Mice without the genes responsible for the development of the T helper 17 (TH17) cell demonstrated significant resistance to melanoma tumor growth, suggesting that the growth of such cancers could be inhibited by blockade of the TH17 cell pathway. The mice also expressed abundant interleukin-9, a T cell cytokine that also appeared to inhibit melanoma growth.

“These were unexpected results, which led us to examine a possible contribution of interleukin-9 to cancer growth suppression,” explained Rahul Purwar, PhD, of the Department of Dermatology at Brigham and Women’s Hospital (BWH) in Boston, Massachusetts, in a statement issued by BWH. Purwar and Thomas S. Kupper, MD, chair of the BWH Department of Dermatology, led the study. Their group’s findings were published online by Nature Medicine.

After noting these findings, the investigators gave the melanoma-bearing mice T helper cell 9 (TH9), an immune cell that produces interleukin-9. These mice also showed a profound resistance to melanoma growth. According to the BWH statement, this is the first reported finding showing an anti-tumor effect of TH9 cells.

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The researchers also found a higher number of TH9 cells in normal human skin and blood than in the metastatic lesions of persons with stage IV melanoma. Overall, concluded the study authors, the results suggest a role for interleukin-9 in tumor immunity and offer insight into potential therapeutic strategies.