Abstract
<title>Abstract</title> <p>Background: Hepatocellular carcinoma (HCC) ranks as the third leading cause of cancer-related mortality, and sorafenib remains the first-line systemic therapy for advanced HCC. Nevertheless, up to 70% of patients exhibit intrinsic sorafenib resistance with unclear molecular mechanisms. Methods: In vitro cellular phenotypes including sorafenib sensitivity, proliferation, migration and invasion were assessed via functional experiments. Western blotting, RT-qPCR, RNA immunoprecipitation, immunocytochemistry and RNA-seq analyses were employed to verify the regulatory effect of PCBP1 on BAG1 and the SOX2/β-catenin signaling pathway, as well as to elucidate the mechanism underlying the compensatory restoration of BAG1-p36. In vivo xenograft models were constructed in nude mice to further validate the modulatory role of PCBP1 in sorafenib therapeutic responsiveness, and western blotting was performed to detect the expression of PCBP1, BAG1 and SOX2 in HCC tissues from drug-resistant and non-resistant patients. Results: PCBP1 is significantly upregulated in sorafenib-tolerant HCC tissues and linked to poor prognosis. Physiologically, PCBP1 confers sorafenib resistance, characterized by enhanced sorafenib-induced apoptosis rather than ferroptosis upon transient or stable PCBP1 downregulation in HCC cells. Mechanistically, PCBP1 knockdown induces immediate BAG1-p36 decrease and persistent SOX2 downregulation to promote dramatic sensitivity of HCC cells to sorafenib. Upon sustained PCBP1 knockdown, decreased BAG1-p36 expression recovers over time via compensatory PTBP1 upregulation, but cells retain partial sorafenib sensitivity. Further investigation reveals that persistent suppression of SOX2/β-catenin signaling is attributed to impaired SOX2 mRNA stability and translation following PCBP1 depletion, which weakens HCC stemness. Co-targeting BAG1 and SOX2 synergistically sustains low BAG1-p36 levels and promotes sorafenib sensitivity. Likewise, PCBP1 depletion effectively inhibits HCC cell proliferation, metastasis and xenograft tumor growth, along with the elevated therapeutic efficacy of sorafenib. Finally, we verified high expression of PCBP1, SOX2 and BAG1 in HCC tissues from patients with post-treatment recurrence. Conclusions: Our findings unveil PCBP1 as an intrinsic culprit for sorafenib resistance in HCC, and BAG1-p36 adaptive recovery renders acquired resistance. Thus, dual targeting of PCBP1/SOX2 axis and BAG1 would be an impressive strategy to overcome the intrinsic and delay the acquired sorafenib resistance in HCC.</p>