The adenomatous polyposis coli tumor suppressor and Wnt signaling in the regulation of apoptosis

Genetic predisposition to polyposis syndromes

Hereditary polyposis syndromes are significant contributors to colorectal cancer (CRC). These syndromes are characterized by the development of various types and numbers of polyps, distinct inheritance patterns, and extracolonic manifestations. This review explores these syndromes with a focus on their genetic characteristics. Advances in diagnostics, particularly the identification of pathogenic germline variants through massive sequencing technologies, have enhanced our understanding of the genetic alterations associated with polyp formation and CRC risk. Identifying pathogenic variants beyond traditional diagnostic criteria improves the management and surveillance of these syndromes. Genetic diagnosis not only refines patient treatment and surveillance, but also informs relatives of potential risks, enabling appropriate management. However, challenges persist in determining the pathogenicity of newly discovered mutations due to their low prevalence. This review covers hereditary polyposis syndromes, from well-established to newly recognized types, providing insights into their genetic landscapes and highlighting the need for tailored surveillance based on genotype.

From Crypts to Cancer: A Holistic Perspective on Colorectal Carcinogenesis and Therapeutic Strategies

Colorectal cancer (CRC) represents a significant global health burden, with high incidence and mortality rates worldwide. Recent progress in research highlights the distinct clinical and molecular characteristics of colon versus rectal cancers, underscoring tumor location's importance in treatment approaches. This article provides a comprehensive review of our current understanding of CRC epidemiology, risk factors, molecular pathogenesis, and management strategies. We also present the intricate cellular architecture of colonic crypts and their roles in intestinal homeostasis. Colorectal carcinogenesis multistep processes are also described, covering the conventional adenoma-carcinoma sequence, alternative serrated pathways, and the influential Vogelstein model, which proposes sequential APC, KRAS, and TP53 alterations as drivers. The consensus molecular CRC subtypes (CMS1-CMS4) are examined, shedding light on disease heterogeneity and personalized therapy implications.

Uncovering novel therapeutic targets in glucose, nucleotides and lipids metabolism during cancer and neurological diseases

BACKGROUND

Cell metabolism functions without a stop in normal and pathological cells. Different metabolic changes occur in the disease. Cell metabolism influences biochemical and metabolic processes, signaling pathways, and gene regulation. Knowledge regarding disease metabolism is limited.

OBJECTIVE

The review examines the cell metabolism of glucose, nucleotides, and lipids during homeostatic and pathological conditions of neurotoxicity, neuroimmunological disease, Parkinson's disease, thymoma in myasthenia gravis, and colorectal cancer.

METHODS

Data collection includes electronic databases, the National Center for Biotechnology Information, and Google Scholar, with several inclusion criteria: cell metabolism, glucose metabolism, nucleotide metabolism, and lipid metabolism in health and disease patients suffering from neurotoxicity, neuroinflammation, Parkinson's disease, thymoma in myasthenia gravis. The initial number of collected and analyzed papers is 250. The final analysis included 150 studies out of 94 selected papers. After the selection process, 62.67% remains useful.

RESULTS AND CONCLUSION

A literature search shows that signaling molecules are involved in metabolic changes in cells. Differences between cancer and neuroimmunological diseases are present in the result section. Our finding enables insight into novel therapeutic targets and the development of scientific approaches for cancer and neurological disease onset, outcome, progression, and treatment, highlighting the importance of metabolic dysregulation. Current understanding, emerging research technologies and potential therapeutic interventions in metabolic programming is disucussed and highlighted.

Uncovering Oncogenic Mechanisms of Tumor Suppressor Genes in Breast Cancer Multi-Omics Data

Tumor suppressor genes (TSGs) are essential genes in the development of cancer. While they have many roles in normal cells, mutation and dysregulation of the TSGs result in aberrant molecular processes in cancer cells. Therefore, understanding TSGs and their roles in the oncogenic process is crucial for prevention and treatment of cancer. In this research, multi-omics breast cancer data were used to identify molecular mechanisms of TSGs in breast cancer. Differentially expressed genes and differentially coexpressed genes were identified in four large-scale transcriptomics data from public repositories and multi-omics data analyses of copy number, methylation and gene expression were performed. The results of the analyses were integrated using enrichment analysis and meta-analysis of a p-value summation method. The integrative analysis revealed that TSGs have a significant relationship with genes of gene ontology terms that are related to cell cycle, genome stability, RNA processing and metastasis, indicating the regulatory mechanisms of TSGs on cancer cells. The analysis frame and research results will provide valuable information for the further identification of TSGs in different types of cancers.

