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Newly discovered immune system molecule could stop melanoma growth

Cancer Cells

Researchers have discovered a key molecule in the immune system that may effectively inhibit the growth of melanoma – a revolutionary find that could pave the way for new treatments of skin cancer.

The study, published in the online issue of Nature Medicine, detailed the cell-signaling molecule, interleukin-9, which scientists at Brigham and Women’s Hospital (BWH) found inadvertently.

“It was really kind of an accident,” Dr. Thomas Kupper, chair of the BWH Department of Dermatology and one of the study’s lead authors, told FoxNews.com.  “We were interested in a different kind of T cell – T helper cell 17 (TH17).  These so called TH17 cells are pretty recently discovered type of T cells that are supposed to be important for protecting us against infections by bacteria.  But there’s controversy over whether these cells, if directed towards cancer, would be effective against blocking cancer or would not just be ineffective, but give cancer a boost.”

To see exactly what effect these T cells had on cancer, Kupper and his colleagues developed a group of transgenic mice lacking a key factor allowing for the production of TH17.  After introducing aggressive skin cancer cells in the mice, the researchers found that tumor growth was inhibited, suggesting that TH17 cells were hindering the rejection of cancer.

Further analysis of the mice by Kupper’s colleague Dr. Rahul Purwar revealed that the genetically altered mice expressed high amounts of interleukin-9.

“It turns out there’s a class of T cells (TH9) that make lots of interleukin-9,” Kupper said.  “With this clue we asked whether this could have something to do with the ability of mice to reject cancer.  We went on to do experiments to see if these TH cells that make interleukin-9 cells were good at rejecting cancer, and these are extremely effective at rejecting cancer cells – especially melanoma.”

In order to determine if their discovery could translate to a potential human cancer treatment, Kupper and Purwar went on to show that TH9 cells are present in normal human blood and skin.

“We wanted to be sure that this wasn’t just something unique to mice,” Kupper said.  “So we were able to show that… clearly these cells are present in humans.  We also went to look at patients with advanced melanoma.  In their lesions there were very low levels of interleukin-9.  So if we can increase those levels, we might see the same thing we saw in those [mouse] models.”

As more and more immunotherapies are developed for the treatment of cancer, Kupper said the discovery of interleukin-9 could be incorporated into existing  immunotherapy options to more effectively eradicate the disease.

“Right now the therapies that are out there - what both of those do is take the breaks off the T cell part of the immune system, allowing the T cells to get activated and fight melanoma even more effectively,” Kupper said.  “What we’re trying to do is figure out what kinds of T cells do this best.  It’s really sort of complimentary work.  If we can identify the right type of T cell you want to make, that sort of thinking combined with taking the breaks off the T cells – that could be synergistic.”

According to the National Library of Medicine, melanoma is the most dangerous form of skin cancer and the leading cause of skin disease death in the United States.  The National Cancer Institute estimates that there will be over 76,000 new cases of melanoma in the U.S. in 2012 – resulting in approximately 9,180 deaths.

With the potential to save thousands of lives on the horizon, Kupper and his team are hopeful but know that there’s a long road ahead.

“We’re scientists, so we’re enthusiastic about our results but also very cautious,”  Kupper said.  “We’ve shown pretty conclusively that this works in an animal model, but it’s a long path – although a clear path – to go from these sorts of studies to human clinical trials.”