Intestinal microbiota regulates anti-tumor effect of disulfiram combined with Cu2+in a mice model

Background A growing number of studies show that intestinal microbiota affect the therapeutic effects of antineoplastic agents. Disulfiram (tetraethylthiuram disulfide, DSF) is an old alcohol-aversion drug that has been shown to be effective against various types of cancers in preclinical studies, while few studies are carried out to explore its mechanism. Methods A mice model of melanoma xenograft was generated and treated with antibiotics (Abx), disulfiram/copper (DSF/Cu2+), Abx + DSF/Cu2+, and the tumor volume and survival curve were observed. Hematoxylin-eosin (HE) staining and western blotting (WB) were used to observe the protein changes related to cell morphology, inflammation, and apoptosis in tumor tissues. Quantitative real time polymerase chain reaction (qPCR) was used to detect the expression of pro-inflammatory cytokines in tumors. High-throughput sequencing was used to detect the effects of Abx and DSF/Cu(2+)on intestinal microbiota. Results The DSF/Cu(2+)and Abx + DSF/Cu(2+)markedly delayed tumor progression and prolonged mice survival, of which the combination of Abx and DSF/Cu(2+)possessed the best anti-tumor effect. Abx + DSF/Cu(2+)significantly reduced the pro-inflammatory cytokines Interleukin-1 beta (IL-1 beta), IL-6 and tumor necrosis factor alpha (TNF-alpha) in tumors, and significantly reduced the expression of phosphorylated-protein kinase B (p-AKT)/protein kinase B (AKT), toll-like receptors 4 (TLR-4), and phosphorylated- nuclear factor kappa-B (p-NF kappa B)/NF kappa B in tumors. Moreover our high-throughput sequencing first indicated that the sound anti-cancer effect of Abx + DSF/Cu(2+)had a strong connection with the increased abundance of intestinal beneficial bacteriaAkkermansia, as well as the reduced abundance of opportunistic pathogenic bacteriaCampylobacterales,Helicobacteraceae, andCoriobacteriaceae. Conclusions The disturbed intestinal microbiota (increased abundance of opportunistic pathogensCampylobacterales,Helicobacteraceae, andCoriobacteriaceae) and the over-activated TLR4/NF-kappa B signaling pathway in tumor tissues deteriorated the cancer development, and the using of antibiotics is benefit to enhance the therapeutic effect of DSF on tumors via inhibiting the growth of opportunistic pathogenic bacteria.