The MASTL/YBX1/PAK4 axis regulated by stress-activated STK24 triggers lenvatinib resistance and tumor progression in hepatocellular carcinoma

Background and Aims: Many patients with hepatocellular carcinoma (HCC) present inadequate responses to lenvatinib therapy. Therefore, it is important to elucidate the underlying mechanisms of resistance and to formulate effective reversal strategies. Methods: We conducted comprehensive transcriptome and proteome sequencing analyses of lenvatinib-resistant cell lines and patient tissues to identify critical genes and proteins associated with lenvatinib resistance. Subcutaneous mouse models were established, the half maximal inhibitory concentration (IC 50 ) was determined, and colony formation assays were employed to investigate the biological role of microtubule-associated serine/threonine kinase-like (MASTL) in tumor progression and therapeutic resistance. Molecular and biochemical methodologies, including RNA sequencing, chromatin immunoprecipitation sequencing, and mass spectrometry, were employed to explore the underlying mechanisms by which MASTL contributes to poor responses to lenvatinib in HCC. Results: MASTL was frequently upregulated in lenvatinib-resistant HCC cells and tissues. Increased expression of MASTL drove lenvatinib resistance through reactivation of mitogen-activated protein kinase (MAPK) signaling pathways, which is typically inhibited by lenvatinib. Mechanistically, MASTL directly phosphorylated Y-box binding protein-1 (YBX1) at S102, thereby facilitating its transcriptional activation of p21-activated kinase 4 (PAK4). PAK4 subsequently activated MEK1/2, thereby promoting lenvatinib resistance. Additionally, the findings revealed that STK24, a stress-regulated kinase, can activate MASTL under lenvatinib exposure. Notably, disrupting the MASTL/YBX1/PAK4 axis restored sensitivity to lenvatinib. Conclusion: We propose that the MASTL/YBX1/PAK4 axis, which is activated by stress-induced STK24, plays a crucial role in lenvatinib tolerance. Inhibiting this axis by targeting MASTL effectively overcomes lenvatinib resistance in HCC.