Effects of DACT1 methylation status on invasion and metastasis of nasopharyngeal carcinoma

BACKGROUND: The purpose of the present study was to investigate the role of the methylation status of the DACT1 gene on the invasion and metastasis of nasopharyngeal carcinoma cells. METHODS: The levels of methylation and expression of the DACT1 gene in nasopharyngeal carcinoma tissues and CNE2 cells were determined by methylation-specific PCR and RT-PCR, respectively. CNE2 cells were treated with 5-aza-2-deoxycytidine, and the variation in the methylation status of the DACT1 gene was detected, as well as the influence of methylation on invasiveness of nasopharyngeal carcinoma cells. RESULTS: The DACT1 gene was hyper-methylated in 44 of 62 cases of nasopharyngeal carcinoma. The DACT1 gene was hyper-methylated in 32 of 38 cases of nasopharyngeal carcinoma with lymph node metastasis, and the DACT1 gene was hyper-methylated in 7 of 24 cases of nasopharyngeal carcinoma without lymph node metastasis. The DACT1 mRNA level was weakly expressed or not expressed in all nasopharyngeal carcinoma tissues with hyper-methylated DACT1 genes; however, the DACT1 mRNA level was highly expressed in nasopharyngeal carcinoma tissues with low expression of the methylated DACT1 gene. The DACT1 gene was hyper-methylated and not expressed in CNE2 cells that did not have 5-aza-2-deoxycytidine treatment. After 5-aza-2-deoxycytidine treatment, the DACT1 gene was demethylated and the expression of DACT1 was restored. Moreover, the invasion ability was inhibited in CNE2 cells treated with 5-aza-2-deoxycytidine. CONCLUSION: The expression of DACT1 was related to the methylation status. High expression of DACT1 may inhibit the invasion and metastasis of nasopharyngeal carcinoma cells.

Growth Difference between CNE-2 and S-18 Cell Lines after Subcutaneous Xenograft / 昆明医科大学学报

Objective To study the growth difference and possible mechanism between nasopharyngeal carcinoma (NPC) cell line CNE-2 and its subclone S-18.Methods CNE-2 and S-18 cells were cultured in vitro.6 x 105 cells/mouse were xenografted subcutaneously in the back of nude mice.The volumes of rumors were measured on the 3 rd,7 th,10 th,14 th day after grafting.Mice were sacrificed on the 14 th day and tumors were isolated and weighed.RNA from tumor tissues were extracted and transcriptional levels of HSP27 and NF-K B were detected.Results (1) S-18,instead of CNE-2,grew to form tumor mass 7 days after xenografting subcutaneously;both cell lines formed tumor mass 10 days after xenografting,however,the volumes of S-18 tumors [(223.13 ± 21.32) mm3,10 th day;(420.25 ± 24.52) mm3,14 th day] were significant bigger than CNE-2tumors [(113.70±11.70) mm3,10thday;(279.86±25.78) mm3,14thday];The weights of S-18 umors were significantly higher than CNE-2 tumors on the 14 th day after xenografting;(2) The transcriptional levels of HSP27 and NF-KB in S-18 tumor were significantly higher than in CNE-2 tumor.Conclusion Xenografted S-18 NPC grows faster than Xenografted CNE-2 NPC.HSP27 and NF-κ B are probably involved in the regulation of growth in NPC.

Inhibitory effect and its molecular mechanisms of MicroRNA-34a on human na-sopharyngeal carcinoma CNE-2 cell line subcutaneous xenograft tumor in nude mice / 中国免疫学杂志

