Epigenetic downregulation of human disabled homolog 2 switches TGF-beta from a tumor suppressor to a tumor promoter

C1orf106 (INAVA) Is a SMAD3-Dependent TGF-β Target Gene That Promotes Clonogenicity and Correlates with Poor Prognosis in Breast Cancer

Transforming Growth Factor-β (TGF-β) can have both tumour-promoting and tumour-suppressing activity in breast cancer. Elucidating the key downstream mediators of pro-tumorigenic TGF-β signalling in this context could potentially give rise to new therapeutic opportunities and/or identify biomarkers for anti-TGF-β directed therapy. Here, we identify C1orf106 (also known as innate immunity activator INAVA) as a novel TGF-β target gene which is induced in a SMAD3-dependent but SMAD2/SMAD4-independent manner in human and murine cell lines. C1orf106 expression positively correlates with tumourigenic or metastatic potential in human and murine breast cancer cell line models, respectively, and is required for enhanced migration and invasion in response to TGF-β stimulation. C1orf106 promoted self-renewal and colony formation in vitro and may promote tumour-initiating frequency in vivo. High C1orf106 mRNA expression correlates with markers of aggressiveness and poor prognosis in human breast cancer. Taken together, our findings indicate that C1orf106 may act as a tumour promoter in breast cancer.

Advances and Challenges in Targeting TGF-β Isoforms for Therapeutic Intervention of Cancer: A Mechanism-Based Perspective

The TGF-β family is a group of 25 kDa secretory cytokines, in mammals consisting of three dimeric isoforms (TGF-βs 1, 2, and 3), each encoded on a separate gene with unique regulatory elements. Each isoform plays unique, diverse, and pivotal roles in cell growth, survival, immune response, and differentiation. However, many researchers in the TGF-β field often mistakenly assume a uniform functionality among all three isoforms. Although TGF-βs are essential for normal development and many cellular and physiological processes, their dysregulated expression contributes significantly to various diseases. Notably, they drive conditions like fibrosis and tumor metastasis/progression. To counter these pathologies, extensive efforts have been directed towards targeting TGF-βs, resulting in the development of a range of TGF-β inhibitors. Despite some clinical success, these agents have yet to reach their full potential in the treatment of cancers. A significant challenge rests in effectively targeting TGF-βs' pathological functions while preserving their physiological roles. Many existing approaches collectively target all three isoforms, failing to target just the specific deregulated ones. Additionally, most strategies tackle the entire TGF-β signaling pathway instead of focusing on disease-specific components or preferentially targeting tumors. This review gives a unique historical overview of the TGF-β field often missed in other reviews and provides a current landscape of TGF-β research, emphasizing isoform-specific functions and disease implications. The review then delves into ongoing therapeutic strategies in cancer, stressing the need for more tools that target specific isoforms and disease-related pathway components, advocating mechanism-based and refined approaches to enhance the effectiveness of TGF-β-targeted cancer therapies.

Disabled-2: a protein up-regulated by high molecular weight hyaluronan has both tumor promoting and tumor suppressor roles in ovarian cancer

Although the pro-tumorigenic functions of hyaluronan (HA) are well documented there is limited information on the effects and targets of different molecular weight HA. Here, we investigated the effects of 27 kDa, 183 kDa and 1000 kDa HA on ES-2 ovarian cancer cells overexpressing the stem cell associated protein, Notch3. 1000 kDA HA promoted spheroid formation in ES-2 cells mixed with ES-2 overexpressing Notch3 (1:3). We report disabled-2 (DAB2) as a novel protein regulated by 1000 kDa HA and further investigated its role in ovarian cancer. DAB2 was downregulated in ovarian cancer compared to normal tissues but increased in metastatic ovarian tumors compared to primary tumors. High DAB2 expression was associated with poor patient outcome and positively correlated with HA synthesis enzyme HAS2, HA receptor CD44 and EMT and macrophage markers. Stromal DAB2 immunostaining was significantly increased in matched ovarian cancer tissues at relapse compared to diagnosis and associated with reduced survival. The proportion of DAB2 positive macrophages was significantly increased in metastatic ovarian cancer tissues compared to primary cancers. However, DAB2 overexpression significantly reduced invasion by both A2780 and OVCAR3 cells in vivo. Our research identifies a novel relationship between HA signalling, Notch3 and DAB2. We highlight a complex relationship of both pro-tumorigenic and tumor suppressive functions of DAB2 in ovarian cancer. Our findings highlight that DAB2 has a direct tumor suppressive role on ovarian cancer cells. The pro-tumorigenic role of DAB2 may be mediated by tumour associated macrophages and requires further investigation.

Expression Pattern of DAB Adaptor Protein 2 in Left- and Right-Side Colorectal Carcinoma

Left-sided and right-sided colorectal cancer (L-CRC and R-CRC) have relatively different clinical pictures and pathophysiological backgrounds. The aim of this study was to investigate the presence of DAB adapter protein 2 (DAB2) as a potential molecular mechanism that contributes to this diversity in terms of malignancy and responses to therapy. The expression of the suppressor gene DAB2 in colon cancer has already been analyzed, but its significance has not been fully elucidated. Archived samples from 34 patients who underwent colon cancer surgery were included in this study, with 13 patients with low-grade CRC and 21 with high-grade CRC. Twenty of the tumors were R-CRC, while 14 were L-CRC. DAB2 expression was analyzed immunohistochemically in the tumor tissue and the colon resection margin was used as a control. Tumors were divided into L-CRC and R-CRC, with splenic flexure as the cutoff point for each side. The results showed that R-CRC had lower DAB2 protein expression compared to L-CRC (p = 0.01). High-grade tumors had reduced DAB2 expression compared to low-grade tumors (p = 0.02). These results are consistent with the analysis of DAB2 gene expression data that we exported from the TCGA Colon and Rectal Cancer Study (COADREAD). In 736 samples of colon cancer, lower DAB2 gene expression was found in R-CRC compared to L-CRC (p < 0.0001). DAB2 gene expression was significantly higher in the sigmoid colon than in the cecum and ascending colon (p < 0.01). The analysis confirmed a lower expression of the DAB2 in tumors with positive microsatellite instability (p < 0.001). In conclusion, DAB2 has a role in the biological differences between R-CRC and L-CRC and its therapeutic and diagnostic potential needs to be further examined.

Methyltransferase Inhibition Enables Tgf Driven Induction of CDKN2A and B in Cancer Cells

CDKN2A/B deletion or silencing is common across human cancer, reinforcing the general importance of bypassing its tumor suppression in cancer formation or progression. In rhabdomyosarcoma (RMS) and neuroblastoma, two common childhood cancers, the three CDKN2A/B transcripts are independently expressed to varying degrees, but one, ARF, is uniformly silenced. Although TGFβ induces certain CDKN2A/B transcripts in HeLa cells, it was unable to do so in five tested RMS lines unless the cells were pretreated with a broadly acting methyltransferase inhibitor, DZNep, or one targeting EZH2. CDKN2A/B induction by TGFβ correlated with de novo appearance of three H3K27Ac peaks within a 20 kb cis element ∼150 kb proximal to CDKN2A/B. Deleting that segment prevented their induction by TGFβ but not a basal increase driven by methyltransferase inhibition alone. Expression of two CDKN2A/B transcripts was enhanced by dCas9/CRISPR activation targeting either the relevant promoter or the 20 kb cis elements, and this "precise" manipulation diminished RMS cell propagation in vitro. Our findings show crosstalk between methyltransferase inhibition and TGFβ-dependent activation of a remote enhancer to reverse CDKN2A/B silencing. Though focused on CDKN2A/B here, such crosstalk may apply to other TGFβ-responsive genes and perhaps govern this signaling protein's complex effects promoting or blocking cancer.

