Involvement of AMP-activated protein kinase in mediating pyrrolo-1,5-benzoxazepine–induced apoptosis in neuroblastoma cells

A Synthetic Overview of Benzoxazines and Benzoxazepines as Anticancer Agents

Benzoxazines and benzoxazepines are nitrogen and oxygen-containing six and seven-membered benzo-fused heterocyclic scaffolds, respectively. Benzoxazepines and benzoxazines are well-known pharmacophores in pharmaceutical chemistry, which are of significant interest and have been extensively studied because of their promising activity against various diseases including their wide range of anticancer activity. Several reports are known for synthesizing benzoxazine and benzoxazepine-based compounds in the literature. Herein this review provides a critical analysis of synthetic strategies towards benzoxazines and benzoxazepines along with various ranges of anticancer activities based on these molecules that have been reported from 2010 onwards. This review also focuses on the structure-activity relationship of the benzoxazine and benzoxazepine scaffolds containing bioactive compounds and describes how the structural modification affects their anticancer activity.

1,5-Benzoxazepines as a unique and potent scaffold for activity drugs: A review

Benzoxazepines constitute a huge number of organic compounds widely described in the literature. Many of them are distinguished by their biological properties. Among them, our attention was drawn to 1,5-benzoxazepine derivatives due to their interesting pharmacological properties. As is reported in the literature, these compounds are not only good building blocks in organic synthesis but also have interesting biological and pharmacological properties. This article is the first review publication to describe the synthesis methods and unique properties of 1,5-benzoxazepines. Literature reports widely describe the biological properties of 1,5-benzoxazepine, like anticancer, antibacterial, or antifungal activities. 1,5-Benzoxazepine derivatives can also interact with G-protein-coupled receptors and could be incorporated into new potential drugs, among others, in treating neuronal disorders like Alzheimer's and Parkinson's disease.

Disruption of the exocyst induces podocyte loss and dysfunction

Although the slit diaphragm proteins in podocytes are uniquely organized to maintain glomerular filtration assembly and function, little is known about the underlying mechanisms that participate in trafficking these proteins to the correct location for development and homeostasis. Identifying these mechanisms will likely provide novel targets for therapeutic intervention to preserve podocyte function following glomerular injury. Analysis of structural variation in cases of human nephrotic syndrome identified rare heterozygous deletions of EXOC4 in two patients. This suggested that disruption of the highly-conserved eight-protein exocyst trafficking complex could have a role in podocyte dysfunction. Indeed, mRNA profiling of injured podocytes identified significant exocyst down-regulation. To test the hypothesis that the exocyst is centrally involved in podocyte development/function, we generated homozygous podocyte-specific Exoc5 (a central exocyst component that interacts with Exoc4) knockout mice that showed massive proteinuria and died within 4 weeks of birth. Histological and ultrastructural analysis of these mice showed severe glomerular defects with increased fibrosis, proteinaceous casts, effaced podocytes, and loss of the slit diaphragm. Immunofluorescence analysis revealed that Neph1 and Nephrin, major slit diaphragm constituents, were mislocalized and/or lost. mRNA profiling of Exoc5 knockdown podocytes showed that vesicular trafficking was the most affected cellular event. Mapping of signaling pathways and Western blot analysis revealed significant up-regulation of the mitogen-activated protein kinase and transforming growth factor-β pathways in Exoc5 knockdown podocytes and in the glomeruli of podocyte-specific Exoc5 KO mice. Based on these data, we propose that exocyst-based mechanisms regulate Neph1 and Nephrin signaling and trafficking, and thus podocyte development and function.

Structure-activity relationships, biological evaluation and structural studies of novel pyrrolonaphthoxazepines as antitumor agents

Microtubule-targeting agents (MTAs) are a class of clinically successful anti-cancer drugs. The emergence of multidrug resistance to MTAs imposes the need for developing new MTAs endowed with diverse mechanistic properties. Benzoxazepines were recently identified as a novel class of MTAs. These anticancer agents were thoroughly characterized for their antitumor activity, although, their exact mechanism of action remained elusive. Combining chemical, biochemical, cellular, bioinformatics and structural efforts we developed improved pyrrolonaphthoxazepines antitumor agents and their mode of action at the molecular level was elucidated. Compound 6j, one of the most potent analogues, was confirmed by X-ray as a colchicine-site MTA. A comprehensive structural investigation was performed for a complete elucidation of the structure-activity relationships. Selected pyrrolonaphthoxazepines were evaluated for their effects on cell cycle, apoptosis and differentiation in a variety of cancer cells, including multidrug resistant cell lines. Our results define compound 6j as a potentially useful optimized hit for the development of effective compounds for treating drug-resistant tumors.

