Indole-3-carbinol inhibits prostate cancer cell migration via degradation of beta-catenin

AhR and Wnt/β-Catenin Signaling Pathways and Their Interplay

As evolutionarily conserved signaling cascades, AhR and Wnt signaling pathways play a critical role in the control over numerous vital embryonic and somatic processes. AhR performs many endogenous functions by integrating its signaling pathway into organ homeostasis and into the maintenance of crucial cellular functions and biological processes. The Wnt signaling pathway regulates cell proliferation, differentiation, and many other phenomena, and this regulation is important for embryonic development and the dynamic balance of adult tissues. AhR and Wnt are the main signaling pathways participating in the control of cell fate and function. They occupy a central position in a variety of processes linked with development and various pathological conditions. Given the importance of these two signaling cascades, it would be interesting to elucidate the biological implications of their interaction. Functional connections between AhR and Wnt signals take place in cases of crosstalk or interplay, about which quite a lot of information has been accumulated in recent years. This review is focused on recent studies about the mutual interactions of key mediators of AhR and Wnt/β-catenin signaling pathways and on the assessment of the complexity of the crosstalk between the AhR signaling cascade and the canonical Wnt pathway.

From Nucleus to Organs: Insights of Aryl Hydrocarbon Receptor Molecular Mechanisms

The aryl hydrocarbon receptor (AHR) is a markedly established regulator of a plethora of cellular and molecular processes. Its initial role in the detoxification of xenobiotic compounds has been partially overshadowed by its involvement in homeostatic and organ physiology processes. In fact, the discovery of its ability to bind specific target regulatory sequences has allowed for the understanding of how AHR modulates such processes. Thereby, AHR presents functions in transcriptional regulation, chromatin architecture modifications and participation in different key signaling pathways. Interestingly, such fields of influence end up affecting organ and tissue homeostasis, including regenerative response both to endogenous and exogenous stimuli. Therefore, from classical spheres such as canonical transcriptional regulation in embryonic development, cell migration, differentiation or tumor progression to modern approaches in epigenetics, senescence, immune system or microbiome, this review covers all aspects derived from the balance between regulation/deregulation of AHR and its physio-pathological consequences.

The interplay of aryl hydrocarbon receptor/WNT/CTNNB1/Notch signaling pathways regulate amyloid beta precursor mRNA/protein expression and effected the learning and memory of mice

The amyloid beta precursor protein (APP) plays a pathophysiological role in the development of Alzheimer's disease as well as a physiological role in neuronal growth and synaptogenesis. The aryl hydrocarbon receptor (AhR)/WNT/Catenin Beta 1 (CTNNB1)/Notch signaling pathways stamp in many functions, including development and growth of neurons. However, the regulatory role of AhR-/WNT-/CTNNB1-/Notch-induced APP expression and its influence on hippocampal-dependent learning and memory deficits is not clear. Male BALB/C mice received 6-formylindolo[3,2-b]carbazole (an AhR agonist), CH223191(an AhR antagonist), DAPT (an inhibitor of Notch signaling), and XAV-939 (a WNT pathway inhibitor) at a single dose of 100 μg/kg, 1, 5 , and 5 mg/kg of body weight, respectively, via intraperitoneal injection alone or in combination. Gene expression analyses and protein assay were performed on the 7th and 29th days. To assess the hippocampal-dependent memory, all six mice also underwent contextual fear conditioning on the 28th day after treatments. Our results showed that endogenous ligand of AhR has a regulatory effect on APP gene. Also, the interaction of AhR/WNT/CTNNB1 has a positive regulatory effect, but Notch has a negative regulatory effect on the mRNA and protein expression of APP, which have a correlation with mice's learning skills and memory.

