cqvip:Background/Aims: Hepatocellular carcinomas (HCC) often show resistance to the effects of transforming growth factor-β(TGF-β). This study focuses on molecular mechanisms of this resistance to explore ways to overcome it. Methods: Transcription and protein expression of TGF-βtype I and type II receptors (TGF-βRI/RII) were analyzed in clinical HCCs and the human hepatoma cell lines HuH-7 and HepG2. HuH-7 cells were transiently and stably transfected with a constitutively active TGF-βRI mutant (CATGF-βRI). Resulting growth kinetics, integrin expression, invasiveness, TGF-β-mediated activation of human plasminogen activator inhibitor type-1 (PAI-1) promoter and Smad expression were determined. Results: In clinical HCCs, there was less TGF-βRII (6/10 cases) and more TGF-βRI (8/10 cases) protein expression detectable in tumor compared to adjacent liver tissue. In HuH-7 cells, TGF-βRII expression was likewise decreased. Cells transiently transfected with CA TGF-βRI exhibited strong TGF-β-related PAI-1 promoter activation. Stably transfected cells showed an attenuated response of the PAI-1 promoter, but increased Smad7 expression. Proliferation of stable clones was decreased. There was no change in integrin expression or invasiveness. Conclusions: Decreased TGF-βRII protein expression might cause TGF-βresistance in a subset of clinical HCCs. Stable transfection with CA TGF-βRI reverses this in HuH-7 cells without increasing invasiveness.
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