The efficacy of autocatalytic casapse-3 driven by human telomerase reverse transcriptase promoter on human ovarian carcinoma

Abstract

To construct recombinant adenoviral vector expressing autocatalysis caspase-3 driven by human telomerase reverse transcriptase promoter (hTERTp), and investigate its antitumor effect on ovarian cancer in vitro and in vivo. Recombinant adenovirus expressing autocatalytic caspase-3 (rev-csapase-3) driven by hTERTp, AdHT-rev-casp3, was constructed. Ad-rev-casp3 expressing rev-caspase-3 driven by cytomegalovirus promoter (CMVp) was used as a positive control. hTERT positive human ovarian cancer cells of the line AO and hTERT-negative human umbilical venous endothelial cells (HUVECs) were cultured and transfected with AdHT-rev-casp3, Ad-rev-casp3, or Ad-EGFG expressing enhanced green fluorescent protein as control group. Western blotting, Cell Counting Kit (CCK-8), flow cytometry, and TUNEL were used to detect the expression of p17, active subunit of caspase-3, and p85, a poly ADP-ribose polymerase (PARP) cleavage fragment, and they were also used to measure the cell survival rate and apoptotic rate. Western blotting was used to detect the expression of active caspase-3 and its substrate PARP in the AO cells and HUVECs. Twenty nude BALB/c mice were inoculated subcutaneously with AO cells to establish subcutaneous tumor models, when the tumor grew to the volume of 150 mm3 the rats were divided into 4 equal groups to undergo intra-tumor injection of AdHT-rev-casp3, Ad-rev-casp3, Ad-EGFG, and phosphate-buffered saline (PBS) respectively, the survival rate tumor inhibition rate was observed, 72 days later the mice were killed with their livers and tumors taken out, and Western blotting was used to detect the expression of active caspase-3. Another 40 mice underwent intraperitoneal injection of AO cells to establish intraperitoneal transplanted tumor models, 21 days later the rats were divided into 4 equal groups to be injected intraperitoneally with AdHT-rev-casp3, Ad-rev-casp3, Ad-EGFG, or PBS, the survival rate was observed, and the blood levels of alanine transaminase (ALT) and aspartate transaminase (AST) were detected. Following the administration of AdHT-rev-casp3, active caspase-3 protein was significantly expressed, and the levels of p17 and p85 expressions were significantly elevated in AO cells, while no expressions of p17 and p85 was observed in HUVEC. In contrast, both AO and HUVEC expressed high levels of p17 and p85 protein after administrations of Ad-rev-casp3. AdHT-rev-casp3 dose-dependently killed the hTERT positive AO cells, however, showed no killing effect on the hTERT-negative HUVEC cells; whereas Ad-rev-casp3 was cytotoxic independent of the hTERT status of the cells. The killing effect of Ad-rev-casp3 was stronger than that of AdHT-rev-casp3. Treated with AdHT-rev-cap3 the expression levels of the caspase-3 fragment p17 and PARP cleavage fragment p85 of the AO cells were significantly higher than those before the treatment, however, the expression levels of p17 and p85 were both weaker than those of the AO cells treated with Ad-rev-casp-3. Though treated with AdHT-rev-casp-3, there was still no remarkable expression of p17 and p85 in the HUVECs, however, rather high protein expression levels of p17 and p85 was shown. After treatment with AdHT-rev-casp3 remarkable expression of active caspase-3 was seen in the tumor collected from the mouse body, but not in the liver; however, high caspase-3 expression level was shown in both the liver and tumor after the treatment of Ad-rev-casp-3. 53 days after treatment the tumor suppression rate of the AdHT-rev-casp3 and ad-rev-casp-3 groups were 60% and 70% respectively, both significantly higher than that of the control group. The survival rates of the mice treated with AdHT-rev-casp3 and Ad-rev-casp-3 were both significantly longer than that of the PBS group; however the survival rate of the Ad-rev-casp-3 group was longer than that of the AdHT-rev-casp3 group. The serum ALT and AST levels were not significantly elevated in the AdHT-rev-casp3-treated mice, whereas 7-9-times that before treatment in the Ad-rev-casp3-treated mice. Recombinant adenovirus AdHT-rev-casp3 expressing rev-caspase-3 driven by hTERTp effectively causes cell apoptosis targeting tumor, significantly suppresses tumor growth and prolongs the mouse survival duration, with mild liver toxicity.