A multiscale cell-based model of tumor growth for chemotherapy assessment and tumor-targeted therapy through a 3D computational approach

OBJECTIVES

Computational modeling of biological systems is a powerful tool to clarify diverse processes contributing to cancer. The aim is to clarify the complex biochemical and mechanical interactions between cells, the relevance of intracellular signaling pathways in tumor progression and related events to the cancer treatments, which are largely ignored in previous studies.

MATERIALS AND METHODS

A three-dimensional multiscale cell-based model is developed, covering multiple time and spatial scales, including intracellular, cellular, and extracellular processes. The model generates a realistic representation of the processes involved from an implementation of the signaling transduction network.

RESULTS

Considering a benign tumor development, results are in good agreement with the experimental ones, which identify three different phases in tumor growth. Simulating tumor vascular growth, results predict a highly vascularized tumor morphology in a lobulated form, a consequence of cells' motile behavior. A novel systematic study of chemotherapy intervention, in combination with targeted therapy, is presented to address the capability of the model to evaluate typical clinical protocols. The model also performs a dose comparison study in order to optimize treatment efficacy and surveys the effect of chemotherapy initiation delays and different regimens.

CONCLUSIONS

Results not only provide detailed insights into tumor progression, but also support suggestions for clinical implementation. This is a major step toward the goal of predicting the effects of not only traditional chemotherapy but also tumor-targeted therapies.

APC gene promoter methylation as a potential biomarker for lung cancer diagnosis: A meta-analysis

BACKGROUND

The aim of this study was to quantitatively analysis the diagnostic performance of adenomatous polyposis coli (APC) gene promoter methylation in serum or sputum/bronchoalveolar lavage fluid (BLAF) as a biomarker for lung cancer identification through pooling of open published data.

METHODS

The relevant electronic MEDLINE, EMBASE, Ovid, web of science and CNKI databases were systematically searched to identify the studies related to APC gene promoter methylation for lung cancer diagnosis. Data of true positive (tp), false positive (fp), false negative (fn) and true negative (tn) were extracted from the publications included in the study. The pooled diagnostic sensitivity, specificity and area under summary receiver operating characteristic (SROC) curve (AUC-SROC) of APC gene promoter methylation were calculated. Publication bias was evaluated by Begg's funnel plot and Egger's line regression test.

RESULTS

Fourteen studies associated with APC gene promoter methylation and lung cancer were identified in the databases and finally included in the meta-analysis. The data was pooled using a random effect model due to significant statistical heterogeneity across the 14 studies (p < 0.05). Using the APC gene promoter methylation as a reference for lung cancer identification, the pooled diagnostic sensitivity and specificity were 0.43 (95% CI: 0.40-0.45), and 0.92 (95% CI: 0.90-0.95), respectively with combined diagnostic positive likelihood ratio (+LR) and negative likelihood ratio (-LR) of 7.15 (95% CI: 3.62-14.12) and 0.63 (95% CI: 0.57-0.71). The pooled diagnostic odds ratio (DOR) and AUC-SROC of APC gene promoter methylation for lung cancer diagnosis were 9.84 (95% CI: 5.77-16.79) and 0.7, respectively. The Begg's funnel plot and Egger's line regression test both indicated statistical publication bias (t = 5.40, p < 0.05).

CONCLUSIONS

APC gene promoter methylation in serum or sputum/BLAF is a potential biomarker for lung cancer diagnosis with high specificity. However, due to its low sensitivity, it may not be suitable for lung cancer screening in the general population.

Synthetic mRNAs; Their Analogue Caps and Contribution to Disease

The structure of synthetic mRNAs as used in vaccination against cancer and infectious diseases contain specifically designed caps followed by sequences of the 5′ untranslated repeats of β-globin gene. The strategy for successful design of synthetic mRNAs by chemically modifying their caps aims to increase resistance to the enzymatic deccapping complex, offer a higher affinity for binding to the eukaryotic translation initiation factor 4E (elF4E) protein and enforce increased translation of their encoded proteins. However, the cellular homeostasis is finely balanced and obeys to specific laws of thermodynamics conferring balance between complexity and growth rate in evolution. An overwhelming and forced translation even under alarming conditions of the cell during a concurrent viral infection, or when molecular pathways are trying to circumvent precursor events that lead to autoimmunity and cancer, may cause the recipient cells to ignore their differential sensitivities which are essential for keeping normal conditions. The elF4E which is a powerful RNA regulon and a potent oncogene governing cell cycle progression and proliferation at a post-transcriptional level, may then be a great contributor to disease development. The mechanistic target of rapamycin (mTOR) axis manly inhibits the elF4E to proceed with mRNA translation but disturbance in fine balances between mTOR and elF4E action may provide a premature step towards oncogenesis, ignite pre-causal mechanisms of immune deregulation and cause maturation (aging) defects.

