Wnt breakers in colon cancer

Koetjapic acid: unveiling its potential as a saviour in the realm of biological and medicinal properties, with a focus on anticancer mechanism of action

Scientists have been compelled to search for alternative treatments due to the increasing prevalence of chemoresistance as well as the agonising and distressing side effects of both chemotherapy and radiation. Plant extracts have been exploited to treat various medical conditions for ages. Considering this fact, the main focus of various recent studies that are being conducted to find new and potent anticancer drugs involves the identification and utilisation of potential therapeutic chemicals present in plant extracts. Koetjapic acid (KJA), which belongs to the family of triterpenes, is primarily isolated from Sandoricum koetjape. Ongoing investigations into its therapeutic applications have revealed its tendency to impede the growth and proliferation of cancer cells. Koetjapic acid activates the intrinsic apoptotic pathway and promotes the death of cancer cells. Moreover, it inhibits angiogenesis and the dissemination of tumour (metastasis) by targeting the VEGF signalling cascade. Therefore, this study aims to elucidate the underlying mechanism of anticancer activity of koetjapic acid, providing significant insight into the compound's potential as an anticancer agent.

Human Neuralized is a novel tumour suppressor targeting Wnt/β-catenin signalling in colon cancer

While there is growing evidence that many epigenetically silenced genes in cancer are tumour suppressor candidates, their significance in cancer biology remains unclear. Here, we identify human Neuralized (NEURL), which acts as a novel tumour suppressor targeting oncogenic Wnt/β-catenin signalling in human cancers. The expression of NEURL is epigenetically regulated and markedly suppressed in human colorectal cancer. We, therefore, considered NEURL to be a bona fide tumour suppressor in colorectal cancer and demonstrate that this tumour suppressive function depends on NEURL-mediated oncogenic β-catenin degradation. We find that NEURL acts as an E3 ubiquitin ligase, interacting directly with oncogenic β-catenin, and reducing its cytoplasmic levels in a GSK3β- and β-TrCP-independent manner, indicating that NEURL-β-catenin interactions can lead to a disruption of the canonical Wnt/β-catenin pathway. This study suggests that NEURL is a therapeutic target against human cancers and that it acts by regulating oncogenic Wnt/β-catenin signalling.

The Effects and Mechanisms of Sennoside A on Inducing Cytotoxicity, Apoptosis, and Inhibiting Metastasis in Human Chondrosarcoma Cells

Currently, developing therapeutic strategies for chondrosarcoma (CS) remains important. Sennoside A (SA), a dianthrone glycoside from Senna and Rhubarb, is widely used as an irritant laxative, weight-loss agent, or dietary supplement, which possesses various bioactive properties such as laxative, antiobesity, and hypoglycemic activities. For the first time, our results suggested that cell proliferation and metastasis were inhibited by SA in CS SW1353 cells. SA induced cell growth arrest by inhibiting cell proliferation. The changes of N-cadherin and E-cadherin levels, the markers associated with epithelial mesenchymal transition (EMT), suggested the EMT-related mechanism of SA in inhibiting cell metastasis. Besides, SA significantly stimulated apoptosis in CS SW1353 cells, leading to cell death. The increase of Bax/Bcl2 ratio confirmed that the internal mitochondrial pathway of apoptosis was regulated by SA. In addition, the prediction of network pharmacology analysis suggested that the possible pathways of SA treatment for CS included the Wnt signaling pathway. Notably, the protein levels of the components in the Wnt pathway, such as Wnt3a, β-catenin, and c-Myc, were downregulated by SA in CS SW1353 cells. To sum up, these results demonstrated that the suppression of the growth, metastasis and the stimulation of cytotoxicity, and apoptosis mediated by SA in CS SW1353 cells were possibly caused by the inhibition of the Wnt/β-catenin pathway, indicating an underlying therapeutic prospect of SA for chondrosarcoma.

Chromatin profiles classify castration-resistant prostate cancers suggesting therapeutic targets

In castration-resistant prostate cancer (CRPC), the loss of androgen receptor (AR) dependence leads to clinically aggressive tumors with few therapeutic options. We used ATAC-seq (assay for transposase-accessible chromatin sequencing), RNA-seq, and DNA sequencing to investigate 22 organoids, six patient-derived xenografts, and 12 cell lines. We identified the well-characterized AR-dependent and neuroendocrine subtypes, as well as two AR-negative/low groups: a Wnt-dependent subtype, and a stem cell-like (SCL) subtype driven by activator protein-1 (AP-1) transcription factors. We used transcriptomic signatures to classify 366 patients, which showed that SCL is the second most common subtype of CRPC after AR-dependent. Our data suggest that AP-1 interacts with the YAP/TAZ and TEAD proteins to maintain subtype-specific chromatin accessibility and transcriptomic landscapes in this group. Together, this molecular classification reveals drug targets and can potentially guide therapeutic decisions.

Large remodeling of the Myc-induced cell surface proteome in B cells and prostate cells creates new opportunities for immunotherapy

MYC is a powerful transcription factor overexpressed in many human cancers including B cell and prostate cancers. Antibody therapeutics are exciting opportunities to attack cancers but require knowledge of surface proteins that change due to oncogene expression. To identify how MYC overexpression remodels the cell surface proteome in a cell autologous fashion and in different cell types, we investigated the impact of MYC overexpression on 800 surface proteins in three isogenic model cell lines either of B cell or prostate cell origin engineered to have high or low MYC levels. We found that MYC overexpression resulted in dramatic remodeling (both up- and down-regulation) of the cell surfaceome in a cell type-dependent fashion. We found systematic and large increases in distinct sets of >80 transporters including nucleoside transporters and nutrient transporters making cells more sensitive to toxic nucleoside analogs like cytarabine, commonly used for treating hematological cancers. Paradoxically, MYC overexpression also increased expression of surface proteins driving cell turnover such as TNFRSF10B, also known as death receptor 5, and immune cell attacking signals such as the natural killer cell activating ligand NCR3LG1, also known as B7-H6. We generated recombinant antibodies to these two targets and verified their up-regulation in MYC overexpression cell lines and showed they were sensitive to bispecific T cell engagers (BiTEs). Our studies demonstrate how MYC overexpression leads to dramatic bidirectional remodeling of the surfaceome in a cell type-dependent but functionally convergent fashion and identify surface targets or combinations thereof as possible candidates for cytotoxic metabolite or immunotherapy.

SCC-S2 Facilitates Tumor Proliferation and Invasion via Activating Wnt Signaling and Depressing Hippo Signaling in Colorectal Cancer Cells and Predicts Poor Prognosis of Patients

SCC-S2 overexpression has been implicated in several human cancers, its correlation with prognosis and the mechanism how it reserved biological roles are still uncertain. The current study demonstrated that, in 142 archived colorectal carcinoma (CRC) tissue samples, SCC-S2 expression was significantly correlated with higher histological grade ( p=0.001), tumor invasion ( p=0.001), advanced Dukes staging ( p=0.002), positive regional lymph node metastasis ( p=0.024), and poor overall survival ( p<0.001). MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and Transwell assays showed that SCC-S2 significantly promoted the proliferation and invasion. SCC-S2 expression was also accompanied by the overexpression CyclinD1, matrix metalloproteinase-7 (MMP-7), active-β-catenin, yes-associated protein (YAP), and connective tissue growth factor (CTGF), as well as the depression of p-large tumor suppressor kinase 1 (p-LATS1) and p-YAP. Moreover, SCC-S2 interacted and colocalized with LATS1, the interaction may interrupt Hippo signaling and thereafter activate canonical Wnt signaling. In conclusion, our data suggested that SCC-S2 was associated with the progression and unfavorable prognosis of CRCs. Meanwhile, SCC-S2 facilitated canonical Wnt signaling and its downstream effectors (CyclinD1, MMP-7) and promoted tumor proliferation and invasion, which depended on the inhibition of Hippo signaling induced by SCC-S2-LATS1 interaction. These results indicated that SCC-S2 might be used as a novel target for the prevention and treatment of colorectal cancer.

