People with a type of brain tumor called glioblastoma live 12 months on average, so new forms of treatment for this malignancy are badly needed.
Viruses designed to kill cancer cells offer a safe way to treat these tumors, but the therapy doesn't work as well as expected.
This study found that a patient's immune system tries to eliminate the anticancer virus and blocking this immune activity gave the virus more time to kill cancer cells.
Doctors now use cancer-killing viruses to treat some patients with lethal, fast-growing brain tumors. Clinical trials show that these therapeutic viruses are safe but less effective than expected.
A new study led by researchers at the Ohio State University Comprehensive Cancer Center - Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC - James) shows that the reason for this is in part due to the patient's own immune system, which quickly works to eliminate the anticancer virus.
The findings, published in the journal Nature Medicine, show that the body responds to the anticancer virus as it does to an infection. Within hours, specialized immune cells called natural killer (NK) cells move in to eliminate the therapeutic virus in the brain.
The researchers discovered that the NK cells attack the viruses when they express specific molecules on their surface called NKp30 and NKp46. "These receptor molecules enable the NK cells to recognize and destroy the anticancer viruses before the viruses can destroy the tumor," says co-senior author Dr. Michael A. Caligiuri, director of Ohio State's Comprehensive Cancer Center and CEO of the James Cancer Hospital and Solove Research Institute, and a senior author of the study.
"When we blocked those receptors, the virus has more time to work, and mice with these brain tumors live longer. The next step is to block these molecules on NK cells in glioblastoma patients and see if we can improve their outcome," says Caligiuri, who is also the John L. Marakas Nationwide Insurance Enterprise Foundation Chair in Cancer Research. This study of cancer-cell-killing, or oncolytic, viruses is an example of the value of translational research, in which a problem observed during clinical trials is studied in the laboratory to devise a solution.
"In this case, clinical trials of oncolytic viruses proved safe for use in the brain, but we noticed substantial numbers of immune cells in brain tumors after treatment," says senior author and neurosurgeon Dr. E. Antonio Chiocca, who was professor and chair of neurological surgery while at Ohio State University.