Targeting the 4EBP1/HSP90β/Nrf2 Axis Sensitizes β-catenin-mutant Hepatocellular Carcinoma to mTOR Inhibitors via Ferroptosis Induction.

The aberrant activation of the mTOR pathway and its crosstalk with other signaling cascades represent key drivers of hepatocellular carcinoma (HCC) progression. mTOR-mediated ferroptosis suppression has been implicated in HCC resistance to chemotherapy. This study aimed to elucidate the mechanisms underlying mTOR inhibitor resistance and to evaluate the therapeutic potential of multidrug combinations in β-catenin-mutant HCC. MHCC97H and SNU449 cells were transfected with 4EBP1WT, 4EBP1A4, or HSP90β expression plasmids and then treated with rapamycin to assess their effects on ferroptosis and rapamycin sensitivity. The role of 4EBP1 in regulating ferroptosis was further explored by Western blotting, co-immunoprecipitation, and immunofluorescence. The inhibitory effects of mTOR inhibitors (rapamycin, MLN0128), ERK inhibitors (PD901), and their combination (MLN0128 + PD901) on tumor cells were evaluated. HCC mouse models were generated via hydrodynamic tail vein injection of c-Met/β-cateninΔN90 or c-Met/β-cateninΔN90/4EBP1A4 plasmids to evaluate the therapeutic effects of the four treatment regimens. Rapamycin more potently inhibited mTOR/RPS6 than mTOR/4EBP1 and concurrently induced ferroptosis. 4EBP1A4 promoted ferroptosis and potentiated rapamycin efficacy. Mechanistically, 4EBP1A4 competitively bound HSP90β, displacing Keap1, thereby increasing Keap1-Nrf2 complex formation and promoting Nrf2 degradation. Furthermore, rapamycin, MLN0128, PD901, and their combination reduced p-4EBP1 levels, induced ferroptosis, and inhibited HCC cell proliferation, thereby suppressing tumor growth, with the combination exhibiting the strongest effect. 4EBP1A4 enhances Nrf2 ubiquitination and degradation via the HSP90β/Keap1 axis, relieving mTOR-mediated ferroptosis suppression and synergistically improving rapamycin efficacy. Additionally, rapamycin, MLN0128, and PD901 suppress HCC progression by inducing ferroptosis, with their combination showing superior potency.