Recent data suggest a strong association between the gut microbiome and the development of colorectal cancer (CRC), one of the world’s most widely identified malignancies (Jobin, 2013). A significant shift in composition was reported when comparing the gut microbiome of CRC patients with healthy individuals, a phenomenon commonly referred to as dysbiosis. Particularly, the presence of certain types of bacteria such as Bacteroides fragilis and Escherichia coli have been associated with an increased risk for the development of CRC (Wu et al., 2009; Eaton and Yang, 2015), while Lachnospiraceae species seem to have an antitumor effect in the colon by producing metabolites such as short-chain fatty acid butyrate promoting apoptosis of colonic cancer cells (Hague et al., 1995; Ruemmele et al., 2003). Various observations suggest that microbial dysbiosis leads to loss of protective and the enrichment of cancer-promoting populations (Jobin, 2013; Zackular et al., 2013).
Radiotherapy, plays a vital adjunctive role in the management of CRC recurrence (that range from 20 to 30% after curative surgery). However, the usage of radiotherapy has been known to cause mucositis and radiation induced ulceration which expose the underlying tissues to bacteria, thereby changing the host–microbial interaction and as such driving substantial changes in the gut microbiome leading to intestinal dysbiosis (Meyers, Sasson and Sigurdson, 2003; Fuzun et al., 2004; Bowne et al., 2005). This dysbiosis is often characterised by symptoms such as diarrhoea, rectal bleeding and malabsorption which is accompanied by epithelial destruction and mucosal ulceration, that could also have prognostic values for tumour recurrence.
Fecal microbial transplantation (FMT) re-establishes the balance of nature within the gut microbiome. This 1950 old remedy,(Eiseman et al., 1958), is nowadays mainly used for the recurrent Clostridium difficile infection (CDI) with an average 91% success rate (Bakken et al., 2011). Additionally, FMT was able to cure the irritable bowel disease and showed remarkable improvement in 52% of patients (Borody et al., 1989). Although antibiotics and probiotics have been available for a long time, the exact agent or combination of agents within FMT that affect the cure is unknown and it is likely that a structured network of microorganisms is responsible for the efficiency (Bakken et al., 2011; Allegretti and Hamilton, 2014). It is for these reasons that FMT was only recently re-evaluated in several trials (www.clinicaltrials.gov) and few companies have recently been established (OpenBiome /USA and NDFB/Netherlands) to prepare FMTs and investigate additional applications.
The application of FMT to cancer patient is a novel niche, where only a few publications are available. In 2015, FMT was applied to resolve the CDI in a single cancer patient (Blackburn et al., 2015) and a more recent publication studied the relationship between gut microbiome and radio-sensitivity –in mice, in which they reported a protective characteristic of FMT when exposed to lethal radiation doses (Cui et al., 2017). Yet the application of FMT in CRC mouse model has never been tested before which highlights the relevance of this proposal.