Grape seed extract efficacy against azoxymethane-induced colon tumorigenesis in A/J mice: interlinking miRNA with cytokine signaling and inflammation.

Colorectal cancer (CRC) is the second leading cause of cancer-associated deaths, suggesting that additional strategies are needed to prevent/control this malignancy. As CRC growth and progression involve a large window (10-15 years), chemopreventive intervention could be a practical/translational strategy. Azoxymethane (AOM)-induced colon tumorigenesis in mice resembles human CRC in terms of progression of ACF to polyps, adenoma, and carcinomas and associated molecular mechanisms. Accordingly, herein we investigated grape seed extract (GSE) efficacy against AOM-induced colon tumorigenesis in A/J mice. GSE was fed in diet at 0.25% or 0.5% (w/w) dose starting 2 weeks after last AOM injection for 18 or 28 weeks. Our results showed that GSE feeding significantly decreases colon tumor multiplicity and overall tumor size. In biomarker analysis, GSE showed significant antiproliferative and pro-apoptotic activities. Detailed mechanistic studies highlighted that GSE strongly modulates cytokines/interleukins and miRNA expression profiles as well as miRNA processing machinery associated with alterations in NF-κB, β-catenin, and mitogen-activated protein kinase (MAPK) signaling. Additional studies using immunohistochemical analyses found that indeed GSE inhibits NF-κB activation and decreases the expression of its downstream targets (COX-2, iNOS, VEGF) related to inflammatory signaling, downregulates β-catenin signaling and decreases its target gene c-myc, and reduces phosphorylated extracellular signal-regulated kinase (ERK)1/2 levels. Together, these finding suggested that inflammation, proliferation, and apoptosis are targeted by GSE to prevent CRC. In summary, this study for the first time shows alterations in the expression of miRNAs and cytokines by GSE in its efficacy against AOM-induced colon tumorigenesis in A/J mouse sporadic CRC model, supporting its translational potential in CRC chemoprevention.