The Expression Of NDRG2 In Esophageal Equamous Eell Carcinomaand It's Influence On Proliferation And Apoptosis Of ESCC Eell LineEca-109

The esophageal cancer was one of the most common carcinomas of thegastro-intestinal cancer. Two main types of esophageal carcinoma, esophagealsquamous cell carcinoma (ESCC) and esophageal adenocarcinoma, with distinctetiological and pathological characteristics , occur worldwide with variablegeographic distribution. China and Asian area has the highest incidence ofESCC all over the world. The mortality rate of ESCC in China was the fourth in62 kinds of carcinomas. Although many progresses have been achieved incomprehensive treatment of esophageal cancer, the prognosis was still poor.Therefore, to reveal molecular biological mechanism involved in oncogenesis andprogression of esophageal cancer will be very helpful for both diagnosis andtreatment of this fatal disease.The NDRG2 gene (N-myc downstream regulated gene 2) was firstdiscovered and cloned from normal human whole brain cDNA library by ourlaboratory in 1999. The NDRG2 gene is located at chromosome 14q11.2, including 16 exons and 15 introns. For the highly homologous in amino acids toN-myc downstream-regulated gene 1(NDRG1), the entire mRNA of NDRG2 is2024 bp in length and it encodes a deduced 357 amino acids protein with acalculated molecular mass of 41 kDa. Our preliminary studies showed that theNDRG2 gene act as a candidate tumor suppressor gene and tightly relate to cellgrowth, differentiation, apoptosis, stress response and so on. We already knewthat the expression of NDRG2 is lower in cancer tissues such as hepatoma, breastcancer, colon cancer, pancreatic adenocarcinoma, prostatic carcinomathan than inadjacent normal tissues. Moreover, when NDRG2 was transferred into sometumor cells, the cell proliferation would be suppressed and cell apoptosis wasinduced. All the results indicate that NDRG2 may be an potential tumor suppressgene. But up to now, there have been no reports about the relationship betweenthe tumorigenesis and development of esophageal carcinoma and the humanNDRG2 gene.In our study we investigated the expression of NDRG2 in esophagealsquamous cell carcinoma(ESCC) tissues and the function it on proliferation andapoptosis of ESCC cell line Eca-109 in vitro. Firstly, Reverse transcriptasepolymerasechain reaction(RT-PCR)method and immunohistochemical SPmethod was adopted to detect the expression of NDRG2 in ESCC tissues andtheir matched adjacent normal esophageal tissues. The relationship betweenprotein expression and clinicopathological features were analyzed. Secondly, Eca-109 cells were transfected with adenovirus vector containing NDRG2 gene. Theexpression of message RNA and protein of NDRG2 were detected by RT-PCRand Western blot respectively. Then, the cell growth curve was drawn by methylthiazolyl-tetrazolium assay(MTT). Flow cytometry (FCM) was adopted toanalyze quantitatively the cell cycle and apoptosis in each group. Our results showed that NDRG2 expression was significantly lower in 7 cancer cases ascompared to adjacent and normal tissue of the same individual. The results ofIHC also showed a significant difference in NDRG2 expression(P< 0.01). Therelationship between NDRG2 expression and histological grade , clinical phase ,lymphacyte metastasis was significant. The results of MTT showed that thegrowth was markedly slowed down in NDRG2 over expressing cells comparedwith normal Eca-109 cells. FCM showed that the G2 phase cells were decreasedsignificantly (P<0.01), whereas S phase cells were obviously increased. Moreover,apoptotic cells reached 16% after adenovirus transfection. The above resultssuggested that the overexpression of NDRG2 was closely related to proliferationand apoptosis in esophageal cancer.In summary, the expression of NDRG2 in ESCC tissues and the adjacent normaltissues show a significant distinction. It can significantly inhibit cell growth andmarkedly induce the apoptosis of Eca-109 cells in vitro. Our study indicated thatNDRG2 may be involved in proliferation and differentiation of ESCC . Thus,NDRG2 gene could be a potential target for gene diagnosis and therapy of humanESCC.