The integrin-coupled signaling adaptor p130Cas suppresses Smad3 function in transforming growth factor-beta signaling

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.

The role of transient receptor potential channels in metastasis

Metastasis is the hallmark of failed tumor treatment and is typically associated with death due to cancer. Transient receptor potential (TRP) channels affect changes in intracellular calcium concentrations and participate at every stage of metastasis. Further, they increase the migratory ability of tumor cells, promote angiogenesis, regulate immune function, and promote the growth of tumor cells through changes in gene expression and function. In this review, we explore the potential mechanisms of action of TRP channels, summarize their role in tumor metastasis, compile inhibitors of TRP channels relevant in tumors, and discuss current challenges in research on TRP channels involved in tumor metastasis.

Bcar1/p130Cas is essential for ventricular development and neural crest cell remodelling of the cardiac outflow tract

AIMS

The adapter protein p130Cas, encoded by the Bcar1 gene, is a key regulator of cell movement, adhesion, and cell cycle control in diverse cell types. Bcar1 constitutive knockout mice are embryonic lethal by embryonic days (E) 11.5-12.5, but the role of Bcar1 in embryonic development remains unclear. Here, we investigated the role of Bcar1 specifically in cardiovascular development and defined the cellular and molecular mechanisms disrupted following targeted Bcar1 deletions.

METHODS AND RESULTS

We crossed Bcar1 floxed mice with Cre transgenic lines allowing for cell-specific knockout either in smooth muscle and early cardiac tissues (SM22-Cre), mature smooth muscle cells (smMHC-Cre), endothelial cells (Tie2-Cre), second heart field cells (Mef2c-Cre), or neural crest cells (NCC) (Pax3-Cre) and characterized these conditional knock outs using a combination of histological and molecular biology techniques. Conditional knockout of Bcar1 in SM22-expressing smooth muscle cells and cardiac tissues (Bcar1SM22KO) was embryonically lethal from E14.5-15.5 due to severe cardiovascular defects, including abnormal ventricular development and failure of outflow tract (OFT) septation leading to a single outflow vessel reminiscent of persistent truncus arteriosus. SM22-restricted loss of Bcar1 was associated with failure of OFT cushion cells to undergo differentiation to septal mesenchymal cells positive for SMC-specific α-actin, and disrupted expression of proteins and transcription factors involved in epithelial-to-mesenchymal transformation (EMT). Furthermore, knockout of Bcar1 specifically in NCC (Bcar1PAX3KO) recapitulated part of the OFT septation and aortic sac defects seen in the Bcar1SM22KO mutants, indicating a cell-specific requirement for Bcar1 in NCC essential for OFT septation. In contrast, conditional knockouts of Bcar1 in differentiated smooth muscle, endothelial cells, and second heart field cells survived to term and were phenotypically normal at birth and postnatally.

CONCLUSION

Our work reveals a cell-specific requirement for Bcar1 in NCC, early myogenic and cardiac cells, essential for OFT septation, myocardialization and EMT/cell cycle regulation and differentiation to myogenic lineages.

Integrative immunogenomic analysis reveals transcriptional and immune-related differences in hepatocellular carcinoma patients with different disease-free survival

A comprehensive investigation of the neoantigen spectrum and immune infiltration in patients with hepatocellular carcinoma (HCC) is lacking. This study aimed to examine the molecular features correlating with better prognoses in HCC patients. 27 paired tumor and normal tissues from 27 HCC patients were collected and performed with whole-exome sequencing. The most frequently mutated gene in 27 HCC patients was TP53 (16/27, 59.26%). Based on the whole median disease-free survival (DFS), all patients were divided into 'long-term' (n = 14, median DFS = 318 weeks) and 'short-term' (n = 13, median DFS = 11 weeks) groups. RNA-seq was performed to compare differentially expressed genes, immune infiltration, and neoantigens. Immunohistochemistry was performed to evaluate the immune infiltration. There were no significant differences in tumor mutation burden, immune score, cytolytic activity score, or neoantigen load between two groups. Compared with the long-term group, significantly increased B lineage (P = 0.0463), myeloid dendritic cells (P = 0.0152), and fibroblast (P = 0.0244) infiltration levels were observed in the short-term group, in which genes involved in ribosome, proteasome, and ECM-receptor interaction pathways were also overexpressed. Additionally, 16 patients with tumor thrombus were explored to identify specific biomarkers for prognosis. We found that patients with tumor thrombus carrying TP53/ARID2 neoantigens had significantly longer DFS. In conclusion, higher B lineage, myeloid dendritic cells, and fibroblast infiltration levels might cause poor prognosis in the short-term group, which also showed higher expression of genes involved in ribosome, proteasome, and ECM-receptor interaction pathways. In patients with tumor thrombus, specific TP53/ARID2 neoantigens may be used as biomarkers toward personalized immunotherapy.

Tumor-Derived Exosomes Modulate Primary Site Tumor Metastasis

Tumor-derived exosomes (TDEs) are actively produced and released by tumor cells and carry messages from tumor cells to healthy cells or abnormal cells, and they participate in tumor metastasis. In this review, we explore the underlying mechanism of action of TDEs in tumor metastasis. TDEs transport tumor-derived proteins and non-coding RNA to tumor cells and promote migration. Transport to normal cells, such as vascular endothelial cells and immune cells, promotes angiogenesis, inhibits immune cell activation, and improves chances of tumor implantation. Thus, TDEs contribute to tumor metastasis. We summarize the function of TDEs and their components in tumor metastasis and illuminate shortcomings for advancing research on TDEs in tumor metastasis.

p130Cas induces bone invasion by oral squamous cell carcinoma by regulating tumor epithelial-mesenchymal transition and cell proliferation

