Because many viruses have RNA genomes, the immune system has developed systems for detecting and attacking foreign RNA. Yale researchers have exploited this system to set the immune system on cancers, as reported in the Journal of Experimental Medicine.Researchers, led by Akiko Iwasaki, PhD, Waldemar Von Zedtwitz Professor of Immunobiology and professor of molecular, cellular and developmental biology, and Anna Marie Pyle, PhD, Sterling Professor of Molecular, Cellular, and Developmental Biology and professor of chemistry, induced melanoma growth in mice, then injected the tumors with a solution of an RNA molecule called SL14. The RNA injection slowed tumor growth, increased survival, and boosted the effects of an immunotherapy drug.Current immunotherapies, which ramp up the immune response, can only kill tumors that stimulate an immune response in the first place. Accordingly, immunotherapies do not work on many tumors. Iwasaki, Pyle, and colleagues found that SL14 injection stimulated immune responses against what are usually non-immunogenic tumors, perhaps making them more immunogenic.