Ligase IV inhibitor SCR7 enhances gene editing directed by CRISPR-Cas9 and ssODN in human cancer cells

Background

Precise genome editing is essential for both basic and translational research. The recently developed CRISPR/Cas9 system can specifically cleave a designated site of target gene to create a DNA double-strand break, which triggers cellular DNA repair mechanism of either inaccurate non-homologous end joining, or site-specific homologous recombination. Unfortunately, homology-directed repair (HDR) is challenging due to its very low efficiency. Herein, we focused on improving the efficiency of HDR using a combination of CRISPR/Cas9, eGFP, DNA ligase IV inhibitor SCR7, and single-stranded oligodeoxynucleotides (ssODN) in human cancer cells.

Results

When Cas9, gRNA and eGFP were assembled into a co-expression vector, the disruption rate more than doubled following GFP-positive cell sorting in transfected cells compared to those unsorted cells. Using ssODNs as templates, SCR7 treatment increased targeted insertion efficiency threefold in transfected cells compared to those without SCR7 treatment. Moreover, this combinatorial approach greatly improved the efficiency of HDR and targeted gene mutation correction at both the GFP-silent mutation and the β-catenin Ser45 deletion mutation cells.

Conclusion

The data of this study suggests that a combination of co-expression vector, ssODN, and ligase IV inhibitor can markedly improve the CRISPR/Cas9-directed gene editing, which should have significant application in targeted gene editing and genetic disease therapy.

Extracts of Zuo Jin Wan, a traditional Chinese medicine, phenocopies 5-HTR1D antagonist in attenuating Wnt/β-catenin signaling in colorectal cancer cells

Background

In vitro and in vivo studies have shown that Zuo Jin Wan (ZJW), a herbal formula of traditional Chinese medicine (TCM), possessed anticancer properties. However, the underlying mechanism for the action of ZJW remains unclear. Various subtypes of 5-Hydroxytryptamine receptor (5-HTR) have been shown to play a role in carcinogenesis and cancer metastasis. 5-HTR1D, among the subtypes, is highly expressed in colorectal cancer (CRC) cell lines and tissues. The present study aimed at investigating effect of ZJW extracts on the biological function of CRC cells, the expression of 5-HTR1D, and molecules of Wnt/β-catenin signaling pathway.

Methods

In this study, the effect of ZJW extracts on 5-HTR1D expression and Wnt/β-catenin signaling pathway were investigated and contrasted with GR127935 (GR), a known 5-HTR1D antagonist, using the CRC cell line SW403. The cells were respectively treated with GR127935 and different doses of ZJW extracts. Proliferation, apoptosis, migration, and invasion of SW403 cells were compared between ZJW and GR127935 treatments. The expression of 5-HTR1D and signaling molecules involved in the canonic Wnt/β-catenin pathway were determined by Western blot analysis.

Results

After ZJW extracts treatment and GR127935 treatment, G1 arrest in cell cycle of SW403 was increased. Cell apoptosis was pronounced, and cell migration and invasion were suppressed. SW403 cells showed a dose-dependently decreased expression of 5-HTR1D, meanwhile, β-catenin level was significantly decreased in nucleus of cells cultured with GR127935. Treatment of ZJW extracts dose-dependently resulted in decreased 5-HTR1D and a concomitant reduction in the Wnt/β-catenin signal transduction, an effect indistinguishable from GR127935 treatment.

Conclusion

The anticancer activity of ZJW extracts may be partially achieved through attenuation of the 5-HTR1D-Wnt/β-catenin signaling pathway.

E-Cadherin/β-Catenin Complex: A Target for Anticancer and Antimetastasis Plants/Plant-derived Compounds

Plants reputed to have cancer-inhibiting potential and putative active components derived from those plants have emerged as an exciting new field in cancer study. Some of these compounds have cancer-inhibiting potential in different clinical staging levels, especially metastasis. A few of them which stabilize cell-cell adhesions are controversial topics. This review article introduces some effective herbal compounds that target E-cadherin/β-catenin protein complex. In this article, at first, we briefly review the structure and function of E-cadherin and β-catenin proteins, Wnt signaling pathway, and its target genes. Then, effective compounds of the Teucrium persicum, Teucrium polium, Allium sativum (garlic), Glycine max (soy), and Brassica oleracea (broccoli) plants, which influence stability and cellular localization of E-cadherin/β-catenin complex, were studied. Based on literature review, there are some compounds in these plants, including genistein of soy, sulforaphane of broccoli, organosulfur compounds of garlic, and the total extract of Teucrium genus that change the expression of variety of Wnt target genes such as MMPs, E-cadherin, p21, p53, c-myc, and cyclin D1. So they may induce cell-cycle arrest, apoptosis and/or inhibition of Epithelial-Mesenchymal Transition (EMT) and metastasis.

The Regulations of Deubiquitinase USP15 and Its Pathophysiological Mechanisms in Diseases

Deubiquitinases (DUBs) play a critical role in ubiquitin-directed signaling by catalytically removing the ubiquitin from substrate proteins. Ubiquitin-specific protease 15 (USP15), a member of the largest subfamily of cysteine protease DUBs, contains two conservative cysteine (Cys) and histidine (His) boxes. USP15 harbors two zinc-binding motifs that are essential for recognition of poly-ubiquitin chains. USP15 is grouped into the same category with USP4 and USP11 due to high degree of homology in an N-terminal region consisting of domains present in ubiquitin-specific proteases (DUSP) domain and ubiquitin-like (UBL) domain. USP15 cooperates with COP9 signalosome complex (CSN) to maintain the stability of cullin-ring ligase (CRL) adaptor proteins by removing the conjugated ubiquitin chains from RBX1 subunit of CRL. USP15 is also implicated in the stabilization of the human papillomavirus type 16 E6 oncoprotein, adenomatous polyposis coli, and IκBα. Recently, reports have suggested that USP15 acts as a key regulator of TGF-β receptor-signaling pathways by deubiquitinating the TGF-β receptor itself and its downstream transducers receptor-regulated SMADs (R-SMADs), including SMAD1, SMAD2, and SMAD3, thus activating the TGF-β target genes. Although the importance of USP15 in pathologic processes remains ambiguous so far, in this review, we endeavor to summarize the literature regarding the relationship of the deubiquitinating action of USP15 with the proteins involved in the regulation of Parkinson’s disease, virus infection, and cancer-related signaling networks.

Inherited Variants in Wnt Pathway Genes Influence Outcomes of Prostate Cancer Patients Receiving Androgen Deprivation Therapy

Aberrant Wnt signaling has been associated with many types of cancer. However, the association of inherited Wnt pathway variants with clinical outcomes in prostate cancer patients receiving androgen deprivation therapy (ADT) has not been determined. Here, we comprehensively studied the contribution of common single nucleotide polymorphisms (SNPs) in Wnt pathway genes to the clinical outcomes of 465 advanced prostate cancer patients treated with ADT. Two SNPs, adenomatous polyposis coli (APC) rs2707765 and rs497844, were significantly (p ≤ 0.009 and q ≤ 0.043) associated with both prostate cancer progression and all-cause mortality, even after multivariate analyses and multiple testing correction. Patients with a greater number of favorable alleles had a longer time to disease progression and better overall survival during ADT (p for trend ≤ 0.003). Additional, cDNA array and in silico analyses of prostate cancer tissue suggested that rs2707765 affects APC expression, which in turn is correlated with tumor aggressiveness and patient prognosis. This study identifies the influence of inherited variants in the Wnt pathway on the efficacy of ADT and highlights a preclinical rationale for using APC as a prognostic marker in advanced prostate cancer.