Poly adenosine diphosphate-ribosylation, a promising target for colorectal cancer treatment

The development of colorectal cancer (CRC) can result from changes in a variety of cellular systems within the tumor microenvironment. Particularly, it is primarily associated with genomic instability that is the gradual accumulation of genetic and epigenetic changes consisting of a characteristic set of mutations crucial for pathways in CRC progression. Based on this background, the potential to focus on poly [adenosine diphosphate (ADP)-ribose] polymerase (PARP)-1 and poly-ADP ribosylation (PARylation) as the main causes of malignant formation of CRC may be considered. One of the important functions of PARP-1 and PARylation is its deoxyribonucleic acid (DNA) repair function, which plays a pivotal role in the DNA damage response and prevention of DNA damage maintaining the redox homeostasis involved in the regulation of oxidation and superoxide. PARP-1 and PARylation can also alter epigenetic markers and chromatin structure involved in transcriptional regulation for the oncogenes or tumor suppressor genes by remodeling histone and chromatin enzymes. Given the high importance of these processes in CRC, it can be considered that PARP-1 and PARylation are at the forefront of the pathological changes required for CRC progression. Therefore, this review addresses the current molecular biological features for understanding the multifactorial function of PARP-1 and PARylation in CRC related to the aforementioned roles; furthermore, it presents a summary of recent approaches with PARP-1 inhibition in non-clinical and clinical studies targeting CRC. This understanding could help embrace the importance of targeting PARP-1 and PARylation in the treatment of CRC, which may present the potential to identify various research topics that can be challenged both non-clinically and clinically.

Poly adenosine diphosphate-ribosylation, a promising target for colorectal cancer treatment

The development of colorectal cancer (CRC) can result from changes in a variety of cellular systems within the tumor microenvironment. Particularly, it is primarily associated with genomic instability that is the gradual accumulation of genetic and epigenetic changes consisting of a characteristic set of mutations crucial for pathways in CRC progression. Based on this background, the potential to focus on poly [adenosine diphosphate (ADP)-ribose] polymerase (PARP)-1 and poly-ADP ribosylation (PARylation) as the main causes of malignant formation of CRC may be considered. One of the important functions of PARP-1 and PARylation is its deoxyribonucleic acid (DNA) repair function, which plays a pivotal role in the DNA damage response and prevention of DNA damage maintaining the redox homeostasis involved in the regulation of oxidation and superoxide. PARP-1 and PARylation can also alter epigenetic markers and chromatin structure involved in transcriptional regulation for the oncogenes or tumor suppressor genes by remodeling histone and chromatin enzymes. Given the high importance of these processes in CRC, it can be considered that PARP-1 and PARylation are at the forefront of the pathological changes required for CRC progression. Therefore, this review addresses the current molecular biological features for understanding the multifactorial function of PARP-1 and PARylation in CRC related to the aforementioned roles; furthermore, it presents a summary of recent approaches with PARP-1 inhibition in non-clinical and clinical studies targeting CRC. This understanding could help embrace the importance of targeting PARP-1 and PARylation in the treatment of CRC, which may present the potential to identify various research topics that can be challenged both non-clinically and clinically.

Graviola mitigates acetic acid-induced ulcerative colitis in rats: insight on apoptosis and Wnt/Hh signaling crosstalk