Bone invasion is a critical factor in determining the prognosis of oral squamous cell carcinoma (OSCC) patients. Transforming growth factor β (TGF-β) is abundantly expressed in the bone matrix and is involved in the acquisition of aggressiveness by tumors. TGF-β is also important to cytoskeletal changes during tumor progression. In this study, we examined the relationship between TGF-β signaling and cytoskeletal changes during bone invasion by OSCC. Immunohistochemical staining of OSCC samples from five patients showed the expression of p130Cas (Crk-associated substrate) in the cytoplasm and phosphorylated Smad3 expression in the nucleus in OSCC cells. TGF-β1 induced the phosphorylation of Smad3 and p130Cas, as well as epithelial-mesenchymal transition (EMT) accompanied by the downregulation of the expression of E-cadherin, a marker of epithelial cells, and the upregulation of the expression of N-cadherin, or Snail, a marker of mesenchymal cells, in human HSC-2 cells and mouse squamous cell carcinome VII (SCCVII) cells. SB431542, a specific inhibitor of Smad2/3 signaling, abrogated the TGF-β1-induced phosphorylation of p130Cas and morphological changes. Silencing p130Cas using an short hairpin RNA (shRNA) or small interfering RNA in SCCVII cells suppressed TGF-β1-induced cell migration, invasion, EMT and matrix metalloproteinase-9 (MMP-9) production. Compared with control SCCVII cells, SCCVII cells with silenced p130Cas strongly suppressed zygomatic and mandibular destruction in vivo by reducing the number of osteoclasts, cell proliferation and MMP-9 production. Taken together, these results showed that the expression of TGF-β/p130Cas might be a new target for the treatment of OSCC bone invasion.

Mutant TP53 interacts with BCAR1 to contribute to cancer cell invasion

BACKGROUND

Mutant TP53 interacts with other proteins to produce gain-of-function properties that contribute to cancer metastasis. However, the underlying mechanisms are still not fully understood.

METHODS

Using immunoprecipitation and proximity ligation assays, we evaluated breast cancer anti-estrogen resistance 1 (BCAR1) as a novel binding partner of TP53R273H, a TP53 mutant frequently found in human cancers. The biological functions of their binding were examined by the transwell invasion assay. Clinical outcome of patients was analysed based on TP53 status and BCAR1 expression using public database.

RESULTS

We discovered a novel interaction between TP53R273H and BCAR1. We found that BCAR1 translocates from the cytoplasm into the nucleus and binds to TP53R273H in a manner dependent on SRC family kinases (SFKs), which are known to enhance metastasis. The expression of full-length TP53R273H, but not the BCAR1 binding-deficient mutant TP53R273HΔ102-207, promoted cancer cell invasion. Furthermore, among the patients with mutant TP53, high BCAR1 expression was associated with a poorer prognosis.

CONCLUSIONS

The interaction between TP53R273H and BCAR1 plays an important role in enhancing cancer cell invasion. Thus, our study suggests a disruption of the TP53R273H-BCAR1 binding as a potential therapeutic approach for TP53R273H-harbouring cancer patients.

Development of in vitro-grown spheroids as a 3D tumor model system for solid-state NMR spectroscopy

Recent advances in the field of in-cell NMR spectroscopy have made it possible to study proteins in the context of bacterial or mammalian cell extracts or even entire cells. As most mammalian cells are part of a multi-cellular complex, there is a need to develop novel NMR approaches enabling the study of proteins within the complexity of a 3D cellular environment. Here we investigate the use of the hanging drop method to grow spheroids which are homogenous in size and shape as a model system to study solid tumors using solid-state NMR (ssNMR) spectroscopy. We find that these spheroids are stable under magic-angle-spinning conditions and show a clear change in metabolic profile as compared to single cell preparations. Finally, we utilize dynamic nuclear polarization (DNP)-supported ssNMR measurements to show that low concentrations of labelled nanobodies targeting EGFR (7D12) can be detected inside the spheroids. These findings suggest that solid-state NMR can be used to directly examine proteins or other biomolecules in a 3D cellular microenvironment with potential applications in pharmacological research.

Esophageal Cancer Development: Crucial Clues Arising from the Extracellular Matrix

In the last years, the extracellular matrix (ECM) has been reported as playing a relevant role in esophageal cancer (EC) development, with this compartment being related to several aspects of EC genesis and progression. This sounds very interesting due to the complexity of this highly incident and lethal tumor, which takes the sixth position in mortality among all tumor types worldwide. The well-established increase in ECM stiffness, which is able to trigger mechanotransduction signaling, is capable of regulating several malignant behaviors by converting alteration in ECM mechanics into cytoplasmatic biochemical signals. In this sense, it has been shown that some molecules play a key role in these events, particularly the different collagen isoforms, as well as enzymes related to its turnover, such as lysyl oxidase (LOX) and matrix metalloproteinases (MMPs). In fact, MMPs are not only involved in ECM stiffness, but also in other events related to ECM homeostasis, which includes ECM remodeling. Therefore, the crucial role of distinct MMPs isoform has already been reported, especially MMP-2, -3, -7, and -9, along EC development, thus strongly associating these proteins with the control of important cellular events during tumor progression, particularly in the process of invasion during metastasis establishment. In addition, by distinct mechanisms, a vast diversity of glycoproteins and proteoglycans, such as laminin, fibronectin, tenascin C, galectin, dermatan sulfate, and hyaluronic acid exert remarkable effects in esophageal malignant cells due to the activation of oncogenic signaling pathways mainly involved in cytoskeleton alterations during adhesion and migration processes. Finally, the wide spectrum of interactions potentially mediated by ECM may represent a singular intervention scenario in esophageal carcinogenesis natural history and, due to the scarce knowledge on the cellular and molecular mechanisms involved in EC development, the growing body of evidence on ECM’s role along esophageal carcinogenesis might provide a solid base to improve its management in the future.

