.