Selenoproteins and oxidative stress-induced inflammatory tumorigenesis in the gut

Selenium is an essential micronutrient that is incorporated into at least 25 selenoproteins encoded by the human genome, many of which serve antioxidant functions. Because patients with inflammatory bowel disease (IBD) demonstrate nutritional deficiencies and are at increased risk for colon cancer due to heightened inflammation and oxidative stress, selenoprotein dysfunction may contribute to disease progression. Over the years, numerous studies have analyzed the effects of selenoprotein loss and shown that they are important mediators of intestinal inflammation and carcinogenesis. In particular, recent work has focused on the role of selenoprotein P (SEPP1), a major selenium transport protein which also has endogenous antioxidant function. These experiments determined SEPP1 loss altered immune and epithelial cellular function in a murine model of colitis-associated carcinoma. Here, we discuss the current knowledge of SEPP1 and selenoprotein function in the setting of IBD, colitis, and inflammatory tumorigenesis.

Depletion of UBA protein 2-like protein inhibits growth and induces apoptosis of human colorectal carcinoma cells

Ubiquitin-proteasome system regulates cell proliferation, apoptosis, angiogenesis, and motility, which are processes with particular importance for carcinogenesis. UBA protein 2-like protein (UBAP2L) was found to be associated with proteasome; however, its biological function is largely unknown. In this study, the mRNA levels of UBAP2L in human normal and colorectal carcinoma tissues were analyzed using the datasets from the publicly available Oncomine database ( www.oncomine.org ) and found UBAP2L was overexpressed in colorectal carcinoma tissues. Furthermore, we elucidated the role of UBAP2L in human colorectal cancer via an RNA interference lentivirus system in three colorectal carcinoma cell lines HCT116, SW1116, and RKO. Knockdown of UBAP2L led to suppressed cell proliferation and impaired colony formation. UBAP2L depletion in HCT116 and RKO cells also induced cell cycle arrest as well as apoptosis. Moreover, the phosphorylation of PRAS40, Bad, and the cleavage of PARP were remarkably increased after UBAP2L knockdown by Intracellular signaling array and also the activation of P38 was obviously decreased and the cleavage of Caspase 3 and Bax were increased after UBAP2L silencing by western blot assay, indicated that UBAP2L might be involved in the cell growth by the regulation of apoptosis-related proteins. Our findings indicated that UBAP2L may be essential for colorectal carcinoma growth and survival. Lentivirus-mediated small interfering RNA against UBAP2L might serve as a potential therapeutic approach for the treatment of colorectal cancer.

Alternative splicing within the Wnt signaling pathway: role in cancer development

BACKGROUND

The Wnt signaling cascade plays a fundamental role in embryonic development, adult tissue regeneration, homeostasis and stem cell maintenance. Abnormal Wnt signaling has been found to be prevalent in various human cancers. Also, a role of Wnt signaling in the regulation of alternative splicing of several cancer-related genes has been established. In addition, accumulating evidence suggests the existence of multiple splice isoforms of Wnt signaling cascade components, including Wnt ligands, receptors, components of the destruction complex and transcription activators/suppressors. The presence of multiple Wnt signaling-related isoforms may affect the functionality of the Wnt pathway, including its deregulation in cancer. As such, specific Wnt pathway isoform components may serve as therapeutic targets or as biomarkers for certain human cancers. Here, we review the role of alternative splicing of Wnt signaling components during the onset and progression of cancer.

CONCLUSIONS

Splice isoforms of components of the Wnt signaling pathway play distinct roles in cancer development. Isoforms of the same component may function in a tissue- and/or cancer-specific manner. Splice isoform expression analyses along with deregulated Wnt signaling pathway analyses may be of help to design efficient diagnostic and therapeutic strategies.

Effects on the transcriptome upon deletion of a distal element cannot be predicted by the size of the H3K27Ac peak in human cells

Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with increased risk for colorectal cancer (CRC). A molecular understanding of the functional consequences of this genetic variation is complicated because most GWAS SNPs are located in non-coding regions. We used epigenomic information to identify H3K27Ac peaks in HCT116 colon cancer cells that harbor SNPs associated with an increased risk for CRC. Employing CRISPR/Cas9 nucleases, we deleted a CRC risk-associated H3K27Ac peak from HCT116 cells and observed large-scale changes in gene expression, resulting in decreased expression of many nearby genes. As a comparison, we showed that deletion of a robust H3K27Ac peak not associated with CRC had minimal effects on the transcriptome. Interestingly, although there is no H3K27Ac peak in HEK293 cells in the E7 region, deletion of this region in HEK293 cells decreased expression of several of the same genes that were downregulated in HCT116 cells, including the MYC oncogene. Accordingly, deletion of E7 causes changes in cell culture assays in HCT116 and HEK293 cells. In summary, we show that effects on the transcriptome upon deletion of a distal regulatory element cannot be predicted by the size or presence of an H3K27Ac peak.

Gastrokine 1 induces senescence and apoptosis through regulating telomere length in gastric cancer

The present study aims to investigate whether gastrokine 1 (GKN1) induces senescence and apoptosis in gastric cancer cells by regulating telomere length and telomerase activity. Telomere length, telomerase activity, and hTERT expression decreased significantly in AGSGKN1 and MKN1GKN1 cells. Both stable cell lines showed increased expression of TRF1 and reduced expression of the hTERT and c-myc proteins. In addition, TRF1 induced a considerable decrease in cell growth, telomerase activity, and expression of hTERT mRNA and protein. GKN1 completely counteracted the effects of c-myc on cell growth, telomere length, and telomerase activity. Interestingly, GKN1 directly bound to c-myc and down-regulated its expression as well as inhibited its binding to the TRF1 protein and a hTERT promoter. Furthermore, GKN1 triggered senescence, followed by apoptosis via up-regulating the p53, p21, p27, and p16 proteins and down-regulating Skp2. Telomere length in 35 gastric cancers was shortened significantly compared with the corresponding gastric mucosae, whereas GKN1 expression was inversely correlated with telomere length and c-myc and hTERT mRNA expression. Taken together, these results suggest that GKN1 may shorten telomeres by acting as a potential c-myc inhibitor that eventually leads to senescence and apoptosis in gastric cancer cells.

Systematically Prioritizing Functional Differentially Methylated Regions (fDMRs) by Integrating Multi-omics Data in Colorectal Cancer

While genome-wide differential DNA methylation regions (DMRs) have been extensively identified, the comprehensive prioritization of their functional importance is still poorly explored. Here, we aggregated multiple data resources rooted in the genome, epigenome and transcriptome to systematically prioritize functional DMRs (fDMRs) in colorectal cancer (CRC). As demonstrated, the top-ranked fDMRs from all of the data resources showed a strong enrichment for known methylated genes. Additionally, we analyzed those top 5% DMR-coupled coding genes using functional enrichment, which resulted in significant disease-related biological functions in contrast to the tail 5% genes. To further confirm the functional importance of the top-ranked fDMRs, we applied chromatin modification alterations of CRC cell lines to characterize their functional regulation. Specifically, we extended the utility of the top-ranked DMR-coupled genes to serve as classification and survival biomarkers, which showed a robust performance across diverse independent data sets. Collectively, our results established an integrative framework to prioritize fDMRs, which could help characterize aberrant DNA methylation-induced potential mechanisms underlying tumorigenesis and uncover epigenome-based biomarkers for clinical diagnosis and prognosis.