Targeting the tumour stroma to improve cancer therapy

Cancers are not composed merely of cancer cells alone; instead, they are complex 'ecosystems' comprising many different cell types and noncellular factors. The tumour stroma is a critical component of the tumour microenvironment, where it has crucial roles in tumour initiation, progression, and metastasis. Most anticancer therapies target cancer cells specifically, but the tumour stroma can promote the resistance of cancer cells to such therapies, eventually resulting in fatal disease. Therefore, novel treatment strategies should combine anticancer and antistromal agents. Herein, we provide an overview of the advances in understanding the complex cancer cell-tumour stroma interactions and discuss how this knowledge can result in more effective therapeutic strategies, which might ultimately improve patient outcomes.

5-HT2 and 5-HT2B antagonists attenuate pro-fibrotic phenotype in human adult dermal fibroblasts by blocking TGF-β1 induced non-canonical signaling pathways including STAT3 : implications for fibrotic diseases like scleroderma

BACKGROUND

Release of 5-hydroxytryptamine (5-HT; serotonin) from activated platelets following microvascular injury leads to tissue fibrosis. 5-HT strongly induces extracellular matrix synthesis in dermal fibroblasts in a transforming growth factor beta 1 (TGF-β1)-dependent manner.

AIM

To evaluate anti-fibrotic properties of inhibitors of 5-HT2 and 5-HT2B (terguride, SB204741) respectively in human adult dermal fibroblasts (HADF) derived from a patient with scleroderma.

METHODS

Anti-fibrotic efficacy of 5-HT2 and 5-HT2B inhibitors was evaluated as per two strategies: HADF were incubated with 5-HT (1 μM)/TGF-β1 (10 ng/mL) for 1 hour followed by 5-HT (1 μM)/TGF-β1 (10 ng/mL) and terguride or SB204741 (1 μM, each) for 24 hours (post-treatment strategy) and HADF were treated with terguride or SB204741 (1 μM, each) for 1 hour followed by 5-HT (1 μM)/TGF-β1 (10 ng/mL) for 24 hours (pre-treatment strategy). Real time quantitative polymerase chain reaction for expression of pro-fibrotic (TGFΒ1, COL1A1, COL1A2, ACTA2, CTGF and FN1) and anti-fibrotic genes (MMP2/TIMP1) was performed. Expression of type I collagen, alpha smooth muscle actin (α-SMA), phosphorylation of Smad3, ERK1/2 and STAT3 was examined by immunoblotting.

RESULTS

Stimulation of HADF cells with 5-HT/TGF-β1 led to the increased expression of pro-fibrotic genes which was significantly reduced by both terguride and SB204741. Expression of anti-fibrotic genes was not affected upon incubation with the inhibitors. In 5-HT-stimulated HADF, treatment with terguride and SB204741 decreased type I collagen and α-SMA. In 5-HT/TGF-β1 stimulated HADF, terguride and SB204741 treatment reduced ERK1/2 and STAT3 phosphorylation but did not influence Smad3 phosphorylation.

CONCLUSION

Terguride and SB204741 reduce pro-fibrotic potential of HADF cells and suppress TGF-β1-mediated non-canonical pathways, ERK1/2 and STAT3 which have been implicated in the regulation of pro-fibrotic genes and in the development of fibrosis. Taken together, our data suggest that 5-HT inhibitors might reduce fibrosis via suppression of TGF-beta1-mediated non-canonical signaling pathways. These observations have important therapeutic implications for fibrotic disorders like scleroderma.

Chemoresistance and the Self-Maintaining Tumor Microenvironment

The progression of cancer is associated with alterations in the tumor microenvironment, including changes in extracellular matrix (ECM) composition, matrix rigidity, hypervascularization, hypoxia, and paracrine factors. One key malignant phenotype of cancer cells is their ability to resist chemotherapeutics, and elements of the ECM can promote chemoresistance in cancer cells through a variety of signaling pathways, inducing changes in gene expression and protein activity that allow resistance. Furthermore, the ECM is maintained as an environment that facilitates chemoresistance, since its constitution modulates the phenotype of cancer-associated cells, which themselves affect the microenvironment. In this review, we discuss how the properties of the tumor microenvironment promote chemoresistance in cancer cells, and the interplay between these external stimuli. We focus on both the response of cancer cells to the external environment, as well as the maintenance of the external environment, and how a chemoresistant phenotype emerges from the complex signaling network present.

Profilin-1 deficiency leads to SMAD3 upregulation and impaired 3D outgrowth of breast cancer cells

BACKGROUND

Adhesion-mediated activation of FAK/ERK signalling pathway, enabled by the formation of filopodial protrusions (FLP), has been shown to be an important event for triggering of dormancy-to-proliferation switch and metastatic outgrowth of breast cancer cells (BCC). We studied the role of actin-binding protein profilin1 (Pfn1) in these processes.

METHODS

Quantitative immunohistochemistry (IHC) of BC tissue microarray (TMA) and survival analyses of curated transcriptome datasets of BC patients were performed to examine Pfn1's association with certain clinicopathological features. FLP formation and single cell outgrowth of BCC were assessed using a 3D matrigel culture that accurately predicts dormant vs metastatic outgrowth phenotypes of BCC in certain microenvironment. Gene expression studies were performed to identify potential biological pathways that are perturbed under Pfn1-depleted condition.

RESULTS

Lower Pfn1 expression is correlated with lower nuclear grade of breast tumours and longer relapse-free survival of BC patients. Pfn1 depletion leads to defects in FLP and outgrowth of BCC but without impairing either FAK or ERK activation. Guided by transcriptome analyses, we further showed that Pfn1 depletion is associated with prominent SMAD3 upregulation. Although knockdown and overexpression experiments revealed that SMAD3 has an inhibitory effect on the outgrowth of breast cancer cells, SMAD3 knockdown alone was not sufficient to enhance the outgrowth potential of Pfn1-depleted BCC suggesting that other proliferation-regulatory pathways in conjunction with SMAD3 upregulation may underlie the outgrowth-deficient phenotype of BCC cells upon depletion of Pfn1.

