The cancer-preventive activities of quercetin have been extensively studied in invasive breast cancer; however, the role of quercetin on triple-negative breast cancer (TNBC) with overexpression of insulin-like growth factor-1 receptor (IGF1R) has not been resolved. In this article, we demonstrated that quercetin inhibited the activation of IGF1R and its downstream kinases Akt and Erk1/2 in a dose-dependent manner in human MDA-MB-231 breast cancer cells (TNBC cell line). Related to this, quercetin markedly suppressed the metastatic phenotype and epithelial–mesenchymal transition (EMT) of MDA-MB-231 cells by inhibiting the expression of EMT transcription factors Snail and Slug. Quercetin also increased the secretion of IGF-binding protein-3 in the conditioned medium of MDA-MB-231 cells while reducing the secretion of IGF1; thus, quercetin interrupted the autocrine or paracrine loop of IGF1 signaling. In xenograft mouse models, the administration of quercetin blocked the growth of MDA-MB-231 tumor xenografts and their lung metastasis, accompanied by the inactivation of IGF1R and the downregulation of the expression of Snail, Slug, and mesenchymal markers fibronectin and vimentin. These results suggest that quercetin has cancer-preventive value for TNBC by inhibiting IGF1/IGF1R signaling and preventing the consequent EMT and metastasis of TNBC.

Background: Prostate cancer is highly prevalent with a high mortality among males worldwide. Naringenin has been demonstrated to exhibit multiple cellular functions. In this study, we examined the effects of naringenin on prostate cancer. Materials and Methods: Transwell and zymography assays were used to detect cell migration and urokinase plasminogen activator (uPA) activity, respectively. Alternation of protein expression was measured by western blot analysis. Results: Transwell assay and zymography revealed that naringenin suppressed the migration and invasion of PC-3 cells and uPA activity in proportion to the concentration of naringenin. Western blot analysis indicated that naringenin up-regulated E-cadherin expression, but down-regulated the expression of vimentin, SNAIL family zinc finger 1 (SNAI1), SNAIL family zinc finger 2 (SNAI2), and TWIST family bHLH transcription factor 1 (TWIST1). Conclusion: Naringenin inhibited the migration and invasion of PC-3 cells by reversing expression of proteins involved in epithelial–to–mesenchymal transition and down-regulation of uPA activity. Thus, naringenin may be a promising anti-metastasis agent for prostate cancer.

Huntington’s disease (HD) is a progressive and fatal neurodegenerative disease caused by CAG repeat expansion in the coding region of huntingtin (HTT) protein. The accumulation of mutant HTT (mHTT) contributes to neurotoxicity by causing autophagy defects and oxidative stress that ultimately lead to neuronal death. Interestingly, epidemiologic studies have demonstrated that the prevalence of type-2 diabetes, a metabolic disease mainly caused by defective insulin signaling, is higher in patients with HD than in healthy controls. Although the precise mechanisms of mHTT-mediated toxicity remain unclear, the blockade of brain insulin signaling may initiate or exacerbate mHTT-induced neurodegeneration. In this study, we used an in vitro HD model to investigate whether neuronal insulin signaling is involved in mHTT-mediated neurotoxicity. Our results demonstrated that mHTT overexpression significantly impairs insulin signaling and causes apoptosis in neuronal cells. However, treatment with liraglutide, a GLP-1 analogue, markedly restores insulin sensitivity and enhances cell viability. This neuroprotective effect may be attributed to the contribution of the upregulated expression of genes associated with endogenous antioxidant pathways to oxidative stress reduction. In addition, liraglutide stimulates autophagy through AMPK activation, which attenuates the accumulation of HTT aggregates within neuronal cells. Our findings collectively suggest that liraglutide can rescue impaired insulin signaling caused by mHTT and that GLP-1 may potentially reduce mHTT-induced neurotoxicity in the pathogenesis of HD.

Invasive breast cancer is the major cause of death among females and its incidence is closely linked to HER2 (human epidermal growth factor receptor 2) overexpression. Pterostilbene, a natural analog of resveratrol, exerts its cancer chemopreventive activity similar to resveratrol by inhibiting cancer cell proliferation and inducing apoptosis. However, the anti‐invasive effect of pterostilbene on HER2‐bearing breast cancer has not been evaluated. Here, we used heregulin‐β1 (HRG‐β1), a ligand for HER3, to transactivate HER2 signaling. We found that pterostilbene was able to suppress HRG‐β1‐mediated cell invasion, motility and cell transformation of MCF‐7 human breast carcinoma through down‐regulation of matrix metalloproteinase‐9 (MMP‐9) activity and growth inhibition. In parallel, pterostilbene also inhibited protein and mRNA expression of MMP‐9 driven by HRG‐β1, suggesting that pterostilbene decreased HRG‐β1‐mediated MMP‐9 induction via transcriptional regulation. Examining the signaling pathways responsible for HRG‐β1‐associated MMP‐9 induction and growth inhibition, we observed that pterostilbene, as well as SB203580 (p38 kinase inhibitor), can abolish the phosphorylation of p38 mitogen‐activated protein kinase (p38 kinase), a downstream HRG‐β1‐responsive kinase responsible for MMP‐9 induction. In addition, HRG‐β1‐driven Akt phosphorylation required for cell proliferation was also suppressed by pterostilbene. Taken together, our present results suggest that pterostilbene may serve as a chemopreventive agent to inhibit HRG‐β1/HER2‐mediated aggressive and invasive phenotype of breast carcinoma through down‐regulation of MMP‐9, p38 kinase and Akt activation.

Huntington’s disease (HD) is an autosomal-dominant brain disorder caused by mutant huntingtin (mHtt). Although the detailed mechanisms remain unclear, the mutational expansion of polyglutamine in mHtt is proposed to induce protein aggregates and neuronal toxicity. Previous studies have shown that the decreased insulin sensitivity is closely related to mHtt-associated impairments in HD patients. However, how mHtt interferes with insulin signaling in neurons is still unknown. In the present study, we used a HD cell model to demonstrate that the miR-302 cluster, an embryonic stem cell-specific polycistronic miRNA, is significantly downregulated in mHtt-Q74-overexpressing neuronal cells. On the contrary, restoration of miR-302 cluster was shown to attenuate mHtt-induced cytotoxicity by improving insulin sensitivity, leading to a reduction of mHtt aggregates through the enhancement of autophagy. In addition, miR-302 also promoted mitophagy and stimulated Sirt1/AMPK-PGC1α pathway thereby preserving mitochondrial function. Taken together, these results highlight the potential role of miR-302 cluster in neuronal cells, and provide a novel mechanism for mHtt-impaired insulin signaling in the pathogenesis of HD.