Pro-tumoral role of gut bacteria: sabotaging immune cell recruitment

The gut is populated by trillions of bacteria impacting on metabolism, immune system development and overall fitness (1,2). In the past five years, the role of commensal bacterial in the responsiveness to anti-cancer treatments has emerged. Initial studies have focused on the association between response to chemotherapy and gut colonization by specific bacterial strains (3,4). More recently, gut colonization by defined bacterial species has been shown to critically influence responsiveness to immunological checkpoint blockade in melanoma and epithelial cancers (5-8). Although mechanisms remain largely elusive (9), these data have emphasized the possibility of actively conditioning the intestinal flora by colonization with specific bacterial strains, as cancer treatment to complement established therapeutic protocols.