CONCLUSION

Overall, these data suggest that Pfn1 may be a novel biomarker for BC recurrence and a possible target to reduce metastatic outgrowth of BCC.

Extracellular matrix glycation and receptor for advanced glycation end-products activation: a missing piece in the puzzle of the association between diabetes and cancer

A growing body of epidemiologic evidence suggests that people with diabetes are at a significantly higher risk of many forms of cancer. However, the molecular mechanisms underlying this association are not fully understood. Cancer cells are surrounded by a complex milieu, also known as tumor microenvironment, which contributes to the development and metastasis of tumors. Of note, one of the major components of this niche is the extracellular matrix (ECM), which becomes highly disorganized during neoplastic progression, thereby stimulating cancer cell transformation, growth and spread. One of the consequences of chronic hyperglycemia, the most frequently observed sign of diabetes and the etiological source of diabetes complications, is the irreversible glycation and oxidation of proteins and lipids leading to the formation of the advanced glycation end-products (AGEs). These compounds may covalently crosslink and biochemically modify structure and functions of many proteins, and AGEs accumulation is particularly high in long-living proteins with low biological turnover, features that are shared by most, if not all, ECM proteins. AGEs-modified proteins are recognized by AGE-binding proteins, and thus glycated ECM components have the potential to trigger Receptor for advanced glycation end-products-dependent mechanisms. The biological consequence of receptor for advanced glycation end-products activation mechanisms seems to be connected, in different ways, to drive some hallmarks of cancer onset and tumor growth. The present review intends to highlight the potential impact of ECM glycation on tumor progression by triggering receptor for advanced glycation end-products-mediated mechanisms.

The miR-24-3p/p130Cas: a novel axis regulating the migration and invasion of cancer cells

MicroRNAs (miRNAs) are small non-coding RNAs that negatively regulate gene expression by suppressing translation or facilitating mRNA decay. Differential expression of miRNAs is involved in the pathogenesis of several diseases including cancer. Here, we investigated the role of-miR-24-3p as a downregulated miRNA in metastatic cancer. miR-24-3p was decreased in metastatic cancer and lower expression of miR-24-3p was related to poor survival of cancer patients. Consistently, ectopic expression of miR-24-3p suppressed the cell migration, invasion, and proliferation of MCF7, Hep3B, B16F10, SK-Hep1, and PC-3 cells by directly targeting p130Cas. Stable expression of p130Cas restored miR-24-3p-mediated inhibition of cell migration and invasion. These results suggest that miR-24-3p functions as a tumor suppressor and the miR-24-3p/p130Cas axis is a novel factor of cancer progression by regulating cell migration and invasion.

Forkhead Box F1 promotes breast cancer cell migration by upregulating lysyl oxidase and suppressing Smad2/3 signaling

Background

Epithelial-mesenchymal transition (EMT) increases cell migration and is implicated in cancer cell invasion and metastasis. We have previously described the involvement of the transcription factors, nuclear factor I-C2 (NFI-C2) and Forkhead box F1 (FoxF1), in the regulation of EMT and invasion during breast tumor progression. NFI-C2 counteracts these processes and FoxF1 is a directly repressed target of NFI-C2. FoxF1 induces EMT and invasiveness and enhances xenograft tumorigenicity in nude mice. Here we identify oppositely regulated targets of NFI-C2 and FoxF1 involved in these processes and further study a possible role for FoxF1 in tumorigenesis.

Methods

We used Affymetrix microarray to detect changes in the transcriptome of a mouse mammary epithelial cell line upon overexpression of NFI-C2 or FoxF1. To elucidate the effects and signaling events following FoxF1 overexpression we investigated in vitro invasion capacity and changes in transcription and protein expression resulting from RNAi and inhibitor treatment.

Results

The extracellular matrix enzyme lysyl oxidase (LOX) was negatively regulated by NFI-C2 and positively regulated by FoxF1, and upregulation of LOX following FoxF1 overexpression in mouse mammary epithelial cells increased in vitro cell invasion. In the nuclei of FoxF1-overexpressing cells, the phosphorylation of Smad2 decreased, while that of p38 increased. Depletion of LOX by RNAi enhanced phosphorylation of Smad2 by a focal adhesion kinase (FAK)-dependent mechanism. In addition, induced expression of FoxF1 in a non-malignant human mammary epithelial cell line showed that the increase in LOX transcription and the suppression of Smad2 activity are early effects of FoxF1.

Conclusion

These data show that FoxF1 enhances invasion in a LOX-dependent manner, is involved in the regulation of Smad2 signaling, and that FoxF1 overexpression ultimately leads to activation of p38 MAPK signaling. These findings provide new insights into the regulation of signaling pathways known to be important during breast tumor progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2196-2) contains supplementary material, which is available to authorized users.