In this study, we elucidated the potential protective effects of graviola leaves, compared with sulfasalazine, against acetic acid (AA)-induced ulcerative colitis (UC) in rats. Twenty-eight mature male rats were divided into four groups, Sham, Colitis, Colitis/Sulfa, and Colitis/Graviola, and were treated orally with either saline, saline, sulfasalazine (100 mg/kg/day), or graviola (100 mg/kg/day), respectively, for 7 days. On the 4th day, UC was induced by transrectal administration of 4% AA. Colon tissues were excised for macroscopic and histopathological evaluation and immunohistochemical analysis of caspase-3, B-cell lymphoma 2 (Bcl-2), and Bcl-2-associated X protein (Bax). Also, levels of oxidative mediators, Wnt family member1 (Wnt1), smoothened (Smo), and glioblastoma-1 (Gli1) were evaluated. Macroscopic and histopathological examination revealed that both graviola and sulfasalazine significantly mitigated colonic damage. Besides, both treatments significantly alleviated AA-induced oxidative stress, as evidenced by reduced nitric oxide (No) and malondialdehyde (MDA) levels and myeloperoxidase (MPO) activity and raised reduced glutathione (GSH) content. Both treatments significantly attenuated AA-induced apoptosis via downregulating the expression of Bax and caspase-3 and upregulating the expression of the anti-apoptotic protein, Bcl-2. Furthermore, downregulation of mRNA expression of Wnt1 with concomitant upregulation of Smo and Gli1 was observed in rats treated with either sulfasalazine or graviola. Based on these observations, graviola may attenuate AA-induced UC, at least partially, by modulating apoptosis and Wingless/Int1 (Wnt) and hedgehog (Hh) signaling crosstalk.

Pharmacological mechanism of Sishen Wan® attenuated experimental chronic colitis by inhibiting wnt/β-catenin pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Sishen Wan (SSW) is a commercial and frequently used Chinese patent medicine listed in the Chinese Pharmacopeia, which is usually used to treat chronic colitis.

AIM OF THE STUDY

We explored the pharmacological mechanism of Sishen Wan attenuated experimental chronic colitis by inhibiting Wnt/β-catenin pathway.

MATERIALS AND METHODS

Experimental chronic colitis was induced by trinitrobenzene sulfonic acid (TNBS). The therapeutic effect of SSW were analyzed by index of colonic weight, colonic length, pathological score. Cytokines expression were analyzed by ELISA, while the apoptosis level was checked by TUNEL staining. These proteins of Wnt/β-catenin signaling pathway was analyzed by Western blot assay.

RESULTS

Rats with TNBS-induced chronic colitis were treated by SSW for 10 days. The efficacy of SSW was demonstrated by improved macroscopic and microscopic colonic damage. SSW increased the level of ATP in colonic mucosa, while SSW inhibited β-catenin, ubiquitination of Nemo-like-kinase-associated ring finger protein and T-cell factor, and expression of Wnt/β-catenin downstream proteins (including c-Myc, cyclo-oxygenase-2, cyclin D1, survivin, signal transducer and activator of transcription 3 and zipper-interacting protein kinase), and improved lymphoid enhancer factor ubiquitination and β-TrCP activity, followed by excessive apoptosis of colonic epithelial cells.

CONCLUSIONS

SSW effectively attenuated experimental chronic colitis induced by TNBS, which was realized by inhibition of the Wnt/β-catenin signaling pathway.

Tumor suppressor genes in familial adenomatous polyposis

Colorectal cancer (CRC) is mostly due to a series of genetic alterations that are being greatly under the influence of the environmental factors. These changes, mutational or epigenetic modifications at transcriptional forefront and/or post-transcriptional effects via miRNAs, include inactivation and the conversion of proto-oncogene to oncogenes, and/or inactivation of tumor suppressor genes (TSG). Here, a thorough review was carried out on the role of TSGs with the focus on the APC as the master regulator, mutated genes and mal-/dysfunctional pathways that lead to one type of hereditary form of the CRC; namely familial adenomatous polyposis (FAP). This review provides a venue towards defining candidate genes that can be used as new PCR-based markers for early diagnosis of FAP. In addition to diagnosis, defining the modes of genetic alterations will open door towards genome editing to either suppress the disease or reduce its progression during the course of action.

Association between Hepatitis C Virus Infection, p53 Phenotypes, and Gene Variants of Adenomatous Polyposis Coli in Hepatocellular Carcinomas

OBJECTIVE

To investigate the clinical value of p53 codon 72 single nucleotide polymorphisms (SNPs) and variants of adenomatous polyposis coli (APC) in hepatocellular carcinomas (HCCs).

METHODS

DNA and RNA from 51 HCCs and their matching, uninvolved liver tissues were analyzed for p53 mutations, and the methylation and expression of APC variants were determined. Proliferation of each HCC was assessed by Ki67 immunohistochemistry. The results were correlated with the demographic and clinicopathologic features and patient survival.