Disabled-2 (DAB2): A Key Regulator of Anti- and Pro-Tumorigenic Pathways

Disabled-2 (DAB2), a key adaptor protein in clathrin mediated endocytosis, is implicated in the regulation of key signalling pathways involved in homeostasis, cell positioning and epithelial to mesenchymal transition (EMT). It was initially identified as a tumour suppressor implicated in the initiation of ovarian cancer, but was subsequently linked to many other cancer types. DAB2 contains key functional domains which allow it to negatively regulate key signalling pathways including the mitogen activated protein kinase (MAPK), wingless/integrated (Wnt) and transforming growth factor beta (TGFβ) pathways. Loss of DAB2 is primarily associated with activation of these pathways and tumour progression, however this review also explores studies which demonstrate the complex nature of DAB2 function with pro-tumorigenic effects. A recent strong interest in microRNAs (miRNA) in cancer has identified DAB2 as a common target. This has reignited an interest in DAB2 research in cancer. Transcriptomics of tumour associated macrophages (TAMs) has also identified a pro-metastatic role of DAB2 in the tumour microenvironment. This review will cover the broad depth literature on the tumour suppressor role of DAB2, highlighting its complex relationships with different pathways. Furthermore, it will explore recent findings which suggest DAB2 has a more complex role in cancer than initially thought.

Discovering biomarkers for hormone-dependent tumors: in silico study on signaling pathways implicated in cell cycle and cytoskeleton regulation

Malignancies dependent on hormone homeostasis include breast, ovary, cervical, prostate, testis and uterine tumors. Hormones are involved in signal transduction which orchestrate processes, such as apoptosis, proliferation, cell cycle or cytoskeleton organization. Currently, there is a need for novel biomarkers which would help to diagnose cancers efficiently. In this study, the genes implicated in signaling that is important in hormone-sensitive carcinogenesis were investigated regarding their prognostic significance. Data of seven cancer cohorts were collected from FireBrowse. 54 gene sets implicated in specific pathways were browsed through MSig database. Profiling was assessed via Monocle3, while gene ontology through PANTHER. For confirmation, correlation analysis was performed using WGCNA. Protein-protein networks were visualized via Cytoscape and impact of genes on survival, as well as cell cycle or cytoskeleton-related prognostic signatures, was tested. Several differences in expression profile were identified, some of them allowed to distinguish histology. Functional annotation revealed that various regulation of cell cycle, adhesion, migration, apoptosis and angiogenesis underlie these differences. Clinical traits, such as histological type or cancer staging, were found during evaluation of module-trait relationships. Of modules, the TopHubs (COL6A3, TNR, GTF2A1, NKX3-1) interacted directly with, e.g., PDGFB, ITGA10, SP1 or AKT3. Among TopHubs and interacting proteins, many showed an impact on hazard ratio and affected the cell cycle or cytoskeleton-related prognostic signatures, e.g., COL1A1 or PDGFB. In conclusion, this study laid the foundation for further hormone-sensitive carcinogenesis research through identification of genes which prove that crosstalk between cell cycle and cytoskeleton exists, opening avenues for future therapeutic strategies.

Sporothrix schenckii regulates macrophage inflammatory responses via the c-JUN-induced Dab2 transcription

Macrophages, which serve as a bridge between innate and adaptive immunity, play an important role in sporotrichosis. Sporothrix schenckii infections can produce immune responses such as macrophage polarization and inflammatory factor secretion. In the early stages of inflammation, the expression of DAB2 in macrophages is increased, which controls the secretion of inflammatory factors and affects the polarization of macrophages. However, the expressions and mechanisms of DAB2 in sporotrichosis are not clear. In this study, we examined the expression of DAB2 and its regulation of inflammatory factors under conditions of Sporothrix schenckii infection. Our results indicated that the Sporothrix schenckii infection increased the expression of DAB2 and revealed a mixed M1/M2-like type of gene expression in BMDMs with the inhibited Il6, Il1β and Arg1, and induced Tnfα, Il10 and Mgl1. The deficiency of Dab2 gene suspended the changes of cytokines. In addition, JNK activity in BMDMs was inhibited by Sporothrix schenckii infection, leading to an increase in c-JUN. We also identified c-JUN as a transcription factor for Dab2 through chromatin immunoprecipitation and luciferase reporter assays. In an in vivo mouse model, sporotrichosis induced skin lesions were accompanied with an upregulation of c-JUN and inhibition of JNK activity, which were in accord with findings from in vitro experiments. Taken together, these findings indicate that in the early stages of Sporothrix schenckii infection there is a promotion of DAB2 expression through the JNK/c-JUN pathway, effects which can then control the expression of inflammatory factors.

Glycoprotein NMB promotes tumor formation and malignant progression of laryngeal squamous cell carcinoma

Laryngeal squamous cell carcinoma (LSCC), although one of the most common head and neck cancers, has a static or slightly decreased survival rate because of difficulties in early diagnosis, lack of effective molecular targeting therapy, and severe dysfunction after radical surgical treatments. Therefore, a novel therapeutic target is crucial to increase treatment efficacy and survival rates in these patients. Glycoprotein NMB (GPNMB), whose role in LSCC remains elusive, is a type 1 transmembrane protein involved in malignant progression of various cancers, and its high expression is thought to be a poor prognostic factor. In this study, we showed that GPNMB expression levels in LSCC samples are significantly higher than those in normal tissues, and GPNMB expression is observed mostly in growth‐arrested cancer cells. Furthermore, knockdown of GPNMB reduces monolayer cellular proliferation, cellular migration, and tumorigenic growth, while GPNMB protein displays an inverse relationship with Ki‐67 levels. Therefore, we conclude that GPNMB may be an attractive target for future LSCC therapy.

IGFBP-3 and TGF-β inhibit growth in epithelial cells by stimulating type V TGF-β receptor (TβR-V)-mediated tumor suppressor signaling

The TGF-β type V receptor (TβR-V) mediates growth inhibition by IGFBP-3 and TGF-β in epithelial cells and loss of TβR-V expression in these cells leads to development of carcinoma. The mechanisms by which TβR-V mediates growth inhibition (tumor suppressor) signaling remain elusive. Previous studies revealed that IGFBP-3 and TGF-β inhibit growth in epithelial cells by stimulating TβR-V-mediated IRS-1/2-dependent activation and cytoplasm-to-nucleus translocation of IGFBP-3- or TGF-β-stimulated protein phosphatase (PPase), resulting in dephosphorylation of pRb-related proteins (p107, p130) or pRb, and growth arrest. To define the signaling, we characterized/identified the IGFBP-3- and TGF-β-stimulated PPases in cell lysates and nucleus fractions in Mv1Lu cells treated with IGFBP-3 and TGF-β, using a cell-free assay with 32P-labeled casein as a substrate. Both IGFBP-3- and TGF-β-stimulated PPase activities in cell lysates are abolished when cells are co-treated with TGF-β/IGFBP-3 antagonist or RAP (LRP-1/TβR-V antagonist). However, the IGFBP-3-stimulated PPase activity, but not TGF-β-stimulated PPase activity, is sensitive to inhibition by okadaic acid (OA). In addition, OA or PP2Ac siRNA reverses IGFBP-3 growth inhibition, but not TGF-β growth inhibition, in Mv1Lu and 32D cells. These suggest that IGFBP-3- and TGF-β-stimulated PPases are identical to PP2A and PP1, respectively. By Western blot/phosphorimager/immunofluorescence-microscopy analyses, IGFBP-3 and TGF-β stimulate TβR-V-mediated IRS-2-dependent activation and cytoplasm-to-nucleus translocation of PP2Ac and PP1c, resulting in dephosphorylation of p130/p107 and pRb, respectively, and growth arrest. Small molecule TGF-β enhancers, which potentiate TGF-β growth inhibition by enhancing TβR-I-TβR-II-mediated canonical signaling and thus activating TβR-V-mediated tumor suppressor signaling cascade (TβR-V/IRS-2/PP1/pRb), could be used to prevent and treat carcinoma.

Loss of CD73 shifts transforming growth factor-β1 (TGF-β1) from tumor suppressor to promoter in endometrial cancer

In many tumors, CD73 (NT5E), a rate-limiting enzyme in adenosine biosynthesis, is upregulated by TGF-β and drives tumor progression. Conversely, CD73 is downregulated in endometrial carcinomas (EC) despite a TGF-β-rich environment. Through gene expression analyses of normal endometrium samples of the uterine cancer TCGA data set and genetic and pharmacological studies, we discovered CD73 loss shifts TGF-β1 from tumor suppressor to promoter in EC. TGF-β1 upregulated CD73 and epithelial integrity in vivo in the normal endometrium and in vitro in early stage EC cells. With loss of CD73, TGF-β1-mediated epithelial integrity was abrogated. EC cells developed TGF-β1-mediated stress fibers and macromolecule permeability, migration, and invasion increased. In human tumors, CD73 is downregulated in deeply invasive stage I EC. Consistent with shifting TGF-β1 activity, CD73 loss increased TGF-β1-mediated canonical signaling and upregulated cyclin D1 (CCND1) and downregulated p21 expression. This shift was clinically relevant, as CD73^Low/CCND1^High expression associated with poor tumor differentiation, increased myometrial and lymphatic/vascular space invasion, and patient death. Further loss of CD73 in CD73^Low expressing advanced stage EC cells increased TGF-β-mediated stress fibers, signaling, and invasiveness, whereby adenosine A1 receptor agonist, CPA, dampened TGF-β-mediated invasion. These data identify CD73 loss as essential for shifting TGF-β activity in EC.

Short chain fatty acids delay the development of hepatocellular carcinoma in HBx transgenic mice

Chronic infection with hepatitis B virus (HBV) is a major risk factor for the development of hepatocellular carcinoma (HCC). The HBV encoded oncoprotein, HBx, alters the expression of host genes and the activity of multiple signal transduction pathways that contribute to the pathogenesis of HCC by multiple mechanisms independent of HBV replication. However, it is not clear which pathways are the most relevant therapeutic targets in hepatocarcinogenesis. Short chain fatty acids (SCFAs) have strong anti-inflammatory and anti-neoplastic properties, suggesting that they may block the progression of chronic liver disease (CLD) to HCC, thereby identifying the mechanisms relevant to HCC development. This hypothesis was tested in HBx transgenic (HBxTg) mice fed SCFAs. Groups of HBxTg mice were fed with SCFAs or vehicle from 6 to 9 months of age and then assessed for dysplasia, and from 9 to 12 months of age and then assessed for HCC. Livers from 12 month old mice were then analyzed for changes in gene expression by mass spectrometry-based proteomics. SCFA-fed mice had significantly fewer dysplastic and HCC nodules compared to controls at 9 and 12 months, respectively. Pathway analysis of SCFA-fed mice showed down-regulation of signaling pathways altered by HBx in human CLD and HCC, including those involved in inflammation, phosphatidylinositol 3-kinase, epidermal growth factor, and Ras. SCFA treatment promoted increased expression of the tumor suppressor, disabled homolog 2 (DAB2). DAB2 depresses Ras pathway activity, which is constitutively activated by HBx. SCFAs also reduced cell viability in HBx-transfected cell lines in a dose-dependent manner while the viability of primary human hepatocytes was unaffected. These unique findings demonstrate that SCFAs delay the pathogenesis of CLD and development of HCC, and provide insight into some of the underlying mechanisms that are relevant to pathogenesis in that they are responsive to treatment.

Functions of Dendritic Cells and Its Association with Intestinal Diseases

Dendritic cells (DCs), including conventional DCs (cDCs) and plasmacytoid DCs (pDCs), serve as the sentinel cells of the immune system and are responsible for presenting antigen information. Moreover, the role of DCs derived from monocytes (moDCs) in the development of inflammation has been emphasized. Several studies have shown that the function of DCs can be influenced by gut microbes including gut bacteria and viruses. Abnormal changes/reactions in intestinal DCs are potentially associated with diseases such as inflammatory bowel disease (IBD) and intestinal tumors, allowing DCs to be a new target for the treatment of these diseases. In this review, we summarized the physiological functions of DCs in the intestinal micro-environment, their regulatory relationship with intestinal microorganisms and their regulatory mechanism in intestinal diseases.

The role of disabled-2 (Dab2) in diseases

Disabled-2 (Dab2/DOC-2) is a mitogen-responsive adaptor protein required for multiple cellular functions. It is involved in many signaling pathways and plays an integral role in vesicular uptake and trafficking, modulating immune function, protein-protein interactions, cellular homeostasis and differentiation, oncogenesis, and inflammatory processes in organ systems. It contains domains for binding to NPXY motif-containing and SH3 domain-containing adapter proteins, phosphoinositides, glycoprotein 100 (gp100, or megalin), integrins, clathrin, and myosin VI. However, the molecular mechanism(s) of Dab2's biological function still remain to be elucidated. In this review, we provide an extensive up-to-date understanding of the function of Dab2 and its regulation in cardiovascular diseases, immune disorders, tumorigenesis, and central nervous system disorders.

Prevalence and architecture of posttranscriptionally impaired synonymous mutations in 8,320 genomes across 22 cancer types

Somatic synonymous mutations are one of the most frequent genetic variants occurring in the coding region of cancer genomes, while their contributions to cancer development remain largely unknown. To assess whether synonymous mutations involved in post-transcriptional regulation contribute to the genetic etiology of cancers, we collected whole exome data from 8,320 patients across 22 cancer types. By employing our developed algorithm, PIVar, we identified a total of 22,948 posttranscriptionally impaired synonymous SNVs (pisSNVs) spanning 2,042 genes. In addition, 35 RNA binding proteins impacted by these identified pisSNVs were significantly enriched. Remarkably, we discovered markedly elevated ratio of somatic pisSNVs across all 22 cancer types, and a high pisSNV ratio was associated with worse patient survival in five cancer types. Intriguing, several well-established cancer genes, including PTEN, RB1 and PIK3CA, appeared to contribute to tumorigenesis at both protein function and posttranscriptional regulation levels, whereas some pisSNV-hosted genes, including UBR4, EP400 and INTS1, exerted their function during carcinogenesis mainly via posttranscriptional mechanisms. Moreover, we predicted three drugs associated with two pisSNVs, and numerous compounds associated with expression signature of pisSNV-hosted genes. Our study reveals the prevalence and clinical relevance of pisSNVs in cancers, and emphasizes the importance of considering posttranscriptional impaired synonymous mutations in cancer biology.

(-)-Epigallocatechin Gallate Promotes MicroRNA 145 Expression against Myocardial Hypoxic Injury through Dab2/Wnt3a/β-catenin

MicroRNA 145 (miR-145) is a critical modulator of cardiovascular diseases. The downregulation of myocardial miR-145 is followed by an increase in disabled-2 (Dab2) expression in cardiomyocytes. (-)-epigallocatechin gallate (EGCG) is a flavonoid that has been evaluated extensively due to its diverse pharmacological properties including anti-inflammatory effects. The aim of this study was to investigate the cardioprotective effects of EGCG under hypoxia-induced stress in vitro and in vivo. The hypoxic insult led to the suppression of miR-145 expression in cultured rat cardiomyocytes in a concentration-dependent manner. Western blotting and real-time PCR were performed. In rat myocardial infarction study, in situ hybridization, and immunofluorescent analyses were adopted. The western blot and real-time PCR data revealed that hypoxic stress with 2.5% O2 suppressed the expression of miR-145 and Wnt3a/[Formula: see text]-catenin in cultured rat cardiomyocytes but augmented Dab2. Treatment with EGCG attenuated Dab2 expression, but increased Wnt3a and [Formula: see text]-catenin in hypoxic cultured cardiomyocytes. Following in vivo myocardial infarction (MI) study, the data revealed the myocardial infarct area reduced by 48.5%, 44.6%, and 48.5% in EGCG (50[Formula: see text]mg/kg) or miR-145 dominant or Dab2 siRNA groups after myocardial infarction for 28 days, respectively. This study demonstrated that EGCG increased miR-145, Wnt3a, and [Formula: see text]-catenin expression but attenuated Dab2 expression. Moreover, EGCG ameliorated myocardial ischemia in vivo. The novel suppressive effect was mediated through the miR-145 and Dab2/Wnt3a/[Formula: see text]-catenin pathways.

A New Switch for TGFβ in Cancer

The TGFβ cytokine plays dichotomous roles during tumor progression. In normal and premalignant cancer cells, the TGFβ signaling pathway inhibits proliferation and promotes cell-cycle arrest and apoptosis. However, the activation of this pathway in late-stage cancer cells could facilitate the epithelial-to-mesenchymal transition, stemness, and mobile features to enhance tumorigenesis and metastasis. The opposite functions of TGFβ signaling during tumor progression make it a challenging target to develop anticancer interventions. Nevertheless, the recent discovery of cellular contextual determinants, especially the binding partners of the transcription modulators Smads, is critical to switch TGFβ responses from proapoptosis to prometastasis. In this review, we summarize the recently identified contextual determinants (such as PSPC1, KLF5, 14-3-3ζ, C/EBPβ, and others) and the mechanisms of how tumor cells manage the context-dependent autonomous TGFβ responses to potentiate tumor progression. With the altered expression of some contextual determinants and their effectors during tumor progression, the aberrant molecular prometastatic switch might serve as a new class of theranostic targets for developing anticancer strategies.

Overexpression of matrix metalloproteinase-9 in breast cancer cell lines remarkably increases the cell malignancy largely via activation of transforming growth factor beta/SMAD signalling

OBJECTIVES

Matrix metalloproteinase 9 (MMP-9) has been frequently noticed in the breast cancers. In this study, we aim to investigate the associations of MMP-9 with the activation of transforming growth factor beta (TGF-β)/SMAD signalling and the malignancy of breast malignant tumour cells.

MATERIALS AND METHODS

The distributions of MMP-9 and TGF-β in the tissues of canine breast cancers were screened by immunohistochemical assays. A recombinant plasmid expressing mouse MMP-9 was generated and transiently transfected into three different breast cancer cell lines. Cell Counting Kit-8 and colony formation assay were used to study cell viability. Migration and invasion ability were analysed by wound assay and transwell filters. Western blot and quantitative real-time PCR were used to determine the protein and mRNA expression.

RESULT

Remarkable strong MMP-9 and TGF-β signals were observed in the malignant tissues of canine breast cancers. In the cultured three cell lines receiving recombinant plasmid expressing mouse MMP-9, the cell malignancy was markedly increased, including the cell colony formation, migration and epithelial-mesenchymal transition. The levels of activated TGF-β, as well as SMAD4, SMAD2/3 and phosphorylation of SMAD2, were increased, reflecting an activation of TGF-β/SMAD signalling. We also demonstrated that the inhibitors specific for MMP-9 and TGF-β sufficiently blocked the overexpressing MMP-9 induced the activation of SMAD signalling and enhancement on invasion in the tested breast cancer cell lines.

CONCLUSION

Overexpression of MMP-9 increases the malignancy of breast cancer cell lines, largely via activation of the TGF-β/SMAD signalling.

Loss of Disabled-2 Expression in Pancreatic Cancer Progression

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer type characterized by rapid metastasis and resistance to chemotherapy, properties that are shared by cancer stem cells (CSCs). In pancreatic cancer, tumor cells which possess the properties of CSCs also phenotypically resemble cells that have undergone epithelial-to-mesenchymal transition or EMT. Disabled-2 (Dab2) is a multifunctional scaffold protein frequently downregulated in cancer that has been linked to the process of EMT. However, the role of Dab2 in pancreatic cancer development and progression remains unclear. Downregulation of Dab2 expression in pancreatic cancer cell lines was found to trigger induction of genes characteristic of EMT and the CSC phenotype, while overexpression of Dab2 in the Panc1 cell line blocked the process of TGFβ-stimulated EMT. In addition, selective inhibition of the TGFβRI/RII receptors was found to reverse genes altered by Dab2 downregulation. Dab2 mRNA expression was found to be decreased in PDAC tumor samples, as compared to levels observed in normal pancreatic tissue. Methylation of the Dab2 gene promoter was demonstrated in Stage I PDAC tumors and in the MiaPaCa2 cell line, suggesting that promoter methylation may silence Dab2 expression early in pancreatic cancer progression. These results suggest that Dab2 may function as a tumor suppressor in pancreatic cancer by modulation of the TGFβ-stimulated EMT and CSC phenotype.

The role of TGFβ in hematopoiesis and myeloid disorders

The role of transforming growth factor-β (TGFβ) signaling in embryological development and tissue homeostasis has been thoroughly characterized. Its canonical downstream cascade is well known, even though its true complexity and other non-canonical pathways are still being explored. TGFβ signaling has been described as an important pathway involved in carcinogenesis and cancer progression. In the hematopoietic compartment, the TGFβ pathway is an important regulator of proliferation and differentiation of different cell types and has been implicated in the pathogenesis of a diverse variety of bone marrow disorders. Due to its importance in hematological diseases, novel inhibitors of this pathway are being developed against a number of hematopoietic disorders, including myelodysplastic syndromes (MDS). In this review, we provide an overview of the TGFβ pathway, focusing on its role in hematopoiesis and impact on myeloid disorders. We will discuss therapeutic interventions with promising results against MDS.

Rapid Downregulation of DAB2 by Toll-Like Receptor Activation Contributes to a Pro-Inflammatory Switch in Activated Dendritic Cells

Dendritic cells (DCs) are pivotal in regulating tolerogenic as well as immunogenic responses against microorganisms by directing both the innate and adaptive immune response. In health, phenotypically different DC subsets found in the gut mucosa are maintained in their tolerogenic state but switch to a pro-inflammatory phenotype during infection or chronic autoinflammatory conditions such as inflammatory bowel disease (IBD). The mechanisms that promote the switch among the mucosal DCs from a tolerogenic to an immunogenic, pro-inflammatory phenotype are incompletely understood. We hypothesized that disabled homolog 2 (DAB2), recently described as a negative regulator of DC immunogenicity during their development, is regulated during intestinal inflammation and modulates mucosal DC function. We show that DAB2 is highly expressed in colonic CD11b⁺CD103⁻ DCs, a subset known for its capacity to induce inflammatory Th1/Th17 responses in the colon, and is downregulated predominantly in this DC subset during adoptive T cell transfer colitis. Administration of Dab2-deficient DCs (DC2.4^Dab2−/− cells) modulated the course of DSS colitis in wild-type mice, enhanced mucosal expression of Tnfa, Il6, and Il17a, and promoted neutrophil recruitment. In bone-marrow derived dendritic cells (BMDC), DAB2 expression correlated with CD11b levels and DAB2 was rapidly and profoundly inhibited by TLR ligands in a TRIF- and MyD88-dependent manner. The negative modulation of DAB2 was biphasic, initiated with a quick drop in DAB2 protein, followed by a sustained reduction in Dab2 mRNA. DAB2 downregulation promoted a more functional and activated DC phenotype, reduced phagocytosis, and increased CD40 expression after TLR activation. Furthermore, Dab2 knockout in DCs inhibited autophagy and promoted apoptotic cell death. Collectively, our results highlight the immunoregulatory role for DAB2 in the intestinal dendritic cells and suggest that DAB2 downregulation after microbial exposure promotes their switch to an inflammatory phenotype.

Transforming growth factor-β signaling in head and neck squamous cell carcinoma: Insights into cellular responses

Head and neck squamous cell carcinoma (HNSCC) arises in the oral cavity, salivary glands, larynx, pharynx, nasal cavity and paranasal sinuses, and is characterized by high morbidity and metastasis rates. Transforming growth factor-β (TGF-β) is a homodimeric protein known to be a multifunctional regulator in target cells and to serve a pivotal role in numerous types of cancer, including HNSCC. The role of TGF-β signaling in carcinogenesis can change from tumor-suppressing to tumor-promoting. In addition, TGF-β induces epithelial-mesenchymal transition and restrains immune surveillance on malignant cells. In the present review, the effects of TGF-β signaling at a cellular level were discussed, which includes the regulation of tumor cells, immune cells and other stromal cells, as well as the possible mechanisms underlying the conversion from a tumor suppressor to a tumor promoter in HNSCC. Further research is required to improve the understanding on how this network is involved in carcinogenesis, progression and metastases in HNSCC.

Deficiency of Dab2 (Disabled Homolog 2) in Myeloid Cells Exacerbates Inflammation in Liver and Atherosclerotic Plaques in LDLR (Low-Density Lipoprotein Receptor)-Null Mice-Brief Report

OBJECTIVE

Inflammatory macrophages promote the development of atherosclerosis. We have identified the adaptor protein Dab2 (disabled homolog 2) as a regulator of phenotypic polarization in macrophages. The absence of Dab2 in myeloid cells promotes an inflammatory phenotype, but the impact of myeloid Dab2 deficiency on atherosclerosis has not been shown.

APPROACH AND RESULTS

To determine the role of myeloid Dab2 in atherosclerosis, Ldlr-/- mice were reconstituted with either Dab2-positive or Dab2-deficient bone marrow and fed a western diet. Consistent with our previous finding that Dab2 inhibits NFκB (nuclear factor κ-light-chain-enhancer of activated B cells) signaling in macrophages, Ldlr-/- mice reconstituted with Dab2-deficient bone marrow had increased systemic inflammation as evidenced by increased serum IL-6 (interleukin-6) levels and increased inflammatory cytokine expression levels in liver. Serum lipid levels were significantly lower in Ldlr-/- mice reconstituted with Dab2-deficient bone marrow, and further examination of livers from these mice revealed drastically increased inflammatory tissue damage and massive infiltration of immune cells. Surprisingly, the atherosclerotic lesion burden in Ldlr-/- mice reconstituted with Dab2-deficient bone marrow was decreased compared with Ldlr-/- mice reconstituted with wild-type bone marrow. Further analysis of aortic root sections revealed increased macrophage content and evidence of increased apoptosis in lesions from Ldlr-/- mice reconstituted with Dab2-deficient bone marrow but no difference in collagen or α-smooth muscle actin content.

CONCLUSIONS

Dab2 deficiency in myeloid cells promotes inflammation in livers and atherosclerotic plaques in a mouse model of atherosclerosis. Nevertheless, decreased serum lipids as a result of massive inflammatory liver damage may preclude an appreciable increase in atherosclerotic lesion burden in mice reconstituted with Dab2-deficient bone marrow.

miR‑149 promotes the myocardial differentiation of mouse bone marrow stem cells by targeting Dab2

To investigate the role of microRNA (miR)‑149 in the cardiac differentiation of mouse bone marrow mesenchymal stem cells (MSCs) in vitro, MSCs were infected with a lentivirus overexpressing miR‑149 and the effect on cardiac differentiation was determined. The quantitative polymerase chain reaction results demonstrated that miR‑149 promoted the expression of cardiac‑specific markers in MSCs. Western blotting and a luciferase activity assay demonstrated that disabled homolog 2 (Dab2) was a direct target of miR‑149. Dab2 ectopic expression and Wnt/β‑catenin signaling pathway inhibition was able to reverse the increased expression of cardiac‑specific markers induced by miR‑149. In conclusion, miR‑149 was able to target Dab2 and promote the cardiac differentiation of mouse MSCs in vitro, which depended upon the Wnt/β‑catenin signaling pathway.

Reduced SMAD2/3 activation independently predicts increased depth of human cutaneous squamous cell carcinoma

The incidence of cutaneous squamous cell carcinoma (cSCC) is rising. Whilst the majority are cured surgically, aggressive metastatic cSCC carry a poor prognosis. Inactivating mutations in transforming growth factor beta (TGF-β) receptors have been identified amongst genetic drivers of sporadic tumours and murine models of cSCC, suggesting a tumour suppressor function for TGF-β in normal skin. However, paradoxically, TGF-β acts as a tumour promoter in some murine model systems. Few studies have analysed the role of TGF-β/activin signalling in human normal skin, hyper-proliferative skin disorders and cSCC. Antibodies recognising phospho-SMAD proteins which are activated during canonical TGF-β/activin signalling were validated for use in immunohistochemistry. A tissue microarray comprising FFPE lesional and perilesional tissue from human primary invasive cSCC (n=238), cSCC in-situ (n=2) and keratocanthoma (n=9) were analysed in comparison with tissues from normal human scalp (n=10). Phosphorylated SMAD2 and SMAD3 were detected in normal interfollicular epidermal keratinocytes and were also highly localised to inner root sheath, matrix cells and Keratin 15 positive cells. Lesional cSCC tissue had significantly reduced activated SMAD2/3 compared to perilesional tissue, consistent with a tumour suppressor role for SMAD2/3 activators in cSCC. Increased cSCC tumour thickness inversely correlated with the presence of phospho-SMADs in tumour tissue suggesting that a reduction in canonical TGF-β/activin signalling may be associated with disease progression.

Low disabled-2 expression promotes tumor progression and determines poor survival and high recurrence of esophageal squamous cell carcinoma

Patients with esophageal squamous cell carcinomas (ESCCs) have poor survival and high recurrence rate, but lack a prognostic biomarker. Disabled-2 (DAB2) is a crucial tumor suppressor, but its roles in ESCCs are uncertain. We investigated whether low DAB2 expression in ESCCs could lead into tumor progression and poor prognosis. Our results found patients with low-DAB2 expression ESCCs had significantly larger tumor size, deeper tumor invasion depth, lymph node metastasis, worse survival, and higher recurrence rate (P<0.05). The Cox-regression model revealed low-DAB2 expression was an independent factor of poor survival (P<0.05), and also of tumor recurrence with the predictive performance superior to clinical TNM stage (P<0.05). Low-DAB2 cancer cells, validated by DAB2 knockdown or over-expression, had higher phosphorylated ERK and migration abilities, which could be suppressed by ERK inhibitor treatment. TGF-β-induced epithelial-to-mesenchymal transition (EMT) only existed in the high-DAB2 cells, and related to worse prognosis of high-DAB2 ESCCs (P<0.05). In conclusion, DAB2 can suppress the ERK signaling, but correlate to have TGF-β-induced EMT in ESCCs. DAB2 expression could be a biomarker to identify patients with worse survival and high recurrence. Our data suggest DAB2 expression can stratify patients in need of aggressive surveillance and with possible benefit from anti-ERK or anti-TGF-β therapies.

Paradoxical roles of TGF-β signaling in suppressing and promoting squamous cell carcinoma

Transforming growth factor β (TGF-β) signaling either promotes or inhibits tumor formation and/or progression of many cancer types including squamous cell carcinoma (SCC). Canonical TGF-β signaling is mediated by a number of downstream proteins including Smad family proteins. Alterations in either TGF-β or Smad signaling can impact cancer. For instance, defects in TGF-β type I and type II receptors (TGF-βRI and TGF-βRII) and in Smad2/3/4 could promote tumor development. Conversely, increased TGF-β1 and activated TGF-βRI and Smad3 have all been shown to have tumor-promoting effects in experimental systems of human and mouse SCCs. Among TGF-β/Smad signaling, only TGF-βRII or Smad4 deletion in mouse epithelium causes spontaneous SCC in the mouse model, highlighting the critical roles of TGF-βRII and Smad4 in tumor suppression. Herein, we review the dual roles of the TGF-β/Smad signaling pathway and related mechanisms in SCC, highlighting the potential benefits and challenges of TGF-β/Smad-targeted therapies.

Frequent methylation of DAB2, a Wnt pathway antagonist, in oral and oropharyngeal squamous cell carcinomas

BACKGROUND

Aberrations in Wnt signaling pathway are related to the pathogenesis of head and neck carcinomas and their activation frequently results from epigenetic alterations. This study aimed to assess the frequency of the methylation of DAB2, which acts as a negative regulator of Wnt signaling, and correlate it with clinicopathological features in a group of oral cancer patients.

MATERIAL AND METHODS

Forty nine patients with primary oral squamous cell carcinoma were enrolled in the study. DNA samples were isolated from surgical sections using phenol-chloroform extraction. Methylation-specific PCR was used to detect gene promoter methylation.

RESULTS

The analysis of the occurrence of DAB2 promoter methylation in primary oral carcinomas indicated that the gene is methylated in 70% of cases. However, no correlation was found between its methylation and TNM staging or overall survival.

CONCLUSIONS

Our findings corroborate that DAB2 is a frequent target of epigenetic silencing in oral carcinomas and may be potentially used for tumor detection.

Disabled-2: A modular scaffold protein with multifaceted functions in signaling

Disabled-2 (Dab2) is a multimodular scaffold protein with signaling roles in the domains of cell growth, trafficking, differentiation, and homeostasis. Emerging evidences place Dab2 as a novel modulator of cell-cell interaction; however, its mode of action has remained largely elusive. In this review, we highlight the relevance of Dab2 function in cell signaling and development and provide the most recent and comprehensive analysis of Dab2's action as a mediator of homotypical and heterotypical interactions. Accordingly, Dab-2 controls the extent of platelet aggregation through various motifs within its N-terminus. Dab2 interacts with the cytosolic tail of the integrin receptor blocking inside-out signaling, whereas extracellular Dab2 competes with fibrinogen for integrin αIIb β3 receptor binding and, thus, modulates outside-in signaling. An additional level of regulation results from Dab2's association with cell surface lipids, an event that defines the extent of cell-cell interactions. As a multifaceted regulator, Dab2 acts as a mediator of endocytosis through its association with the [FY]xNPx[YF] motifs of internalized cell surface receptors, phosphoinositides, and clathrin. Other emerging roles of Dab2 include its participation in developmental mechanisms required for tissue formation and in modulation of immune responses. This review highlights the various novel mechanisms by which Dab2 mediates an array of signaling events with vast physiological consequences.

Targeting TGF-β Signaling for Therapeutic Gain

Transforming growth factor βs (TGF-βs) are closely related ligands that have pleiotropic activity on most cell types of the body. They act through common heterotetrameric TGF-β type II and type I transmembrane dual specificity kinase receptor complexes, and the outcome of signaling is context-dependent. In normal tissue, they serve a role in maintaining homeostasis. In many diseased states, particularly fibrosis and cancer, TGF-β ligands are overexpressed and the outcome of signaling is diverted toward disease progression. There has therefore been a concerted effort to develop drugs that block TGF-β signaling for therapeutic benefit. This review will cover the basics of TGF-β signaling and its biological activities relevant to oncology, present a summary of pharmacological TGF-β blockade strategies, and give an update on preclinical and clinical trials for TGF-β blockade in a variety of solid tumor types.

Targeting TGF-β Signaling for Therapeutic Gain

Transforming growth factor βs (TGF-βs) are closely related ligands that have pleiotropic activity on most cell types of the body. They act through common heterotetrameric TGF-β type II and type I transmembrane dual specificity kinase receptor complexes, and the outcome of signaling is context-dependent. In normal tissue, they serve a role in maintaining homeostasis. In many diseased states, particularly fibrosis and cancer, TGF-β ligands are overexpressed and the outcome of signaling is diverted toward disease progression. There has therefore been a concerted effort to develop drugs that block TGF-β signaling for therapeutic benefit. This review will cover the basics of TGF-β signaling and its biological activities relevant to oncology, present a summary of pharmacological TGF-β blockade strategies, and give an update on preclinical and clinical trials for TGF-β blockade in a variety of solid tumor types.

Switching Roles of TGF-β in Cancer Development: Implications for Therapeutic Target and Biomarker Studies

TGF-β induces complicated and even opposite responses in numerous biological processes, e.g., tumor suppression in pre-malignant cells and metastasis promotion in cancer cells. However, the cellular contextual determinants of these different TGF-β roles remain elusive, and the driver genes triggering the determinants’ changes have not been identified. Recently, however, several findings have provided new insights on the contextual determinants of Smads in TGF-β’s biological processes. These novel switches and their effectors may serve as prognostic biomarkers and therapeutic targets of TGF-β-mediated cancer progression.

Endocytosis and Physiology: Insights from Disabled-2 Deficient Mice

Disabled-2 (Dab2) is a clathrin and cargo binding endocytic adaptor protein, and cell biology studies revealed that Dab2 plays a role in cellular trafficking of a number of transmembrane receptors and signaling proteins. A PTB/PID domain located in the N-terminus of Dab2 binds the NPXY motif(s) present at the cytoplasmic tails of certain transmembrane proteins/receptors. The membrane receptors reported to bind directly to Dab2 include LDL receptor and its family members LRP1 and LRP2 (megalin), growth factor receptors EGFR and FGFR, and the cell adhesion receptor beta1 integrin. Dab2 also serves as an adaptor in signaling pathways. Particularly, Dab2 facilitates the endocytosis of the Ras activating Grb2/Sos1 signaling complex, controls its disassembly, and thereby regulates the Ras/MAPK signaling pathway. Cellular analyses have suggested several diverse functions for the widely expressed proteins, and Dab2 is also considered a tumor suppressor, as loss or reduced expression is found in several cancer types. Dab2 null mutant mice were generated and investigated to determine if the findings from cellular studies might be important and relevant in intact animals. Dab2 conditional knockout mice mediated through a Sox2-Cre transgene have no obvious developmental defects and have a normal life span despite that the Dab2 protein is essentially absent in the mutant mice. The conditional knockout mice were grossly normal, though more recent investigation of the Dab2-deficient mice revealed several phenotypes, which can be accounted for by several previously suggested mechanisms. The studies of mutant mice established that Dab2 plays multiple physiological roles through its endocytic functions and modulation of signal pathways.

Cathepsin-B-mediated cleavage of Disabled-2 regulates TGF-β-induced autophagy

Transforming growth factor-β (TGF-β) induces the expression of Disabled-2 (Dab2), an endocytic adaptor and tumour suppressor, concomitant with the induction of an epithelial-mesenchymal transition (EMT) in mammary epithelial cells. Here we show that following TGF-β-mediated EMT, sustained TGF-β treatment leads to proteolytic degradation of Dab2 by cathepsin B (CTSB), loss of the mesenchymal phenotype and induction of autophagy. CTSB inhibition or expression of a CTSB-resistant Dab2 mutant maintains Dab2 expression and shifts long-term TGF-β-treated cells from autophagy to apoptosis. We further show that Dab2 interacts with Beclin-1 to promote casein-kinase-2-mediated phosphorylation of Beclin-1, preventing Beclin-1-Vps34 interaction and subsequent autophagosome assembly. Thus, CTSB-mediated degradation of Dab2 allows Beclin-1-Vps34 induction of autophagy, whereas sustained Dab2 expression prevents autophagy and promotes apoptosis by stabilizing the pro-apoptotic Bim protein. In vivo studies suggest that Dab2-mediated regulation of autophagy modulates chemotherapeutic resistance and tumour metastasis.

Metformin inhibits proliferation and migration of glioblastoma cells independently of TGF-β2

To this day, glioblastoma (GBM) remains an incurable brain tumor. Previous research has shown that metformin, an oral anti-diabetic drug, may decrease GBM cell proliferation and migration especially in brain tumor initiating cells (BTICs). As transforming growth factor β 2 (TGF-β2) has been reported to promote high-grade glioma and is inhibited by metformin in other tumors, we explored whether metformin directly interferes with TGF-β2-signaling. Functional investigation of proliferation and migration of primary BTICs after treatment with metformin+/-TGF-β2 revealed that metformin doses as low as 0.01 mM metformin thrice a day were able to inhibit proliferation of susceptible cell lines, whereas migration was impacted only at higher doses. Known cellular mechanisms of metformin, such as increased lactate secretion, reduced oxygen consumption and activated AMPK-signaling, could be confirmed. However, TGF-β2 and metformin did not act as functional antagonists, but both rather inhibited proliferation and/or migration, if significant effects were present. We did not observe a relevant influence of metformin on TGF-β2 mRNA expression (qRT-PCR), TGF-β2 protein expression (ELISA) or SMAD-signaling (Western blot). Therefore, it seems that metformin does not exert its inhibitory effects on GBM BTIC proliferation and migration by altering TGF-β2-signaling. Nonetheless, as low doses of metformin are able to reduce proliferation of certain GBM cells, further exploration of predictors of BTICs' susceptibility to metformin appears justified.

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.

Disabled homolog 2 controls macrophage phenotypic polarization and adipose tissue inflammation

Acute and chronic tissue injury results in the generation of a myriad of environmental cues that macrophages respond to by changing their phenotype and function. This phenotypic regulation is critical for controlling tissue inflammation and resolution. Here, we have identified the adaptor protein disabled homolog 2 (DAB2) as a regulator of phenotypic switching in macrophages. Dab2 expression was upregulated in M2 macrophages and suppressed in M1 macrophages isolated from both mice and humans, and genetic deletion of Dab2 predisposed macrophages to adopt a proinflammatory M1 phenotype. In mice with myeloid cell-specific deletion of Dab2 (Dab2fl/fl Lysm-Cre), treatment with sublethal doses of LPS resulted in increased proinflammatory gene expression and macrophage activation. Moreover, chronic high-fat feeding exacerbated adipose tissue inflammation, M1 polarization of adipose tissue macrophages, and the development of insulin resistance in DAB2-deficient animals compared with controls. Mutational analyses revealed that DAB2 interacts with TNF receptor-associated factor 6 (TRAF6) and attenuates IκB kinase β-dependent (IKKβ-dependent) phosphorylation of Ser536 in the transactivation domain of NF-κB p65. Together, these findings reveal that DAB2 is critical for controlling inflammatory signaling during phenotypic polarization of macrophages and suggest that manipulation of DAB2 expression and function may hold therapeutic potential for the treatment of acute and chronic inflammatory disorders.

MicroRNA-106b is involved in transforming growth factor β1-induced cell migration by targeting disabled homolog 2 in cervical carcinoma

BACKGROUND

MicroRNA-106b (miR-106b) was recently identified as an oncogene participating in cancer progression. Transforming growth factor β1(TGF-β1) is an indispensable cytokine regulating the local microenvironment, thereby promoting cervical cancer progression. However, the roles of miR-106b in cervical carcinoma progression and TGF-β1-involvement in the tumorigenesis of cervical cancer remain unknown.

METHODS

The expression of miR-106b in human cervical specimens was detected by real-time PCR analysis and in situ hybridization assay. The effect of miR-106b on cell migration was analyzed by scratch and transwell assays. TGF-β1 was used to induce cell migration. The expression of the miR-106b target gene DAB2 in human cervical tissues and cell lines were measured by qRT-PCR, western blot and immunohistochemistry. Dual-luciferase reporter assay was used to identify DAB2 as a miR-106b-directed target gene.

RESULTS

miR-106b was frequently up-regulated in human cervical carcinoma specimens and cervical cancer cell lines. Over-expression of miR-106b significantly promoted HeLa and SiHa cells migration. Likewise, inhibition of miR-106b decreased HeLa and SiHa cells migration. The multifunctional cytokine TGF-β facilitates metastasis in cervical carcinoma. miR-106b inhibitor treatment decreased the TGF-β1-stimulated migration of HeLa and SiHa cells. DAB2, a predicted target gene of miR-106b, was inhibited by TGF-β1 partly through miR-106b and was involved in TGF-β1-induced cervical cancer cell migration. The expression of DAB2 was low in cervical cancer tissues, and negatively correlated with miR-106b expression. Finally, DAB2 was identified as a miR-106b-directed target gene by dual-luciferase reporter assay.

CONCLUSION

Our data suggest that the TGF-β1/miR-106b/DAB2 axis may be involved in the pathogenesis of cervical carcinoma.

Intrinsic TGF-β2-triggered SDF-1-CXCR4 signaling axis is crucial for drug resistance and a slow-cycling state in bone marrow-disseminated tumor cells

Dormant or slow-cycling disseminated tumor cells (DTCs) in bone marrow (BM) are resistant to conventional therapy in various cancers including head and neck squamous cell carcinoma (HNSCC), although the molecular mechanisms remain largely unknown. This study aimed to identify the intrinsic molecular mechanisms underlying drug resistance in BM-DTCs. We used in vivo selection of the human HNSCC cell line HEp3, which mimics non-proliferative BM-DTCs in mice, to establish BM-DTC-derived (BM-HEp3) and lung metastases-derived (Lu-HEp3) sublines. Both sublines had higher migration activity and shortened survival in a murine xenograft model compared with parental (P-HEp3) cells. Slow-cycling BM-HEp3 cells had intrinsically enhanced cisplatin resistance compared with Lu-HEp3 cells, which also manifested this resistance but proliferated rapidly. The drug resistance and slow-cycling state of BM-HEp3 cells depended on enhanced positive feedback of the signaling axis of stromal cell-derived factor-1 (SDF-1)-C-X-C chemokine receptor-4 (CXCR4) via their overexpression. Interestingly, BM-DTCs highly expressed transforming growth factor-beta 2 (TGF-β2) to maintain SDF-1-CXCR4 overexpression. Inhibition of SDF-1-CXCR4 signaling by down-regulating TGF-β2 fully reversed the drug resistance of BM-HEp3 cells via reactivation of cell proliferation. These data suggest that the intrinsic TGF-β2-triggered SDF-1-CXCR4 signaling axis is crucial for drug resistance dependent on a slow-cycling state in BM-DTCs.

Micro ribonucleic acid-93 promotes proliferation and migration of esophageal squamous cell carcinoma by targeting disabled 2

Background

Accumulated evidence has revealed that the dysregulation of micro ribonucleic acids (miRNAs) may contribute to esophageal squamous cell carcinoma (ESCC). MiR-93, which is a member of the miRNA cluster miR-106b∼25, has been widely studied for its tumor promoting effect on different types of cancers. However, our knowledge of miR-93 function in ESCC remains unclear.

Methods

The expression levels of miR-93 in ESCC and the adjacent non-tumor tissues were measured by real-time polymerase chain reaction. Cell counting kit-8, flow cytometry, and 5-ethynyl-2′-deoxyuridine incorporation and transwell migration assays were employed to explore the effects of miR-93 on proliferation and migration capabilities in EC109 cells. To determine the possible target gene of miR-93, cell transfection, Western blot analysis and luciferase reporter gene assays were performed.

Results

A significant upregulation of miR-93 expression in ESCC tissues was determined, combined with a downregulation of the predicted target gene, disabled 2 (DAB2). The introduction of miR-93 significantly promotes cell proliferation, cell cycle progression, and the metastatic capability of EC109 cells. By cell transfection and luciferase reporter assay, DAB2 was confirmed as a direct target of miR-93. In addition, the knockdown of DAB2 by small interfering RNA displayed a consentaneous phenocopy with miR-93 overexpression in EC109 cells.

Conclusion

Our results indicate that miR-93 acts as a tumor promoter in ESCC, and its promotion effects on ESCC cell proliferation and migration depend largely upon DAB2 suppression.

The translational significance of epithelial-mesenchymal transition in head and neck cancer

Positive markers of epithelial-mesenchymal transition (EMT) in head and neck cancers complicate clinical management and are associated with reduced survival. We discuss recent translational discoveries in EMT and suggest additional actionable molecular pathways, biomarkers, and clinical agents.

Hormonal induction and roles of Disabled-2 in lactation and involution

Disabled-2 (Dab2) is a widely expressed endocytic adaptor that was first isolated as a 96 KDa phospho-protein, p96, involved in MAPK signal transduction. Dab2 expression is lost in several cancer types including breast cancer, and Dab2 is thought to have a tumor suppressor function. In mammary epithelia, Dab2 was induced upon pregnancy and further elevated during lactation. We constructed mutant mice with a mosaic Dab2 gene deletion to bypass early embryonic lethality and to investigate the roles of Dab2 in mammary physiology. Loss of Dab2 had subtle effects on lactation, but Dab2-deficient mammary glands showed a strikingly delayed cell clearance during involution. In primary cultures of mouse mammary epithelial cells, Dab2 proteins were also induced by estrogen, progesterone, and/or prolactin. Dab2 null mammary epithelial cells were refractory to growth suppression induced by TGF-beta. However, Dab2 deletion did not affect Smad2 phosphorylation; rather TGF-beta-stimulated MAPK activation was enhanced in Dab2-deficient cells. We conclude that Dab2 expression is induced by hormones and Dab2 plays a role in modulating TGF-beta signaling to enhance apoptotic clearance of mammary epithelial cells during involution.

Dab2 inhibits the cholesterol-dependent activation of JNK by TGF-β

TGF-β signals through Smad-dependent and non-Smad pathways, depending on cell context. In ovarian cancer cells, the clathrin adaptor Dab2 enhances internalization of the type I TGF-β receptor, restricts its lateral mobility, and inhibits TGF-β–mediated, cholesterol-dependent JNK activation.

Transforming growth factor-β (TGF-β) ligands activate Smad-mediated and noncanonical signaling pathways in a cell context–dependent manner. Localization of signaling receptors to distinct membrane domains is a potential source of signaling output diversity. The tumor suppressor/endocytic adaptor protein disabled-2 (Dab2) was proposed as a modulator of TGF-β signaling. However, the molecular mechanism(s) involved in the regulation of TGF-β signaling by Dab2 were not known. Here we investigate these issues by combining biophysical studies of the lateral mobility and endocytosis of the type I TGF-β receptor (TβRI) with TGF-β phosphoprotein signaling assays. Our findings demonstrate that Dab2 interacts with TβRI to restrict its lateral diffusion at the plasma membrane and enhance its clathrin-mediated endocytosis. Small interfering RNA–mediated knockdown of Dab2 or Dab2 overexpression shows that Dab2 negatively regulates TGF-β–induced c-Jun N-terminal kinase (JNK) activation, whereas activation of the Smad pathway is unaffected. Moreover, activation of JNK by TGF-β in the absence of Dab2 is disrupted by cholesterol depletion. These data support a model in which Dab2 regulates the domain localization of TβRI in the membrane, balancing TGF-β signaling via the Smad and JNK pathways.

Endocytosis and cancer

Endocytosis entails selective packaging of cell-surface proteins, such as receptors for cytokines and adhesion components, in cytoplasmic vesicles (endosomes). The series of sorting events that determines the fate of internalized proteins, either degradation in lysosomes or recycling back to the plasma membrane, relies on intrinsic sequence motifs, posttranslational modifications (e.g., phosphorylation and ubiquitination), and transient assemblies of both Rab GTPases and phosphoinositide-binding proteins. This multicomponent process is enhanced and skewed in cancer cells; we review mechanisms enabling both major drivers of cancer, p53 and Ras, to bias recycling of integrins and receptor tyrosine kinases (RTKs). Likewise, cadherins and other junctional proteins of cancer cells are constantly removed from the cell surface, thereby disrupting tissue polarity and instigating motile phenotypes. Mutant forms of RTKs able to evade Cbl-mediated ubiquitination, along with overexpression of the wild-type forms and a variety of defective feedback regulatory loops, are frequently detected in tumors. Finally, we describe pharmacological attempts to harness the peculiar endocytic system of cancer, in favor of effective patient treatment.

Epigenetic silencing of DACH1 induces loss of transforming growth factor-β1 antiproliferative response in human hepatocellular carcinoma

Human dachshund homolog 1 (DACH1) is a major component of the Retinal Determination Gene Network (RDGN) and functions as a tumor suppressor. However, the regulation of DACH1 expression and its function in hepatocellular carcinoma (HCC) remain unclear. In this study, epigenetic changes of DACH1 were analyzed in HCC cell lines and primary cancers. We found that promoter region hypermethylation was correlated with loss or reduction of DACH1 expression, and restoration of DACH1 expression was induced by 5-aza-2'-deoxycytidine (5-AZA) in HCC cell lines. Promoter region methylation was found in 42% of primary HCC. Reduced expression of DACH1 was associated with poor differentiation of HCC nodules and higher serum aspartate aminotransferase/alanine aminotransferase ratio. DACH1 suppressed cellular growth by reactivating transforming growth factor beta (TGF-β) signaling. Ectopic expression of DACH1 enhanced chemosensitivity to 5-fluorouracil (5-FU) by inducing p21 expression in HCC cells.

CONCLUSION

DACH1 is frequently methylated in HCC and DACH1 expression is regulated by promoter hypermethylation. Down-regulation of DACH1 is a novel mechanism for gaining resistance to the antiproliferative signaling of TGF-β1 and 5-FU resistance.

Differential requirement for Dab2 in the development of embryonic and extra-embryonic tissues

BACKGROUND

Disabled-2 (Dab2) is an endocytic adaptor protein involved in clathrin-mediated endocytosis and cargo trafficking. Since its expression is lost in several cancer types, Dab2 has been suggested to be a tumor suppressor. In vitro studies indicate that Dab2 establishes epithelial cell polarity and organization by directing endocytic trafficking of membrane glycoproteins. Dab2 also modulates cellular signaling pathways by mediating the endocytosis and recycling of surface receptors and associated signaling components. Previously, two independent gene knockout studies have been reported, with some discrepancies in the observed embryonic phenotypes. To further clarify the in vivo roles of Dab2 in development and physiology, we designed a new floxed allele to delete dab2 gene.

RESULTS

The constitutive dab2 deleted embryos showed a spectrum in the degree of endoderm disorganization in E5.5 and no mutant embryos persisted at E9.5. However, the mice were grossly normal when dab2 deletion was restricted to the embryo proper and the gene was retained in extraembryonic tissues using Meox2-Cre and Sox2-Cre. Adult Dab2-deficient mice had a small but statistically significant increase in serum cholesterol levels.

CONCLUSION

The study of the new dab2 mutant allele in embryos and embryoid bodies confirms a role for Dab2 in extraembryonic endoderm development and epithelial organization. Experimental results with embryoid bodies suggest that additional endocytic adaptors such as Arh and Numb could partially compensate for Dab2 loss. Conditional deletion indicates that Dab2 is dispensable for organ development, when the vast majority of the embryonic cells are dab2 null. However, Dab2 has a physiological role in the endocytosis of lipoproteins and cholesterol metabolism.

Analysis of microRNA-target interactions across diverse cancer types

Little is known about the extent to which individual microRNAs (miRNAs) regulate common processes of tumor biology across diverse cancer types. Using molecular profiles of >3,000 tumors from 11 human cancer types in The Cancer Genome Atlas, we systematically analyzed expression of miRNAs and mRNAs across cancer types to infer recurrent cancer-associated mi RNA-target relationships. As we expected, the inferred relationships were consistent with sequence-based predictions and published data from miRNA perturbation experiments. Notably, miRNAs with recurrent target relationships were frequently regulated by genetic and epigenetic alterations across the studied cancer types. We also identify new examples of miRNAs that coordinately regulate cancer pathways, including the miR-29 family, which recurrently regulates active DNA demethylation pathway members TET1 and TDG. The online resource http://cancerminer.org allows exploration and prioritization of miRNA-target interactions that potentially regulate tumorigenesis.