Killing effect of TNF-related apoptosis inducing ligand regulated by tetracycline on gastric cancer cell line NCI-N87

Regulation of Tumor Necrosis Factor-related Apoptosis-inducing Ligand Expression in Primary Acute Leukemic Cells by Chemotherapeutics

Objective: The expression of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein and its regulation by chemotherapeutics were analyzed in primary acute leukemic cells.

Materials and Methods: Peripheral blood was collected from 16 patients with acute leukemia on days 0, 1, 3, and 5 of chemotherapy. The mononuclear cells were separated from the peripheral blood, and TRAIL expression was assessed by flow cytometry. The bone marrow mononuclear cells of patients with acute leukemia were separated before chemotherapy and cultured in vitro with VP-16 and/or interferon (IFN). The TRAIL expression level was detected after the cell culture.

Results: TRAIL expression in the mononuclear cells of peripheral blood was significantly upregulated on day 1 (p<0.05) and then significantly decreased on day 5 after chemotherapy (p<0.05). Results from the in vitro culture revealed that VP-16 upregulated TRAIL expression in the bone marrow mononuclear cells of patients with acute leukemia, but the binding of VP-16 to IFN did not enhance TRAIL expression as compared with VP-16 alone (p>0.05).

onclusion: OA single chemotherapy mechanism for leukemia may suffice to induce TRAIL expression and promote the apoptosis of leukemic cells.

Conflict of interest:None declared.

Apoptosis-inducing effect of recombinant Caspase-3 expressed by constructed eukaryotic vector on gastric cancer cell line SGC7901

AIM: To investigate the apoptosis-inducing effect of Caspases-3 expressed by constructed eukaryotic vector on gastric cancer cell line SGC7901.

METHODS: PCR was employed to amplify the sequences of both small and large subunits of Caspases-3. Its products were separately cloned into the Sma I site of pBluescript KS⁺ to generate both plasmids pBS/SS and pBS/LS. The small subunit fragment was excised from plasmid pBS/SS with BamH I and then inserted into the BamH I site of plasmid pBS/LS preceding that of the large subunit to yield plasmid pBS/Rev-Caspase-3. Rev-Caspase-3 cDNA was excised with Kpn I + Xba I and then subcloned into plasmid pcDNA3.1 (+) to construct Rev-Caspase-3 eukaryotic expression vector pcDNA/Rev-Caspase-3, which was used to transiently transfect SGC7901 cell line. Cell count, MTT assay and electron microscopy were used to confirm the antiproliferation and apoptosis-inducing effect of Rev-Caspase-3 expression on gastric cancer cells.

RESULTS: Plasmid pBS/Rev-Caspase-3 and eukaryotic expression vector pcDNA/Rev-Caspase-3 were successfully constructed. SGC7901 cells were transiently transfected by either pcDNA/Rev-Caspase-3 or pcDNA3.1 (+) for 24, 48, 72, and 96 h respectively. Cell growth was measured by cell count and MTT assay. In cell count assay, the cell numbers were 1.8 × 10⁶, 1.55 × 10⁶, 2.0 × 10⁶, and 3.1 × 10⁶ in the experimental group and 2.5 × 10⁶, 3.1 × 10⁶, 4.0 × 10⁶, and 5.7 × 10⁶ in the control group at 24, 48, 72 and 96 h respectively. The growth of SGC7901 cells was suppressed by Rev-Caspase-3 in a time-dependent manner (P < 0.05). The results of MTT assay were similar to that of cell count (P < 0.05). The characteristics of apoptosis such as chromatin condensation, crescent formation and margination were seen and more obvious with time in the given-experimental period in the experimental group, but not easily observed in the control group.

CONCLUSION: The expression of Rev-Caspase-3 by the constructed eukaryotic vector can significantly induce apoptosis of gastric cancer cell line SGC7901, which may exhibit a potential way in gastric cancer gene therapy.

Synergistic antitumor effect of TRAIL and doxorubicin on colon cancer cell line SW480

AIM: TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) has been reported to specifically induce apoptosis of cancer cells although only a small percentage of cell lines were sensitive to it. Cell lines not responding to TRAIL in vitro were said to be more prone to apoptosis when TRAIL was combined with another anticancer agent. Generally, factors affecting drug-sensitivity involve many apoptosis-related proteins, including p53. The expression of wild-type p53 gene was proposed as an important premise for tumor cells responding to chemotherapy. The present study was to investigate the cell killing action of TRAIL on colon cancer cell line SW480, its synergistic effect with doxorubicin, and the possible mechanisms.

METHODS: SW480 cells were cultured in the regular condition and incubated with different levels of agents. Morphologic changes in these cells after treatment were observed under phase-contrast microscope and cytotoxicity by TRAIL alone and in combination with doxorubicin was quantified by a 1-day microculture tetrazolium dye (MTT) assay. In addition, flow cytometry assay (FCM) and transmission electron microscopy were used to detect apoptosis among these cells. Variation of p53 protein level among different groups according to concentrations of agents was measured by Western blot assay.