3‑Bromopyruvate sensitizes human breast cancer cells to TRAIL‑induced apoptosis via the phosphorylated AMPK‑mediated upregulation of DR5

Previous studies have indicated that the sensitivity of breast cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis is associated with the expression of death receptors on the cell membrane. However, drug resistance limits the use of TRAIL in cancer therapy. Numerous studies have indicated that death receptors, which induce apoptosis, are upregulated by the endoplasmic reticulum (ER) stress response. 3-Bromopyruvate (3-BP), an anticancer agent, inhibits cell growth and induces apoptosis through interfering with glycolysis. In the present study, it was demonstrated that 3-BP synergistically sensitized breast cancer cells to TRAIL-induced apoptosis via the upregulation of death receptor 5 (DR5). Furthermore, we found that the protein levels of glucose-related protein 78 (GRP78) and CCAAT-enhancer-binding protein homologous protein (CHOP) increased following treatment with 3-BP. The expression of Bax (in MCF-7 cells) and caspase-3 (in MDA-MB-231 cells) increased following co-treatment with 3-BP and TRAIL, whereas the expression of the anti-apoptotic protein Bcl-2 decreased. In order to investigate the molecular mechanism regulating this effect, the expression of adenosine monophosphate-activated protein kinase (AMPK), activated by 3-BP, was determined. It was demonstrated that phosphorylated-AMPK was upregulated following treatment with 3-BP. Notably, Compound C, an AMPK inhibitor, reversed the effects of 3-BP. Finally, a synergistic antitumor effect of 3-BP and TRAIL was observed in MCF-7 cell xenografts in nude mice. In conclusion, these results indicated that 3-BP sensitized breast cancer cells to TRAIL via the AMPK-mediated upregulation of DR5.

GDM-Induced Macrosomia Is Reversed by Cav-1 via AMPK-Mediated Fatty Acid Transport and GLUT1-Mediated Glucose Transport in Placenta

Objective

To investigate if the role of Cav-1 in GDM-induced macrosomia is through regulating AMPK signaling pathway in placenta.

Methods

We used diagnostic criteria of gestational diabetes mellitus (GDM) and macrosomia to separate and compare placental protein and mRNA levels from GDM with macrosomia group (GDMM), GDM with normal birth weight group (GDMN) and normal glucose tolerance (NGT) with normal birth weight group (CON). Western blotting was performed to examine differentially expressed proteins of caveolin-1 (Cav-1) and Adenosine monophosphate-activated protein kinase (AMPK) signaling pathway related proteins, including phosphorylated-AMPKα(Thr172), AMPKα, phosphorylated-Acetyl-CoA carboxylase(Ser79) (p-ACC(Ser79)), ACC and glucose transporter 1 (GLUT1) in placenta between the three groups. The mRNA levels of Cav-1, AMPKα, ACC and GLUT1 in placenta were measured by real time-PCR.

Results

In the GDMM placenta group, both protein and mRNA levels of Cav-1 were down-regulated, while GLUT1 was up-regulated; the phosphorylation and mRNA levels of ACC and AMPKα were decreased, but total ACC protein levels were increased compared to both the GDMN (p<0.05) and CON groups (p<0.05). In GDMM placenta group, there was a significant negative correlation observed between neonatal birth weight (NBW) and protein expression levels of Cav-1, p-ACC(Ser79) and p-AMPKα(Thr172) (p<0.05), while positive relationship with ACC and GLUT1 protein levels. Besides, in GDMM group placental mRNA levels, NBW had a positive correlation with GLUT1 (p<0.05), while negative with Cav-1, AMPKα and ACC expression (p<0.05). Cav-1 protein expression was positively associated with p-AMPK and p-ACC (p<0.05), and negatively associated with GLUT1 (p<0.05). Interestingly, p-AMPK protein expression was closely related to p-ACC (p<0.05), but not with GLUT1.

Conclusion

GDM-induced macrosomias have more severe inhibition of Cav-1 expression in placenta. Cav-1 is associated with placental glucose and fatty acid transport via the induction of AMPK signaling pathway and the reduction of GLUT1 signaling pathway to reverse GDM-induced macrosomia.

Isoorientin induces apoptosis, decreases invasiveness, and downregulates VEGF secretion by activating AMPK signaling in pancreatic cancer cells

Isoorientin (or homoorientin) is a flavone, which is a chemical flavonoid-like compound, and a 6-C-glucoside of luteolin. Isoorientin has been demonstrated to have anti-cancer activities against various tumors, but its effects on pancreatic cancer (PC) have not been studied in detail. In this study, we aim to investigate whether isoorientin has potential anti-PC effects and its underlying mechanism. In PC, isoorientin strongly inhibited the survival of the cells, induced cell apoptosis, and decreased its malignancy by reversing the expression of epithelial-mesenchymal transition and matrix metalloproteinase and decreased vascular endothelial growth factor expression. Meanwhile, we investigated the activity of the AMP-activated protein kinase (AMPK) signaling pathway after isoorientin treatment, which was forcefully activated by isoorientin, as expected. In addition, in the PC cells that were transfected with lentivirus to interfere with the expression of the gene PRKAA1, there were no differences in the apoptosis rate and the expression of malignancy biomarkers in the tumors of the isoorientin-treated and untreated groups. Thus, we demonstrated that isoorientin has potential antitumor effects via the AMPK signaling pathway, and isoorientin merits further investigation.