Dietary Impacts on Changes in Diversity and Abundance of the Murine Microbiome During Progression and Treatment of Cancer

Abstract

The microbiome has been recognized as being highly impactful for cancer outcomes, both with respect to the diversity and composition of the microbial population, as well as overall abundance. Presence or absence of certain microbial species has been correlated to improved cancer outcomes, in concert with specific treatments. However, little research has been performed to consider the reciprocal of this relationship: how different treatments, or the progression of disease, impact the microbiome. Further, though correlations have been demonstrated between dietary intake of both fats and carbohydrates and the composition and breadth of the microbiome, no studies have investigated the microbiome population as it is impacted by cancer and therapeutic treatments under different dietary regiments. This study aims to investigate how dietary patterns, in concert with progression of cancer and both surgical and therapeutic interventions, impact the diversity and abundance of the murine microbiome. A total of 116 c57BI/6 female mice (7‐8 weeks old) were randomized into four groups (n=29/group, each) one week post ovariectomy. Mice received a specific, semi‐purified diet consisting of A) low sucrose, high omega 3 fatty acid; B) low sucrose, low omega 3 fatty acid; C) high sucrose, high omega 3 fatty acid; or D) high sucrose, high omega 3 fatty acid. For high omega 3 fatty acid groups, 2% of daily calories were supplied to the mice as EPA and DHA in a 1.5:1 ratio. One week after implementation of diets all mice were inoculated with E0771 breast cancer cells. Twelve days following inoculation all mice were subject to lumpectomy. Eight days following, measurement procedures were repeated, as at baseline. Ten days following lumpectomy, half of the mice from each dietary cohort were treated with saline, while the other half were treated with a chemotherapeutic agent (9 mg/kg body weight doxorubicin and 90 mg/kg body weight cyclophosphamide). Six days later, the experiment ended, and mice were sacrificed following IACUC guidelines. Fecal samples, which had been collected at each time point noted above, were processed using QIAmp® PowerFecal® DNA isolation kit and were sent to MCIC (OSU Wooster Campus) for 16S ribosomal genetic profiling. A genomic library was generated, using previously validated primers for the V4 region. FASTQ files were filtered, trimmed, dereplicated, and denoised. Cleaned FASTQ files were then used to infer ASVs. Over the progression of cancer, there has been a consistent decrease in the alpha diversity of the microbiome. The effect of diet was mitigated by introduction of chemotherapeutic agents, though the significance of this effect is yet to be determined. While the analysis is still ongoing, it has been determined that there is a clear dietary effect which interacts with abundance. Multiple ASVs have been shown to be positively associated with high fat consumption, though inverse effects, as well as timepoint and treatment effects, have also been noted. Akkermansia muciniphila was a highly present bacter...

Insights from Bacterial 16S rRNA Gene into Bacterial Genera and Predicted Metabolic Pathways Associated with Stool Consistency in Rectal Cancer Patients: A Proof of Concept

“…(Blake et al, 2016; Vandeputte et al, 2016). While maintaining GI health during cancer treatment may be challenging (Paden et al, 2022; Touchefeu et al, 2014), fortunately visual representation (shape and apparent texture of the stool) of stool consistency using short stool form scales has facilitated the GI assessment in clinical and research practice, perhaps becoming a key component in the description of normal or altered bowel habits (Blake et al, 2016). In addition, in patients with chronic diseases including cancer, stool consistency is an important parameter associated with the symptoms of diarrhea (Blake et al, 2016; Caroff et al, 2014) and constipation (Chen et al, 2019).…”

“…This in turn may limit the growth of microbes through decreased nutrient mobility and inhibited enzymatic activity. It is also plausible that the toxicity of cancer treatments may reduce the diversity of the gut microbiome, which could influence GI motility and may increase the GI-side effects of treatment (Chen et al, 2019), resulting in higher risk of opportunistic infections (Paden et al, 2022). In one study among healthy women ( n = 53), species’ richness (Chao1) significantly declined with stool firmness, while stool consistency was positively associated with the Bacteroidetes-to-Firmicutes ratio and to Akkermansia and Methanobrevibacter abundances (Vandeputte et al, 2016).…”