Downregulation of microRNA-362-3p and microRNA-329 promotes tumor progression in human breast cancer

p130Cas regulates cancer progression by driving tyrosine receptor kinase signaling. Tight regulation of p130Cas expression is necessary for survival, apoptosis, and maintenance of cell motility in various cell types. Several studies revealed that transcriptional and post-translational control of p130Cas are important for maintenance of its expression and activity. To explore novel regulatory mechanisms of p130Cas expression, we studied the effect of microRNAs (miRs) on p130Cas expression in human breast cancer MCF7 cells. Here, we provide experimental evidence that miR-362-3p and miR-329 perform a tumor-suppressive function and their expression is downregulated in human breast cancer. miR-362-3p and miR-329 inhibited cellular proliferation, migration, and invasion, thereby suppressing tumor growth, by downregulating p130Cas. Ectopic expression of p130Cas attenuated the inhibitory effects of the two miRs on tumor progression. Relative expression levels of miR-362-3p/329 and p130Cas between normal and breast cancer correlated inversely; miR-362-3p/329 expression was decreased, whereas that of p130Cas increased in breast cancers. Furthermore, we showed that downregulation of miR-362-3p and miR-329 was caused by differential DNA methylation of miR genes. Enhanced DNA methylation (according to methylation-specific PCR) was responsible for downregulation of miR-362-3p and miR-329 in breast cancer. Taken together, these findings point to a novel role for miR-362-3p and miR-329 as tumor suppressors; the miR-362-3p/miR-329-p130Cas axis seemingly has a crucial role in breast cancer progression. Thus, modulation of miR-362-3p/miR-329 may be a novel therapeutic strategy against breast cancer.

Breast cancer anti-estrogen resistance 3 inhibits transforming growth factor β/Smad signaling and associates with favorable breast cancer disease outcomes

INTRODUCTION

This study helps to define the implications of breast cancer anti-estrogen resistance 3 (BCAR3) in breast cancer and extends the current understanding of its molecular mechanism of action. BCAR3 has been shown to promote cell proliferation, migration and attachment to extracellular matrix components. However, in a cohort of metastatic breast cancer patients who received tamoxifen treatment, high BCAR3 mRNA levels were associated with favorable progression-free survival outcome. These results suggest that, besides its established roles, BCAR3 may have additional mechanisms of action that regulate breast cancer aggressive phenotype. In this study, we investigated whether BCAR3 is a novel antagonist of the canonical transforming growth factor β (TGFβ) pathway, which induces potent migration and invasion responses in breast cancer cells.

METHODS

We surveyed functional genomics databases for correlations between BCAR3 expression and disease outcomes of breast cancer patients. We also studied how BCAR3 could regulate the TGFβ/Smad signaling axis using Western blot analysis, coimmunoprecipitation and luciferase assays. In addition, we examined whether BCAR3 could modulate TGFβ-induced cell migration and invasion by using an automated imaging system and a confocal microscopy imaging-based matrix degradation assay, respectively.

RESULTS

Relatively low levels of BCAR3 expression in primary breast tumors correlate with poor distant metastasis-free survival and relapse-free survival outcomes. We also found a strong correlation between the loss of heterozygosity at BCAR3 gene alleles and lymph node invasion in human breast cancer, further suggesting a role for BCAR3 in preventing disease progression. In addition, we found BCAR3 to inhibit Smad activation, Smad-mediated gene transcription, Smad-dependent cell migration and matrix digestion in breast cancer cells. Furthermore, we found BCAR3 to be downregulated by TGFβ through proteasome degradation, thus defining a novel positive feedback loop mechanism downstream of the TGFβ/Smad signaling pathway.

CONCLUSION

BCAR3 is considered to be associated with aggressive breast cancer phenotypes. However, our results indicate that BCAR3 acts as a putative suppressor of breast cancer progression by inhibiting the prometastatic TGFβ/Smad signaling pathway in invasive breast tumors. These data provide new insights into BCAR3's molecular mechanism of action and highlight BCAR3 as a novel TGFβ/Smad antagonist in breast cancer.

The extracellular matrix modulates the hallmarks of cancer

The extracellular matrix regulates tissue development and homeostasis, and its dysregulation contributes to neoplastic progression. The extracellular matrix serves not only as the scaffold upon which tissues are organized but provides critical biochemical and biomechanical cues that direct cell growth, survival, migration and differentiation and modulate vascular development and immune function. Thus, while genetic modifications in tumor cells undoubtedly initiate and drive malignancy, cancer progresses within a dynamically evolving extracellular matrix that modulates virtually every behavioral facet of the tumor cells and cancer-associated stromal cells. Hanahan and Weinberg defined the hallmarks of cancer to encompass key biological capabilities that are acquired and essential for the development, growth and dissemination of all human cancers. These capabilities include sustained proliferation, evasion of growth suppression, death resistance, replicative immortality, induced angiogenesis, initiation of invasion, dysregulation of cellular energetics, avoidance of immune destruction and chronic inflammation. Here, we argue that biophysical and biochemical cues from the tumor-associated extracellular matrix influence each of these cancer hallmarks and are therefore critical for malignancy. We suggest that the success of cancer prevention and therapy programs requires an intimate understanding of the reciprocal feedback between the evolving extracellular matrix, the tumor cells and its cancer-associated cellular stroma.

Transforming growth factor-β1 signaling represses testicular steroidogenesis through cross-talk with orphan nuclear receptor Nur77

Transforming growth factor- β1 (TGF-β1) has been reported to inhibit luteinizing hormone (LH) mediated-steroidogenesis in testicular Leydig cells. However, the mechanism by which TGF-β1 controls the steroidogenesis in Leydig cells is not well understood. Here, we investigated the possibility that TGF-β1 represses steroidogenesis through cross-talk with the orphan nuclear receptor Nur77. Nur77, which is induced by LH/cAMP signaling, is one of major transcription factors that regulate the expression of steroidogenic genes in Leydig cells. TGF-β1 signaling inhibited cAMP-induced testosterone production and the expression of steroidogenic genes such as P450c17, StAR and 3β-HSD in mouse Leydig cells. Further, TGF-β1/ALK5 signaling repressed cAMP-induced and Nur77-activated promoter activity of steroidogenic genes. In addition, TGF-β1/ALK5-activated Smad3 repressed Nur77 transactivation of steroidogenic gene promoters by interfering with Nur77 binding to DNA. In primary Leydig cells isolated from Tgfbr2^flox/flox Cyp17iCre mice, TGF-β1-mediated repression of cAMP-induced steroidogenic gene expression was significantly less than that in primary Leydig cells from Tgfbr2^flox/flox mice. Taken together, these results suggest that TGF-β1/ALK5/Smad3 signaling represses the expression of steroidogenic genes via the suppression of Nur77 transactivation in testicular Leydig cells. These findings may provide a molecular mechanism involved in the TGF-β1-mediated repression of testicular steroidogenesis.

