Behind the Cancer Headlines™
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New Wave of Cancer Drugs

May 30, 2001

An incredibly informative article was just published in The New York Times. It discussed the new wave of biologically engineered drugs that may soon revolutionize the treatment of cancer.

Writer Nicholas Wade cited two avenues of drug research in particular—shutting off the "signaling mechanisms" that cancer cells use to grow and multiply; and targeting specific proteins that are necessary to halt out-of-control cell division.

Importantly, most of these new drugs are "cancer-specific," attacking only cancerous cells and leaving healthy ones intact. This in itself represents an extraordinary leap forward from chemotherapy and other treatments that attack all fast-growing cells—a primary characteristic of cancer cells, but also of certain healthy cells such as hair follicles and cells lining the stomach.

Wade noted one of the most important new custom-designed drugs—STI-571 or Gleevec—has shown measurable results in 90 percent of chronic myelogenous leukemia patients who have taken it, and 60 percent of patients with a rare stomach cancer known as gastrointestinal stromal tumor.

Gleevec is designed to shut down "signaling proteins" that are necessary for cancer cells to grow and multiply. Researchers believe that the same mechanism that Gleevec uses to shut down these proteins in leukemia and stomach cancer may also provide a viable route for inhibiting the growth of other cancers.

Wade points out that the decoding of the human genome has indicated that as many as one-fifth of all human genes make proteins that are involved in signaling. "A special subset of these proteins, known to biologists as tyrosine kinases, are particularly prone to go awry and show up in hyperactive form in many human cancers," he notes. These signaling proteins therefore make enticing targets for cancer drug research.

Wade points out that cancer researchers are also targeting a group of substances that control the cell’s division cycle, in particular two proteins called Rb and p53. Rb’s normal function in the cell is to prevent it from dividing; cancerous cells somehow inhibit the Rb protein in order to grow and multiply.

In addition, when the Rb protein is neutralized, another protein—p53 is supposed to kick in to trigger the cell’s self-destruct mechanism. A cancerous cell must therefore also inhibit the p53 protein to grow unimpeded.

Researchers are now developing genetically altered viruses that kill only cells that have non-functioning Rb and p53 proteins. One of these viruses, known as Onyx-015, has shown significant results in clinical trials for treating head and neck and colorectal cancers.

"We are at a critical juncture where so much has been learned and there is a lot of optimism that new kinds of therapies will be developed," said Dr. Bert Vogelstein, a cancer researcher at Johns Hopkins, as quoted in the article. "I share that optimism, but realistically it is not going to be simple."

SOURCE:

The New York Times, May 29, 2001

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