Objective:To investigate the inhibitory effect and its possible molecular mechanisms of MicroRNA-34a(miR-34a) on the human nasopharyngeal carcinoma CNE-2 cell line subcutaneous xenograft tumor in nude mice.Methods: The human nasopharyngeal carcinoma CNE-2 cell line was cultured in vitro.miR-34a and Scrambled miRNA recombinant plasmids were successfully established and stably transfected into CNE-2 cells.Fifteen six-week-old male nude mice were divided randomly into three groups:miR-34a group(5 mice) ,Scrambled miRNA group(5 mice) ,Blank control group(5 mice).Different CNE-2 cells were subcuta-neously injected on the back near right lower limb.Tumor volumes were examined every 7 days.Mice were executed on the 35 days,and the eventual average tumor volumes and weights were examined.Total RNA and protein were isolated from tumors,and the expression of miR-34a,CDK6,and Bcl-2 mRNA and protein were determined by qRT-PCR and western blot,respectively.Results: The relative expressions of miR-34a was significantly up-regulated in miR-34a transfected group compared to Scrambled miRNA transfected group (P (849.62±101.32) mm3 ,respectively,and the eventual average tumor weights in miR-34a group,Scrambled miRNA group and blank control group were(0.81±0.13)g,(1.47±0.21)g and(1.58±0.37)g,respectively.Both the eventual average tumor volumes and weights in miR-34a group were lower compared to the other two groups(P<0.05).qRT-PCR results revealed that the expression of miR-34a in miR-34a transfected group was significantly higher than in the other two groups,while the mRNA and protein expression of CDK6 and Bcl-2 were lower than the other two groups ( P<0.05 ) .Conclusion: miR-34a may inhibit the growth of human nasopharyngeal carcinoma CNE-2 cell line subcutaneous xenograft tumor in nude mice by down-regulating CDK6 and Bcl-2.

Radiosensitization of lobaplatin on human nasopharyngeal cancer cell line CNE2 in vitro / 中华放射医学与防护杂志

Objective To investigate the effect of lobaplatin combined with irradiation on human nasopharyngeal cancer cell line CNE2,and to illuminate its mechanism of radiosensitization.Methods MTT assay was used to detect the outcome of lobaplatin and irradiation on CNE2 cell proliferation.Clonogenic assay was applied to testify the radiosensitization effect of lobaplatin on the cells.Flow cytometry was used to check the cell cycle distribution and cell apoptosis.Western was used to detect the expression of Bcl-2,Bax and cleaved Caspase-3.Results The proliferation of CNE2 cells was reduced by lobaplatin in a dose-dependent manner.50IC of lobaplatin on CNE2 cells and lobaplatin combined with 4 Gy irradiation was 1.610 μmol/L and 0.077 μmol/L,respectively.The radiosensitization ratio of the combination group was over 3.Within 24 h of drug treatment,the percent of cells in G2/M phase increased with the concentration of lobaplatin.When the concentration of lobaplatin increased to 6 μmol/L,the cells of combination group were arrested at S phase.The apoptosis rate of lobaplatin (5 μmol/L) group,radiotherapy(4 Gy)group and combination group was 15.6％,11.3％ and 61.8％,respectively.Western blot showed that the expressions of Bax and cleaved Caspase-3 increased but Bcl-2 decreased in the combination group.Conclusion Lobaplatin could increase radiosensitization of human nasopharyngeal cancer cell line CNE2,probably by depressing Bcl-2 but enhancing Bax expression and hence activating Bcl-2/Bax-Caspase signaling pathway.

STGC3 inhibits xenograft tumor growth of nasopharyngeal carcinoma cells by altering the expression of proteins associated with apoptosis

STGC3 is a potential tumor suppressor that inhibits the growth of the nasopharyngeal carcinoma cell line CNE2; the expression of this protein is reduced in nasopharyngeal carcinoma compared with normal nasopharyngeal tissue. In this study, we investigated the tumor-suppressing activity of STGC3 in nude mice injected subcutaneously with Tet/pTRE-STGC3/CNE2 cells. STGC3 expression was induced by the intraperitoneal injection of doxycycline (Dox). The volume mean of Tet/pTRE-STGC3/CNE2+Dox xenografts was smaller than that of Tet/pTRE/CNE2+Dox xenografts. In addition, Tet/pTRE-STGC3/CNE2+Dox xenografts showed an increase in the percentage of apoptotic cells, a decrease in Bcl-2 protein expression and an increase in Bax protein expression. A proteomic approach was used to assess the protein expression profile associated with STGC3-mediated apoptosis. Western blotting confirmed the differential up-regulation of prohibitin seen in proteomic analysis. These results indicate that overexpression of STGC3 inhibits xenograft growth in nude mice by enhancing apoptotic cell death through altered expression of apoptosis-related proteins such as Bcl-2, Bax and prohibitin. These data contribute to our understanding of the function of STGC3 in human nasopharyngeal carcinoma and provide new clues for investigating other STGC3-associated tumors.