Immune checkpoints prevent immune responses from being so strong that they destroy healthy cells in the body. Sometimes, however, checkpoints cannot recognize and destroy cancer cells. To combat this, immune checkpoint inhibitors (ICI), lab-made proteins, are used in cancer treatment to block signals from these checkpoints, allowing the immune system to find and attack cancer cells. These inhibitors have transformed melanoma therapy, but only a subset of patients achieves durable responses.
Increasingly, research highlights the gut microbiome’s role in regulating immune responses. As such, understanding that interaction is critical to developing microbiome-based strategies that can improve the efficacy of immunotherapy. In a study in Communications Medicine, Dr. Himel Mallick, assistant professor of population health sciences, and colleagues from George Washington University used a unified analysis pipeline to identify microbiome features associated with response to ICI therapy. They further determined which microbial features reproducibly associate with response and to what extent these associations generalize across studies.
Dr. Mallick's team demonstrated that overlapping sets of bacteria have context-dependent associations with ICI therapies. "Previous studies hinted at a conceptual dead end for cancer microbiome immunotherapy research," said Dr. Mallick. "Our integrated analysis showed that there is signal, if the curation and analysis methods are right. Several butyrate producers were associated with enhanced immunotherapy response, and many of these carried sufficient signal across cohorts to warrant reproducibility testing and experimental follow-up."
The study’s findings thus support a treatment-dependent model in which sets of taxa and functions reproducibly associate with checkpoint inhibitor response. These microbial “communities” can be prioritized for future mechanistic studies and microbiome-informed interventions.
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