DGKH-mediated phosphatidic acid oncometabolism as a driver of self-renewal and therapy resistance in hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) is characterized by metabolic pathway aberrations, which enable cancer cells to meet their energy demands and accelerate malignant progression. Identifying novel metabolic players governing therapy resistance and self-renewal in HCC is crucial, as these properties are likely responsible for tumor recurrence. Clinical traits and RNA-seq of HCC patients in TCGA were used for weighted gene co-expression network analysis, where one module was significantly correlated with advanced pathological stage and stem cell population maintenance. Further analysis of this module by integrating data obtained from HCC patient nonresponders to tyrosine kinase inhibitors identified 361 commonly deregulated genes significantly enriched in the intracellular signal transduction pathway, with diacylglycerol kinase eta (DGKH) ranked as the most enriched gene in poorly differentiated HCC tumors. Clinically, DGKH was elevated in tumor tissues compared to non-tumor tissues. Patients with higher DGKH expression exhibited a more undifferentiated state and were less responsive to TKIs. Functional assays using DGKH-manipulated HCC cell lines demonstrated that DGKH augmented aggressive features, including cancer stemness, therapy resistance, and metastasis. Upstream of DGKH, we discovered that the E1A-associated protein p300 (EP300) binds to DGKH’s promoter region, thereby increasing its transcriptomic expression. Mechanistically, DGKH promotes mTOR signaling by producing phosphatidic acid (PA). In an immunocompetent mouse model, co-treatment with sorafenib and liver-directed AAV8-mediated Dgkh depletion significantly reduced tumor burden, self-renewal, PA production and mTOR signaling. Our research demonstrated that DGKH is a crucial oncometabolic regulator of cancer stemness and therapy resistance, inhibition of which may lead to more effective hepatocellular carcinoma treatment.