RESULTS

Of 51 HCCs, 12% exhibited missense p53 mutations. SNP analysis of p53 codon 72 demonstrated the highest prevalence of the Arg/Arg (56%) phenotype, followed by Arg/Pro (33%) and Pro/Pro (11%). Four of five cases with the Pro/Pro phenotype were African Americans (AAs). All five cases with the Pro/Pro phenotype had hepatitis C virus (HCV) infections, a high Ki67 index, and lower median survival (15.5 months) compared to those with Arg/Arg or Arg/Pro phenotypes (32 months). The overall frequency of APC methylation was 31%, which was found predominantly in Caucasians. There was lower mRNA expression of APC variants-2 and -3 in both HCCs and corresponding adjacent, uninvolved liver tissues as compared to APC variant-1. The expression of APC variant-3, but not variants-1 and -2, was lower in HCCs relative to uninvolved tissues. Expression of all APC variants was lower in HCCs with APC methylation relative to HCCs without APC methylation, and low expression of APC variant-2 was associated with the Pro/Pro phenotype.

CONCLUSIONS

These findings suggest that, for AA patients with HCCs, the p53 Pro/Pro phenotype and low expression of APC variant-2 are associated with aggressive tumor behavior, HCV infection, and poor clinical outcome.

Biologic and molecular markers for staging colon carcinoma

Biomarkers in the field of pathology and oncology may allow for the detection of disease, assessment of prognosis or to predict response to certain therapy. Molecular abnormalities in colorectal cancer genesis may occur due to chromosome instability, microsatellite instability and DNA methylation (CpG island methylator phenotype). These alterations are associated in some cases to sporadic carcinomas whereas in others are seen in syndrome-related tumors and are the basis for the use of different biomarkers in the clinical setting. These may include mismatched repair gene/proteins, RAS, BRAF, PIK3CA, which help to determine tumor prognosis and predict response to certain drugs.

Hyperactivated Wnt signaling induces synthetic lethal interaction with Rb inactivation by elevating TORC1 activities

Inactivation of the Rb tumor suppressor can lead to increased cell proliferation or cell death depending on specific cellular context. Therefore, identification of the interacting pathways that modulate the effect of Rb loss will provide novel insights into the roles of Rb in cancer development and promote new therapeutic strategies. Here, we identify a novel synthetic lethal interaction between Rb inactivation and deregulated Wg/Wnt signaling through unbiased genetic screens. We show that a weak allele of axin, which deregulates Wg signaling and increases cell proliferation without obvious effects on cell fate specification, significantly alters metabolic gene expression, causes hypersensitivity to metabolic stress induced by fasting, and induces synergistic apoptosis with mutation of fly Rb ortholog, rbf. Furthermore, hyperactivation of Wg signaling by other components of the Wg pathway also induces synergistic apoptosis with rbf. We show that hyperactivated Wg signaling significantly increases TORC1 activity and induces excessive energy stress with rbf mutation. Inhibition of TORC1 activity significantly suppressed synergistic cell death induced by hyperactivated Wg signaling and rbf inactivation, which is correlated with decreased energy stress and decreased induction of apoptotic regulator expression. Finally the synthetic lethality between Rb and deregulated Wnt signaling is conserved in mammalian cells and that inactivation of Rb and APC induces synergistic cell death through a similar mechanism. These results suggest that elevated TORC1 activity and metabolic stress underpin the evolutionarily conserved synthetic lethal interaction between hyperactivated Wnt signaling and inactivated Rb tumor suppressor.

Inactivation of Rb tumor suppressor is common in cancers. Therefore, identification of genes and pathways that are synthetic lethal with Rb will provide new insights into the role of Rb in cancer development and promote the development of novel therapeutic approaches. Here we identified a novel synthetic lethal interaction between Rb inactivation and hyperactivated Wnt signaling and showed that this synthetic lethal interaction is conserved in mammalian systems. We demonstrate that hyperactivated Wnt signaling activate TORC1 activity and induce excessive energy stress with inactivated Rb tumor suppressor, which underpins the evolutionarily conserved synthetic lethal interaction. This study provides novel insights into the interactions between the Rb, Wnt, and mTOR pathways in regulating cellular energy balance, cell growth, and survival.

Wnt/β-catenin signaling regulates follicular development by modulating the expression of Foxo3a signaling components

Wnt signaling is an evolutionarily conserved pathway that regulates cell proliferation, differentiation and apoptosis. To investigate the possible role of Wnt signaling in the regulation of ovarian follicular development, secondary follicles were isolated and cultured in vitro in the presence or absence of its activator (LiCl or Wnt3a) or inhibitor (IWR-1). We have demonstrated that activation of β-catenin signals by activators dramatically suppressed follicular development by increasing granulosa cell apoptosis and inhibiting follicle steroidogenesis. In contrast, inhibition of Wnt signaling by IWR-1 was observed with better developed follicles and increased steroidogenesis. Further studies have shown that the transcription factor Forkhead box O3a (Foxo3a) and its downstream target molecules were modulated by the activators or the inhibitor. These findings provide evidence that Wnt signaling might negatively regulate follicular development potentially through Foxo3a signaling components.