Claudins and cancer: Fall of the soldiers entrusted to protect the gate and keep the barrier intact

The role of the tight junctions (TJ) in controlling paracellular traffic of ions and molecules, through the regulation of claudin proteins, is now established. However, it has also become increasingly evident that claudin proteins, as integral components of the TJs, play crucial role in maintaining the cell-cell integrity. In conformity, deregulation of claudin expression and cellular distribution in cancer tissues has been widely documented and correlated with cancer progression and metastasis. However, this correlation is not unidirectional and rather suggests tissue specific regulations. Irrespective, if the widely described correlations between altered claudin expression and cancer initiation/progression could be established, they may serve as important markers for prognostic purposes and potential therapeutic targets. In this review, we summarize data from screening of the cancer tissues, manipulation of claudin expression in cells and animals subjected to cancer models, and how claudins are regulated in cancer. The focus of this article remains analysis of the association between cancer and the claudins and to decipher clinical relevance.

Adenomatous polyposis coli (APC)-induced apoptosis of HT29 colorectal cancer cells depends on mitochondrial oxidative metabolism

Adenomatous polyposis coli (APC) is a tumor suppressor involved in the Wnt signaling, the primary driving force of the intestinal epithelium homeostasis. Alterations of components of the Wnt pathway, and in most cases mutations of APC, have been reported to promote colorectal cancer (CRC). During differentiation the enterocytes migrate from the crypt to the tip of the villus where they undergo apoptosis thus ensuring the continual renewal of the intestinal mucosa. The differentiation process is characterized by an activation gradient of the Wnt signaling pathway accompanied by a metabolic switch from glycolysis to mitochondrial oxidative phosphorylation along the crypt-villus axis. In the present work, we study the relationship between the expression of wild type APC protein and mitochondrial oxidative metabolism in HT29 colorectal cancer cells, originally carrying endogenous inactive APC alleles. By generating mtDNA-depleted (rho0) APC-inducible HT29 cells, we demonstrate for the first time that the APC-dependent apoptosis requires the production of reactive oxygen species (ROS) by the mitochondrial respiratory chain. The possible role of mitochondria as putative target in the prevention and/or therapy of colorectal cancer is herein discussed.

Novel strategies targeting cancer stem cells through phytochemicals and their analogs

Cancer stem cells (CSCs) are cells that exist within a tumor with a capacity of self-renewal and an ability to differentiate, giving rise to heterogeneous populations of cancer cells. These cells are increasingly being implicated in resistance to conventional therapeutics and have also been implicated in tumor recurrence. Several cellular signaling pathways including Notch, Wnt, phosphoinositide-3-kinase-Akt-mammalian target of rapamycin pathways, and known markers such as CD44, CD133, CD166, ALDH, etc. have been associated with CSCs. Here, we have reviewed our current understanding of self-renewal pathways and factors that help in the survival of CSCs with special emphasis on those that have been documented to be modulated by well characterized natural agents such as curcumin, sulforaphane, resveratrol, genistein, and epigallocatechin gallate. With the inclusion of a novel derivative of curcumin, CDF, we showcase how natural agents can be effectively modified to increase their efficacy, particularly against CSCs. We hope that this article will generate interest among researchers for further mechanistic and clinical studies exploiting the cancer preventive and therapeutic role of nutraceuticals by targeted elimination of CSCs.

Targets of Wnt/ß-catenin transcription in penile carcinoma

Penile squamous cell carcinoma (PeCa) is a rare malignancy and little is known regarding the molecular mechanisms involved in carcinogenesis of PeCa. The Wnt signaling pathway, with the transcription activator ß-catenin as a major transducer, is a key cellular pathway during development and in disease, particularly cancer. We have used PeCa tissue arrays and multi-fluorophore labelled, quantitative, immunohistochemistry to interrogate the expression of WNT4, a Wnt ligand, and three targets of Wnt-ß-catenin transcription activation, namely, MMP7, cyclinD1 (CD1) and c-MYC in 141 penile tissue cores from 101 unique samples. The expression of all Wnt signaling proteins tested was increased by 1.6 to 3 fold in PeCa samples compared to control tissue (normal or cancer adjacent) samples (p<0.01). Expression of all proteins, except CD1, showed a significant decrease in grade II compared to grade I tumors. High magnification, deconvolved confocal images were used to measure differences in co-localization between the four proteins. Significant (p<0.04-0.0001) differences were observed for various permutations of the combinations of proteins and state of the tissue (control, tumor grades I and II). Wnt signaling may play an important role in PeCa and proteins of the Wnt signaling network could be useful targets for diagnosis and prognostic stratification of disease.

Epsin is required for Dishevelled stability and Wnt signalling activation in colon cancer development

Uncontrolled canonical Wnt signalling supports colon epithelial tumour expansion and malignant transformation. Understanding the regulatory mechanisms involved is crucial for elucidating the pathogenesis of and will provide new therapeutic targets for colon cancer. Epsins are ubiquitin-binding adaptor proteins upregulated in several human cancers; however, the involvement of epsins in colon cancer is unknown. Here we show that loss of intestinal epithelial epsins protects against colon cancer by significantly reducing the stability of the crucial Wnt signalling effector, dishevelled (Dvl2), and impairing Wnt signalling. Consistently, epsins and Dvl2 are correspondingly upregulated in colon cancer. Mechanistically, epsin binds Dvl2 via its epsin N-terminal homology domain and ubiquitin-interacting motifs and prohibits Dvl2 polyubiquitination and degradation. Our findings reveal an unconventional role for epsins in stabilizing Dvl2 and potentiating Wnt signalling in colon cancer cells to ensure robust colon cancer progression. The pro-carcinogenic role of Epsins suggests that they are potential therapeutic targets to combat colon cancer.

Eya1 interacts with Six2 and Myc to regulate expansion of the nephron progenitor pool during nephrogenesis

Self-renewal and proliferation of nephron progenitor cells and the decision to initiate nephrogenesis are crucial events directing kidney development. Despite recent advancements in defining lineage and regulators for the progenitors, fundamental questions about mechanisms driving expansion of the progenitors remain unanswered. Here we show that Eya1 interacts with Six2 and Myc to control self-renewing cell activity. Cell fate tracing reveals a developmental restriction of the Eya1(+) population within the intermediate mesoderm to nephron-forming cell fates and a common origin shared between caudal mesonephric and metanephric nephrons. Conditional inactivation of Eya1 leads to loss of Six2 expression and premature epithelialization of the progenitors. Six2 mediates translocation of Eya1 to the nucleus, where Eya1 uses its threonine phosphatase activity to control Myc phosphorylation/dephosphorylation and function in the progenitor cells. Our results reveal a functional link between Eya1, Six2, and Myc in driving the expansion and maintenance of the multipotent progenitors during nephrogenesis.

Signaling mechanisms of the epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) is an essential mechanism in embryonic development and tissue repair. EMT also contributes to the progression of disease, including organ fibrosis and cancer. EMT, as well as a similar transition occurring in vascular endothelial cells called endothelial-mesenchymal transition (EndMT), results from the induction of transcription factors that alter gene expression to promote loss of cell-cell adhesion, leading to a shift in cytoskeletal dynamics and a change from epithelial morphology and physiology to the mesenchymal phenotype. Transcription program switching in EMT is induced by signaling pathways mediated by transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP), Wnt-β-catenin, Notch, Hedgehog, and receptor tyrosine kinases. These pathways are activated by various dynamic stimuli from the local microenvironment, including growth factors and cytokines, hypoxia, and contact with the surrounding extracellular matrix (ECM). We discuss how these pathways crosstalk and respond to signals from the microenvironment to regulate the expression and function of EMT-inducing transcription factors in development, physiology, and disease. Understanding these mechanisms will enable the therapeutic control of EMT to promote tissue regeneration, treat fibrosis, and prevent cancer metastasis.

