Thus, tumor-infiltrating Napabucasin mw myeloid cells appear to be primed directly or indirectly by gut commensal bacterial LPS through the TLR4 receptor for responsiveness to the TLR9 ligand CpG-ODN. The overall composition of the fecal microbiota was also found to segregate mice that showed either high or low TNF responses to CpG-OGN. In particular, the abundance of several Gram-positive and Gram-negative bacterial species in the fecal microbiota was found to positively correlate with the response of tumor myeloid cells to CpG-ODN, whereas the abundance of certain commensal Lactobacillus species showed a negative

correlation [22]. The enhancement of the CpG-ODN response by the Gram-negative Alistipes shaii, and its attenuation by L. fermentum were directly demonstrated by in vivo association experiments [22]. In the same study, the effectiveness of the treatment GSK1120212 chemical structure of mouse sterile subcutaneous transplanted tumor with the platinum compounds oxaliplatin and cisplatin

was also observed to be dramatically reduced in antibiotic-treated or GF mice compared with conventional mice [22]. Platinum compounds are cytotoxic by virtue of forming platinum-DNA adducts that primarily accumulate intrastrand cross-links, and these in turn inhibit proliferation and induce apoptosis, in part by recruitment of the ataxia telangiectasia and rad3-related kinase to the DNA lesion and p53 activation [168]. In

addition to their direct cytotoxic effect, oxaliplatin but not cisplatin has been shown to induce immunogenic cell death, which releases endogenous activators of inflammation, Sitaxentan such as high-mobility group protein B1 and ATP, thus driving activation of antigen-presenting cells and antitumor T-cell immunity [169, 170]. In antibiotic-treated mice, although the formation of platinum adducts to tumor cell DNA was not impaired, a significant decrease in DNA damage and cytotoxicity compared with conventional mice was already observed at day 2 after treatment, suggesting that antibiotics administration had suppressed the early genotoxic effect of the drug rather than the inflammatory/immune activation induced by immunogenic cell death [22]. Clear evidence suggests that H2O2 is important for the DNA damage and apoptosis induction effected by platinum compounds [171]. Antibiotics treatment was shown to inhibit the oxaliplatin-induced enhanced expression of genes related to inflammation, and in particular to monocyte differentiation, activation, and function, whereas it prevented the oxaliplatin-induced downregulation of genes related to normal cellular function, such as metabolism, transcription, translation, and DNA replication [22].