N-myc downstream-regulated gene 1: Diverse and complicated functions in human hepatocellular carcinoma (Review)

N-myc downstream-regulated gene 1 (NDRG1) has been reported to be a multifunctional protein associated with carcinogenesis and tumor progression. However, the cellular function of NDRG1 remains elusive in human hepatocellular carcinoma (HCC). No NDRG1 expression is observed in normal liver tissue. Overexpression of NDRG1 has been observed in human HCC, particularly with aggressive invasion, metastasis, poor differentiation and short patient survival. In addition, recent studies have shown that NDRG1 exhibits an inhibitory effect on HCC growth in vitro and in vivo, which contrasts with previous reports indicating that NDRG1 promotes the proliferation and invasion of HCC cell lines. Further studies have shown that the localization of NDRG1 is variable, translocating to the nucleus or membrane according to the cell state, which may relate to the diverse function of NDRG1. The present study reviews our current knowledge with regard to the functions of NDRG1 in HCC and other types of human cancer.