Lactate-driven pyrimidine synthesis promotes ferroptosis resistance in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) remains highly lethal, and emerging therapeutic strategies increasingly focus on harnessing ferroptosis to overcome treatment resistance. However, ferroptosis resistance has emerged as a major barrier to these approaches, highlighting the need to identify metabolic cues in the tumor microenvironment that drive this evasion. Here, we identify lactate as a critical metabolite that mediates detrimental metabolic crosstalk between HCC cells and hepatic stellate cells (HSCs), coupling this interaction to pyrimidine biosynthesis and enhanced extracellular matrix (ECM) production within the tumor microenvironment. We show that tumor-derived lactate activates mechanistic target of rapamycin complex 1 (mTORC1)-carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD) signaling, enhancing de novo pyrimidine biosynthesis and pre-ribosomal RNA synthesis, thereby promoting ECM protein translation. The resulting ECM deposition drives Yes-associated protein (YAP)/TEA domain family member (TEAD)-dependent upregulation of the cystine/glutamate antiporter (xCT) in HCC cells, conferring marked resistance to sorafenib-induced ferroptosis. Inhibition of dihydroorotate dehydrogenase, the rate-limiting enzyme in pyrimidine synthesis, disrupts ECM production and restores ferroptosis sensitivity in vitro and in vivo. Clinical data further support these findings, indicating that phosphorylated CAD (p-CAD) levels in HSCs are associated with both poor prognosis and lactate-associated ECM enrichment in HCC patients. Collectively, our study identifies lactate-fueled pyrimidine biosynthesis as a key driver of ECM remodeling and ferroptosis resistance in HCC. Targeting this metabolic axis offers a promising therapeutic strategy to overcome ECM-mediated drug resistance and improve outcomes with ferroptosis-based HCC therapies.