Antibody found to shrink cancer cells

Apr 2 2012 - 1:33pm

In a potential breakthrough for cancer research, Stanford University immunologists discovered they can shrink or even get rid of a wide range of human cancers by treating them with a single antibody.

The experiments were done on cancerous tumors transplanted into mice, but the researchers hope to move to human clinical trials within the next couple of years.

"We have made what we think is a big advancement ... and we're going to push as hard as we can and as fast we can," said Dr. Irving Weissman, pathology professor at the Stanford University School of Medicine and director of Stanford's Institute of Stem Cell Biology and Regenerative Medicine.

The researchers focused on blocking a protein, which they refer to as the "don't eat me" molecule because it sits on tumor cells signaling the body's immune system not to attack it. By introducing the antibody, the scientists were able to block the protective signal, otherwise known as CD47, allowing the immune system to go after the cancer cells.

Researchers say CD47 is the only target found so far on the surface of all cancer cells. That means the antibody offers hope as a weapon against a broad range of cancers -- breast, ovarian, colon, bladder, brain, liver and prostate.

The research involved taking cells from Stanford cancer patients, planting them into matching locations in the bodies of mice, and then administering the antibody. The antibody completely destroyed the tumor in some cases but also prevented the cancer from spreading.

"The most common result was the tumor growth was inhibited -- not fully cured -- but in a few weeks dramatically decreased," said Stephen Willingham, postdoctoral researcher and co-lead author of the study.

The study, published online this week in the journal Proceedings of the National Academy of Sciences, has drawn praise from other researchers.

"The data is indeed exciting, and the effects are significant," said Tyler Jacks, director of the Koch Institute for Integrative Cancer Research at the Massachusetts Institute of Technology, who was not involved in the study.

But Jacks noted that the research has been limited to mice, and disease in humans tends to be much more complex.

"That's a commonly used preclinical model, but there are other examples when therapeutic effectiveness in such models has not translated well in real disease," Jacks said. "We need to see what happens when the treatments are (used) in patients."

The Stanford team said the "don't eat me" CD47 signal has long been identified and is associated, in particular, with the treatment of leukemia. CD47 is found in healthy cells but tends to be expressed in higher levels in cancerous cells.

The researchers were concerned that any treatment would single out normal cells as well as malignant ones. They discovered, however, that the antibody selected older, red blood cells, causing mild and temporary anemia and no other adverse side effects.

"That was the best moment. We found a way to utilize this antibody to treat (the cancer) without having major toxicity," said Dr. Jens-Peter Volkmer, the study's other lead author.

The team's research funded by a grant from the California Institute for Regenerative Medicine. The organization was created by Proposition 71, passed by voters in 2004 to support stem cell research.

(Victoria Colliver is a San Francisco Chronicle staff writer. vcolliver@sfchronicle.com)

(Distributed by Scripps Howard News Service, www.scrippsnews.com.)

 

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