Tumour cell invasion: an emerging role for basal epithelial cell extrusion

Metastasis is the leading cause of cancer-related deaths, but it is unclear how cancer cells escape their primary sites in epithelia and disseminate to other sites in the body. One emerging possibility is that transformed epithelial cells could invade the underlying tissue by a process called cell extrusion, which epithelia use to remove cells without disrupting their barrier function. Typically, during normal cell turnover, live cells extrude apically from the epithelium into the lumen and later die by anoikis; however, several oncogenic mutations shift cell extrusion basally, towards the tissue that the epithelium encases. Tumour cells with high levels of survival and motility signals could use basal extrusion to escape from the tissue and migrate to other sites within the body.

Interaction between gastric cancer stem cells and the tumor microenvironment

Gastric cancer (GC) remains a leading cause of cancer-related deaths worldwide. Cancer stem cells (CSCs) are selectively capable of tumor initiation and are implicated in tumor relapse and metastasis, thus, governing the prognosis of GC patients. Stromal cells and extracellular matrix adjacent to cancer cells are known to form a supportive environment for cancer progression. CSC properties are also regulated by their microenvironment through cell signaling and related factors. This review presents the current findings regarding the influence of the tumor microenvironment on GC stem cells, which will support the development of novel therapeutic strategies for patients with GC.

Methylation epigenotypes and genetic features in colorectal laterally spreading tumors

Aberrant DNA methylation plays an important role in genesis of colorectal cancer (CRC). Previously, we identified Group 1 and Group 2 methylation markers through genome-wide DNA methylation analysis, and classified CRC and protruded adenoma into three distinct clusters: high-, intermediate- and low-methylation epigenotypes. High-methylation epigenotype strongly correlated with BRAF mutations and these aberrations were involved in the serrated pathway, whereas intermediate-methylation epigenotype strongly correlated with KRAS mutations. Here, we investigated laterally spreading tumors (LSTs), which are flat, early CRC lesions, through quantitative methylation analysis of six Group 1 and 14 Group 2 methylation markers using pyrosequencing. Gene mutations in BRAF, KRAS and PIK3CA, and immunostaining of TP53 and CTNNB1 as well as other clinicopathological factors were also evaluated. By hierarchical clustering using methylation information, LSTs were classified into two subtypes; intermediate-methylation epigenotype correlating with KRAS mutations (p = 9 × 10(-4)) and a granular morphology (LST-G) (p = 1 × 10(-7)), and low-methylation epigenotype correlating with CTNNB1 activation (p = 0.002) and a nongranular morphology (LST-NG) (p = 1 × 10(-7)). Group 1 marker methylation and BRAF mutations were barely detected, suggesting that high-methylation epigenotype was unlikely to be involved in LST development. TP53 mutations correlated significantly with malignant transformation, regardless of epigenotype or morphology type. Together, this may suggest that two molecular pathways, intermediate methylation associated with KRAS mutations and LST-G morphology, and low methylation associated with CTNNB1 activation and LST-NG morphology, might be involved in LST development, and that involvement of TP53 mutations could be important in both subtypes in the development from adenoma to cancer.

Raloxifene and antiestrogenic gonadorelin inhibits intestinal tumorigenesis by modulating immune cells and decreasing stem-like cells

Studies suggest that estrogen plays a contributing role in colorectal cancer. This project examined the preventive effects of raloxifene, a selective estrogen receptor modulator (SERM), and gonadorelin, an antiestrogenic drug, in female Apc(Min/+) mouse intestinal tumorigenesis. Six-week-old Apc(Min/+)mice were fed diet containing 1 ppm raloxifene or control diet. Gonadorelin (150 ng/mouse) was injected subcutaneously into one treatment group. Intestinal tumors were evaluated for tumor multiplicity and size. Mice treated with raloxifene and gonadorelin showed colon tumor inhibition of 80% and 75%, respectively. Both drugs significantly inhibited small intestinal tumor multiplicity and size (75%-65%, P < 0.0001). Raloxifene and gonadorelin showed significant tumor inhibition with 98% and 94% inhibition of polyps >2 mm in size. In mice fed with raloxifene or injected with gonadorelin, tumors showed significantly reduced proliferating cell nuclear antigen expression (58%-65%, P < 0.0001). Raloxifene treatment decreased β-catenin, cyclin D1, laminin 1β, Ccl6, and stem-like cells (Lgr 5, EpCAM, CD44/CD24), as well as suppressed inflammatory genes (COX-2, mPGES-1, 5-LOX,). Gonadorelin showed significant decrease in COX-2, mPGES-1, iNOS, and stem-like cells or increased NK cells and chemokines required for NK cells. Both drugs were effective in suppressing tumor growth albeit with different mechanisms. These observations show that either suppression of estrogen levels or modulation of estrogen receptor dramatically suppresses small intestinal and colonic tumor formation in female Apc(Min/+) mice. These results support the concept of chemoprevention by these agents in reducing endogenous levels of estrogen or modulating ER signaling.

Myofibroblast-derived SFRP1 as potential inhibitor of colorectal carcinoma field effect

Epigenetic changes of stromal-epithelial interactions are of key importance in the regulation of colorectal carcinoma (CRC) cells and morphologically normal, but genetically and epigenetically altered epithelium in normal adjacent tumor (NAT) areas. Here we demonstrated retained protein expression of well-known Wnt inhibitor, secreted frizzled-related protein 1 (SFRP1) in stromal myofibroblasts and decreasing epithelial expression from NAT tissues towards the tumor. SFRP1 was unmethylated in laser microdissected myofibroblasts and partially hypermethylated in epithelial cells in these areas. In contrast, we found epigenetically silenced myofibroblast-derived SFRP1 in CRC stroma. Our results suggest that the myofibroblast-derived SFRP1 protein might be a paracrine inhibitor of epithelial proliferation in NAT areas and loss of this signal may support tumor proliferation in CRC.

Influence of anthropometric factors on tumour biological characteristics of colorectal cancer in men and women: a cohort study

Background

Obesity is a well established risk factor of colorectal cancer (CRC), but how body size influences risk of colorectal cancer defined by key molecular alterations remains unclear. In this study, we investigated the relationship between height, weight, body mass index (BMI), waist- and hip circumference, waist-hip ratio (WHR) and risk of CRC according to expression of beta-catenin, cyclin D1, p53 and microsatellite instability status of the tumours in men and women, respectively.

Methods

Immunohistochemical expression of beta-catenin, cyclin D1, p53 and MSI-screening status was assessed in tissue microarrays with tumours from 584 cases of incident CRC in the Malmö Diet and Cancer Study. Six anthropometric factors: height, weight, BMI, waist- and hip circumference, and WHR were categorized by quartiles of baseline measurements and relative risks of CRC according to expression of beta-catenin, cyclin D1, p53 and MSI status were calculated using multivariate Cox regression models.

Results

High height was associated with risk of cyclin D1 positive, and p53 negative CRC in women but not with any investigative molecular subsets of CRC in men. High weight was associated with beta-catenin positive, cyclin D1 positive, p53 negative and microsatellite stable (MSS) tumours in women, and with beta-catenin negative and p53 positive tumours in men. Increased hip circumference was associated with beta-catenin positive, p53 negative and MSS tumours in women and with beta-catenin negative, cyclin D1 positive, p53 positive and MSS tumours in men. In women, waist circumference and WHR were not associated with any molecular subsets of CRC. In men, both high WHR and high waist circumference were associated with beta-catenin positive, cyclin D1 positive and p53 positive tumours. WHR was also associated with p53 negative CRC, and waist circumference with MSS tumours. High BMI was associated with increased risk of beta-catenin positive and MSS CRC in women, and with beta-catenin positive, cyclin D1 positive and p53 positive tumours in men.