HIF-1α expression correlates with cellular apoptosis, angiogenesis and clinical prognosis in rectal carcinoma

Regional hypoxia caused by accelerated cell proliferation and overgrowth is an important characteristic of neoplasm. Hypoxia can cause a series of changes in gene transcription and protein expression, thereby not only inducing tumor cell resistance to radiotherapy and chemotherapy but also promoting tumor invasion and metastasis. This study aimed to investigate the relationship between HIF-1α expression and cellular apoptosis, angiogenesis and clinical prognosis in rectal carcinoma. In 113 rectal carcinoma cases, cellular apoptosis was analyzed by the in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay, whereas the levels of HIF-1α expression, VEGF expression, microvessel density (MVD) and lymphatic vessel density(LVD) were examined by immunohistochemical staining. HIF-1 expression was detected in 67 of 113 rectal carcinoma cases (59.3 %). A positive correlation was found among HIF-1α expression, cellular apoptosis and angiogenesis. The 5-year survival rate in the HIF-1α-negative group was significantly higher than that in the HIF-1α-positive group (81.34 % versus 50 %, P < 0.05). According to the Cox regression analysis, HIF-1α expression, VEGF expression and cellular apoptosis index were independent risk factors for clinical prognosis in rectal carcinoma. Aberrant HIF-1α expression correlates with apoptosis inhibition, angiogenesis and poor prognosis in rectal carcinoma.

A discrimination index for selecting markers of tumor growth dynamic across multiple cancer studies with a cure fraction

To identify genomic markers with consistent effect on tumor dynamics across multiple cancer series, discrimination indices based on proportional hazards models can be used since they do not depend heavily on the sample size. However, the underlying assumption of proportionality of the hazards does not always hold, especially when the studied population is a mixture of cured and uncured patients, like in early-stage cancers. We propose a novel index that quantifies the capability of a genomic marker to separate uncured patients, according to their time-to-event outcomes. It allows to identify genomic markers characterizing tumor growth dynamic across multiple studies. Simulation results show that our index performs better than classical indices based on the Cox model. It is neither affected by the sample size nor the cure rate fraction. In a cross-study of early-stage breast cancers, the index allows to select genomic markers with a potential consistent effect on tumor growth dynamics.

The Wnt/β-catenin pathway cross-talks with STAT3 signaling to regulate survival of retinal pigment epithelium cells

Wnt/β-catenin signaling is an essential pathway that regulates numerous cellular processes, including cell survival. The molecular mechanisms contributing to pro-survival Wnt signaling are mostly unknown. Signal transducer and activator of transcription proteins (STATs) are a well-described family of transcription factors. STAT3 induces expression of anti-apoptotic genes in many tissues and is a downstream mediator of protective growth factors and cytokines. In this study, we investigated whether pro-survival Wnt signaling is mediated by STAT3. The Wnt3a ligand activated Wnt signaling in the retinal pigment epithelium ARPE-19 cell line and significantly increased the viability of cells exposed to oxidative stress. Furthermore, Wnt3a increased STAT3 activation and nuclear translocation, as measured by an antibody against phosphorylated STAT3. Reducing STAT3 levels with siRNA eliminated Wnt3a-dependent protection from oxidative stress. Together, these data demonstrate a previously unknown link between Wnt3a-mediated activation of STAT3 and cell survival, and indicate cross-talk between two important pro-survival signaling pathways.

Activation of Wnt/β-catenin signalling affects differentiation of cells arising from the cerebellar ventricular zone

Development of the cerebellum proceeds under the precise spatio-temporal control of several key developmental signalling pathways, including the Wnt/β-catenin pathway. We recently reported the activity of Wnt/β-catenin signalling in the perinatal cerebellar ventricular zone (VZ), a germinal centre in the developing cerebellum that gives rise to GABAergic and glial cells. In order to investigate the normal function of Wnt/β-catenin signalling in the VZ and the cell lineages it gives rise to, we used a combination of ex vivo cerebellar slice culture and in vivo genetic manipulation to dysregulate its activity during late embryonic development. Activation of the pathway at the cerebellar ventricular zone led to a reduction in the number of cells expressing the glial lineage markers Sox9 and GFAP and the interneuron marker Pax2, but had no consistent effect on either proliferation or apoptosis. Our findings suggest that activation of the Wnt/β-catenin pathway in the cerebellar ventricular zone causes a shift in the cell types produced, most likely due to disruption of normal differentiation. Thus, we propose that regulation of Wnt/β-catenin signalling levels are required for normal development of cells arising from the cerebellar ventricular zone during late embryogenesis.

