Fig. 2.

Microbiota may influence the chemotherapeutic agents utilized in pancreatic cancer treatment in multiple ways. The presence of bacteria expressing cytidine deaminase can directly metabolize gemcitabine and therefore render the drug inactive [31]. Fusobacterium nucleatum can elevate cancer cell antiapoptotic signaling and induce a therapeutic resistance towards 5-FU [98]. However, not all the microbial components are deleterious toward chemotherapy efficacy. Gut microbiota could prime the action of myeloid producing reactive oxygen species in response to oxaliplatin to achieve an improved cytotoxicity [100]. In addition, the microbiota can increase the toxicity of chemotherapeutic regimens. Bacteria expressing β-glucuronidases can cleave the inactive irinotecan into its active form and induce gut toxicity and mucositis, subsequently limiting the effective dose of chemotherapy that can be delivered [85,99].