A team of researchers from the University of Texas MD Anderson Cancer Center has discovered a new role for histamine receptors, the common allergy medication, suggesting novel treatment approaches in combination with checkpoint inhibitors to overcome immunotherapy resistance and improve outcomes, particularly for patients with pre-existing allergies or high plasma histamine levels. The preclinical study, published in Cancer Cell journal, demonstrated that the histamine receptor H1 (HRH1) acts in tumor-associated macrophages (TAMs) to suppress T cell activation in the tumor microenvironment. “Looking closer at this relationship, we discovered that histamine, through its receptor HRH1, can promote cancer cell immune evasion and resistance to immunotherapy,” said Yi Xiao, Instructor of Molecular & Cellular Oncology at the University.