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The stemness and metastasis of cancer cells are crucial features in determining cancer progression. Argonaute-2 (AGO2) overexpression was reported to be associated with microRNA (miRNA) biogenesis, supporting the self-renewal and differentiation characteristics of cancer stem cells (CSCs). Ursolic acid (UA), a triterpene compound, has multiple biological functions, including anticancer activity. In this study, we find that UA inhibits the proliferation of MDA-MB-231 and MCF-7 breast cancer cell lines using the CCK-8 assay. UA induced a significant decrease in the fraction of CSC in which it was examined by changes in the expression of stemness biomarkers, including the Nanog and Oct4 genes. UA altered invasion and migration capacities by significant decreases in the levels of epithelial-to-mesenchymal transition (EMT) proteins of slug and vimentin. Furthermore, the co-reduction in oncogenic miRNA levels (miR-9 and miR-221) was a result of the down-modulation in AGO2 in breast cancer cells in vitro. Mechanically, UA increases PTEN expression to inactivate the FAK/PI3K/Akt/mTOR signaling pathway and the decreased level of c-Myc in quantitative RT-PCR and Western blot imaging analyses. Our current understanding of the anticancer potential of UA in interrupting between EMT programming and the state of CSC suggests that UA can contribute to improvements in the clinical practice of breast cancer. [ABSTRACT FROM AUTHOR]

The anti-tumor activity of diosgenin, a new steroidal constituent present in fenugreek, on two human breast cancer cell lines, MCF-7 and Hs578T, was studied. Diosgenin treatment resulted in cell growth inhibition, cell cycle arrest, and apoptosis in concentration- and time-dependent manners in both cell lines. Western blot analyses of whole cell lysates for cell cycle proteins showed that diosgenin altered phosphorylated cyclin checkpoint1 (p-Chk1Ser345) and cyclin B expression, which resulted in G2/M phase blockade. Mechanistically, Cdc25C-Cdc2 signaling was involved in inactivating Chk1Ser345 by p53-dependence in MCF-7 cells and p21-dependence in Hs578T cells that are p53-deficient. Moreover, diosgenin induced a significant loss of the mitochondrial membrane potential in breast cancer cells, and prominently affected cell death through down-regulation of the anti-apoptotic protein, Bcl-2. This released cytochrome c and activated the caspase signaling cascade. Taken together, these findings reveal that the anti-proliferative activity of diosgenin involves the induction of G2/M phase arrest via modulating the Cdc25C-Cdc2-cyclin B pathway and mitochondria-mediated apoptosis in human breast cancer cell lines. This suggests the potential usefulness of diosgenin in treating breast cancer. [ABSTRACT FROM AUTHOR]

Resveratrol functions as an agonist for estrogen receptor (ER)-mediated transcription. However, other researchers have reported that resveratrol decreases proliferation of breast cancer cells that are either ER-positive or ER-negative, which suggests that the interaction of resveratrol with the ER may not fully explain its inhibitory effect on proliferation. Similar to those effects associated with caloric restriction (CR), resveratrol has multiple beneficial activities, such as increased life span and delay in the onset of diseases associated with aging. One key enzyme thought to be activated during CR is the AMP-activated kinase (AMPK), a sensor of cellular energy levels. The suppression of nonessential energy expenditure by activated AMPK along with the CR mimetic and antiproliferative properties of resveratrol has led us to hypothesize that resveratrol activity might have an important role in the activation of AMPK. Here, we show that resveratrol activated AMPK in both ER-positive and ER-negative breast cancer cells. Once activated, AMPK inhibited 4E-BP1 signaling and mRNA translation via mammalian target of rapamycin (mTOR). Moreover, we also found that AMPK activity mediated by resveratrol in cancer cells was due to inducing the expression of Sirtuin type 1 (SIRT1) via elevation in the cellular NAD(+)/NADH in ER-positive cells. To our knowledge, we demonstrate here for the first time that resveratrol induces the expression of SIRT1 protein in human cancer cells. These observations raise the possibility that SIRT1 functions as a novel upstream regulator for AMPK signaling and may additionally modulate tumor cell proliferation. Targeting SIRT1/AMPK signaling by resveratrol may have potential therapeutic implications for cancer and age-related diseases.

Phage display has been used to engineer DNA-binding proteins with new sequence specificities, which has allowed applications in the blockage or enhancement of gene expression as well as targeting specific sites on DNA for methylation, recombination, and cleavage. To effectively and quickly conduct selections that consider the synergistic mode of DNA binding by zinc fingers, Isalan and Choo in Aaron Klug's lab devised a bipartite phage display approach that enables selection and recombination of variants of zinc finger DNA-binding domains from a pair of premade complementary phage libraries for any given 9-bp DNA sequence. The bipartite phage display has the advantage of rapid, high-throughput selection of sequence-specific zinc finger DNA-binding domains for use in diverse applications of expression control and gene targeting.