MedicalResearch.com Interview with: Nina Bhardwaj, MD, PhD and Director of Immunotherapy and professor of Hematology and Medical Oncology Benjamin Greenbaum, PhD Assistant Professor The Tisch Cancer Institute at the Icahn School of Medicine at Mount Sinai   Medical Research: How did the discovery of the group of non-coding RNA molecules in cancer cells that sets off an immune response come about? Dr. Greenbaum: Our work is a collaboration between my lab, which is computational, and the Bhardwaj lab, focused on cancer immunology. I had previously made the observation that certain RNA viruses were avoiding certain motifs, such as CpG dinucleotide containing motifs, and the Bhardwaj lab tested whether those motifs could set off an immune response. Recent work had shown that tumors transcribe unusual RNA with immunological consequences, so we investigated whether the same sort of approaches we had used for viral RNA worked here. Dr. Bhardwaj: It has recently become clear that, due to epigenetic alterations, tumors transcribe non-coding RNAs that are typically silenced. Often such RNA emanates from the “dark matter” genome. Many of these regions consist of repetitive elements and endogenous retroelements that are rarely transcribed in normal tissue. At the same time, due to immunotherapy, understanding the role of the immune system and immune activation in tumors has become critically important. The activation of specific elements of the innate immune system in a tumor may have either beneficial or detrimental effects for patients. Moreover, recent work has suggested that endogenous element activation can lead to improved immunotherapy outcomes. Therefore, it is critically important to understand the nature of innate immune activation in tumors and what triggers are responsible for these responses. We have been developing methods to detect abnormal patterns in viral RNA that may indicate activation of the innate immune system. We have found that patterns of motif usage avoided in the evolution of viruses, such as influenza, indicate RNA features that provoke an innate immune response. The innate immune system is capable of sensing motifs in viruses. We tested directly whether these avoided patterns are immunostimulatory. Medical Research: What are the main findings? Dr. Bhardwaj: We used a novel quantitative approach, derived from methods in statistical physics, to characterize all of the non-coding RNA transcribed by normal tissue and compared them to the non-coding RNA found in tumors. We found that while the non-coding RNA transcribed in normal tissue displays patterns of motif usage consisting with that of coding RNA, the RNA transcribed in tumors, yet rarely found in normal tissue, can have motif usage more typically associated with viral and bacterial genomes. We predicted a handful of such RNA are immunostimulatory and validated this prediction in antigen presenting cells. We then showed that this sensing may come from a subset of the innate immune system associated with pathogen RNA sensing. We called these RNA “i-ncRNA”, for immunostimulatory non-coding RNA. (more…)