Insulin-Like Growth Factor 1 Receptor Drives Hepatocellular Carcinoma Growth and Invasion by Activating Stat3-Midkine-Stat3 Loop.

Background: Activation of the insulin-like growth factor 1 receptor (IGF-1R)-mediated Janus kinase (JAK)1/2-Stat3 pathway contributes to hepatocarcinogenesis. Specifically, a previous study showed that IGF-1R inhibition downregulated Midkine expression in hepatocellular carcinoma (HCC). Aims: The present study investigated the role of IGF-1R-JAK1/2-Stat3 and Midkine signaling in HCC, in addition to the molecular link between the IGF-1R-Stat3 pathway and Midkine. Methods: The expression levels of IGF-1R, Stat3, and Midkine were measured using reverse transcription-quantitative PCR, following which the association of IGF-1R with Stat3 and Midkine expression was evaluated in HCC. The molecular link between the IGF-1R-Stat3 pathway and Midkine was then investigated in vitro before the effect of IGF-1R-Stat3 and Midkine signaling on HCC growth and invasion was studied in vitro and in vivo. Results: IGF-1R, Stat3, and Midkine mRNA overexpressions were all found in HCC, where the levels of Stat3 and Midkine mRNA correlated positively with those of IGF-1R. In addition, Midkine mRNA level also correlated positively with Stat3 mRNA expression in HCC tissues. IGF-1R promoted Stat3 activation, which in turn led to the upregulation of Midkine expression in Huh7 cells. Similarly, Midkine also promoted Stat3 activation through potentiating JAK1/2 phosphorylation. Persistent activation of this Stat3-Midkine-Stat3 positive feedback signal loop promoted HCC growth and invasion, the inhibition of which resulted in significant antitumor activities both in vitro and in vivo. Conclusions: Constitutive activation of the IGF-1R-mediated Stat3-Midkine-Stat3 positive feedback loop is present in HCC, the inhibition of which can serve as a potential therapeutic intervention strategy for HCC. [ABSTRACT FROM AUTHOR]