EXPRESSION OF THE O^6－METHYLGUANINE－DNA METHYLTRANSFERASE GENE IN EIGHT HUMAN TUMOR CELL LINES

O6-methylguanine-DNA methyltransferase (MGMT) gene expression in 6 Mer+ (HeLa S3, SMMC-7721,SGC-7901, B-239, AGZY83-a, and Cc80 1) and 2 Mer- (SHG-44 , and HeLa MR) human tumor cell lines was examined. Southern blot analysis revealed no deletion, amplification, or rearrangement of the MGMT gene in these cell lines. However ,～ 1. 0 kb transcripts were detected in the 6 Mer+ cell lines but not in the 2 Mer-cell lines by Northern blot analysis. Furthermore,a rough correlation between MGMT activity and mRNA level in these cell lines was observed. These results suggest that transcriptional regulation of the MGMT gene is the molecular basis of the absence of MGMT activity in Mer-cell lines.

Human ovarian neoplasm cell CD147 stimulates production and activation of matrix metalloproteinases in co-cultures with mouse fibroblasts

Objective: To investigate the expression of CD147 on human ovarian neoplasm cell lines and its influence on production and activation of matrix metallproteinases(MMPs). Methods: The expression of CD147 on different human ovarian neoplasm cell lines was studied by western blotting. Co-culture was carried out to investigate the stimulative effect of the positive expression CD147 cell HO-8910 on the production of MMPs of fibroblast cell in vitro. Zymography and immune blotting were used to study the production and activity of positive MMPs, at the time, to explore the relation between CD147 and MMPs. Results: CD147 was positively presented in 2 ovarian neoplasm cell lines(HO-8910,3-AO), but in SKOV3, TC-1,NIN3T3 cell was negative. MMP-2 and MMP-9 were detected by HO-8910 cell line, mouse fibroblast cell and co-culture cells; but the expression in co-culture cell is obviously higher than individual cultures of each type alone.CD147 stimulated MMPs in dose-dependent manner. Conclusion: CD147 causes increased production and activation of MMP-2, MMP-9.CD147 is probably a indirect marker of some ovarian cancer cells with invasion and metastasis.

STUDY ON EFFECTS OF ARSENIC TRIOXIDE ON GASTRIC CANCER CELL LINES

Objective To evaluate the effects of arsenic trioxide (As-2O-3) on apoptosis and differentiation of gastric cancer cell lines (GCCL). Methods MKN45 and SGC7901 cells were treated with As-2O-3 at different concentrations, then the apoptosis rates and cell cycle were determined by flow cytometry assays, the morphologic changes were observed under fluorescence microscopy and electronic microscopy, and the gene expressions were tested with immunohistologic staining. Results Higher apoptosis rates of GCCL were seen in the As-2O-3-treated group at concentrations of 5μmol and 10μmol, as compared with those in the 5-Fu-treated group. Cell-nuclear pyknosis and chromosomal condensation were observed. The As-2O-3 at a concentration of 0.5 μmol could induce the cell cycle changes of GCCL, revealing an increase in the proportion of G1/G0 phase cells and a decrease in the proportion of S phase cells. From the fifth day after treatment of SGC7901 with As-2O-3 at a low concentration, P53 and bcl-XL genes expression rates were reduced, Bax gene expression rate increased, and bcl-2 gene expression showed little change. Conclusion As-2O-3 could induce GCCL apoptosis at a high concentration and differentiation at a low concentration, but it could not completely reverse the malignant biological behaviours of cancer cells.

Experimental study on anti-neoplastic activity of epigallocatechin-3-gallate to digestive tract carcinomas

Background Epigallocatechin-3-gallate （EGCG） has been demonstrated to have anti-neoplastic activity, but the effective concentration of EGCG and its possible mechanisms are uncertain. The study on the killing effects of EGCG on different digestive tract cancer cell lines can find target sites of its anti-neoplastic effect and provide a theoretical basis for its clinical application in the treatment of cancers. Methods Methyl thiazolyl tetrazolium （MTT） analysis was made to detect the differential sensitivities of eight digestive tract cancer cell lines to EGCG. The effect of EGCG on cell cycle distribution of sensitive cancer cell line was measured by flow cytometry. By polymerase chain reaction （PCR）-enzyme linked immunosorbent assay （ELISA） protocol, the influence of EGCG on telomerase activity of sensitive cancer cell line was also investigated. RT-PCR method was employed to detect the influence of EGCG on the expressions of hTERT, cmyc, p53 and madl genes in sensitive cancer cell line. Results EGCG exhibited dose-dependent killing effects on all eight disgestive tract cancer cell lines. The 50% inhibitory concentration （IC50） of SW1116, MKN45, BGC823, SGC7901, AGS, MKN28, HGC27 and LoVo cells were 51.7 μmol/L, 55.9 μmol/L, 68.5 μmol/L, 79. 1 μmol/L, 83.8 μmol/L, 119.8 μmol/L, 183.2 μmol/L and 194. 6 μmol/L, respectively. There were no apparent changes in cell cycle distribution of sensitive cancer cell line MKN45 48 hours after incubating with three different concentrations of EGCG compared with the controls. It was found that EGCG could suppress the telomerase activity of MKN45 cells, and the effects were dose- and time-dependent. After EGCG administration, the expression of hTERT and c-myc genes in MKN45 cells was decreased, that of the madl gene increased, and that of the p53 gene unchanged. Conclusions EGCG has dose-dependent killing effects on different digestive tract cancer cell lines. Administration of EGCG has no obvious effect on cell cycle distribution of sensitive cancer cell line MKN45. The anti-neoplastic activity of EGCG might be due to the inhibition of telomerase activity by means of its influence on hTERT and the up-stream regulation genes.