Proofing against radiation promises breakthrough in cancer therapy

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Published: 22 October, 2009, 15:59
Edited: 23 October, 2009, 01:55

Scientists may have stumbled on a way to making radiation treatment of cancer much more effective. By blocking a certain protein in cells they protected healthy tissue from radiation, while making tumors vulnerable.

Radiotherapy is used for treatment of many kids of cancer. Irradiation of tumors kills them, but it affects surrounding healthy tissue too. The damage may lead to a number of negative side effects, including fatigue, nausea, skin sores and loss of hair.

American researchers at the University of Pittsburgh’s School of Medicine and the National Cancer Institute believe they have found a way to overcome this drawback. They’ve discovered that preventing a protein called thrombospondin-1, or THBS1, from binding to its cell surface receptor, the CD47 greatly enhances the cell’s ability to withstand radiation. Experiments on mice have shown that the treatment gives protection even against very high doses of radiation.

"We almost couldn't believe what we were seeing," said Dr. Jeff S. Isenberg, one of the co-authors of the paper detailing the research, which was published in Science Translational Medicine. "This dramatic protective effect occurred in skin, muscle and bone marrow cells, which is very encouraging. Cells that might have died from radiation exposure remained viable and functional when pre-treated with agents that interfere with the thrombospondin-1/CD47 pathway."

Surprisingly, not only did the treatment protect normal cells, but it also made tumors more vulnerable to radiotherapy, contrary to the fears that it would do otherwise. “In our experiments, suppression of CD47 robustly delayed the re-growth of tumors in radiation-treated mice," noted senior author David D. Roberts, Ph.D., of the NCI's Center for Cancer Research.

Scientists are not sure why this happens this way. Among the possible explanations is that blocking the pathway somehow protects immune cells in the organism and thus allows them to better fight cancer. It may also weaken the tumor directly or improve blood flow to the tumor and made the immune attack on it more vigorous.

Researchers say they’ve tested the method on several species of animals including mice, rats, pigs and cows. It has also worked in human tissue. However it needs several years of clinical testing before it may be approved for use in oncology hospitals.