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

[BACKGROUND AND AIMS] 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.

[APPROACH AND RESULTS] Clinical traits and RNA-seq of patients with HCC in The Cancer Genome Atlas were used for weighted gene coexpression network analysis, where 1 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. Intriguingly, these genes are 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 nontumor tissues. Patients with higher DGKH expression exhibited a more undifferentiated state and were less responsive to tyrosine kinase inhibitors. 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. In an immunocompetent mouse model, cotreatment with sorafenib and liver-directed AAV8-mediated Dgkh depletion significantly reduced tumor burden, self-renewal, phosphatidic acid production, and mTOR signaling.

[CONCLUSIONS] Our research demonstrated that DGKH is a crucial oncometabolic regulator of cancer stemness and therapy resistance, suggesting that inhibiting DGKH may lead to more effective HCC treatment.