Muscadine Grape Extract Reduces Lung and Liver Metastasis in Mice with Triple Negative Breast Cancer in Association with Changes in the Gut Microbiome (P05-017-19)

The goal of this study was to determine if a proprietary muscadine grape seed and skin extract (MGE) inhibits triple negative breast cancer (TNBC) metastasis and alters the gut microbiota. 4T1 TNBC cells were injected into the mammary fat pad of 6-week-old female Balb/c mice. After 2 weeks, tumors were surgically removed and mice were placed into a control group (n = 8) or a treatment group that received 0.1 mg/mL total phenolics MGE (Piedmont R&D) in the drinking water (n = 8). Mice were sacrificed after 4 weeks; tissues and fecal samples were collected for analysis. Immunohistochemistry (Ki67, α-SMA) and hemotoxylin and eosin staining were used to quantify metastases using the inForm© 2.2 software. Gut microbial composition was determined by 16S rRNA sequencing and short chain fatty acids were detected by gas chromatography (Microbiome Insights). Data are expressed as means ± SEM using student's t-test. MGE reduced Ki67 cell positivity in the lungs and livers of mice, indicating reduced metastatic proliferation (9.3 ± 0.9% vs 6.2 ± 0.7% and 5.0 ± 1.5% vs 0.77 ± 0.2% cells, respectively; P < 0.01), and decreased cancer associated fibroblasts in the lungs (5.3 ± 1.0% vs 3.0 ± 0.5% cells; P < 0.05), which are associated with metastasis. MGE significantly reduced the number (4.7 ± 0.7 vs 2.2 ± 0.4 tumors/field; P < 0.01) and size (1358 ± 48 vs 1121 ± 47 pixels; P < 0.01) of liver metastases, resulting in decreased metastatic tumor burden (6656 ± 1220 vs 3096 ± 644 total area in pixels; P < 0.01). Attenuated TNBC metastasis correlated with MGE-induced changes in gut microbiota. Alpha diversity (4.15 ± 0.10 vs 4.51 ± 0.13 Shannon index; P < 0.05) and the Firmicutes to Bacteroidetes ratio (0.37 ± 0.07 vs 0.76 ± 0.12; P < 0.05) were significantly increased in MGE-treated mice, indicating enhanced microbial richness and increased energy harvest by the gut microbiome. Butyrate-producing bacteria, such as Ruminococcus, Butyricicoccus and Lachnospiraceae, were increased with MGE (P < 0.05) as well as the anti-inflammatory compound butyrate relative to other short-chain fatty acids (25.0 ± 2.7% vs 75.3 ± 15.5%; P < 0.01). These data show that MGE attenuates TNBC metastasis in association with alterations in the gut microbiome, suggesting that MGE may be an effective treatment against TNBC metastatic progression. Chronic Disease Research Fund.