Our laboratory has been investigating the cancer inhibitory potential of cranberry proanthocyanidins (C-PAC) against esophageal adenocarcinoma (EAC), a cancer characterized by rapidly rising incident rates and poor survival (18% 5-year survival rate for all stages combined). Utilizing a panel of validated human esophageal cancer cell lines and OE19 xenograft bearing mice, our laboratory reported that C-PAC activates autophagic cell machinery leading to caspase-independent cancer cell death, yet linked to bile acid sensitivity. Reflux of bile and stomach acid into the lower esophagus is considered the major risk factor for progression to EAC. Building on our initial research, we next investigated mechanisms by which C-PAC inhibits reflux-induced EAC with a focus on gut microbiome alterations and modulation of bile acid metabolites. Bile acids undergo secondary metabolism in the intestinal tract, but have not been evaluated in this context. We utilized the rat surgical esophagogastroduodenal anastomosis (EGDA) model for reflux-induced EAC. EGDA+ and non-surgical Sprague Dawley rats were treated with water or C-PAC (650 µg/rat/day) for 25 or 40 weeks and assessed for cancer progression via extensive histopathological characterization. Additionally, at 40 weeks, fecal microbiome profiling was investigated and metabolic profiling conducted on esophageal, liver and fecal samples. Methods included 16s rRNA sequencing of rat fecal DNA, paired end sequencing on Illumina MiSeq and data analysis using Qiime and the R packages phyloseq, and edgeR to assess C-PAC-induced microbiome changes. For metabolite profiling homogenized esophagi, liver and fecal samples were extracted in methanol and characterized by Reverse Phase Ultra high Performance Liquid Chromatography-Tandem Mass Spectrometry RP/UPLC-MS/MS, followed by metabolite identification based on Metabolon’s library of authenticated standards. Study results support that C-PAC significantly inhibits the formation of EAC with concomitant restoration of the gut microbial profile, i.e., the bacterial profile shifted toward increased favorable Gram+ Firmicutes and away from inflammatory-linked Gram negative Bacteroidetes. In addition, C-PAC treatment significantly reduced primary and secondary bile acid metabolite levels in the esophagus of reflux/EGDA+ rats. Other metabolites significantly reduced by C-PAC included a number of pro-inflammatory Eicosanoids. In summary, these results support that (1) reflux-induced microbial impairment correlates with the stimulation of bile acid metabolism, and (2) C-PAC mitigates reflux-induced inflammation and injury in the esophagus in association with EAC inhibition. Future research with C-PAC in patients with gastroesophageal reflux disease should include assessments of bile acid metabolites and bacterial profiles as potential cancer-inhibitory mechanisms.
Citation Format: Katherine M. Weh, Nita H. Salzman, Amy B. Howell, Jennifer L. Clarke, Bridget A. Tripp, Laura A. Kresty. Cranberry proanthocyanidins reverse microbial dysbiosis and inhibit bile acid metabolism in association with esophageal cancer prevention [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5250. doi:10.1158/1538-7445.AM2017-5250