New Study Shows Bladder Cancer Cells Killed by Modified Cold Virus

Last updated: July 2019

A recent study conducted by researchers at the University of Surrey showed promising results: a genetically modified cold virus helped destroy bladder cancer cells in 15 patients with the disease. In one patient, the entire tumor was destroyed.1 The kind of bladder cancer treated in this study is called non-muscle invasive bladder cancer, and it is the most common type of bladder cancer.

The results are very exciting and suggest a potential new path for treating cancer without side effects. However, the study looked at only 15 people, so researchers cannot draw sweeping, general conclusions about treating all people with bladder cancer.

According to Professor Hardev Pandha, Principal Investigator of the study and Professor of Medical Oncology at the University of Surrey, “We are very excited about it. The virus gets into the cancer and replicates, like a little factory of viruses. It heats up the tumor environment, and is very specific in targeting the cancer - it had the least toxicity I have seen for years.”2

How common is bladder cancer?

Bladder cancer develops when cells inside the bladder become cancerous and start growing in an uncontrolled manner. More than 90% of bladder cancer cases begin in the cells in the innermost lining of the bladder.3 When the cancer stays in this area and does not penetrate more deeply into the muscle that forms the bladder, it is called “non-invasive.” Invasive cancers are harder to treat.4

According to the National Cancer Institute, more than 80,000 Americans are projected to be diagnosed with bladder cancer in 2019. Bladder cancer represents nearly 5% of all cancer cases and nearly 3% of all cancer deaths.5

How do you treat bladder cancer?

Current treatments for bladder cancer involve invasive surgery and frequent monitoring, since bladder cancer recurs, or comes back in 50-70% of patients. Additionally, 10-20% of patients develop more serious bladder cancer within 2-5 years of diagnosis.6

Sometimes doctors use chemotherapy after surgery to reduce the chance of the cancer recurring. But chemotherapy medicines can be very toxic and often have unpleasant side effects such as nausea, vomiting, and hair loss.7

More about the cold virus study – Phase 1 clinical trial

The University of Surrey study examining the potential for cold viruses to help treat bladder cancer was a phase 1 clinical trial. The main purpose of this kind of clinical trial is to evaluate the safety of a particular treatment. If it is safe, researchers will go on to test it in more people (in phase 2 and 3 trials) to determine whether the treatment is effective and what the optimal dose is.

How was the study conducted?

Researchers recruited 15 patients with non-muscle invasive bladder cancer. The strain of the virus they used, called CAVATAK, has been well studied in laboratory settings. It is one strain of a common cold virus called coxsackie virus A21 (CVA21).

One week before surgery, researchers injected CAVATAK directly into the bladder of the patients in the study. This technique is called intravesical administration.

One group of patients (9 people) received the virus alone. A second group (6 people) also received a very low dose of a chemotherapy agent called mitomycinC. MitomycinC also increases the presence of a specific molecule, called ICAM-1, on the surface of bladder cancer cells. ICAM-1 is the molecule that this cold virus seeks out and binds to in the process of infecting a cell. In theory, a cancer cell showing more ICAM-1 molecules on its surface has a higher chance of being infected by the CAVATAK cold virus.

What were the results?

Researchers saw signs that bladder cancer cells had been killed in all patients in the study. In one patient, the entire tumor had disappeared. The researchers also saw evidence of increased immune system activity in patients who had received the virus. The other very positive finding was that none of the patients in the study experienced toxicity or side effects.

How does a cold virus kill cancer cells?

Researchers believe that the cold viruses work in a couple of ways. First, they specifically target and infect these bladder cancer cells.1 And as with many viruses, once a virus infects a cell, it hijacks the cell’s normal machinery and causes it to produce more viruses. Bloated with newly formed viruses, the infected cells explode, releasing millions of newly formed viruses. These next-generation viruses then go on to infect and kill more cells.

The researchers also suspect that the damage the cold viruses do to the cancer cells triggers the body’s own immune system to attack and kill the cancer. One reason cancer can be so difficult to treat is that tumors often shield themselves from detection by the immune system. These are known as “cold tumors” in the medical world.8 However, dying and exploding cells release signals that activate the immune system. Likewise, cells infected by viruses also trigger the immune system, causing the tumor environment to become “hot,” or full of active targets for the immune system to attack.

"Traditionally viruses have been associated with illness, however in the right situation they can improve our overall health and well-being by destroying cancerous cells," said Dr. Nicola Annels, Research Fellow at the University of Surrey and first author of the study. "Oncolytic viruses such as the coxsackievirus could transform the way we treat cancer and could signal a move away from more established treatments such as chemotherapy," she added.8

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