Conclusions

Findings from this large prospective cohort study indicate sex-related differences in the relationship between obesity and CRC risk according to key molecular characteristics, and provide further support of an influence of lifestyle factors on different molecular pathways of colorectal carcinogenesis.

Combination of selenium and green tea improves the efficacy of chemoprevention in a rat colorectal cancer model by modulating genetic and epigenetic biomarkers

Dietary supplementation of selenium and green tea holds promise in cancer prevention. In this study, we evaluated the efficacies of selenium and green tea administered individually and in combination against colorectal cancer in an azoxymethane (AOM)-induced rat colonic carcinogenesis model and determined the underlying mechanisms of the protection. Four-week old Sprague-Dawley male rats were fed with diets containing 0.5% green tea extract, 1 ppm selenium as selenium-enriched milk protein, or combination of 1 ppm selenium and 0.5% green tea extract. Animals received 2 AOM (15 mg/kg) treatments to induce colonic oncogenesis. Rats were killed 8 or 30 wk later after the last AOM to examine the effect of dietary intervention on aberrant crypt foci (ACF) formation or tumor development. On sacrifice, colons were examined for ACF and tumors, the mRNA levels of SFRP5 and Cyclin D1, and the proteins levels of ß-catenin, COX-2, Ki-67, DNMT1 and acetyl histone H3. The combination of selenium and green tea resulted in a significant additive inhibition of large ACF formation, this effect was greater than either selenium or green tea alone, P<0.01; the combination also had a significant additive inhibition effect on all tumor endpoints, the effect of the combination diet on tumor incidence, multiplicity and size was greater than selenium or green tea alone, P<0.01. Rats fed the combination diet showed marked reduction of DNMT1 expression and induction of histone H3 acetylation, which were accompanied by restoration of SFRP5 mRNA in normal-appearing colonic crypts. The combination diet also significantly reduced ß-catenin nuclear translocation, Cyclin D1 expression and cell proliferation. These data show, for the first time, that combination of selenium and green tea is more effective in suppressing colorectal oncogenesis than either agent alone. The preventive effect is associated with regulation of genetic and epigenetic biomarkers implicated in colonic carcinogenesis.

Associations of beta-catenin alterations and MSI screening status with expression of key cell cycle regulating proteins and survival from colorectal cancer

Background

Despite their pivotal roles in colorectal carcinogenesis, the interrelationship and prognostic significance of beta-catenin alterations and microsatellite instability (MSI) in colorectal cancer (CRC) needs to be further clarified. In this paper, we studied the associations between beta-catenin overexpression and MSI status with survival from CRC, and with expression of p21, p27, cyclin D1 and p53, in a large, prospective cohort study.

Methods

Immunohistochemical MSI-screening status and expression of p21, p27 and p53 was assessed in tissue microarrays with tumours from 557 cases of incident CRC in the Malmö Diet and Cancer Study. Chi Square and Spearman’s correlation tests were used to explore the associations between beta-catenin expression, MSI status, clinicopathological characteristics and investigative parameters. Kaplan-Meier analysis and Cox proportional hazards modelling were used to assess the relationship between beta-catenin overexpression, MSI status and cancer specific survival (CSS).

Results

Positive MSI screening status was significantly associated with older age, female sex, proximal tumour location, non-metastatic disease, and poor differentiation, and inversely associated with beta-catenin overexpression. Beta-catenin overexpression was significantly associated with distal tumour location, low T-stage and well-differentiated tumours. Patients with MSI tumours had a significantly prolonged CSS in the whole cohort, and in stage III-IV disease, also in multivariable analysis, but not in stage I-II disease. Beta-catenin overexpression was associated with a favourable prognosis in the full cohort and in patients with stage III-IV disease. Neither MSI nor beta-catenin status were predictive for response to adjuvant chemotherapy in curatively treated stage III patients. P53 and p27 expression was positively associated with beta-catenin overexpression and inversely associated with MSI. Cyclin D1 expression was positively associated with MSI and beta-catenin overexpression, and p21 expression was positively associated with MSI but not beta-catenin overexpression.

Conclusions

Findings from this large, prospective cohort study demonstrate that MSI screening status in colorectal cancer is an independent prognostic factor, but not in localized disease, and does not predict response to adjuvant chemotherapy. Beta-catenin overexpression was also associated with favourable outcome but not a treatment predictive factor. Associations of MSI and beta-catenin alterations with other investigative and clinicopathological factors were in line with the expected.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8778585058652609

Developmental pathways in colon cancer: crosstalk between WNT, BMP, Hedgehog and Notch

A hallmark of cancer is reactivation/alteration of pathways that control cellular differentiation during developmental processes. Evidence indicates that WNT, Notch, BMP and Hedgehog pathways have a role in normal epithelial cell differentiation, and that alterations in these pathways accompany establishment of the tumorigenic state. Interestingly, there is recent evidence that these pathways are intertwined at the molecular level, and these nodes of intersection may provide opportunities for effective targeted therapies. This review will highlight the role of the WNT, Notch, BMP and Hedgehog pathways in colon cancer.

PDGF upregulates Mcl-1 through activation of β-catenin and HIF-1α-dependent signaling in human prostate cancer cells

BACKGROUND

Aberrant platelet derived growth factor (PDGF) signaling has been associated with prostate cancer (PCa) progression. However, its role in the regulation of PCa cell growth and survival has not been well characterized.

METHODOLOGY/PRINCIPAL FINDINGS

Using experimental models that closely mimic clinical pathophysiology of PCa progression, we demonstrated that PDGF is a survival factor in PCa cells through upregulation of myeloid cell leukemia-1 (Mcl-1). PDGF treatment induced rapid nuclear translocation of β-catenin, presumably mediated by c-Abl and p68 signaling. Intriguingly, PDGF promoted formation of a nuclear transcriptional complex consisting of β-catenin and hypoxia-inducible factor (HIF)-1α, and its binding to Mcl-1 promoter. Deletion of a putative hypoxia response element (HRE) within the Mcl-1 promoter attenuated PDGF effects on Mcl-1 expression. Blockade of PDGF receptor (PDGFR) signaling with a pharmacological inhibitor AG-17 abrogated PDGF induction of Mcl-1, and induced apoptosis in metastatic PCa cells.

CONCLUSIONS/SIGNIFICANCE

Our study elucidated a crucial survival mechanism in PCa cells, indicating that interruption of the PDGF-Mcl-1 survival signal may provide a novel strategy for treating PCa metastasis.

Adherens junctions and cancer

Cadherins and catenins are the central cell-cell adhesion molecules in adherens junctions (AJs). This chapter reviews the knowledge concerning the role of cadherins and catenins in epithelial cancer and examines the published literature demonstrating the changes in the expression and function of these proteins in human cancer and the association of these changes with patient outcomes. The chapter also covers the mechanistic studies aiming at uncovering the significance of changes in cadherin and catenin expression in cancer and potential molecular mechanisms responsible for the causal role of AJs in cancer initiation and progression.