RESULTS: (1) SW480 cells were not sensitive to TRAIL, with IC₅₀ > 1 mg•l^-1 and dose-independent cytotoxicity. (2) SW480 cells were sensitive to doxorubicin at a certain degree, with dose-dependent cytotoxicity and IC₅₀ = 65.25 ± 3.48 μmol•l^-1. (3) TRAIL could synergize with doxorubicin to kill SW480 cells effectively, which was represented by the boosted killing effect of doxorubicin on theses cells. IC₅₀ of doxorubicin against SW480 cells sharply reduced when it was combined with TRAIL. (4) Subtoxic TRAIL (100 μg•l^-1), combined with subtoxic doxorubicin (0.86 μmol•l^-1), could kill SW480 cells sufficiently. Cytotoxicity by MTT assay arrived at 80.12% ± 2.67%, which was significantly higher than that by TRAIL or doxorubicin alone, with P = 0.006 and 0.003 respectively. This killing effect was partly due to apoptosis. It was proved by large amounts of apoptotic cells under phase-contrast microscopy, cell apoptosis rate of 76.82% ± 1.93% by FCM assay and typical apoptotic morphology observed through transmission electron microscopy. Increase of apoptosis after combined treatment had no relation with protein level of p53 (P > 0.05).

CONCLUSION: SW480 cells are not sensitive to TRAIL, but TRAIL can synergize with lower concentration of doxorubicin to induce apoptosis effectively. The status of p53 protein is not involved in the mechanism of synergistic apoptosis. It suggests the potential therapeutic applicability of the combination of TRAIL with doxorubicin against colon cancers.

Cytotoxicity of TRAIL on colon cancer cell line SW480

AIM: To study cytotoxic effect of TRAIL on colon cancer cell line SW480.

METHODS: The viability of SW480 cells was measured by MTT assay and the apoptotic rate was determined by TUNEL method.

RESULTS: Results of TUNEL and MTT assay showed that TRAIL had high antitumor activity in a time- and concentration-dependent manner. Survival rate of SW480 cells after TRAIL(1 000 μg/L) treatment was 18.7%. The apoptotic rates of SW480 cells after exposure TRAIL at concentration of 0, 50, 150, 500, 1 500 and 5 000 μg/L were 6.7%, 29.4%, 42.8%, 50.8%, 84.6% and 87.4%, respectively. The apoptotic rates of SW480 cells after treatment with 500 μg/L TRAIL for 0, 6, 12, 18, 24 and 30 hours were 7.8%, 21.4%, 41.8%, 60.6%, 73.8% and 77.3%, respectively.

CONCLUSION: The results demonstrate that TRAIL can induce apoptosis and destruction of SW480 cells, and is a potential new cytotoxic drug in cancer therapy.

The effects of vitamin E succinate on the expression of c-jun gene and protein in human gastric cancer SGC-7901 cells

AIM

To investigate the effects of vitamin E succinate (VES) on the expression of c-jun gene and protein in human gastric cancer SGC-7901 cells.

METHODS

After SGC-7901 cells were treated with VES at different doses (5,10,20 mg x L(-1)) at different time, reverse transcription-PCR technique was used to detect the level of c-jun mRNA; Western Blot was applied to measure the expression of c-jun protein.

RESULTS

After the cells were treated with VES at 20 mg x L(-1) for 3 h, the expression rapidly reached its maximum that was 3.5 times of UT control (P<0.01). The level of c-jun mRNA was also increased following treatment of VES for 6 h. However,the expression after treatment of VES at 5 mg x L(-1) for 24 h was 1.6 times compared with UT control (P<0.01). Western blot analysis showed that the level of c-jun protein was obviously elevated in VES-treated SGC-7901 cells at 20 mg x L(-1) for 3 h. The expression of c-jun protein was gradually increased after treatment of VES at 20 mg x L(-1) for 3, 6, 12 and 24 h, respectively, with an evident time-effect relationship.

CONCLUSION

The levels of c-jun mRNA and protein in VES-treated SGC-7901 cells were increased in a dose- and time-dependent manner; the expression of c-jun was prolonged by VES, indicating that c-jun is involved in VES-induced apoptosis in SGC-7901 cells.

Expression and bioactivity identification of soluble MG7 scFv

AIM

To examine the molecular mass and identify the bioactivity of MG7 scFv for its application as a targeting mediator in gene therapy of gastric cancer.

METHODS

Two strongly positive recombinant phage clones screened from MG7 recombinant phage antibody library were separately transfected into E.coli TG1. Plasmid was isolated from the transfected E.coli TG1 and digested by EcoR I and Hind III to examine the length of exogenous scFv gene. Then, the positive recombinant phage clones were individually transfected into E.coli HB2151. The transfectant was cultured and induced by IPTG. Perplasmic extracts was prepared from the induced transfectant by osmotic shock. ELISA was used to examine the antigen-binding affinity of the soluble MG7 scFv. Immunodotting assay was adopted to evaluate the yield of soluble MG7 scFv produced by transfected E.coli HB2151. Western blot was used to examine the molecular mass of MG7 scFv. Finally, the nucleotide sequence of MG7 scFv was examined by DNA sequencing.

RESULTS

Two positive recombinant phage clones were found to contain the exogenous scFv gene. ELISA showed that MG7 scFv had strong antigen-binding affinity. Immuodotting assay showed that transfected E.coli HB2151 could successfully produce the soluble MG7 scFv with high yield via induction by IPTG. The molecular mass of MG7 scFv was 30 kDa by western blot. DNA sequencing demonstrated that the VH and VL genes of MG7 scFv were 363 bp and 321 bp,respectively.

CONCLUSION

We have successfully developed the soluble MG7 scFv which possessed strong antigen-binding affinity.