p53-expressing conditionally replicative adenovirus CNHK500-p53 against hepatocellular carcinoma in vitro

AIM： To develop a conditionally replicative gene-viral vector system called CNHK500-p53, which contains dual promoters within the E1 region, and combines the advantages of oncolytic virus and gene therapies for hepatocellular carcinoma （HCC）. METHODS： CNHK500-p53 was constructed by using human telomerase reverse transcriptase （hTERT） promoter to drive adenovirus E1a gene and hypoxia response element （HRE） promoter to drive adenovirus E1b gene. p53 gene expressing cassette was inserted into the genome of replicative virus. Viral replication experiments, cytopathic effect （CPE） and methyl thiazolyl tetrazolium （MTT） assay were performed to test the selective replication and oncolytic efficacy of CNHK500-p53. RESULTS： Immunohistochemistry verified that infection with CNHK500-p53 was associated with selective replication of adenovirus and production of p53 protein in telomerase-positive and hypoxia-inducible factordependent HCC cells, p53 protein secreted from HepG2, infected with CNHK500-p53 was significantly higher than that infected with nonreplicative adenovirus Ad-p53 in vitro （388 ± 34.6 μg/L vs 76.3 ± 13.17 μg/L）. Viral replication experiments showed that replication of CNHK500-p53 and CNHK500 or WtAd5, was much stronger than that of Ad-p53 in tested HCC cell lines. CPE and H1-F assay indicated that CNHK500-p53 selectively replicated in and killed HCC cells while leaving normal cells unaffected. CONCLUSION： A more efficient gene-viral system is developed by combining selective oncolysis with exogenous expression of p53 against HCC cells.

Preliminary Evaluation of Safety of Conditionally Replication Adenovirus M4

Conditionally replication adenovirus M4, which was constructed in our lab, was proved to have good clinical application prospect for its good antitumor and antimetastasis effect. However, clinically applying M4 faces many problems. One of the most important is the safety of M4. In this study, we investigated the safety of M4 by comparing with Adv-TK, which was proved to be safe in Ⅰ–Ⅲ phase clinical trials. M4 and Adv-TK were injected into mice via the tail vein separately, and the mice were sacrificed at the indicated time. Blood was collected for biochemical tests, the liver was harvested for hematoxylin and eosin (H&E) staining and viral quantification, and splenic lymphocytes were separated for adenovirus specific cellular immune response. Our results showed that M4 had no obvious effect on mouse general symptoms. A transient reversible infiltration of inflammatory cells in collect abbacy was only observed in M4 group, and a transient slight increase in Cr level was detected both after M4 and Adv-TK injection. The adenovirus specific cellular immune response induced by M4 was similar to that by Adv-TK, and the distribution and metabolism of M4 in the mouse liver were also similar to those of Adv-TK. It was concluded that conditionally replication adenovirus M4 had the same safety as Adv-TK. The study provides safety basis for the coming clinical trials of M4.

The study of RNAi-mediated by conditionally replicating adenovirus silencing on Survivin gene in colon cancer cell lastingly

Objective： To investigate the effect of RNAj-mediated Survivin gene with conditionally replicating adenovirus silencing on Survivin gene in colon carcinoma cell lines HT-29 lastingly. Methods： We transfected Ad-delE1655KD-shRNA / Survivin-EGFP to HT-29 （control was replication defective adenovirus and liposome vector which was contained the same shRNA as Ad-delE1b55KD-shRNA / Survivin-EGFP）. The expressions of EGFP, Survivin mRNA and Survivin protein in HT- 29 were detected at the 1st, 7th, 14th and 28th days alter transfection. Results： The expression of EGFP, the inhibition of Survivin mRNA and Survivin protein in HT-29 were high in each group at the 7th day alter transfection, among the total, the effect of Ad-delE1655KD-shRNA/Survivin-EGFP group was the highest; at the 14th day, the effects of replication defective adenovirus group and liposome vector group were decreased obviously, and it was still high in Ad-delE1655KD-shRNA / Survivin-EGFP group; at the 28th day, the effects of control groups were disappeared, and it was still high in Ad-delE1b55KD- shRNA/Survivin-EGFP group like before （P 〈 0.05）. Conclusion： RNAi-mediated Survivin gene with conditionally replicating adenovirus can silence Survivin gene in colon carcinoma cell lines HT-29 lastingly.

An Oncolytic Adenovirus Expressing Herpes Simplex Virus-Thymidine Kinase for Targeting Cancer Therapy:An in vitro Evaluation

Objective： Oncolytic adenovirus, also called conditionally replicating adenovirus （CRAD）, has been developed for the treatment of cancer. However, there is a tremendous need to enhance their antitumor efficacy. Here we wish to evaluate whether a strategy that combines the herpes simplex virus-thymidine kinase with oncolytic effects offers a therapeutic advantage. Methods： A novel adenovirus Ad-ETK containing a sequentially positioned promoter of human telomerase reverse transcriptase （hTERT）, the coding sequence of E1A gene, an internal ribosome entry site sequence （IRES） and the coding sequence of herpes simplex virus-thymidine kinase （HSV-TK） was constructed. Infection of various cells with Ad-ETK followed by RT-PCR confirmed the expression of E1A and HSV-TK. The oncolytic ability and synergism between oncolytic effects and HSV-TK system was measured. The infection efficiency was determined by flow cytometry. Results： Ad-ETK deliverys E1A and HSV-TK gene, which selectively replicates in hTERT-positive tumor cells, and the progeny virus can reach up to 150 IU/cell. Our in vitro study showed that Ad-ETK plus ganciclovir （GCV） induced an obvious cell death. Conclusion： An oncolytic adenovirus plus the HSV-TK/GCV suicide gene system resulted in a significant improvement in treatment efficacy and it may offer important considerations in the development and preclinical assessments of oncolytic virotherapy.