Effects of S-adenosylmethionine and methylthioadenosine on inflammation-induced colon cancer in mice

Chronic inflammation is an underlying risk factor for colon cancer. Tumor necrosis factor alpha (TNF-α) plays a critical role in the development of inflammation-induced colon cancer in a mouse model. S-adenosylmethionine (SAMe) and its metabolite methylthioadenosine (MTA) can inhibit lipopolysaccharide-induced TNF-α expression in macrophages. The aim of this work was to examine whether SAMe and MTA are effective in preventing inflammation-induced colon cancer and if so identify signaling pathways affected. Balb/c mice were treated with azoxymethane (AOM) and dextran sulfate sodium to induce colon cancer. Two days after AOM treatment, mice were divided into three groups: vehicle control, SAMe or MTA. Tumor load, histology, immunohistochemistry, gene and protein expression were determined. SAMe and MTA treatment reduced tumor load by ∼40%. Both treatments raised SAMe and MTA levels but MTA also raised S-adenosylhomocysteine levels. MTA treatment prevented the induction of many genes known to play pathogenetic roles in this model except for TNF-α and inducible nitric oxide synthase (iNOS). SAMe also had no effect on TNF-α or iNOS and was less inhibitory than MTA on the other genes. In vivo, both treatments induced apoptosis but inhibited proliferation, β-catenin, nuclear factor kappa B activation and interleukin (IL) 6 signaling. Effect of SAMe and MTA on IL-6 signaling was examined using Colo 205 colon cancer cells. In these cells, SAMe and MTA inhibited IL-6-induced IL-10 expression. MTA also inhibited IL-10 transcription and signal transducer and activator of transcription 3 activation. In conclusion, SAMe and MTA reduced inflammation-induced colon cancer and inhibited several pathways important in colon carcinogenesis.

Survival of pancreatic beta cells is partly controlled by a TCF7L2-p53-p53INP1-dependent pathway

The transcription factor T-cell factor 7-like 2 (TCF7L2) confers type 2 diabetes risk mainly through impaired insulin secretion, perturbed incretin effect and reduced beta-cell survival. The aim of this study was to identify the molecular mechanism through which TCF7L2 influences beta-cell survival. TCF7L2 target genes in INS-1 cells were identified using Chromatin Immunoprecipitation. Validation of targets was obtained by: siRNA silencing, real-time quantitative polymerase chain reaction, electrophoretic mobility shift assay, luciferase reporter assays and western blot. Apoptosis rate was measured by DNA degradation and caspase-3 content. Islet viability was estimated by measuring metabolic rate. TCF7L2 binds to 3646 gene promoters in INS-1 cells in high or low glucose, including Tp53, Pten, Uggt1, Adamts9 and Fto. SiRNA-mediated reduction in TCF7L2 activity resulted in increased apoptosis and increased expression of Tp53, which resulted in elevated p53 protein activity and an increased expression of the p53 target gene Tp53inp1 (encoding p53-induced-nuclear-protein 1). Reversing the increase in p53INP1 protein expression, seen after Tcf7l2 silencing, protected INS-1 cells from Tcf7l2 depletion-induced apoptosis. This result was replicated in primary rat islets. The risk T-allele of rs7903146 is associated with increased TCF7L2 mRNA expression and transcriptional activity. On the other hand, in vitro silencing of TCF7L2 lead to increased apoptosis. One possibility is that the risk T-allele increases expression of an inhibitory TCF7L2 isoform with lower transcriptional activity. These results identify the p53-p53INP1 pathway as a molecular mechanism through which TCF7L2 may affect beta-cell survival and established a molecular link between Tcf7l2 and two type 2 diabetes-associated genes, Tp53inp1 and Adamts9.

Do shared mechanisms underlying cell cycle regulation and synaptic plasticity underlie the reduced incidence of cancer in schizophrenia?

Evidence from epidemiology suggests that the incidence of cancer is reduced in those with schizophrenia. Clues that could explain this finding have recently emerged from neuroscience--genes that were previously thought only to be involved in cell cycle regulation have additional functions in post-mitotic neurons related to neuronal migration and synaptic plasticity. This brief communication provides a concise summary of this evidence. We propose that this convergence between epidemiology and neuroscience will provide a more tractable search space for candidate genes, and provide clues for etiopathogenesis of schizophrenia.

β-catenin dosage is a critical determinant of tracheal basal cell fate determination

The purpose of this study was to determine whether β-catenin regulates basal cell fate determination in the mouse trachea. Analysis of TOPGal transgene reporter activity and Wnt/β-catenin pathway gene expression suggested a role for β-catenin in basal cell proliferation and differentiation after naphthalene-mediated Clara-like and ciliated cell depletion. However, these basal cell activities occurred simultaneously, limiting precise determination of the role(s) played by β-catenin. This issue was overcome by analysis of β-catenin signaling in tracheal air-liquid interface cultures. The cultures could be divided into two phases: basal cell proliferation and basal cell differentiation. A role for β-catenin in basal cell proliferation was indicated by activation of the TOPGal transgene on proliferation days 3 to 5 and by transient expression of Myc (alias c-myc). Another peak of TOPGal transgene activity was detected on differentiation days 2 to 10 and was associated with the expression of Axin 2. These results suggest a role for β-catenin in basal to ciliated and basal to Clara-like cell differentiation. Genetic stabilization of β-catenin in basal cells shortened the period of basal cell proliferation but had a minor effect on this process. Persistent β-catenin signaling regulated basal cell fate by driving the generation of ciliated cells and preventing the production of Clara-like cells.

The role of nutraceuticals in the regulation of Wnt and Hedgehog signaling in cancer

Multiple cellular signaling pathways have been involved in the processes of cancer cell invasion and metastasis. Among many signaling pathways, Wnt and Hedgehog (Hh) signaling pathways are critically involved in embryonic development, in the biology of cancer stem cells (CSCs) and in the acquisition of epithelial to mesenchymal transition (EMT), and thus this article will remain focused on Wnt and Hh signaling. Since CSCs and EMT are also known to be responsible for cancer cell invasion and metastasis, the Wnt and Hedgehog signaling pathways are also intimately associated with cancer invasion and metastasis. Emerging evidence suggests the beneficial role of chemopreventive agents commonly known as nutraceutical in cancer. Among many such agents, soy isoflavones, curcumin, green tea polyphenols, 3,3'-diindolylmethane, resveratrol, lycopene, vitamin D, etc. have been found to prevent, reverse, or delay the carcinogenic process. Interestingly, these agents have also shown to prevent or delay the progression of cancer, which could in part be due to their ability to attack CSCs or EMT-type cells by attenuating the Wnt and Hedgehog signaling pathways. In this review, we summarize the current state of our knowledge on the role of Wnt and Hedgehog signaling pathways, and their targeted inactivation by chemopreventive agents (nutraceuticals) for the prevention of tumor progression and/or treatment of human malignancies.

GSK-3β: a key regulator in the initiation and progression of colorectal cancer

The Wnt/β-catenin signal transduction pathway plays an important role in the initiation and progression of colorectal cancer. Glycogen synthase kinase-3beta (GSK-3β) is a multi-functional serine/threonine kinase that plays an important regulatory role in the Wnt/β-catenin signal transduction pathway. However, there are two opposing views on the role of GSK-3β in the pathogenesis of colorectal cancer. On one hand, some researchers believe that inhibition of GSK-3β can promote tumor initiation and progression, and tumor growth will be inhibited if GSK-3β is activated. On the other hand, some other researchers hold the view that inhibition of GSK-3β can prevent tumor development, and the initiation and progression of tumors will be promoted if GSK-3β is activated. In this paper, we will review the roles that the Wnt/β-catenin signal transduction pathway and GSK-3β play in the pathogenesis of colorectal cancer.

Can colorectal cancer be prevented or treated by oral hormone replacement therapy?

