NDRG2 positively regulates E-cadherin expression and prolongs overall survival in colon cancer patients

To discover the molecular mechanism of N-Myc downstream-regulated gene 2 (NDRG2), a newly found differentiation-related tumor suppressor, the relationships between NDRG2 and E-cadherin were investigated in tumor cells and tissues. Positive correlations between the expression of E-cadherin and NDRG2 were shown in several colon cancer cell lines as well as in colon cancer tissues. According to the transcription assays using a reporter plasmid containing E-cadherin promoter region (-368~+51), NDRG2 introduction into colon cancer cell lines induced upregulation of E-cadherin promoter activity and its transcription. On the contrary, inhibition of NDRG2 expression by siRNA treatment caused the decrease of E-cadherin transcription. Snail, a zinc-finger transcriptional repressor, was shown to be a mediator of NDRG2-regulated E-cadherin expression. The enhancement of glycogen synthase kinase 3β (GSK-3β) activity by NDRG2 overexpression caused proteasomal degradation of Snail transcription factor followed by transcriptional de-repression of E-cadherin. We also found that NDRG2 could mediate cell density-regulated E-cadherin expression. The increase of NDRG2 expression with cell density preceded E-cadherin expression, and the regulation of Snail activity by GSK-3β was also related to this process.