Myofibroblast‐Specific Msi2 Knockout Inhibits HCC Progression in a Mouse Model

BACKGROUND AND AIMS Myofibroblasts play a pivotal role in the development and progression of HCC. Here, we aimed to explore the role and mechanism of myofibroblast Musashi RNA binding protein 2 (MSI2) in HCC progression. APPROACH AND RESULTS Myofibroblast infiltration and collagen deposition were detected and assessed in the tissues from 117 patients with HCC. Transgenic mice ( Msi2ΔCol1a1 ) with floxed Msi2 allele and collagen type I alpha 1 chain ( Col1a1 )–ligand inducible Cre recombinases ( CreER ) were constructed to generate a myofibroblast‐specific Msi2 knockout model. Mouse HCC cells were orthotopically transplanted into the Msi2ΔCol1a1 or the control mice ( Msi2F/F ). We found that the deposition of collagen fibers, the main product of myofibroblasts, predicted a poor prognosis for HCC; meanwhile, we detected high MSI2 expression in the peritumoral infiltrated myofibroblasts. Conditional deletion of Msi2 in myofibroblasts significantly inhibited the growth of orthotopically implanted HCC, reduced both intrahepatic and lung metastasis, and prolonged the overall survival of tumor‐bearing mice ( P = 0.002). In vitro analysis demonstrated that myofibroblasts promoted cell proliferation, invasion, and epithelial–mesenchymal transformation of HCC cells, whereas Msi2 deletion in myofibroblasts reversed these effects. Mechanically, Msi2 knockout decreased myofibroblast‐derived IL‐6 and IL‐11 secretion by inhibiting the extracellular signal–regulated kinase 1/2 pathway, and thus attenuated the cancer stem cell–promoting effect of myofibroblasts. Interestingly, we found that the simultaneous knockout of Msi2 in myofibroblasts and knockdown of Msi2 in HCC cells could not further attenuate the implanted HCC progression. CONCLUSIONS Myofibroblast‐specific Msi2 knockout abrogated the tumor‐promoting function of myofibroblasts and inhibited HCC progression in mouse models. Targeting myofibroblast MSI2 expression may therefore prove to be a therapeutic strategy for HCC treatment in the future.