Cytotoxicity of pomegranate polyphenolics in breast cancer cells in vitro and vivo: potential role of miRNA-27a and miRNA-155 in cell survival and inflammation

Abstract

Several studies have demonstrated that polyphenolics from pomegranate (Punica granatum L.) are potent inhibitors of cancer cell proliferation and induce apoptosis, cell cycle arrest, and also decrease inflammation in vitro and vivo. There is growing evidence that botanicals exert their cytotoxic and anti-inflammatory activities, at least in part, by decreasing specificity protein (Sp) transcription factors. These are overexpressed in breast-tumors and regulate genes important for cancer cell survival and inflammation such as the p65 unit of NF-κB. Moreover, previous studies have shown that Pg extracts decrease inflammation in lung cancer cell lines by inhibiting phosphatidylinositol 3,4,5-trisphosphate (PI3K)-dependent phosphorylation of AKT in vitro and inhibiting the activation of NF-kB in vivo. The objective of this study was to investigate the roles of miR-27a-ZBTB10-Sp and miR-155-SHIP-1-PI3K on the anti-inflammatory and cytotoxic activity of pomegranate extract. Pg extract (2.5–50 µg/ml) inhibited growth of BT-474 and MDA-MB-231 cells but not the non-cancer MCF-10F and MCF-12F cells. Pg extract significantly decreased Sp1, Sp3, and Sp4 as well as miR-27a in BT474 and MDA-MB-231 cells and increased expression of the transcriptional repressor ZBTB10. A significant decrease in Sp proteins and Sp-regulated genes was also observed. Pg extract also induced SHIP-1 expression and this was accompanied by downregulation of miRNA-155 and inhibition of PI3K-dependent phosphorylation of AKT. Similar results were observed in tumors from nude mice bearing BT474 cells as xenografts and treated with Pg extract. The effects of antagomirs and knockdown of SHIP-1 by RNA interference confirmed that the anti-inflammatory and cytotoxic effects of Pg extract were partly due to the disruption of both miR-27a-ZBTB10 and miR-155-SHIP-1. In summary the anticancer activities of Pg extract in breast cancer cells were due in part to targeting microRNAs155 and 27a. Both pathways play an important role in the proliferative/inflammatory phenotype exhibited by these cell lines

Pomegranate exerts chemoprevention of experimentally induced mammary tumorigenesis by suppression of cell proliferation and induction of apoptosis

“…For example, fermented pomegranate polyphenols, pomegranate juice polyphenols and pomegranate seed oil were found to substantially reduce (42-87%) the number of mammary lesions inflicted by DMBA in a murine mammary gland culture model (30,36). Moreover, an oral pomegranate juice concentrate significantly depressed the volume of BT474 xenografts in nude mice (34). Our present results on anti-breast carcinogenic effect of PE in vivo are in agreement with our previous findings that PE exhibits substantial chemopreventive action against chemically induced rat liver carcinogenesis through multiple cellular and molecular mechanisms (40,46,47).…”

“…Several pomegranate products and phytochemicals inhibited the growth of both estrogen receptor-positive (MCF-7 and BT-474) and -negative (MB-MDA-231) breast carcinoma cell lines (30)(31)(32)(33)(34)(35), mammary organ culture (36), MMTV-Wnt-1 mouse mammary cancer stem cells (37), suppressed the motility and invasion of aggressive breast cancer cells, e.g., MDA-231 and SUM 149 (38), and stimulated adhesion and inhibited the migration and chemotaxis (reminiscent of metastatic behavior) of MCF-7 and MDA-231 cells (39). Pomegranate juice concentrate was found to reduce the volume and weight of xenografted BT-474 tumors in athymic nude mice (34). There is no published report on in vivo chemopreventive effect of pomegranate against breast cancer to the best of our knowledge and belief.…”

Identification of p130Cas/ErbB2-dependent invasive signatures in transformed mammary epithelial cells

“…54,55 Downregulation of genes that trigger proliferation has been already observed in invasive cells, indicating that a reduced proliferation is required for cells to turn on the invasive program. 56 An anti-correlation between miRNAs and putative target genes was found for the downregulated miR-23b, miR-27a, and miR-27b.…”

Dietary flaxseed modulates the miRNA profile in irradiated and non-irradiated murine lungs

“…42 miRNAs can be modulated by botanicals in lung cancer. [43][44][45][46] The effects of curcumin on a human retinal pigment epithelial cell line, ARPE-19, included downregulation of 20 and upregulation of 9 miRNAs. 47 Effects of resveratrol on miRNA have also been studied.…”