Cancer vaccine shrinks tumors, healthy cells escape unscathed

Using DNA extracted from healthy prostates, scientists have designed a vaccine that uses the immune system to attack cancerous cells, curing 80% of the test mice.
Written by Janet Fang, Contributor

UK and Mayo Clinic researchers have created a vaccine that cured prostate tumors in mice.

By using the immune system to attack tumors, this novel ‘immunotherapy’ treatment doesn’t rely on toxic chemotherapy or radiation.

It contains bits of DNA from the organ where tumors can develop – so it’s like a vaccine, which contains weakened viruses to be destroyed and remembered by the immune system. But unlike a traditional vaccine, this therapeutic vaccine doesn’t prevent disease… it treats it.

The researchers assembled genetic snippets from healthy human prostate tissue into a DNA library, and then the DNA bits were inserted into a swarm of viruses. This then was introduced intravenously into mice.

Then their tumors shrank, and 80% of them were cured with 9 virus injections. The researchers say the technique could be applied to many other kinds of aggressive cancers.

So all infections, allergens, and tumors have unique protein tags – called antigens – that trigger a response from the immune system. The prostate DNA made the virus vector produce a wide range of prostate antigens.

After exposure to the mutated viruses, the mouse immune systems recognized the antigens expressed in the virus and produced an immune response that attacked the prostate tumors.

“By expressing all of these proteins in highly immunogenic viruses, we increased their visibility to the immune system,” says study author Richard Vile from Mayo Clinic. “The immune system now thinks it is being invaded by the viruses, which are expressing cancer-related antigens that should be eliminated."

There were no observed side effects and no trace of autoimmune disease in the mice; their immune cells attacked only cancerous cells.

According to study coauthor Alan Melcher of the University of Leeds: "The biggest challenge in immunology is developing antigens that can target the tumor without causing harm elsewhere."

And that’s possible here because the DNA library was harvested from the same organ as the tumor, he explains. The immune system ‘self-selected’ the cancer antigens to respond to and didn't react against other healthy parts of the body.

Clinical trials could begin within the next 2 years.

Just a couple months ago, the FDA approved Bristol-Myers Squibb’s ipilimumab, or Yervoy, an immunotherapy drug for advanced melanoma patients.

The study was published yesterday in Nature Medicine.

Image: syringes by alvimann via morgueFile

This post was originally published on Smartplanet.com

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