A Comprehensive Gene Inventory for Glucosinolate Biosynthetic Pathway in Arabidopsis thaliana

Glucosinolates (GSLs) are plant secondary metabolites comprising sulfur and nitrogen mainly found in plants from the order of Brassicales, such as broccoli, cabbage, and Arabidopsis thaliana. The activated forms of GSL play important roles in fighting against pathogens and have health benefits to humans. The increasing amount of data on A. thaliana generated from various omics technologies can be investigated more deeply in search of new genes or compounds involved in GSL biosynthesis and metabolism. This review describes a comprehensive inventory of A. thaliana GSLs identified from published literature and databases such as KNApSAcK, KEGG, and AraCyc. A total of 113 GSL genes encoding for 23 transcription components, 85 enzymes, and five protein transporters were experimentally characterized in the past two decades. Continuous efforts are still on going to identify all molecules related to the production of GSLs. A manually curated database known as SuCCombase (http://plant-scc.org) was developed to serve as a comprehensive GSL inventory. Realizing lack of information on the regulation of GSL biosynthesis and degradation mechanisms, this review also includes relevant information and their connections with crosstalk among various factors, such as light, sulfur metabolism, and nitrogen metabolism, not only in A. thaliana but also in other crucifers.

Recent progress in natural dietary non-phenolic bioactives on cancers metastasis

From several decades ago to now, cancer continues to be the leading cause of death worldwide, and metastasis is the major cause of cancer-related deaths. For health benefits, there is a great desire to use non-chemical therapy such as nutraceutical supplementation to prevent pathology development. Over 10,000 different natural bioactives or phytochemicals have been known that possessing potential preventive or supplementary effects for various diseases including cancer. Previously, the in vitro and in vivo anti-invasive and anti-metastatic activities of phenolic acids, monophenol, polyphenol and their derivatives and flavonoids and their derivatives have been reviewed. However, a vast number of natural dietary compounds other than phenolics have been demonstrated to potentially possess the ability to inhibit the invasion and metastasis of various cancers. In this review, we summarize the studies in recent decade on in vitro and in vivo effects and molecular mechanisms of natural bioactives, excluding the phenolics in food, in cancer invasion and metastasis. By combining this review of non-phenolics with the previous phenolics reviews, the puzzle for the contribution of natural dietary bioactives on cancer invasive or/and metastatic progress will be almost complete and more clear.

1-Benzyl-indole-3-carbinol is a highly potent new small molecule inhibitor of Wnt/β-catenin signaling in melanoma cells that coordinately inhibits cell proliferation and disrupts expression of microphthalmia-associated transcription factor isoform-M

1-Benzyl-indole-3-carbinol (1-benzyl-I3C), a synthetic analogue of the crucifer-derived natural phytochemical I3C, displayed significantly wider sensitivity and anti-proliferative potency in melanoma cells than the natural compound. Unlike I3C, which targets mainly oncogenic BRAF-expressing cells, 1-benzyl-I3C effectively inhibited proliferation of melanoma cells with a more extensive range of mutational profiles, including those expressing wild-type BRAF. In both cultured melanoma cell lines and in vivo in melanoma cell-derived tumor xenografts, 1-benzyl-I3C disrupted canonical Wnt/β-catenin signaling that resulted in the downregulation of β-catenin protein levels with a concomitant increase in levels of the β-catenin destruction complex components such as glycogen synthase kinase-3β (GSK-3β) and Axin. Concurrent with the inhibition of Wnt/β-catenin signaling, 1-benzyl-I3C strongly downregulated expression of the melanoma master regulator, microphthalmia-associated transcription factor isoform-M (MITF-M) by inhibiting promoter activity through the consensus lymphoid enhancer factor-1 (LEF-1)/T-cell transcription factor (TCF) DNA-binding site. Chromatin immunoprecipitation revealed that 1-benzyl-I3C downregulated interactions of endogenous LEF-1 with the MITF-M promoter. 1-Benzyl-I3C ablated Wnt-activated LEF-1-dependent reporter gene activity in a TOP FLASH assay that was rescued by expression of a constitutively active form of the Wnt co-receptor low-density lipoprotein receptor-related protein (LRP6), indicating that 1-benzyl-I3C disrupts Wnt/β-catenin signaling at or upstream of LRP6. In oncogenic BRAF-expressing melanoma cells, combinations of 1-benzyl-I3C and Vemurafenib, a clinically employed BRAF inhibitor, showed strong anti-proliferative effects. Taken together, our observations demonstrate that 1-benzyl-I3C represents a new and highly potent indolecarbinol-based small molecule inhibitor of Wnt/β-catenin signaling that has intriguing translational potential, alone or in combination with other anti-cancer agents, to treat human melanoma.

