[Cytosine deaminase and thymidine kinase double suicide gene system driven by carcinoembryonic antigen promoter for the treatment of colorectal carcinoma xenograft in nude mice].

OBJECTIVE: To explore the therapeutic efficacy of double suicide gene system driven by carcinoembryonic antigen (CEA) promoter (Cp-CDglyTK) on colorectal carcinoma xenograft in nude mice. METHODS: The plasmid pcDNA3.1(-)Cp-CDglyTK was transfected into the CEA-positive SW480 and CEA-negative HeLa cells respectively. The expression of suicide gene was detected by RT-PCR. And the transfected cells were treated with 5-fluorocytosine (5-FC) and ganciclovir (GCV) at different concentrations and the cell-killing and bystander effects assayed by methyl thiazolyl tetrazolium (MTT). By a transplantation of cultivated cells, SW480 or HeLa cell lines were injected subcutaneously into right axillary of nude mice to establish 96 SW480 and 72 HeLa tumor animal models. Nude mice were completely randomized with statistical software according to tumor volume. For prodrug therapy, 48 SW480-bearing mice were divided equally into 4 groups of I-IV. At the same time, 48 HeLa-bearing mice were divided equally into 4 groups of V-VIII. Groups I & V received an intratumoral injection of PBS, groups II & VIGCV and 5-FC intratumorally, groups III & VII PBS intraperitoneally and groups IV & VIII GCV and 5-FC intraperitoneally. Forty-eight SW480-bearing mice were divided equally into 4 groups of IX∼XII and 24 Hela-bearing ones into groups of & in therapy experiment by suicide gene plus prodrug. Six groups received an intratumoral injection of liposome Lipofectamine and plasmid CP-CDglyTK and then an intraperitoneal injection of drug. The groups of IX and received an injection of PBS, group X GCV, group XI 5-FC and groups XII & GCV and 5-FC. The observation parameters included tumor bulk, tumor weight, survival time and treatment effect in each group. RESULTS: SW480 cells transfected by plasmid pcDNA3.1(-)Cp- CDglyTK expressed CDglyTK gene. The inhibition rates of GCV and 5-FC were significantly higher than those of HeLa cells (59.87% ± 0.21% vs 9.90% ± 0.09%, P < 0.01). And higher inhibition rates and stronger bystander effect existed in double versus single produg (all P < 0.05). Tumor size, final tumor weight and survival time of nude mice in groups ofII, IV, VI & VIII had no significant difference with groups ofI, III, V & VII (all P < 0.05). Final tumor size and weight of group XII was significantly smaller than those of groups of IX, X and XI ((150.0 ± 3.2) vs (522.5 ± 1.9) and (256.8 ± 10.4) and (260.7 ± 2.2) mm(3), (54.1 ± 10.4) vs (682.0 ± 12.0) and (251.8 ± 15.1) and (271.6 ± 17.7) mg, all P < 0.05). Meanwhile, the tumor inhibition rate and survival time of group XII(92.1% and (25.7 ± 0.8)d) were significant higher and longer than group X (63.1% and (21.8 ± 0.5) d) and group XI (60.2% and (18.0 ± 0.9) d) (all P < 0.05). However, no significant difference existed in tumor size, final tumor weight and survival time between groups and (all P > 0.05). The inhibition rate of group was merely 0.9%. CONCLUSION: CDglyTK double suicide gene system driven by CEA promoter may inhibit CEA positive colorectal cancer xenograft in prodrug-treated nude mice.

[Expression of OCT4 in gastric cancer cell lines and its significance].

OBJECTIVE: To detect the expression of octamer-binding protein-4 (OCT4) in gastric cancer cell lines with different differentiation (MKN-28, SGC-7901, BGC-823) and normal gastric mucosal cells line GES-1, and further assess the relationship between OCT4 expression and the differentiation grade of gastric carcinoma cells. METHODS: Expression level of OCT4 in GES-1, MKN-28, SGC-7901 and BGC-823 was detected by reverse transcription-polymerase chain reaction (RT-PCR), and OCT4 siRNA was employed to interfere OCT4 expression in BGC-823 cell lines. Detect the quantity of OCT4 mRNA and OCT4 protein by fluorescent quantitative PCR and Western blot respectively. In addition, the invasion ability was analyzed via Transwell chamber. RESULTS: The normal gastric mucosal cells did not express OCT4 and there was higher expression of OCT4 in gastric cancer cell lines with poorly differentiation (P<0.05). The expression of OCT4 in BGC-823 cells was the highest. The expression of OCT4 mRNA and OCT4 protein were decreased distinctly in BGC-823 cells after being interfered by OCT4 siRNA (P<0.05). After being interfered by OCT4, BGC-823 cells were less aggressive, and the number of penetrating cells was decreased (P<0.05). CONCLUSION: The OCT4 expression level is associated with gastric cancer differentiation. OCT4 may play an important role in the differentiation and invasion of gastric cancer cell and it may serve as a reference index in predicting the malignant grade of gastric cancer.