NDRG2 Gene Expression In Colon Carcinoma And Its Significant Function

The human NDRG2 (N-myc downstream regulated gene 2) cDNA was first cloned and reported from normal human whole brain cDNA library in our lab in 2000. The full length of NDRG2 cDNA is 2,024 bp long. It located on human chromosome 14q11.2. NDRG2 gene consists of 16 exons and 15 introns that encodes a 40 kDa protein with 357 amino acid residues. Preliminary data indicated that NDRG2 was expressed in multiple tissues, with heterogeneous expression in normal brain structures except glioma specimens lacking NDRG2 expression. Until now the reported four members comprise the NDRG family: NDRG1, NDRG2, NDRG3 and NDRG4, with NDRG4 possessing three isoforms: NDRG4-B,NDRG4-Bvar and NDRG4-H. The four NDRG family members share great homology in their composition of amino acid residues with differential expression in diverse tissues. The function of NDRG2 has not been clearly understood .Our results show that NDRG2 is high expressed in normal tissues, while is low or no expressed in cancer tissues and cancer cells. These results indicate that NDRG2 has a close relation with cell differentiation and proliferation of the cancer.To study its function and the relationship of signal transduction has important theoretical meaning. There have been no reports about the precise cellular and molecular function of NDRG2 gene. Our group aimed to establish a colon cancer cell line with NDRG2 gene steady expression and analyze the cellular characteristic, so as to investigate the NDRG2 gene better for future.First, semiquantitative RT-PCR analysis and western-blot were utilized to observe the different expression of NDRG2 gene in SW620, HT29, SW480 after differentiation induced by sodium butyrate. The result indicated that there were many difference in these cancer cell lines. The expression of the NDRG2 gene in SW620, HT29, SW480 could be increased significantly by sodium butyrate.Second,for further investigation on the biological behaviors of HT29 cells, we used flow cytometry, plate clone formation assay and MTT assay to investigate the characteristic of the transfected cells with Ad-NDRG2/HT-29. The cell percentage of G1 phrase was about 57.36%, which is more than each control group. It indicated that the transfection of NDRG2 gene contributed to the inhibition of proliferation and induction of cell cycle arrest in G1 phrase. Compared with control group respectively, the curve of translated cells increased relatively slowly in MTT assay. The plate clone formation assay indicated that plate clone formation efficiency was lower than each control group (p<0.05). These proved that the steady overexpression of NDRG2 could inhibit the proliferation of glioma cells.Conclusion:1. The expression of NDRG2 is significantly increased after induced by sodium butyrate in colon cancer cells, which indicates NDRG2 has a close relation with the differentiation of colon carcinoma cells.2. The propagation of HT29 is significantly suppressed after transfected with Ad-NDRG2 in 72h,with G1 blocking,it indicates that overexpressing NDRG2 can inhibit the growth of colon cancer cells.