The 31-kDa caspase-generated cleavage product of p130Cas antagonizes the action of MyoD during myogenesis

Myogenesis is regulated by the basic helix-loop-helix (bHLH) myogenic regulatory factor MyoD, which induces muscle-specific gene expression by binding to the E-box sequence as a heterodimer with ubiquitous bHLH E2A (E12/E47) proteins. Here, we report that a 31-kDa caspase-generated cleavage product of Crk-associated substrate (p130Cas), herein called 31-kDa, is downregulated during muscle cell differentiation. 31-kDa contains a helix-loop-helix (HLH) domain that shows greater sequence homology with Id (inhibitor of DNA binding) proteins than with bHLH proteins. This HLH domain, lacking the basic region required for DNA binding, mediated the direct interaction of 31-kDa with MyoD. Overexpression of 31-kDa in C3H10T1/2 cells inhibited not only the transcriptional activation of p21(Waf1/Cip1) and E-box-dependent muscle-specific genes by MyoD and/or E2A but also MyoD-induced myosin heavy chain expression and myogenic conversion. In sum, our results suggest a role for 31-kDa as a negative regulator of MyoD in the muscle differentiation program.

Proteomic analysis of proton beam irradiated human melanoma cells

Proton beam irradiation is a form of advanced radiotherapy providing superior distributions of a low LET radiation dose relative to that of photon therapy for the treatment of cancer. Even though this clinical treatment has been developing for several decades, the proton radiobiology critical to the optimization of proton radiotherapy is far from being understood. Proteomic changes were analyzed in human melanoma cells treated with a sublethal dose (3 Gy) of proton beam irradiation. The results were compared with untreated cells. Two-dimensional electrophoresis was performed with mass spectrometry to identify the proteins. At the dose of 3 Gy a minimal slowdown in proliferation rate was seen, as well as some DNA damage. After allowing time for damage repair, the proteomic analysis was performed. In total 17 protein levels were found to significantly (more than 1.5 times) change: 4 downregulated and 13 upregulated. Functionally, they represent four categories: (i) DNA repair and RNA regulation (VCP, MVP, STRAP, FAB-2, Lamine A/C, GAPDH), (ii) cell survival and stress response (STRAP, MCM7, Annexin 7, MVP, Caprin-1, PDCD6, VCP, HSP70), (iii) cell metabolism (TIM, GAPDH, VCP), and (iv) cytoskeleton and motility (Moesin, Actinin 4, FAB-2, Vimentin, Annexin 7, Lamine A/C, Lamine B). A substantial decrease (2.3 x) was seen in the level of vimentin, a marker of epithelial to mesenchymal transition and the metastatic properties of melanoma.

Increased BCAR1 predicts poor outcomes of non-small cell lung cancer in multiple-center patients

OBJECTIVE

This study was designed to determine the prognostic value of BCAR1 expression and its associations with clinical-demographical characteristics in multiple centers of non-small cell lung cancer (NSCLC) patients.

METHODS

Gene expression microarray (mRNA) of 77 adenocarcinomas from Mayo Clinic, RNA-sequencing of 508 NSCLC from The Cancer Genome Atlas (TCGA), and immunohistochemistry stain of BCAR1-protein expression in 150 cases from Daping Hospital were included in the study. The association of mRNA or protein expression with patient clinical characteristics and overall survival was assessed in each dataset. We also predicted microRNAs (miRNA) that target BCAR1 using bioinformatics prediction tools and evaluated miRNA expression patterns with BCAR1 expression in miRNA-sequencing data of 74 lung cancer cases from TCGA dataset.

RESULTS

In the Mayo Clinic dataset, a higher BCAR1-mRNA level correlated significantly with more advanced tumor-stage and lymphatic metastasis. Similar changes were observed in the TCGA RNA-seq dataset. Additionally, higher BCAR1-mRNA levels predicted poorer survival in adenocarcinoma and squamous carcinoma from the TCGA dataset. The protein levels in the adenocarcinoma cases with lymphatic metastasis were significantly higher than of those without metastasis. Tumor tissues demonstrated remarkably higher levels of protein compared with matched normal tissues although there was no significant difference in BCAR1-mRNA expression between tumor and matched normal tissues was detected. In miRNAs that were downregulated in the tumors, Let-7f-2 and miR-22 differed the most (P < 0.001 and P = 0.007, respectively).

CONCLUSIONS

We confirmed that increased BCAR1 expression predicts poorer prognosis in NSCLC. We postulate that mRNA-protein decoupling of BCAR1 may be a result of reduced inhibition of specific miRNAs in tumor tissues, which warrants further study.