Syndromes predisposing to pediatric central nervous system tumors: lessons learned and new promises

Central nervous system (CNS) neoplasms are a leading cause of morbidity and mortality among children with cancer. In contrast to adults, a genetic basis for brain tumors is relatively common in children. A child harboring a germline mutation in a cancer-related gene will be predisposed to develop CNS tumors. These cancer predisposition syndromes are rare but pose overwhelming clinical and psychosocial challenges to families and the treating team. Recent significant advances in our understanding of the biological processes that govern these genetic conditions combined with international efforts to define and treat clinical aspects of these tumors are transforming the lives of these individuals. In this article, we summarize recent progress made for each of the major CNS tumor syndromes. We discuss the biological and clinical relevance of such advances, and suggest a comprehensive approach to a child affected by a predisposition to brain tumors.

The CRM1 nuclear export protein in normal development and disease

CRM1 (Chromosomal Maintenance 1, also known as Exportin 1) is the major mammalian export protein that facilitates the transport of large macromolecules including RNA and protein across the nuclear membrane to the cytoplasm. The gene encoding CRM1 was originally identified in yeast as required to maintain higher order chromosome structure. In mammalian cells, CRM1 was found to bind several nuclear pore proteins hence its role in nuclear-cytosolic transport was discovered. In addition to nuclear-cytosolic transport, CRM1 also plays a role in centrosome duplication and spindle assembly, especially in response to DNA damage. The crystal structure of CRM1 suggests a complex protein that binds the Ran protein bound to GTP, allowing for a conformational change that facilitates binding to different cargo proteins through a nuclear export signal (NES). Included in the cadre of cargo are multiple tumor suppressor and oncoproteins as p53, BRCA1, Survivin, NPM, and APC, which function in the nucleus to regulate transcription or aid in chromosomal assembly and movement. An imbalance in the cytosolic level of these proteins has been observed in cancer cells, resulting in either inactivation (tumor suppressor) or an excess of anti-apoptotic activity (oncoprotein). Thus, the concept of inhibiting CRM1 has been explored as a potential therapeutic intervention. Indeed, inhibition of CRM1 by a variety of small molecules that interfere with cargo-NES binding results in cancer cell death. Whether all of these proteins together are responsible for this phenotype or whether specific proteins are required for this effect is unclear at this time.

Apc bridges Wnt/β-catenin and BMP signaling during osteoblast differentiation of KS483 cells

The canonical Wnt signaling pathway influences the differentiation of mesenchymal cell lineages in a quantitative and qualitative fashion depending on the dose of β-catenin signaling. Adenomatous polyposis coli (Apc) is the critical intracellular regulator of β-catenin turnover. To better understand the molecular mechanisms underlying the role of Apc in regulating the differentiation capacity of skeletal progenitor cells, we have knocked down Apc in the murine mesenchymal stem cell-like KS483 cells by stable expression of Apc-specific small interfering RNA. In routine culture, KSFrt-Apc(si) cells displayed a mesenchymal-like spindle shape morphology, exhibited markedly decreased proliferation and increased apoptosis. Apc knockdown resulted in upregulation of the Wnt/β-catenin and the BMP/Smad signaling pathways, but osteogenic differentiation was completely inhibited. This effect could be rescued by adding high concentrations of BMP-7 to the differentiation medium. Furthermore, KSFrt-Apc(si) cells showed no potential to differentiate into chondrocytes or adipocytes. These results demonstrate that Apc is essential for the proliferation, survival and differentiation of KS483 cells. Apc knockdown blocks the osteogenic differentiation of skeletal progenitor cells, a process that can be overruled by high BMP signaling.

Genetics, cytogenetics, and epigenetics of colorectal cancer

Most of the colorectal cancer (CRC) cases are sporadic, only 25% of the patients have a family history of the disease, and major genes causing syndromes predisposing to CRC only account for 5-6% of the total cases. The following subtypes can be recognized: MIN (microsatellite instability), CIN (chromosomal instability), and CIMP (CpG island methylator phenotype). CIN occurs in 80-85% of CRC. Chromosomal instability proceeds through two major mechanisms, missegregation that results in aneuploidy through the gain or loss of whole chromosomes, and unbalanced structural rearrangements that lead to the loss and/or gain of chromosomal regions. The loss of heterozygosity that occur in the first phases of the CRC cancerogenesis (in particular for the genes on 18q) as well as the alteration of methylation pattern of multiple key genes can drive the development of colorectal cancer by facilitating the acquisition of multiple tumor-associated mutations and the instability phenotype.