Intersection of AHR and Wnt signaling in development, health, and disease

The AHR (aryl hydrocarbon receptor) and Wnt (wingless-related MMTV integration site) signaling pathways have been conserved throughout evolution. Appropriately regulated signaling through each pathway is necessary for normal development and health, while dysregulation can lead to developmental defects and disease. Though both pathways have been vigorously studied, there is relatively little research exploring the possibility of crosstalk between these pathways. In this review, we provide a brief background on (1) the roles of both AHR and Wnt signaling in development and disease, and (2) the molecular mechanisms that characterize activation of each pathway. We also discuss the need for careful and complete experimental evaluation of each pathway and describe existing research that explores the intersection of AHR and Wnt signaling. Lastly, to illustrate in detail the intersection of AHR and Wnt signaling, we summarize our recent findings which show that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced disruption of Wnt signaling impairs fetal prostate development.

The antiproliferative response of indole-3-carbinol in human melanoma cells is triggered by an interaction with NEDD4-1 and disruption of wild-type PTEN degradation

Human melanoma cells displaying distinct PTEN genotypes were used to assess the cellular role of this important tumor-suppressor protein in the antiproliferative response induced by the chemopreventative agent indole-3-carbinol (I3C), a natural indolecarbinol compound derived from the breakdown of glucobrassicin produced in cruciferous vegetables such as broccoli and Brussels sprouts. I3C induced a G1-phase cell-cycle arrest and apoptosis by stabilization of PTEN in human melanoma cells that express wild-type PTEN, but not in cells with mutant or null PTEN genotypes. Importantly, normal human epidermal melanocytes were unaffected by I3C treatment. In wild-type PTEN-expressing melanoma xenografts, formed in athymic mice, I3C inhibited the in vivo tumor growth rate and increased PTEN protein levels in the residual tumors. Mechanistically, I3C disrupted the ubiquitination of PTEN by NEDD4-1 (NEDD4), which prevented the proteasome-mediated degradation of PTEN without altering its transcript levels. RNAi-mediated knockdown of PTEN prevented the I3C-induced apoptotic response, whereas knockdown of NEDD4-1 mimicked the I3C apoptotic response, stabilized PTEN protein levels, and downregulated phosphorylated AKT-1 levels. Co-knockdown of PTEN and NEDD4-1 revealed that I3C-regulated apoptotic signaling through NEDD4-1 requires the presence of the wild-type PTEN protein. Finally, in silico structural modeling, in combination with isothermal titration calorimetry analysis, demonstrated that I3C directly interacts with purified NEDD4-1 protein.

IMPLICATIONS

This study identifies NEDD4-1 as a new I3C target protein, and that the I3C disruption of NEDD4-1 ubiquitination activity triggers the stabilization of the wild-type PTEN tumor suppressor to induce an antiproliferative response in melanoma. Mol Cancer Res; 12(11); 1621-34. ©2014 AACR.

Wnt and SHH in prostate cancer: trouble mongers occupy the TRAIL towards apoptosis

Prostate cancer is a serious molecular disorder that arises because of reduction in tumour suppressors and overexpression of oncogenes. The malignant cells survive within the context of a three-dimensional microenvironment in which they are exposed to mechanical and physical cues. These signals are, nonetheless, deregulated through perturbations to mechanotransduction, from the nanoscale level to the tissue level. Increasingly sophisticated interpretations have uncovered significant contributions of signal transduction cascades in governing prostate cancer progression. To dismantle the major determinants that lie beneath disruption of spatiotemporal patterns of activity, crosstalk between various signalling cascades and their opposing and promoting effects on TRAIL-mediated activities cannot be ruled out. It is important to focus on that molecular multiplicity of cancer cells, various phenotypes reflecting expression of a variety of target oncogenes, reversible to irreversible, exclusive, overlapping or linked, coexist and compete with each other. Comprehensive investigations into TRAIL-mediated mitochondrial dynamics will remain a worthwhile area for underlining causes of tumourigenesis and for unravelling interference options.