High levels of ammonia in tumors leads to fewer T cells and immunotherapy resistance in mouse models of colorectal cancer, findings revealed. Researchers found that ammonia inhibits the growth and function of T cells, which are vital for anti-tumor immunity. "We identified the mechanism of how ammonia dysregulates T cell function and showed that reducing ammonia levels using FDA-approved drugs for hyperammonemia can reduce tumor size in several different models including metastatic colorectal cancer," says Hannah Bell, Ph.D. "Use of this drug also synergizes with immunotherapy. If you treat mice with immunotherapy when you also treat them with this ammonia...