Expression of breast cancer anti-estrogen resistance 1 in relation to vascular endothelial growth factor, p53, and prognosis in esophageal squamous cell cancer

The purpose of this study was to clarify the role of breast cancer anti-estrogen resistance 1 (BCAR1) expression in relation to vascular endothelial growth factor (VEGF), p53, and proliferation in esophageal squamous cell cancer (ESCC). Expression of BCAR1, VEGF, p53, and the ki-67 proliferative index were examined by tissue microarray and immunohistochemistry in 106 specimens with ESCC and matched adjacent normal tissues. Among them, 40 cases were simultaneously examined by Western blot. Both Western blot and immunohistochemistry showed that BCAR1 expression was substantially higher in ESCC than in adjacent normal tissues (P < 0.001). BCAR1 expression was significantly connected with degree of tumor differentiation, with poorly differentiated tumors showing higher BCAR1 expression (P < 0.001). BCAR1 expression was significantly and positively correlated with VEGF and p53 expression levels (r= 0.541, P < 0.001; r= 0.374; P < 0.001) but not proliferative index (r= 0.44; P= 0.066). Additionally, a significant relationship was also observed between VEGF and p53 (r= 0.321; P= 0.001). Kaplan-Meier survival analysis revealed that patients with high BCAR1 expression had significantly shorter survival times than those with low BCAR1 expression levels (median survival 40 months vs. 27 months, P= 0.09). Multivariate analysis also revealed that levels of BCAR1 expression (hazard ratio 2.250, P= 0.015) was a significant and independent prognostic indicator. High expression of BCAR1 is associated with elevated VEGF and p53 expression levels, as well as poor prognosis in ESCC. Therefore, BCAR1 may be a potential candidate for predicting prognosis and a new therapy target for ESCC.

p130Cas: a key signalling node in health and disease

p130Cas/breast cancer anti-oestrogen resistance 1 (BCAR1) is a member of the Cas (Crk-associated substrate) family of adaptor proteins, which have emerged as key signalling nodes capable of interactions with multiple proteins, with important regulatory roles in normal and pathological cell function. The Cas family of proteins is characterised by the presence of multiple conserved motifs for protein-protein interactions, and by extensive tyrosine and serine phosphorylations. Recent studies show that p130Cas contributes to migration, cell cycle control and apoptosis. p130Cas is essential during early embryogenesis, with a critical role in cardiovascular development. Furthermore, p130Cas has been reported to be involved in the development and progression of several human cancers. p130Cas is able to perform roles in multiple processes due to its capacity to regulate a diverse array of signalling pathways, transducing signals from growth factor receptor tyrosine kinases, non-receptor tyrosine kinases, and integrins. In this review we summarise the current understanding of the structure, function, and regulation of p130Cas, and discuss the importance of p130Cas in both physiological and pathophysiological settings, with a focus on the cardiovascular system and cancer.

5-HT(2B) antagonism arrests non-canonical TGF-β1-induced valvular myofibroblast differentiation

Transforming growth factor-β1 (TGF-β1) induces myofibroblast activation of quiescent aortic valve interstitial cells (AVICs), a differentiation process implicated in calcific aortic valve disease (CAVD). The ubiquity of TGF-β1 signaling makes it difficult to target in a tissue specific manner; however, the serotonin 2B receptor (5-HT(2B)) is highly localized to cardiopulmonary tissues and agonism of this receptor displays pro-fibrotic effects in a TGF-β1-dependent manner. Therefore, we hypothesized that antagonism of 5-HT(2B) opposes TGF-β1-induced pathologic differentiation of AVICs and may offer a druggable target to prevent CAVD. To test this hypothesis, we assessed the interaction of 5-HT(2B) antagonism with canonical and non-canonical TGF-β1 pathways to inhibit TGF-β1-induced activation of isolated porcine AVICs in vitro. Here we show that AVIC activation and subsequent calcific nodule formation is completely mitigated by 5-HT(2B) antagonism. Interestingly, 5-HT(2B) antagonism does not inhibit canonical TGF-β1 signaling as identified by Smad3 phosphorylation and activation of a partial plasminogen activator inhibitor-1 promoter (PAI-1, a transcriptional target of Smad3), but prevents non-canonical p38 MAPK phosphorylation. It was initially suspected that 5-HT(2B) antagonism prevents Src tyrosine kinase phosphorylation; however, we found that this is not the case and time-lapse microscopy indicates that 5-HT(2B) antagonism prevents non-canonical TGF-β1 signaling by physically arresting Src tyrosine kinase. This study demonstrates the necessity of non-canonical TGF-β1 signaling in leading to pathologic AVIC differentiation. Moreover, we believe that the results of this study suggest 5-HT(2B) antagonism as a novel therapeutic approach for CAVD that merits further investigation.

Overexpression and cytoplasmic accumulation of Hepl is associated with clinicopathological parameters and poor prognosis in non-small cell lung cancer

Hepl, first described in 2008, is the fourth member of the Crk-associated substrate (CAS) family and is specifically expressed in the lung. Compared to other CAS proteins, Hepl has a varying effect on cell migration in different cell types. We speculated that Hepl may play a role in lung cancer invasion and metastasis. We quantified the expression and subcellular localization of Hepl in 143 non-small cell lung cancer (NSCLC) tissues, adjacent noncancerous tissues, and eight lung cancer cell lines using Western blotting, immunohistochemistry, and immunofluorescent staining. Expression of Hepl was correlated with the clinicopathological features of NSCLC. Hepl was overexpressed in 72.3 % (103/143) of the NSCLC tissues, compared to the adjacent noncancerous lung tissues (P = 0.022). Overexpression of Hepl was associated with lymph node metastasis and high TNM stage (P = 0.005 and P = 0.045, respectively). Kaplan-Meier survival curves and the log-rank test indicated that overexpression of Hepl correlated with poorer overall survival in NSCLC (P < 0.001), and Cox regression analysis demonstrated that overexpression of Hepl was an independent prognostic factor in NSCLC. Furthermore, cytoplasmic accumulation of Hepl was observed in a high metastatic potential lung cancer cell lines (H1299 and BE1), but not in low metastatic potential cell lines (LTE and A549). This study reveals that Hepl is overexpressed in the nucleus and aberrantly accumulates in the cytoplasm of NSCLC cells, and indicates that Hepl may play a role in the progression of lung cancer, including lymph node metastasis and TNM stage. Additionally, Hepl may be a useful prognostic factor in lung cancer.

