DKK1 promotes NUAK1 transcriptional expression through the activation Akt in hepatocellular carcinoma

NUAK1 is a serine/threonine kinase that has been shown to be associated with poor prognosis in several cancers. Although NUAK1 is frequently overexpressed at the transcript level in hepatocellular carcinoma (HCC), the actual role of NUAK1 and the mechanism of its overexpression in HCC has yet to be reported. In the present study, we found that NUAK1 expression was significantly increased in human HCC tumor tissues. Overexpression of NUAK1 dramatically enhanced HCC cells proliferation and migration in vitro. Stable induction of NUAK1 expression promoted tumor growth and tumor metastases to the lungs in the subcutaneous xenograft models and intravenous metastasis models. At the cellular level, enforced expression of Dickkopf-1 (DKK1) activated the Akt signaling pathway, thereby promoting the mRNA and protein expression of NUAK1 in HCC cells. By contrast, depletion of DKK1 was found to attenuate the mRNA and protein expression of NUAK1. In the subcutaneous xenograft models, stable induction of DKK1 expression not only accelerated tumor growth but also increased p-Akt and NUAK1 expression; whereas knockdown of DKK1 inhibited tumor growth, p-Akt and NUAK1 expression. Furthermore, immunohistochemical analysis of 20 HCC clinical samples showed that the expression level of NUAK1 was positively correlated with DKK1 and p-Akt. Taken together, we provide the first evidence that DKK1 promotes NUAK1 transcriptional expression via the activation Akt in HCC.