Modified Polio Vaccine Could Emerge as a Possible Treatment for Brain Cancer

Highlights:

• The oncolytic virus PVSRIPO, an engineered hybrid of poliovirus and rhinovirus, is being investigated for its anticancer effects in malignant glioma
• It appears to act in two ways – by directly killing tumor cells and by activation of the immune system to fight the cancer cells.

A modified poliovirus under investigation for the treatment of malignant glioma appears to attack the cancer directly as well as by stimulating the immune system. The research that revealed the dual effect of the oncolytic virus was published in Science Translational Medicine. The modified virus called PVSRIPO, an engineered hybrid of poliovirus and rhinovirus, appears to act in two ways:

• It directly kills the tumor cells. Once injected into the body, the virus attaches to the CD155 protein, also called the poliovirus receptor, which is abundant on cancer cells. It directly kills most cells and releases tumor antigens in the body. The exposed antigen can stimulate an immune response, that is, it can activate neutrophils (a type of white blood cells) which then attack the cancer.

• It stimulates the body’s immune response to fight the cancer. It enters immune cells called dendritic cells and macrophages. It does not damage these cells but these cells in turn stimulate the immune cells called T-cells, which recognize, infiltrate and attack the cancer cells. The long-lasting immune response produced in this manner can possibly prevent the regrowth of the cancer.

The modified vaccine has been in clinical trials for the treatment of recurrent World Health Organization grade IV malignant glioma. This cancer is considered to be of high grade.

The treatment has recently received a breakthrough therapy designation from the US Food and Drug Administration. Such a designation ensures the expedition of the development process for a drug that has shown substantial clinical improvement over an existing treatment in a serious or life-threatening disease. Further research could see a new treatment that could be used as an adjuvant along with other treatments for the life-threatening cancer.

Malignant Glioma

A glioma is a cancer that arises from the glial or the supporting cells of the brain or spinal cord. Gliomas are of three types, astrocytomas, oligodendrogliomas, and ependymomas. While some gliomas can be benign, around 80% are malignant. They are diagnosed on brain scans and biopsy of the growth. They are usually surgically treated, with radiotherapy and chemotherapy used to kill the cancer cells that remain after surgery.

Oncolytic Virus

Cancer treatment has seen several additions to the conventional surgery, radiotherapy and chemotherapy in the recent years. Oncolytic viruses which selectively break down cancer cells, are among the new treatments that have spurred great interest. T-VEC (talimogene laherparepvec (T-VEC) was the first oncolytic virus approved in the United States for the treatment of metastatic melanoma, a deadly skin cancer arising from the pigment cells called melanocytes.

Reference:

1. Brown MC et al. Cancer immunotherapy with recombinant poliovirus induces IFN-dominant activation of dendritic cells and tumor antigen–specific CTLs. Science Translational Medicine (2017): Vol. 9, Issue 408, eaan4220 DOI: 10.1126/scitranslmed.aan4220
2. Biological Therapies for Cancer - (https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/bio-therapies-fact-sheet#q7)

Source-Medindia