Significance of TRAF4 protein expression in gastric carcinoma

AIM: To investigate the correlation between the expression of tumor necrosis factor receptor-associated factor 4 (TRAF4) protein and tumor onset and evolution in gastric carcinoma.

METHODS: Tissue microarray was used to detect the expression of TRAF4 in 45 gastric carcinoma specimens, 45 tumor-adjacent tissue specimens, and 10 normal gastric tissue specimens. Cell apoptosis in TRAF4-positive gastric carcinoma specimens and normal gastric tissue specimens was detected by TUNEL assay.

RESULTS: TRAF4 was expressed in both the cytoplasm and nucleus in normal gastric tissue and gastric carcinoma. The positive rate of cytoplasmic TRAF4 expression was 80% in normal gastric tissue, 93.3% in dysplasia, and 95.6% in gastric carcinoma (P > 0.05). The positive rate of nuclear TRAF4 expression was significantly higher in normal gastric tissue than in gastric carcinoma (70.0% vs 35.6%, P < 0.05), in highly differentiated carcinoma than in poorly differentiated carcinoma (71.4% vs 26.1%, P < 0.05), and in gastric carcinoma without lymphatic metastasis than in that with lymphatic metastasis (52.4% vs 20.8%, P < 0.05). The apoptosis rate in TRAF4-positive normal gastric tissue was significant higher than that in gastric carcinoma (75% vs 37.2%, P < 0.05).

CONCLUSION: The nuclear expression of TRAF4 in gastric carcinoma is suppressed. Decreased nuclear expression of TRAF4 was positively correlated with tumor differentiation but negatively with tumor metastasis in gastric carcinoma.

Interstitial implantation of iodine-125 seeds induces apoptosis but inhibits cell proliferation in HCT-116-xenografted tumors in nude mice

AIM: To investigate the effect of interstitial implantation of iodine-125 on the growth of adenocarcinoma of the large intestine and to explore potential mechanisms involved.

METHODS: Nude mice bearing HCT-116-xenografted tumors were randomly divided into two groups (n = 24 each): control group and experimental group. The control group underwent implantation of empty seeds, while the experiment group underwent implantation of iodine-125 seeds (14.8 MBq). On days 7, 14, 21 and 28 after implantation, mice were killed to calculate tumor growth, detect the expression of proliferating cell nuclear antigen (PCNA) in tumor tissue by immunohistochemistry, determine the apoptosis of tumor cells by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, and observe the ultrastructural changes of tumor cells by transmission electron microscopy (TEM).

RESULTS: On days 7, 14, 21 and 28 after implantation, both tumor volume and weight were significantly lower in the experiment group than in the control group (tumor volume on day 28: 497.3 mm3 ± 7.8 mm3 vs 947.2 mm3 ± 40.4 mm3, P < 0.01; tumor weight on day 28: 1.131 g ± 0.079 g vs 2.139 g ± 0.094 g, P < 0.01). The reduced rate of tumor growth in the experimental group was higher than that in the control group (on day 28: 47.12% vs 25.77%). The expression of PCNA in the experiment group decreased with time and was significantly lower on day 28 than that in the control group. On day 14, apoptotic bodies began to appear and then gradually increased in number, reaching the peak on day 28.

CONCLUSION: Interstitial implantation of iodine-125 seeds induces apoptosis but inhibits cell proliferation in HCT-116-xenografted tumors in nude mice.

Cell regulation by the Apc protein Apc as master regulator of epithelia

The adenomatous polyposis coli (Apc) protein participates in many of the fundamental cellular processes that govern epithelial tissues: Apc is directly involved in regulating the availability of beta-catenin for transcriptional de-repression of Tcf/LEF transcription factors, it contributes to the stability of microtubules in interphase and mitosis, and has an impact on the dynamics of F-actin. Thus Apc contributes directly and/or indirectly to proliferation, differentiation, migration, and apoptosis. This particular multifunctionality can explain why disruption of Apc is especially detrimental for the epithelium of the gut, where Apc mutations are common in most cancers. We summarise recent data that shed light on the molecular mechanisms involved in the different functions of Apc.