An Overview on Oncolytic Viruses as Cancer Therapy
The current regimen of cancer therapy (chemotherapy and radiotherapy) suffers from disadvantages such as narrow therapeutic index that further facilitates tumor evolves drug resistance and severe side-effects. Oncolytic viruses are therapeutically useful anticancer viruses that will selectively infect and damage cancerous tissues without causing harm to the normal tissues.
Many naturally occurring Oncolytic viruses have a preferential tropism to a tumor or associated endothelial cells and others are genetically engineered to change their cellular or organ tropism toward cancer. Antitumor effect of Oncolytic viruses is either by locale cell death or by initiation of the systemic immune response against the tumor.
Oncolytic Adenovirus, Herpes Simplex Virus, Newcastle Disease Virus, and Reovirus are representative of Oncolytic viruses that have potential to lysis tumor. The effects of the host immune response on the efficacy of Oncolytic viruses are complex. But, using of carrier cells as delivery vehicles could hide the viral antigen from antibodies and complements.
Oncolytic viruses have been combined with many cancer therapies to increase response to cancer. Since many forms of canine or feline neoplasms resemble humane counterpart. So, oncologists believe that Oncolytic virotherapy could soon be a reality in veterinary medicine.
Cancer is one of the leading causes of death in worldwide. Despite significant progress made in cancer therapies, but mortality rates for most malignancies remain terrifyingly high. Cancer results either due to decreased cell death or increased cell birth. The inhibition of cancer growth and succession is one of the major challenges faced by modern medicine. The classical regimen of cancer therapy (chemotherapy and radiotherapy) suffers from disadvantages such as narrow therapeutic index that further facilitates tumor evolves drug resistance and severe side-effects.
The current goal for developing new therapies for the treatment of cancer is to design therapeutic agents that have a large therapeutic index (i.e. high potency against malignant cells) with little or no toxicities to normal cells. Future treatment modalities need to be more selective and specific which allowing effective drug doses reach to each tumor cell.
Oncolytic viruses are therapeutically useful anticancer viruses that will selectively infect and damage cancerous tissues without causing harm to the normal tissues. Each virus has a specific cellular tropism that determines which tissues are preferentially infected. The field of Oncolytic virotherapy began as an observational science more than a century ago, when it was noted that cancer regressions sometimes occurred spontaneously in patients following certain viral infections. Most people think of viruses as pathogenic microorganisms that infect cells, overtake their DNA, RNA and protein synthetic machinery to replicate and then lyse their host cell to spread their progeny, thereby propagating the infection throughout a tissue. Viral infection also results in cytopathic effects, such as induction of cell death and dysfunction.
With the advent of modern biotechnology tools and better understanding of cancer biology and virology, it has become feasible to engineer viruses with increased tumor selectivity and enhanced oncolytic activity. Naturally occurring lytic viruses have evolved to infect, replicate and lyse cells. It is interesting that the replication cycle of many viruses exploits the cellular pathways that are altered in cancer cells.
The anticancer activities of OVs are derived from multimodal cancer-killing mechanisms. The first is the direct oncolysis of cancer cells by the virus. The second is apoptotic and necrotic death of uninfected cells induced by anti-angiogenesis and antivas culture of the Oncolytic viruses as shown in animals and humans. The last is cytotoxicity to cancer and stromal cells by activated innate and tumor-specific immune cells.
Read more at An Overview on Oncolytic Viruses as Cancer Therapy published in IJCR Journal.
