Targeting metabolic vulnerabilities: REV-ERB agonist SR9009 potentiates sorafenib efficacy in liver cancer.

Hepatocellular carcinoma (HCC) is one of the most common cancers and the third leading cause of cancer-related death worldwide. The prognosis is poor, with a median survival of 12-15 months in patients with advanced-stage disease. Early diagnosis and the development of new, more effective therapeutic strategies are needed to address the challenges posed by this malignancy. Although immune checkpoint inhibitors have replaced multikinase inhibitors as first-line therapy, sorafenib continues to represent a valuable option for patients with contraindications to newer treatments. Based on genome-wide RNA-seq analysis, which identified mitochondrial oxidative phosphorylation (OxPhos) and Hmox1 upregulation as potential pro-survival mechanisms in sorafenib-resistant cells, we investigated whether SR9009, a synthetic agonist of the nuclear receptor REV-ERBα/β, heme competitor, and inhibitor of mitochondrial respiration, could enhance the antitumor efficacy of sorafenib in liver cancer models. Co-treatment with SR9009 and sorafenib significantly enhanced cytotoxic effects in both mouse and human liver cancer cells. This synergistic activity was associated with increased levels of free heme and a complete inhibition of mitochondrial OxPhos. In vivo xenograft studies confirmed that the combination was effective even in sorafenib-resistant tumors. Furthermore, in a N-Nitrosodiethylamine (DEN)-induced HCC model, the combination therapy led to a reduction in size in over 90% of tumor nodules, representing a significant improvement over sorafenib alone. The combination was well tolerated, with no evident signs of acute toxicity. These findings support the concept that the efficacy of anticancer therapies can be enhanced by targeting the metabolic adaptations that tumor cells rely on for survival. Combining sorafenib with agents like SR9009, that disrupt metabolic homeostasis, may offer a promising strategy for treating advanced HCC.