Development of a model based on oncolytic adenovirus loaded with L-carnosine as a drug delivery system for cancer therapy

Abstract

Oncolytic viruses are viruses that are able to replicate specifically and infect and destroy only tumor cells. Many clinical studies have shown that the oncolytic approach alone could not efficiently destroy the large tumor mass, thus by limiting an efficacy virotherapy. Combination of oncolytic adenoviruses (Ads) and chemotherapeutic drugs has shown promising therapeutic results due to the synergistic action of virus and drug and is considered as a potential approach for cancer therapy. In the present study, we have optimized a model to use oncolytic adenovirus as a scaffold to deliver active drugs. First, we have developed a strategy to conjugate peptides on viral capsid, based on electrostatic interactions. We have utilized the L-carnosine (β-Ala-His) dipeptide, according to our previous results. L-carnosine is a naturally occurring histidine dipeptide, with a number of biological functions, including a significant antiproliferative activity both in vitro and in vivo. L-carnosine positively charged, consisting of a tail of six lysines (Carnosine6K), has been combined with the surface of oncolytic adenovirus that is negatively charged, to allow the formation of a complex (Ad5D24CpG-Carnosine6K). We have observed using different cancer cell lines that complex at 100vp, is able to reduce significantly cell proliferation and ATP production compared to an uncoated oncolytic adenovirus. Finally, the oncolytic activity of the complex was tested in a lung and colon cancer xenograft model. Nude mice bearing A549 and HCT-116 cell tumors in the flanks were treated intra-tumorally and each tumor was treated with 1x10^8 VP. The tumor growth was followed over time, our results show a reduction in tumor growth in mice treated with complex compared to the mice treated with virus alone or Carnosine6K. Later, we have investigated the molecular mechanisms underlying the effects by oncolytic virus coated with modified L-carnosine on tumor growth reduction. Our results suggest that the oncolytic virus coated with modified L-carnosine induces apoptosis, increases autophagy (LC3), by improving the efficacy of Ad-mediated oncolysis. In conclusion, once validated the proposed model could be used as a novel drug delivery system for cancer therapy.