Neuropilins are multifunctional coreceptors involved in tumor initiation, growth, metastasis and immunity

The neuropilins (Nrps) are multifunctional proteins involved in development, immunity and cancer. Neuropilin-1 (Nrp1), or its homologue neuropilin-2 (Nrp2), are coreceptors that enhance responses to several growth factors (GFs) and other mediators. Nrps are coreceptors for the class 3 semaphorins (SEMA3), involved in axonal guidance, and several members of the vascular endothelial growth factor (VEGF) family. However, recent findings reveal they have a much broader spectrum of activity. They bind transforming growth factor β1 (TGF-β1) and its receptors, hepatocyte growth factor (HGF) and its receptor (cMet), platelet derived growth factor (PDGF) and its receptors, fibroblast growth factors (FGFs), and integrins. Nrps also promote Hedgehog signaling. These ligands and pathways are all relevant to angiogenesis and wound healing. In the immune system, the Nrps are expressed primarily by dendritic cells (DCs) and regulatory T cells (Tregs), and exert mainly inhibitory effects. In cancer, Nrps have been linked to a poor prognosis, which is consistent with their numerous interactions with ligands and receptors that promote tumor progression. We hypothesize that Nrps boost responses by capturing ligands, regulating GF receptor expression, endocytosis and recycling, and possibly also by signaling independently. Importantly, they promote epithelial-mesenchymal transition (EMT), and the survival of cancer stem cells. The recent finding that Nrps bind and internalize cell-penetrating peptides (CPPs) with arginine/lysine-rich C-terminal motifs (C-end rule; e.g., RXXR) is of interest. These CPPs can be coupled to large drugs for cancer therapy. Almost all studies have been preclinical, but findings suggest Nrps are excellent targets for anti-cancer drug development.

A critical role for p130Cas in the progression of pulmonary hypertension in humans and rodents

RATIONALE

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease characterized by pulmonary arterial muscularization due to excessive pulmonary vascular cell proliferation and migration, a phenotype dependent upon growth factors and activation of receptor tyrosine kinases (RTKs). p130(Cas) is an adaptor protein involved in several cellular signaling pathways that control cell migration, proliferation, and survival.

OBJECTIVES

We hypothesized that in experimental and human PAH p130(Cas) signaling is overactivated, thereby facilitating the intracellular transmission of signal induced by fibroblast growth factor (FGF)2, epidermal growth factor (EGF), and platelet-derived growth factor (PDGF).

MEASUREMENTS AND MAIN RESULTS

In patients with PAH, levels of p130(Cas) protein and/or activity are higher in the serum, in the walls of distal pulmonary arteries, in cultured smooth muscle cells (PA-SMCs), and in pulmonary endothelial cells (P-ECs) than in control subjects. These abnormalities in the p130(Cas) signaling were also found in the chronically hypoxic mice and monocrotaline-injected rats as models of human PAH. We obtained evidence for the convergence and amplification of the growth-stimulating effect of the EGF-, FGF2-, and PDGF-signaling pathways via the p130(Cas) signaling pathway. We found that daily treatment with the EGF-R inhibitor gefitinib, the FGF-R inhibitor dovitinib, and the PDGF-R inhibitor imatinib started 2 weeks after a subcutaneous monocrotaline injection substantially attenuated the abnormal increase in p130(Cas) and ERK1/2 activation and regressed established pulmonary hypertension.

CONCLUSIONS

Our findings demonstrate that p130(Cas) signaling plays a critical role in experimental and idiopathic PAH by modulating pulmonary vascular cell migration and proliferation and by acting as an amplifier of RTK downstream signals.

Cas and NEDD9 Contribute to Tumor Progression through Dynamic Regulation of the Cytoskeleton

The Cas family proteins, p130(Cas) (Cas) and NEDD9, are adaptor molecules that regulate cytoskeletal dynamics to promote multiple cellular processes, including migration, invasion, proliferation, and survival. Because these functions are also critical for tumor initiation, growth, and metastasis, Cas and NEDD9 are well positioned to contribute to these oncogenic processes. Indeed, mouse models of cancer show that these proteins function during multiple stages of disease progression. Furthermore, in many human cancers, high expression of Cas and NEDD9 is associated with advanced stage disease and is predictive of poor outcome. This review explores the contribution of Cas and NEDD9 during cellular transformation and neoplastic growth, tumor progression, metastasis, and the development of therapeutic resistance. Given these roles, Cas and NEDD9 may prove to be viable candidates for use as biomarkers and therapeutic targets.

BCAR1 protein plays important roles in carcinogenesis and predicts poor prognosis in non-small-cell lung cancer

Objective

Our previous study suggested the potential clinical implications of BCAR1 in non-small-cell lung cancer (NSCLC) (Mol Diagn Ther. 2011. 15(1): 31–40). Herein, we aim to evaluate the predictive power of BCAR1 as a marker for poor prognosis in NSCLC cases, verify the carcinogenic roles of BCAR1 in the A549 lung adenocarcinoma cell line, and testify to the BCAR1/phospho-p38 axis.

Methods

Between January 2006 and June 2010, there were a total of 182 patients with NSCLC (151 cases with available follow up data, and 31 cases lost to follow-up due to the invalid contact information). We inspected BCAR1, phospho-BCAR1(Tyr410), phospho-p38(Thr180/Tyr182) and p38 expression in NSCLC tissues and matched adjacent normal tissues by immunoblotting and IHC. After BCAR1 -RNA interference in A549 cells, we inspected the protein expression (BCAR1, phospho-BCAR1, phospho-p38 and p38) and performed cell biology experiments (cell growth, migration and cycle).

Results

BCAR1 was overexpressed in NSCLC tissues (177/182) and cell lines (A549 and Calu-3). However, it was not detected in the normal adjacent tissue in 161 of the 182 cases. