Inactivation of ELF/TGF-beta signaling in human gastrointestinal cancer

IQGAP3 signalling mediates intratumoral functional heterogeneity to enhance malignant growth

BACKGROUND

The elevation of IQGAP3 expression in diverse cancers indicates a key role for IQGAP3 in carcinogenesis. Although IQGAP3 was established as a proliferating stomach stem cell factor and a regulator of the RAS-ERK pathway, how it drives cancer growth remains unclear.

OBJECTIVE

We define the function of IQGAP3 in gastric cancer (GC) development and progression.

DESIGN

We studied the phenotypic changes caused by IQGAP3 knockdown in three molecularly diverse GC cell lines by RNA-sequencing. In vivo tumorigenesis and lung metastasis assays corroborated IQGAP3 as a mediator of oncogenic signalling. Spatial analysis was performed to evaluate the intratumoral transcriptional and functional differences between control tumours and IQGAP3 knockdown tumours.

RESULTS

Transcriptomic profiling showed that IQGAP3 inhibition attenuates signal transduction networks, such as KRAS signalling, via phosphorylation blockade. IQGAP3 knockdown was associated with significant inhibition of MEK/ERK signalling-associated growth factors, including TGFβ1, concomitant with gene signatures predictive of impaired tumour microenvironment formation and reduced metastatic potential. Xenografts involving IQGAP3 knockdown cells showed attenuated tumorigenesis and lung metastasis in immunodeficient mice. Accordingly, immunofluorescence staining revealed significant reductions of TGFβ/SMAD signalling and αSMA-positive stromal cells; digital spatial analysis indicated that IQGAP3 is indispensable for the formation of two phenotypically diverse cell subpopulations, which played crucial but distinct roles in promoting oncogenic functions.

CONCLUSION

IQGAP3 knockdown suppressed the RAS-TGFβ signalling crosstalk, leading to a significant reduction of the tumour microenvironment. In particular, IQGAP3 maintains functional heterogeneity of cancer cells to enhance malignant growth. IQGAP3 is thus a highly relevant therapy target in GC.

Advances of Tumorigenesis, Diagnosis at Early Stage, and Cellular Immunotherapy in Gastrointestinal Malignancies

Globally, in 2018, 4.8 million new patients have a diagnosis of gastrointestinal (GI) cancers, while 3.4 million people died of such disorders. GI malignancies are tightly relevant to 26% of the world-wide cancer incidence and occupies 35% of all cancer-associated deaths. In this article, we principally investigated molecular and cellular mechanisms of tumorigenesis in five major GI cancers occurring at esophagus, stomach, liver, pancreas, and colorectal region that illustrate high morbidity in Eastern and Western countries. Moreover, through this investigation, we not only emphasize importance of the tumor microenvironment in development and treatment of malignant tumors but also identify significance of M2PK, miRNAs, ctDNAs, circRNAs, and CTCs in early detection of GI cancers, as well as systematically evaluate contribution of personalized precision medicine including cellular immunotherapy, new antigen and vaccine therapy, and oncolytic virotherapy in treatment of GI cancers.

SPTBN1 inhibits inflammatory responses and hepatocarcinogenesis via the stabilization of SOCS1 and downregulation of p65 in hepatocellular carcinoma

Background: Spectrin, beta, non-erythrocytic 1 (SPTBN1), an adapter protein for transforming growth factor beta (TGF-β) signaling, is recognized as a tumor suppressor in the development of hepatocellular carcinoma (HCC); however, the underlying molecular mechanisms of this tumor suppression remain obscure.

Methods: The effects on expression of pro-inflammatory cytokines upon the inhibition or impairment of SPTBN1 in HCC cell lines and liver tissues of Sptbn1^+/- and wild-type (WT) mice were assessed by analyses of quantitative real-time reverse-transcription polymerase chain reaction (QRT-PCR), enzyme linked immunosorbent assay (ELISA), Western blotting and gene array databases from HCC patients. We investigated the detailed molecular mechanisms underlying the inflammatory responses by immunoprecipitation-Western blotting, luciferase reporter assay, chromatin immunoprecipitation quantitative real time PCR (ChIP-qPCR), immunohistochemistry (IHC) and electrophoretic mobility shift assay (EMSA). The proportion of myeloid-derived suppressor cells in liver, spleen, bone marrow and peripheral blood samples from WT and Sptbn1^+/- mice were measured by fluorescence-activated cell sorting (FACS) analysis. Further, the hepatocacinogenesis and its correlation with inflammatory microenvironment by loss of SPTBN1/SOCS1 and induction of p65 were analyzed by treating WT and Sptbn1^+/- mice with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC).

Results: Loss of SPTBN1 in HCC cells upregulated the expression of pro-inflammatory cytokines including interleukin-1α (IL-1α), IL-1β, and IL-6, and enhanced NF-κB transcriptional activation. Mechanistic analyses revealed that knockdown of SPTBN1 by siRNA downregulated the expression of suppressor of cytokine signaling 1 (SOCS1), an E3 ligase of p65, and subsequently upregulated p65 accumulation in the nucleus of HCC cells. Restoration of SOCS1 abrogated this SPTBN1 loss-associated elevation of p65 in HCC cells. In human HCC tissues, SPTBN1 gene expression was inversely correlated with gene expression of IL-1α, IL-1β and IL-6. Furthermore, a decrease in the levels of SPTBN1 gene, as well as an increase in the gene expression of IL-1β or IL-6 predicted shorter relapse free survival in HCC patients, and that HCC patients with low expression of SPTBN1 or SOCS1 protein is associated with poor survival. Heterozygous loss of SPTBN1 (Sptbn1^+/-) in mice markedly upregulated hepatic expression of IL-1α, IL-1β and IL-6, and elevated the proportion of myeloid-derived suppressor cells (MDSCs) and CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Foxp3⁺Treg) cells in the liver, promoting hepatocarcinogenesis of mouse fed by DDC.

Conclusions: Our findings provided evidence that loss of SPTBN1 in HCC cells increases p65 protein stability via the inhibition of SOCS1 and enhances NF-κB activation, stimulating the release of inflammatory cytokines, which are critical molecular mechanisms for the loss of SPTBN1-induced liver cancer formation. Reduced SPTBN1 and SOCS1 predict poor outcome in HCC patients.

βII spectrin (SPTBN1): biological function and clinical potential in cancer and other diseases

βII spectrin, the most common isoform of non-erythrocyte spectrin, is a cytoskeleton protein present in all nucleated cells. Interestingly, βII spectrin is essential for the development of various organs such as nerve, epithelium, inner ear, liver and heart. The functions of βII spectrin include not only establishing and maintaining the cell structure but also regulating a variety of cellular functions, such as cell apoptosis, cell adhesion, cell spreading and cell cycle regulation. Notably, βII spectrin dysfunction is associated with embryonic lethality and the DNA damage response. More recently, the detection of altered βII spectrin expression in tumors indicated that βII spectrin might be involved in the development and progression of cancer. Its mutations and disorders could result in developmental disabilities and various diseases. The versatile roles of βII spectrin in disease have been examined in an increasing number of studies; nonetheless, the exact mechanisms of βII spectrin are still poorly understood. Thus, we summarize the structural features and biological roles of βII spectrin and discuss its molecular mechanisms and functions in development, homeostasis, regeneration and differentiation. This review highlight the potential effects of βII spectrin dysfunction in cancer and other diseases, outstanding questions for the future investigation of therapeutic targets. The investigation of the regulatory mechanism of βII spectrin signal inactivation and recovery may bring hope for future therapy of related diseases.

A case–control study of microRNA polymorphisms in gastric cancer screening by SNP chip combined with time of flight mass spectrometry

Aims: To explore new SNP sites of miRNAs associated with gastric cancer, thereby providing valuable biomarkers to diagnose and screen gastric cancer. Materials & methods: A 1:1 case–control study was carried out. Microarrays were used to screen the SNP loci of miRNAs in the genomes of matched pairs of patients, 96 with gastric cancer and 96 healthy controls. For validation, mass spectrometry was used to classify miRNA SNP loci in 622 pairs of subjects. Results: rs7143252 was linked to a higher occurrence of gastric cancer. Conclusion: These results suggest that rs7143252 could be used as a specific biomarker to diagnose and screen gastric cancer.

LINC00565 promotes proliferation and inhibits apoptosis of gastric cancer by targeting miR-665/AKT3 axis

Background

Numerous studies have shown that long noncoding RNA (lncRNA) is involved in gastric cancer (GC). A relevant microarray containing gastric cancer-related lncRNAs was downloaded from The Cancer Genome Atlas database.

Methods

qRT-PCR was used to analyze LINC00565 and AKT3 expression in tumor tissues and cell lines. Proliferative, colony formation and apoptotic abilities of GC cells after transfection of sh-LINC00565 were determined by CCK-8, colony formation assay and flow cytometry, respectively. RIP was enrolled to detect the interaction between LINC00565, AKT3 and miR-665. Dual luciferase assay was used to confirm the relation between miR-665 and LINC00565 and AKT3.

Results

Expression level of LINC00565 in GC tissue was highly expressed in GC, which was negatively correlated to prognosis of GC patients. The results showed that knockdown of LINC00565 decreased proliferative and colony formation abilities, and induced apoptosis of GC cells. Pearson analysis showed that LINC00565 was positively correlated with AKT3. Besides, AKT3 was significantly up-regulated in GC. In addition, knockdown of LINC00565 down-regulated AKT3. In order to explore the mechanism, we found that miR-665 could bind to LINC00565 by bioinformatics. Dual-luciferase reporter gene assay and RIP assay both verified the binding relationship between miR-665 and AKT3. Finally, rescue experiments were carried out to explore whether AKT3 could reverse the anti-cancer effect of low-level LINC00565 on GC development.

Conclusion

In summary, the expression of LINC00565 is upregulated in GC. LINC00565 can be used as the sponge of miR-665 to up-regulate the expression of AKT3, thus promoting the progression of GC.

SPTBN1 and cancer, which links?

SPTBN1 is a dynamic intracellular nonpleckstrin homology-domain protein, functioning as a transforming growth factor-β signal transducing adapter protein which is necessary to form Smad3/Smad4 complex. Recently SPTBN1 is considered to be associated with many kinds of cancers. SPTBN1 expression and function differ between different tumor states or types. This review summarizes the recent advances in the expression patterns of SPTBN1 in cancers, and in understanding the mechanisms by which SPTBN1 affects the occurrence, progression, and metastasis of cancer. Identifying SPTBN1 expression and function in cancers will contribute to the clinical diagnosis and treatment of cancer and the investigation of anticancer drugs.

EPB41L5 Mediates TGFβ-Induced Metastasis of Gastric Cancer

PURPOSE

Because of disease heterogeneity, limited studies on effective chemotherapies and therapeutic agents for advanced gastric cancer are available. Erythrocyte membrane protein band 4.1-like 5 (EPB41L5) has critical roles in renal and breast cancer metastasis. However, its role in metastatic gastric cancer remains unknown.

EXPERIMENTAL DESIGN

The specimens of 78 gastric cancer patients were analyzed by oligonucleotide microarray and survival analysis. In vitro experiments and metastatic mice models were used to assess the effects of EPB41L5 on gastric cancer metastasis.

RESULTS

Gastric cancer patients with high EPB41L5 levels had poor prognosis and low survival rate. Further, TGFβ1-induced EPB41L5 expression promoted gastric cancer cell migration and invasion by Smad-dependent TGFβ signaling. Phospho-Smad3 recruitment to the EPB41L5 promoter was significantly inhibited by a TGFβ inhibitor. EPB41L5 overexpression increased lung metastasis of gastric cancer cells in nude mice, which was completely reversed by anti-EPB41L5 monoclonal antibody treatment. Importantly, p120-catenin knockdown abolished EPB41L5-enhanced gastric cancer cell metastasis. Anti-EPB41L5 monoclonal antibody treatment blocked the association of EPB41L5 with p120-catenin.

CONCLUSIONS

TGFβ/EPB41L5/p120-catenin axis regulates gastric cancer cell metastasis, and EPB41L5 is a promising therapeutic target for advanced gastric cancer.

Alcohol, stem cells and cancer

Dosage, gender, and genetic susceptibility to the effects of alcohol remained only partially elucidated. In this review, we summarize the current knowledge of the mechanisms underlying the role of alcohol in liver and gastrointestinal cancers. In addition, two recent pathways- DNA repair and TGF-β signaling which provide new insights into alcohol in the regulation of cancers and stem cells are also discussed here.

Cytokine networks and their association with Helicobacter pylori infection in gastric carcinoma

Cytokine networks as dynamic networks are pivotal aspects of tumor immunology, especially in gastric cancer (GC), in which infection, inflammation, and antitumor immunity are key elements of disease progression. In this review, we describe functional roles of well-known GC-modulatory cytokines, highlight the functions of cytokines with more recently described roles in GC, and emphasize the therapeutic potential of targeting the complex cytokine milieu. We also focus on the role of Helicobacter pylori (HP)-induced inflammation in GC and discuss how HP-induced chronic inflammation can lead to the induction of stem cell hyperplasia, morphological changes in gastric mucosa and GC development.

TGF-β signaling in liver and gastrointestinal cancers

Transforming Growth Factor-β (TGF-β) plays crucial and complex roles in liver and gastrointestinal cancers. These include a multitude of distinct functions, such as maintaining stem cell homeostasis, promoting fibrosis, immune modulating, as a tumor suppressor and paradoxically, as a tumor progressor. However, key mechanisms for the switches responsible for these distinct actions are poorly understood, and remain a challenge. The Cancer Genome Atlas (TCGA) analyses and genetically engineered mouse models now provide an integrated approach to dissect these multifaceted and context-dependent driving roles of the TGF-β pathway. In this review, we will discuss the molecular mechanisms of TGF-β signaling, focusing on colorectal, gastric, pancreatic, and liver cancers. Novel drugs targeting the TGF-β pathway have been developed over the last decade, and some have been proven effective in clinical trials. A better understanding of the TGF-β pathway may improve our ability to target it, thus providing more tools to the armamentarium against these deadly cancers.

Caspase-3/7-mediated Cleavage of β2-spectrin is Required for Acetaminophen-induced Liver Damage

The ubiquitously expressed β2-spectrin (β2SP, SPTBN1) is the most common non-erythrocytic member of the β-spectrin gene family. Loss of β2-spectrin leads to defects in liver development, and its haploinsufficiency spontaneously leads to chronic liver disease and the eventual development of hepatocellular cancer. However, the specific role of β2-spectrin in liver homeostasis remains to be elucidated. Here, we reported that β2-spectrin was cleaved by caspase-3/7 upon treatment with acetaminophen which is the main cause of acute liver injury. Blockage of β2-spectrin cleavage robustly attenuated β2-spectrin-specific functions, including regulation of the cell cycle, apoptosis, and transcription. Cleaved fragments of β2-spectrin were physiologically active, and the N- and C-terminal fragments retained discrete interaction partners and activity in transcriptional regulation and apoptosis, respectively. Cleavage of β2-spectrin facilitated the redistribution of the resulting fragments under conditions of liver damage induced by acetaminophen. In contrast, downregulation of β2-spectrin led to resistance to acetaminophen-induced cytotoxicity, and its insufficiency in the liver promoted suppression of acetaminophen-induced liver damage and enhancement of liver regeneration.

CONCLUSIONS

β2-Spectrin, a TGF-β mediator and signaling molecule, is cleaved and activated by caspase-3/7, consequently enhancing apoptosis and transcriptional control to determine cell fate upon liver damage. These findings have extended our knowledge on the spectrum of β2-spectrin functions from a scaffolding protein to a target and transmitter of TGF-β in liver damage.

The prognostic value of combined TGF-β1 and ELF in hepatocellular carcinoma

BACKGROUND

Tumor suppression of Transforming Growth Factor (TGF-β) signaling pathway requires an adaptor protein, Embryonic Liver Fodrin (ELF). Disruption of ELF expression resulted in miscolocalization of Smad3 and Smad4, then disruption of TGF-β signaling. However, the prognostic significance of ELF for hepatocellular carcinoma (HCC) hasn't been clarified. This study aimed to investigate whether measuring both TGF-β1 and ELF provides a more powerful predictor for HCC prognosis than either marker alone.

METHODS

TGF-β1 and ELF protein were detected by immunohistochemistry. The relationship between TGF-β1/ELF expression and patients' clinicopathologic factors was analyzed. The association between TGF-β1/ELF expression and disease-free survival and overall survival was analyzed by Kaplan-Meier curves, the log-rank test, and Multivariate Cox regression analyses.

RESULTS

The expression of TGF-β1 in HCC tissues was significantly higher than that in normal liver tissues. Conversely, the expression of ELF in HCC tissues declined markedly. ELF protein was correlated with HBsAg, tumor size, tumor number, TNM and recurrence. Data also indicated a significant negative correlation between ELF and TGF-β1. Patients with high TGF-β1 expression or/and low ELF expression appeared to have a poor postoperative disease-free survival and overall survival compared with those with low TGF-β1 expression or/and high ELF expression. Furthermore, the predictive range of ELF combined with TGF-β1 was more sensitive than that of either one alone.

CONCLUSIONS

TGF-β1 and ELF protein are potential and reliable biomarkers for predicting prognosis in HCC patients after hepatic resection. Our current study has demonstrated that the prognostic accuracy of testing can be enhanced by their combination.

Stem cells in gastrointestinal cancers: The road less travelled

Cancer stem cells (CSC) are thought to be malignant cells that have the capacity to initiate and maintain tumor growth and survival. Studies have described CSC in various gastrointestinal neoplasms such as colon, pancreas and liver and gastroesophageal tumors. The mechanism by which CSC develop remains unclear. Several studies have explored the role of dysregulation of the Wnt/β-catenin, transformation growth factor-beta and hedhog pathways in generation of CSC. In this review, we discuss the various molecular abnormalities that may be related to formation of CSC in gastrointestinal malignancies, strategies to identify CSC and therapeutic strategies that are based on these concepts. Identification and targeting CSC is an intriguing area and may provide a new therapeutic option for patients with cancer including gastrointestinal malignancies. Although great progress has been made, many issues need to be addressed. Precise targeting of CSC will require precise isolation and characterization of those cells. This field is also evolving but further research is needed to identify markers that are specific for CSC. Although the application of this field has not entered the clinic yet, there continues to be significant optimism about its potential utility in overcoming cancer resistance and curing patients with cancer.

A meta-analysis of multiple matched copy number and transcriptomics data sets for inferring gene regulatory relationships

Inferring gene regulatory relationships from observational data is challenging. Manipulation and intervention is often required to unravel causal relationships unambiguously. However, gene copy number changes, as they frequently occur in cancer cells, might be considered natural manipulation experiments on gene expression. An increasing number of data sets on matched array comparative genomic hybridisation and transcriptomics experiments from a variety of cancer pathologies are becoming publicly available. Here we explore the potential of a meta-analysis of thirty such data sets. The aim of our analysis was to assess the potential of in silico inference of trans-acting gene regulatory relationships from this type of data. We found sufficient correlation signal in the data to infer gene regulatory relationships, with interesting similarities between data sets. A number of genes had highly correlated copy number and expression changes in many of the data sets and we present predicted potential trans-acted regulatory relationships for each of these genes. The study also investigates to what extent heterogeneity between cell types and between pathologies determines the number of statistically significant predictions available from a meta-analysis of experiments.

SMAD4 suppresses AURKA-induced metastatic phenotypes via degradation of AURKA in a TGFβ-independent manner

SMAD4 has been suggested to inhibit the activity of the WNT/β-catenin signaling pathway in cancer. However, the mechanism by which SMAD4 antagonizes WNT/β-catenin signaling in cancer remains largely unknown. Aurora A kinase (AURKA), which is frequently overexpressed in cancer, increases the transcriptional activity of β-catenin/T-cell factor (TCF) complex by stabilizing β-catenin through the inhibition of GSK-3β. Here, SMAD4 modulated AURKA in a TGFβ-independent manner. Overexpression of SMAD4 significantly suppressed AURKA function, including colony formation, migration, and invasion of cell lines. In addition, SMAD4 bound to AURKA induced degradation of AURKA by the proteasome. A luciferase activity assay revealed that the transcriptional activity of the β-catenin/TCF complex was elevated by AURKA, but decreased by SMAD4 overexpression. Moreover, target gene analysis showed that SMAD4 abrogated the AURKA-mediated increase of β-catenin target genes. However, this inhibitory effect of SMAD4 was abolished by overexpression of AURKA or silencing of AURKA in SMAD4-overexpressed cells. Meanwhile, the SMAD4-mediated repression of AURKA and β-catenin was independent of TGFβ signaling because blockage of TGFβR1 or restoration of TGFβ signaling did not prevent suppression of AURKA and β-catenin signaling by SMAD4. These results indicate that the tumor-suppressive function of SMAD4 is mediated by downregulation of β-catenin transcriptional activity via AURKA degradation in a TGFβ-independent manner.

IMPLICATIONS

SMAD4 interacts with AURKA and antagonizes its tumor-promoting potential, thus demonstrating a novel mechanism of tumor suppression.

Loss of TGF-β adaptor β2SP activates notch signaling and SOX9 expression in esophageal adenocarcinoma

TGF-β and Notch signaling pathways play important roles in regulating self-renewal of stem cells and gastrointestinal carcinogenesis. Loss of TGF-β signaling components activates Notch signaling in esophageal adenocarcinoma, but the basis for this effect has been unclear. Here we report that loss of TGF-β adapter β2SP (SPNB2) activates Notch signaling and its target SOX9 in primary fibroblasts or esophageal adenocarcinoma cells. Expression of the stem cell marker SOX9 was markedly higher in esophageal adenocarcinoma tumor tissues than normal tissues, and its higher nuclear staining in tumors correlated with poorer survival and lymph node invasion in esophageal adenocarcinoma patients. Downregulation of β2SP by lentivirus short hairpin RNA increased SOX9 transcription and expression, enhancing nuclear localization for both active Notch1 (intracellular Notch1, ICN1) and SOX9. In contrast, reintroduction into esophageal adenocarcinoma cells of β2SP and a dominant-negative mutant of the Notch coactivator mastermind-like (dnMAN) decreased SOX9 promoter activity. Tumor sphere formation and invasive capacity in vitro and tumor growth in vivo were increased in β2SP-silenced esophageal adenocarcinoma cells. Conversely, SOX9 silencing rescued the phenotype of esophageal adenocarcinoma cells with loss of β2SP. Interaction between Smad3 and ICN1 via Smad3 MH1 domain was also observed, with loss of β2SP increasing the binding between these proteins, inducing expression of Notch targets SOX9 and C-MYC, and decreasing expression of TGF-β targets p21(CDKN1A), p27 (CDKN1B), and E-cadherin. Taken together, our findings suggest that loss of β2SP switches TGF-β signaling from tumor suppression to tumor promotion by engaging Notch signaling and activating SOX9.

Quantitative and robust assay to measure cell-cell contact assembly and maintenance

Epithelial junction formation and maintenance are multistep processes that rely on the clustering of macromolecular complexes. These events are highly regulated by signalling pathways that involve Rho small GTPases. Usually, when analysing the contribution of different components of Rho-dependent pathways to cell-cell adhesion, the localisation of adhesion receptors at junctions is evaluated by immunofluorescence. However, we find that this method has limitations on the quantification (dynamic range), ability to detect partial phenotypes and to differentiate between the participation of a given regulatory protein in assembly and/or maintenance of cell-cell contacts.In this chapter, we describe a suitable method, the aggregation assay, in which we adapted a quantitative strategy to allow objective and reproducible detection of partial phenotypes. Importantly, this methodology estimates the ability of cells to form junctions and their resistance to mechanical shearing forces (stabilisation).

Loss of transforming growth factor β adaptor protein β-2 spectrin leads to delayed liver regeneration in mice

Liver regeneration, following partial hepatectomy (PHx), occurs through precisely controlled and synchronized cell proliferation, in which quiescent hepatocytes undergo one to two rounds of replication, with restoration of liver mass and function. We previously demonstrated that loss of the Smad3/4 adaptor protein β-2 spectrin (β2SP) is associated with faster entry into S phase, and hepatocellular cancer formation. These observations led us to further pursue the role of β2SP in cell cycle progression in vivo. Liver regeneration studies with PHx in β2SP(+/-) mice reveal a surprising and significant decrease in liver/body weight ratio at 48 hours after PHx in β2SP(+/-) mice in comparison to wildtype mice. At 48 hours after PHx we also observe decreased levels of cyclin E (2.4-fold, P < 0.05), Cdk1 (7.2-fold, P < 0.05), cyclin A, pRb (Ser249/Thr252), proliferative cell nuclear antigen (PCNA), cyclin D1 with elevated levels of pCdk1 (Thr14) (3.6-fold, P < 0.05). Strikingly, at 24 hours elevated levels of p53 (4-fold, P < 0.05), phospho-p53 (ser15 and ser20), and p21 (200-fold, P < 0.05) persisting to 48 hours after PHx further correlated with raised expression of the DNA damage markers pChk2 (Thr68) and γH2AX (S139). However, compromised cell cycle progression with loss of β2SP is not rescued by inhibiting p53 function, and that G(2) /M phase arrest observed is independent and upstream of p53.

CONCLUSION

β2SP deficiency results in dysfunctional hepatocyte cell cycle progression and delayed liver regeneration at 48 hours after PHx, which is p53-independent. β2SP loss may increase susceptibility to DNA damage, impair cell cycle progression, and ultimately lead to hepatocellular cancer.

Transforming growth factor-β adaptor, β2-spectrin, modulates cyclin dependent kinase 4 to reduce development of hepatocellular cancer

Transforming growth factor beta (TGF-β) is an important regulator of cell growth, and loss of TGF-β signaling is a hallmark of carcinogenesis. The Smad3/4 adaptor protein β2-spectrin (β2SP) is emerging as a potent regulator of tumorigenesis through its ability to modulate the tumor suppressor function of TGF-β. However, to date the role of the TGF-β signaling pathway at specific stages of the development of hepatocellular carcinoma (HCC), particularly in relation to the activation of other oncogenic pathways, remains poorly delineated. Here we identify a mechanism by which β2SP, a crucial Smad3 adaptor, modulates cyclin dependent kinase 4 (CDK4), cell cycle progression, and suppression of HCC. Increased expression of β2SP inhibits phosphorylation of the retinoblastoma gene product (Rb) and markedly reduces CDK4 expression to a far greater extent than other CDKs and cyclins. Furthermore, suppression of CDK4 by β2SP efficiently restores Rb hypophosphorylation and cell cycle arrest in G(1) . We further demonstrate that β2SP interacts with CDK4 and Smad3 in a competitive and TGF-β-dependent manner. In addition, haploinsufficiency of cdk4 in β2sp(+/-) mice results in a dramatic decline in HCC formation compared to that observed in β2sp(+/-) mice.

CONCLUSION

β2SP deficiency leads to CDK4 activation and contributes to dysregulation of the cell cycle, cellular proliferation, oncogene overexpression, and the formation of HCCs. Our data highlight CDK4 as an attractive target for the pharmacologic inhibition of HCC and demonstrate the importance of β2sp(+/-) mice as a model of preclinical efficacy in the treatment of HCC.

Tgfbeta signaling directly induces Arf promoter remodeling by a mechanism involving Smads 2/3 and p38 MAPK

We have investigated how the Arf gene product, p19(Arf), is activated by Tgfβ during mouse embryo development to better understand how this important tumor suppressor is controlled. Taking advantage of new mouse models, we provide genetic evidence that Arf lies downstream of Tgfβ signaling in cells arising from the Wnt1-expressing neural crest and that the anti-proliferative effects of Tgfβ depend on Arf in vivo. Tgfβ1, -2, and -3 (but not BMP-2, another member of the Tgfβ superfamily) induce p19(Arf) expression in wild type mouse embryo fibroblasts (MEFs), and they enhance Arf promoter activity in Arf(lacZ/lacZ) MEFs. Application of chemical inhibitors of Smad-dependent and -independent pathways show that SB431542, a Tgfβ type I receptor (TβrI) inhibitor, and SB203580, a p38 MAPK inhibitor, impede Tgfβ2 induction of Arf. Genetic studies confirm the findings; transient knockdown of Smad2, Smad3, or p38 MAPK blunt Tgfβ2 effects, as does Cre recombinase treatment of Tgfbr2(fl/fl) MEFs to delete Tgfβ receptor II. Chromatin immunoprecipitation reveals that Tgfβ rapidly induces Smads 2/3 binding and histone H3 acetylation at genomic DNA proximal to Arf exon 1β. This is followed by increased RNA polymerase II binding and progressively increased Arf primary and mature transcripts from 24 through 72 h, indicating that increased transcription contributes to p19(Arf) increase. Last, Arf induction by oncogenic Ras depends on p38 MAPK but is independent of TβrI activation of Smad 2. These findings add to our understanding of how developmental and tumorigenic signals control Arf expression in vivo and in cultured MEFs.

Smad4-mediated TGF-beta signaling in tumorigenesis

Transforming growth factor-β (TGF-β) family members exert their function via specific type I and type II serine/threonine kinase receptors and intracellular Smad transcription factors, including the common mediator Smad4. The dual effects of TGF-β signaling on tumor initiation and progression are cell-specific and yet to be determined under distinct contexts. A number of genetically manipulated mouse models with alterations in the TGF-β pathway genes, particularly the pivotal Smad4, revealed that these genes play crucial functions in maintaining tissue homeostasis and suppressing tumorigenesis. Loss of Smad4 plays a causal role in initiating squamous cell carcinomas of skin and upper digestive tract as well as adenocarcinomas of gastrointestinal tract. However, for some cancers like pancreatic and cholangiocellular carcinomas, Smad4 deficiency does not initiate the tumorigenesis but acts as a promoter to accelerate or synergize the development and progression of cancers that are started by other oncogenic pathways. Intriguingly, emerging evidences from mouse models have highlighted the important roles of non-cell autonomous effects of Smad4-mediated TGF-β signaling in the inhibition of oncogenesis. All these data have greatly deepened our understanding of molecular mechanisms of cell-autonomous and non-cell autonomous effect of Smad4-mediated TGF-β signaling in suppressing carcinogenesis, which may facilitate the development of successful therapies targeting TGF-β signaling for the treatment of human cancers.

Abnormal growth factor/cytokine network in gastric cancer

Gastric cancer cells express a broad spectrum of the growth factor/cytokine receptor systems that organize the complex interaction between cancer cells and stromal cells in tumor microenvironment, which confers cell growth, apoptosis, morphogenesis, angiogenesis, progression and metastasis. However, these abnormal growth factor/cytokine networks differ in the two histological types of gastric cancer. Importantly, activation of nuclear factor-kB pathway by Helicobacter pylori infection may act as a key player for induction of growth factor/cytokine networks in gastritis and pathogenesis of gastric cancer. Better understanding of these events will no doubt provide new approaches for biomarkers of diagnosis and effective therapeutic targeting of gastric cancer.

Analysis of selected oncogenes (AKT1, FOS, BCL2L2, TGFbeta) on chromosome 14 in granulosa cell tumors (GCTs): a comprehensive study on 30 GCTs combining comparative genomic hybridization (CGH) and fluorescence-in situ-hybridization (FISH)

In previous studies, we have demonstrated a number of cytogenetic alterations in granulosa cell tumors (GCTs), especially on chromosomes X, 12, 14, and 22. However, little is known about specific loci on 14q, which could play an important role in tumor pathology. Therefore, we assessed four important genes in 30 GCTs using fluorescence-in situ-hybridization (FISH). Comparative genomic hybridization (CGH) was performed on paraffin-embedded material. Then, we applied FISH with gene-specific DNA probes for AKT1 (14q32.32), FOS (14q24.3), BCL2L2 (14q11.2-q12), and TGFbeta3 (14q24), and tried to find a correlation between CGH, FISH, tumor stage, and survival. In CGH, 7 of 30 cases (23.3%) showed complete gains on chromosome 14. FISH of the four loci revealed gains of hybridization signals in 8 of 30 cases (26.6%), indicating trisomy of the whole chromosome arm. The same aberration was detected by FISH in 2 of 30 cases (6.6%), which were negative using CGH. One case (1 of 30; 3.3%) was found to have a gain on chromosome 14 by CGH, which could not be confirmed by FISH. A correlation with tumor stage or survival could not be established. Our results suggest that GCTs may be characterized by trisomy of chromosome 14. A specific oncogene that could play a particular role in the tumorigenesis of GCTs was not identified on chromosome 14.

Prevention of stricture development after corrosive esophageal burn with a modified esophageal stent in dogs

OBJECTIVE

We sought to test the feasibility and technical ease of a newly designed nitinol-based modified esophageal stent and its effects on preventing postcaustic stricture in mongrel dogs and to try to explain the result at the molecular level.

METHODS

Twenty-four dogs were included in this controlled study. Stenosis index (wall thickness/intraluminal diameter), pathologic features, hydroxyproline quantities, esophageal compliance, and biomechanics were compared between the injured but unstented and stented dogs. Transforming growth factor beta1, Sma/Mad (Smad)3, and Smad7 mRNA expression and protein levels in esophageal tissue were detected by means of reverse transcriptase-polymerase chain reaction and Western blotting, respectively.

RESULTS

The modified esophageal stent was able to be placed and retrieved successfully and conveniently and was not only intact but there was also no macroscopic esophageal mucosal injury after the stent removal 4 months later. In comparison with the injured but unstented group, esophageal compliance, biomechanics, and the stenosis index were significantly better in the stented group. Histopathologic study revealed that collagen bundles were thinner and its orientation tended toward a regular and parallel pattern. Transforming growth factor beta1 and Smad3 mRNA expression and protein levels increased and Smad7 mRNA expression and protein levels decreased significantly in esophageal tissue in the stented group. These variables showed no statistically significant difference 2 months after stent removal.

CONCLUSIONS

The modified esophageal stent might be a promising stent in preventing stricture formation after corrosive esophageal burns clinically.

Small bowel carcinoid (enterochromaffin cell) neoplasia exhibits transforming growth factor-beta1-mediated regulatory abnormalities including up-regulation of C-Myc and MTA1

BACKGROUND

Although it is known that small intestinal carcinoids are derived from enterochromaffin (EC) cells, these cells remain poorly characterized and little is known of the growth regulatory mechanisms of these neuroendocrine cells. Down-regulation or loss of the transforming growth factor-beta1 (TGFbeta1) cytostatic program and activation of TGFbeta-mediated transcriptional networks is associated with uncontrolled growth and metastasis in other neural tumors, glioblastomas. Whether this phenomenon is common to small intestinal carcinoid tumors was investigated.

METHODS

The effects of TGFbeta1 on cultured normal EC cells (isolated by FACS sorting) and the neoplastic EC cell line, KRJ-I, was assessed using the MTT assay. The TGFbetaRII transcript and protein were identified in tumor cells and the effects of TGFbeta1 on SMAD2 phosphorylation and nuclear translocation quantified. The time-dependent response of SMAD4, SMAD7, c-Myc, and P21(WAF1/CIP1) protein expression and c-Myc and p21(WAF1/CIP1) transcript was measured in response to TGFbeta1 and the transcript expression of candidate downstream targets, MTA1 and E-cadherin, were assessed.

RESULTS

TGFbeta1 inhibited normal EC cell proliferation (IC(50) = 17 pM) but stimulated neoplastic EC cell proliferation (EC(50) = 22 pM). In tumor cells, significantly decreased transcript (P < .01) of TGFbetaRII was identified, but no receptor mutations were identified and protein expression was evident. TGFbeta1 (1 ng/mL) resulted in SMAD2 phosphorylation and <7% nuclear expression compared with 93% in normal EC cells. In neoplastic cells, TGFbeta1 (1 ng/mL) caused a decrease in SMAD4 (>16%, P < .05), whereas SMAD7 and c-Myc transcript and protein were respectively increased >21% (P < .05) and approximately 40% (P < .002). TGFbeta1 (1 ng/mL) also decreased p21(WAF1/CIP1) transcript by 60% (P < .001) and protein that was undetectable at 24 hours. Expression of the downstream targets of the c-Myc pathway, MTA1, was increased (20%) and E-cadherin decreased (30%).

CONCLUSIONS

The neoplastic EC cell is characterized by loss of TGFbeta-1-mediated growth inhibition and, similar to glioblastomas, utilizes the TGFbeta system to induce gene responses associated with growth promotion (c-Myc and the ERK pathway), invasion (E-cadherin), and metastasis (MTA1).

Inactivation of SMAD4 tumor suppressor gene during gastric carcinoma progression

PURPOSE

Mothers against decapentaplegic homologue 4 (SMAD4) is a tumor suppressor gene associated with gastrointestinal carcinogenesis. The aim of the present study is to more precisely characterize its role in the development and progression of human gastric carcinoma.

EXPERIMENTAL DESIGN

The expression of SMAD4 was investigated in 283 gastric adenocarcinomas and related lesions, as well as in 9 gastric carcinoma cell lines. We also analyzed the methylation status of SMAD4 gene by using methylation-specific PCR, examined loss of heterozygosity (LOH) of this gene locus by using a vicinal marker, and detected exon mutation of SMAD4 through exon-by-exon amplification. Moreover, we assessed whether MG132, a proteasome inhibitor, affected the SMAD4 protein level.

RESULTS

We found loss of SMAD4 protein expression in the cytoplasm (36 of 114, 32%) and in the nucleus (46 of 114, 40%) of gastric cancer cells. The loss of nuclear SMAD4 expression in primary tumors correlated significantly with poor survival, and was an independent prognostic marker in multivariate analysis. We also found a substantial decrease in SMAD4 expression at both the RNA and protein level in several human gastric carcinoma cell lines. In addition, we found that LOH (20 of 70, 29%) and promoter hypermethylation (4 of 73, 5%) were associated with the loss of SMAD4 expression. SMAD4 protein levels were also affected in certain gastric carcinoma cell lines following incubation with MG132.

CONCLUSION

Taken together, our results indicate that the loss of SMAD4, especially loss of nuclear SMAD4 expression, is involved in gastric cancer progression. The loss of SMAD4 in gastric carcinomas was due to several mechanisms, including LOH, hypermethylation, and proteasome degradation.

Inactivation of TGF-β signaling in lung cancer results in increased CDK4 activity that can be rescued by ELF

Escape from TGF-beta inhibition of proliferation is a hallmark of multiple cancers including lung cancer. We explored the role of ELF, crucial TGF-beta adaptor protein identified from endodermal progenitor cells, in lung carcinogenesis and cell-cycle regulation. Interestingly, elf-/- mice develop multiple defects that include lung, liver, and cardiac abnormalities. Four out of 6 lung cancer and mesothelioma cell lines displayed deficiency of ELF expression with increased CDK4 expression. Immunohistochemistry and Western blot analysis of primary human lung cancers also showed decreased ELF expression and overexpression of CDK4. Moreover, rescue of ELF in ELF-deficient cell lines decreased the expression of CDK4 and resulted in accumulation of G1/S checkpoint arrested cells. These results suggest that disruption in TGF-beta signaling mediated by loss of ELF in lung cancer leads to cell-cycle deregulation by modulating CDK4 and ELF highlights a key role of TGF-beta adaptor protein in suppressing early lung cancer.