Increased Safety with Preserved Antitumoral Efficacy on Hepatocellular Carcinoma with Dual-Regulated Oncolytic Adenovirus

Abstract

Purpose: A dual-regulated adenovirus variant CNHK500, in which human telomerase reverse transcriptase promoter drove the adenovirus 5 (Ad5) E1a gene and hypoxia-response promoter controlled the E1b gene, was engineered. This virus has broad anticancer spectrum and higher specificity compared with mono-regulated adenovirus CNHK300. The objective of the current study is to show its antitumor selectivity and therapeutic potential. Experimental Design: The antitumor specificity of human telomerase reverse transcriptase and hypoxia response promoters was evaluated in a panel of tumor and normal cells. Under the control of these promoters, the tumor-selective expression of E1a and E1b genes was evaluated. Further in vitro antitumor specificity and potency of this virus were characterized by viral replication and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Subsequently, hepatocellular carcinoma xenografts were established to evaluate CNHK500 antitumor efficacy in vivo by different routes of virus administration and different dosages. Results: Human telomerase reverse transcriptase and hypoxia response promoters were activated in a tumor-selective manner or under hypoxia treatment in a broad panel of cells. Selective adenoviral early gene expression, efficient viral replication, and oncolysis were observed in all tested cancer cells with more attenuated replication capacity in normal cells. Significant regression of hepatocellular carcinoma xenografts and prolonged survival were observed by either i.t. or i.v. administration. Conclusions: CNHK500 greatly reduced side effects in normal cells via dual control of adenoviral essential genes while still preserving potent antitumor efficacy on broad-spectrum cancer cells in vitro and in vivo. It can be used as a powerful therapeutic agent not only for liver cancers but also for other solid tumors.

Assessment of an altered E1B promoter on the specificity and potency of triple-regulated conditionally replicating adenoviruses: implications for the generation of ideal m-CRAs

“…9,10 Furthermore, it is important to note that none of the previous studies examined the necessary activity of an altered E1B promoter to increase the cancer specificity without reducing the anticancer effects. In this regard, the following two points should be noted.…”

“…7 On the other hand, a few previous studies obtained increased cancer specificity by replacing the E1B promoters with cancer-specific promoters in addition to regulating E1A with a different cancer-specific promoter. 9,10 However, the actual utility of this combination remains unclear because the original and modified CRAs were not sufficiently compared. In particular, several crucial and unanswered questions remain, including how much E1B or E1BD55K (E1B/E1BD55K) expression is necessary and how strong of a different cancer-/tissuespecific promoter is necessary to drive E1B/E1BD55K expression to increase cancer specificity without reducing the anticancer effects.…”

Antitumor effects of oncolytic adenovirus armed with Drosophila melanogaster deoxyribonucleoside kinase in colorectal cancer

“…However, because of limitations involving vector delivery and relatively low levels of gene transfer, such vector systems have been proven relatively inefficient for the treatment of large solid tumors (15). One strategy to overcome these limitations is the use of a conditionally replicating adenovirus (CRAd), also called oncolytic adenovirus, which exert intrinsic antitumor activity through selective replication in lysis cancer cells, causing the spread of progeny viruses in neighboring cancer cells, and eventually lysing the infected cancer cells (16)(17)(18)(19). For instance, ONYX-015 an E1B-55 kDa deleted mutant adenovirus with tumor specific replication was introduced for oncolytic gene therapy (20,21).…”

T lymphocyte responses against hepatitis B virus-related hepatocellular carcinoma induced by adenovirus vaccine encoding HBx

“…In addition, high recurrent rate after resection and resistance to conventional treatments have rendered the disease a very serious health problem (3). Thus, the development of novel strategies against HCC is much needed (4)(5)(6).…”