Researchers of the University of Surrey and the Royal Surrey County Hospital investigated the safety and tolerability of exposure to oncolytic coxsackievirus (CVA21), a natural strain of the common cold. The authors, who publish the results in the medical journal Clinical Cancer Research, studied fifteen patients with invasive nonmuscle bladder cancer and found that a strain of this virus attacks, infects and destroys cancer cells in patients with bladder cancer.
Current treatments for this cancer are problematic. Transurethral resection, an invasive procedure that eliminates all visible lesions, has a high rate of tumor recurrence ranging from 50 percent to 70 percent, as well as a high tumor progression rate between 10 percent and 20 percent for a period of two to five years.
Another common treatment, immunotherapy with Bacille Calmette-Guerin, a live bacterium used to treat bladder cancer, has been found to have serious side effects in one third of patients with NMIBC, while one third does not respond to treatment at all. .
During this pioneering study, the fifteen patients received CVA21 through a bladder catheter one week before surgery scheduled to remove their tumors. Examination of tissue samples after surgery found that the virus was highly selective, targeting only the organ's cancer cells and leaving all other cells intact.
The virus was found to have infected cancer cells and it replicated itself causing the cells to break down and die. Urine samples taken from patients on alternate days detected “shedding” of the virus, indicating that once the cancer cells infected with the virus died, the newly replicated virus continued to attack more cancer cells in the organ.
Normally, tumors in the bladder do not have immune cells, which prevents the patient's own immune system from eliminating the cancer as it grows. Evidence suggests that treatment with CVA21 inflames the tumor and causes immune cells to rush to the cancer environment, attacking and destroying cancer cells.
These tumors without immune cells are known as immunologically “cold” areas; however, treatment with the virus causes inflammation and stimulation of immune cells to create an immunological “heat”. In this way, 'hot' tumors are more likely to be rejected by the immune system.
Hardev Pandha, principal investigator of the study and professor of medical oncology in the University of Surrey, explains that “invasive non-muscular bladder cancer is a highly prevalent disease that requires an intrusive and often prolonged treatment plan. Current treatment is ineffective and toxic in a proportion of patients and there is an urgent need for new therapies. “
“The coxsackievirus could help revolutionize the treatment for this type of cancer. The reduction of tumor burden and increased death of cancer cells was observed in all patients and eliminated all traces of the disease in a patient after just one week of treatment, demonstrating its potential efficacy, he says. Notably, no significant side effects were observed in any patient. “