Abstract 4721: An ethanol extract from black raspberries inhibits myeloid cell differentiation, STAT3 phosphorylation and alters T lymphocyte chemotaxis by upregulating CXCR3.

Abstract

Abstract Black raspberries may benefit health as a whole food via their ability to provide complex mixtures of phytochemicals, or as a source of lead compounds for future drug development. In particular, bioactive components from black raspberries have been shown to inhibit proliferation and promote apoptosis of both premalignant and malignant cells. Other reports have also demonstrated that administration of a diet enriched with black raspberries inhibits carcinogenesis in pre-clinical tumor models. Despite these results, little is known regarding the mechanisms by which black raspberries or their bioactive phytochemicals modulate immunologic factors relevant to tumor development and progression. We hypothesized that black raspberries elicit potent immunomodulatory properties that impact cellular mediators relevant to cancer and chronic inflammation. We show that an ethanol extract from black raspberries (BRB-E) significantly inhibited proliferation of activated CD4+ and CD8+ T lymphocytes by CFSE dilution and flow cytometric analysis (p<0.05). In addition, BRB-E significantly enhanced the chemotaxis of CD3/CD28-activated CD8+ T lymphocytes in transwell assays using monokine-induced by gamma (MIG) as an attractant (p=0.01). This enhanced chemotaxis was associated with upregulation the expression of CXCR3 (the receptor for MIG) on CD8+ T lymphocytes. BRB-E also inhibited expansion of myeloid derived suppressor cells (MDSC) from peripheral blood mononuclear cells (PBMCs) cultured with IL-6 + GM-CSF in vitro. Consistent with the reduction in MDSC, pre-treatment of immune cells with BRB E attenuated IL-6-mediated phosphorylation of signal transducer and activator of transcription-3 (STAT3) as determined by immunoblot. We next studied the immunomodulatory effects of anthocyanin and quercitin, two prominent compounds present when BRB-E is metabolized in vivo. Indeed, CD4+ and CD8+ T cell proliferation was significantly inhibited when treated with Cyanidin-3-rutinoside (C3R, anthocyanin metabolite), but not quercitin-3-rutinoside (Q3R, quercitin metabolite) (p<0.05). Similar to cells cultured in BRB-E, C3R also inhibited IL-6 induced pSTAT3. Together these data indicate that bioactive components present within black raspberries or their metabolites possess immunomodulatory properties that deserve further investigation for benefit of chronic inflammation and aberrant expansion of MDSC associated with malignancy. Citation Format: Thomas A. Mace, Zeenath Ameen, Christopher M. Weghorst, Thomas J. Knobloch, Gregory B. Lesinski. An ethanol extract from black raspberries inhibits myeloid cell differentiation, STAT3 phosphorylation and alters T lymphocyte chemotaxis by upregulating CXCR3. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4721. doi:10.1158/1538-7445.AM2013-4721