Some Melanoma Cells May Use the Body's Immune Response to Escape DestructionResearchers have found evidence that some melanomas may use a protein induced by T cells—a type of immune cell that can attack cancer cells—to evade the immune system. The retrospective study involving tumor samples from 150 patients suggests that this protein, called B7-H1, suppresses T cells, ultimately preventing the immune system from destroying the cancer cells.
Treatments that block the B7-H1 pathway may, therefore, benefit patients with melanomas that express this protein, wrote Dr. Janis Taube of the Johns Hopkins Medical Institutions and her colleagues in a study published March 28 in Science Translational Medicine.
Almost 40 percent of the tumor samples expressed B7-H1, and expression of B7-H1 was strongly associated with the presence of tumor-infiltrating lymphocytes. Previous studies had shown that the immune-system protein interferon-gamma (IFN-gamma) induces B7-H1 expression in melanoma, and the Hopkins researchers found IFN-gamma in the B7-H1-positive tumors where the tumor cells came into contact with tumor-infiltrating lymphocytes.
The researchers then examined outcomes in patients with metastatic melanoma and found that overall survival was longer in patients with B7-H1-positive tumors than in those with B7-H1-negative tumors. This may be because B7-H1 expression indicates the presence of an active antitumor response that initially fends off cancer before it is turned off by the melanoma cells.
Monoclonal antibodies that target B7-H1, which may help restore the immune system’s recognition of melanoma cells, are being tested in clinical trials.