Demethylation-induced overexpression of Shc3 drives c-Raf-independent activation of MEK/ERK in HCC

Invasion and intrahepatic metastasis are major factors of poor prognosis in patients with hepatocellular carcinoma (HCC). In this study, we show that increased Src homolog and collagen homolog 3 (Shc3) expression in malignant HCC cell lines associate with HCC invasion and metastasis. Shc3 was significantly upregulated in tumors of 33 HCC patient samples as compared to adjacent normal tissues. Further analysis of 52 HCC patient samples showed that Shc3 expression correlated with microvascular invasion, cancer staging, and poor prognosis. Shc3 interacted with major vault protein (MVP), resulting in activation of MEK1/2 and ERK1/2 independently of Shc1 and c-Raf; this interaction consequently induced epithelial-mesenchymal transition (EMT) and promoted HCC cell proliferation and metastasis. The observed increase in Shc3 levels was due to demethylation of its upstream promoter, which allowed c-Jun binding. In turn, Shc3 expression promoted c-Jun phosphorylation in a positive feedback loop. Analysis of metastasis using a tumor xenograft mouse model further confirmed the role of Shc3 in vivo. Taken together, our results indicate the importance of Shc3 in HCC progression and identify Shc3 as a novel biomarker and potential therapeutic target in HCC.

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