Guanylyl cyclase C (GCC) is the receptor specifically expressed by intestinal cells for the paracrine hormones guanylin and uroguanylin and diarrheagenic bacterial heat-stable enterotoxins. This tissue-specific receptor coordinates lineage-dependent regulation of epithelial homeostasis, and its disruption contributes to intestinal tumorigenesis. It coordinates regenerative and metabolic circuits by restricting the cell cycle and proliferation and programming metabolic transitions central to organizing the dynamic crypt-surface axis. Further, mice deficient in GCC signaling are more susceptible to colon cancer induced by Apc mutations or the carcinogen azoxymethane. Moreover, guanylin and uroguanylin are gene products most commonly lost, early, in colon cancer in animals and humans. The role of GCC as a tumor suppressing receptor regulating proliferation and metabolism, together with the universal loss of guanylin and uroguanylin in tumorigenesis, suggests a model in which colorectal cancer is a paracrine hormone deficiency syndrome. In that context, activation of GCC reverses the tumorigenic phenotype by limiting growth of colorectal cancer cells by restricting progression through the G1/S transition and reprogramming metabolic circuits from glycolysis to oxidative phosphorylation, limiting bioenergetic support for rapid proliferation. These observations suggest a pathophysiological hypothesis in which GCC is a lineage-dependent tumor suppressing receptor coordinating proliferative homeostasis whose dysregulation through hormone loss contributes to neoplasia. The correlative therapeutic hypothesis suggests that colorectal cancer is a disease of hormone insufficiency that can be prevented or treated by oral supplementation with GCC ligands.

Traf2- and Nck-interacting kinase is essential for Wnt signaling and colorectal cancer growth

T-cell factor-4 (TCF4) is a transcription factor essential for maintaining the undifferentiated status and self-renewal of intestinal epithelial cells. It has therefore been considered that constitutive activation of TCF4 by aberrant Wnt signaling is a major force driving colorectal carcinogenesis. We previously identified Traf2- and Nck-interacting kinase (TNIK) as one of the proteins that interact with TCF4 in colorectal cancer cells, but its functional significance has not been elucidated. Here, we report that TNIK is an activating kinase for TCF4 and essential for colorectal cancer growth. TNIK, but not its catalytically inactive mutant, phosphorylated the conserved serine 154 residue of TCF4. Small interfering RNA targeting TNIK inhibited the proliferation of colorectal cancer cells and the growth of tumors produced by injecting colorectal cancer cells s.c. into immunodeficient mice. The growth inhibition was abolished by restoring the catalytic domain of TNIK, thus confirming that its enzyme activity is essential for the maintenance of colorectal cancer growth. Several ATP-competing kinase inhibitors have been applied to cancer treatment and have shown significant activity. Our findings suggest TNIK as a feasible target for pharmacologic intervention to ablate aberrant Wnt signaling in colorectal cancer.

Wild-type BRCA1, but not mutated BRCA1, regulates the expression of the nuclear form of beta-catenin

BRCA1 is an essential caretaker protein in the surveillance of DNA damage, is mutated in approximately 50% of all hereditary breast cancer cases, and its expression is frequently decreased in sporadic breast cancer. beta-Catenin is a multifunctional protein that forms adhesion complex with E-cadherins, alpha-catenin, and actin, and plays a central role in Wnt signaling through its nuclear translocation and activation of beta-catenin-responsive genes. Although significant progress has been made in understanding the Wnt/beta-catenin and BRCA1 signaling cascades, it is not known whether there is a link between beta-catenin and BRCA1. We observed that the expression of the active nuclear form of beta-catenin (also known as ABC, Ser37/Thr41-nonphosphorylated beta-catenin, dephosphorylated beta-catenin) was lower or absent in the nucleus in most BRCA1 familial breast cancer tissues (17 cases) compared with sporadic breast cancer (14 samples) and normal breast tissues. Wild-type-BRCA1, but not mutated BRCA1, interacted with beta-catenin and increased the levels of beta-catenin protein expression in vitro. Furthermore, H(2)O(2) induced the interaction of the nuclear form of beta-catenin with BRCA1. The active form of beta-catenin protein was downregulated upon exposure to H(2)O(2) in the nucleus of BRCA1-deficient HCC1937 breast cancer cells, whereas reconstitution of WT-BRCA1 in HCC1937 cells inhibited this downregulation. This study provides evidence of a novel interaction between BRCA1 and beta-catenin, and that loss of BRCA1 leads to impaired expression of the nuclear form of beta-catenin, which may contribute to the pathogenesis of breast cancer.

Chemoprevention of intestinal tumorigenesis in APCmin/+ mice by silibinin

Chemoprevention is a practical and translational approach to reduce the risk of various cancers including colorectal cancer (CRC), which is a major cause of cancer-related deaths in the United States. Accordingly, here we assessed chemopreventive efficacy and associated mechanisms of long-term silibinin feeding on spontaneous intestinal tumorigenesis in the APC(min/+) mice model. Six-week-old APC(min/+) mice were p.o. fed with vehicle control (0.5% carboxymethyl cellulose and 0.025% Tween 20 in distilled water) or 750 mg silibinin/kg body weight in vehicle for 5 d/wk for 13 weeks and then sacrificed. Silibinin feeding strongly prevented intestinal tumorigenesis in terms of polyp formation in proximal, middle, and distal portions of small intestine by 27% (P < 0.001), 34% (P < 0.001), and 49% (P < 0.001), respectively. In colon, we observed 55% (P < 0.01) reduction in number of polyps by silibinin treatment. In size distribution analysis, silibinin showed significant decrease in large-size polyps (>3 mm) by 66% (P < 0.01) and 88% (P < 0.001) in middle and distal portions of small intestine, respectively. More importantly, silibinin caused a complete suppression in >3 mm sized polyps and 92% reduction in >2 to 3 mm sized polyps in colon. Molecular analyses of polyps suggested that silibinin exerts its chemopreventive efficacy by inhibiting cell proliferation, inflammation, and angiogenesis; inducing apoptosis; decreasing beta-catenin levels and transcriptional activity; and modulating the expression profile of cytokines. These results show for the first time the efficacy and associated mechanisms of long-term p.o. silibinin feeding against spontaneous intestinal tumorigenesis in the APC(min/+) mice model, suggesting its chemopreventive potential against intestinal cancers including CRC.

Downregulation of Dickkopf-1 is responsible for high proliferation of breast cancer cells via losing control of Wnt/beta-catenin signaling

AIM

To investigate the role of DKK-1/Wnt/beta-catenin signaling in high proliferation of LM-MCF-7 breast cancer cells, a sub-clone of MCF-7 cell line.

METHODS

Two cell lines (MCF-7 and LM-MCF-7) with different proliferation abilities were used. LM-MCF-7 cells were transiently transfected with the pcDNA3-DKK-1 plasmid encoding the DKK-1 gene (or MCF-7 cells were transfected siRNA targeting DKK-1 mRNA). Flow cytometry analysis and 5-bromo-2'-deoxyuridine (BrdU) incorporation assay were applied to detect the cell proliferation. The expression levels of beta-catenin, phosphorylated beta-catenin, c-Myc, cyclin D1 and Survivin were examined by Western blot analysis. The regulation of Survivin was investigated by Luciferase reporter gene assay.

RESULTS

Western blot and RT-PCR analysis showed that the expression level of DKK-1 was downregulated in LM-MCF-7 relative to MCF-7 cells. Flow cytometry and BrdU incorporation assay showed DKK-1 could suppress growth of breast cancer cells. Overexpression of DKK-1 was able to accelerate phosphorylation-dependent degradation of beta-catenin and downregulate the expression of beta-catenin, c-Myc, cyclin D1 and Survivin. Luciferase reporter gene assay demonstrated that Survivin could be regulated by beta-catenin/TCF4 pathway.

CONCLUSION

We conclude that the downregulation of DKK-1 is responsible for the high proliferation ability of LM-MCF-7 breast cancer cells via losing control of Wnt/beta-catenin signaling pathway, in which c-Myc, cyclinD1 and Survivin serve as essential downstream effectors. Our finding provides a new insight into the mechanism of breast cancer cell proliferation.