Background: Grape seed extract contains an abundance of oligomeric proanthocyanidins (OPCs) (monomers, dimers and trimers) and a small fraction of larger polymers. Although the anti-cancer properties of OPCs from grape seeds have been well recognized, the molecular mechanisms by which they exert anti-cancer effects are poorly understood.
Purpose: Herein, we cognize the underlying molecular mechanisms of the anti-cancer properties of OPCs by identifying their downstream transcriptional targets.
Methods: First, we assessed the anti-tumorigenic properties of OPCs from grape seeds in colorectal cancer (CRC) cells by proliferation assay, cell cycle analysis and cell migration assay. We then examined the global changes in gene expression induced by OPCs by RNA-sequencing based gene-expression profiling in a panel of CRC cell lines, including HCT116, SW480, SW620, RKO and HT29. We thereafter validated the RNA-sequencing results in HCT116 and SW480 cells, in a xenograft animal model, and in patient-derived organoid models.
Results: We observed that OPCs from grape seeds inhibited cell proliferation, induced cell cycle arrest and inhibited cancer cell migration in CRC cell lines. Additionally, OPCs downregulated EMT-inducing genes ZEB1, ZEB2 and SNAI1, and upregulated epithelial marker E-cadherin. The RNA-sequencing identified differentially expressed genes following OPC treatment, and the KEGG pathway analysis revealed that genes involved in the cell cycle (p=3.63e-09) and DNA replication (p=1.49e-09) were the most significantly modulated pathways across all cell lines. A closer look at these pathways revealed the downregulation of well-characterized oncogenes, including TGFβ3, E2F1 and CCNE2, and the upregulation of tumor suppressor genes SFN, CDKN1A and MAD1L1. We subsequently validated the modulation of these genes independently in cell lines, mice xenografts and patient-derived tumor organoids. Intriguingly, our in vivo experiments revealed that OPCs more potently decreased xenograft tumor growth vs. the unfractionated grape seed extract (GSE) that includes larger polymers of proanthocyanidins, and inhibited organoid formation from patient-derived tumors more robustly than GSE.
Conclusions: We, for the first time, illuminated the genome-wide effects of OPCs from grape seeds in CRC. First, we showed that OPCs modulated multiple cancer-associated cellular pathways, especially the cell cycle and DNA replication. In addition to mice models, we validated the anti-cancer effects of OPCs in a pre-clinical patient-derived tumor organoid models. Secondly, we showed that OPCs have higher efficacy in tumor inhibition in mice xenografts than GSE, possibly due to better absorbability. Consequently, as OPCs block various oncogenic pathways, it could prevent the emergence of acquired resistance in cancer patients undergoing targeted therapies.
Citation Format: Preethi Ravindranathan, Divya Pasham, Uthra Balaji, Shusuke Toden, Ajay Goel. Global transcriptomic profiling reveals anticancer role of oligomeric proanthocyanidins from grape seeds in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2682.