Examining the antitumorigenic effects of Ruminococcus gnavus

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Presentation Time: 11:30 AM - 12:45 PM
Poster Board Number: B155
Abstract ID: 5091

Presenting Author:
Colin Laughlin , Research Technician at Univ. of Pittsburgh Sch. of Med.

Abstract:

Melanoma is one of the most commonly occurring cancers in the world, with increasing occurrence over the past several decades. Common treatment regimens for melanoma include immune checkpoint inhibitor (ICI) therapy, which enhances interferon-γ production in CD8 T cells (Tc1). Despite showing efficacy in some patients, a majority of melanoma patients are resistant to ICI therapy. Prior studies have demonstrated the ability of the gut microbiota to impact Tc1 antitumor responses and ICI therapy efficacy. In analyzing top gut bacteria enriched in ICI-responders, Ruminococcus gnavus (R. gnavus) is a commonly identified species. Here we demonstrate the tumor restraining properties of R. gnavus in subcutaneous, spontaneous, and metastatic cancer models. Further, gnotobiotic monocolonization experiments demonstrate the ability for this bacterium to restrain tumor growth independent of a complex microbiome. Analyzing the mechanism behind how R. gnavus causes melanoma growth suppression in our model, we have demonstrated requirements of bacterial viability and aryl hydrocarbon receptor (AHR) activation. Colonization with R. gnavus at various tumor timepoints was able to induce a significant Tc1 response locally in the tumor and systemically in lymphoid organs. Finally, we found R. gnavus colonization to facilitate ICI efficacy in our model.  This study uncovers a potential mechanism of how a common ICI-response associated bacterium enhances ICI efficacy in melanoma.