Targeting PPP1R15B and ATF4 axis in hepatocellular carcinoma: A novel strategy for overcoming lenvatinib-tolerant persister cells through GPX4-mediated ferroptosis induction.

BACKGROUND: Lenvatinib is a first-line therapy for advanced hepatocellular carcinoma (HCC), yet the emergence of lenvatinib-tolerant persister cells (LTPCs) contributes to therapeutic failure and tumor relapse. The molecular programs that sustain this tolerant state remain insufficiently defined. Here, we investigated the role of the PPP1R15B-ATF4 stress-response axis in mediating lenvatinib tolerance and ferroptosis resistance.

METHODS: LTPCs were generated from multiple HCC cell lines through continuous lenvatinib exposure and confirmed by phenotypic and molecular profiling. Transcriptomic analysis (RNA-seq) was performed to identify pathways enriched in LTPCs. Functional relevance of the PPP1R15B-ATF4-GPX4 axis was evaluated using genetic perturbation (siRNA/CRISPR) and pharmacologic inhibition. Redox homeostasis, lipid peroxidation, and ferroptosis susceptibility were assessed through biochemical and imaging assays. An LTPC xenograft mouse model was used to evaluate in vivo therapeutic efficacy.

RESULTS: RNA-seq revealed that LTPCs exhibit robust activation of the PPP1R15B-ATF4-GPX4 signaling axis, accompanied by enhanced redox buffering and suppression of ferroptotic vulnerability. Mechanistic studies demonstrated that PPP1R15B stabilizes ATF4, which in turn transcriptionally upregulates GPX4, thereby sustaining the drug-tolerant persister phenotype. Genetic or pharmacological inhibition of PPP1R15B disrupted ATF4-GPX4 signaling, impaired redox homeostasis, increased lipid peroxidation, and effectively re-sensitised LTPCs to ferroptosis and lenvatinib. In vivo, PPP1R15B inhibition significantly reduced LTPC survival and restored lenvatinib responsiveness in xenograft models.

CONCLUSION: The PPP1R15B-ATF4-GPX4 axis is a key determinant of lenvatinib tolerance in HCC by orchestrating redox adaptation and ferroptosis resistance. Targeting PPP1R15B represents a promising therapeutic strategy to eliminate lenvatinib-tolerant persister cells and overcome acquired resistance in HCC.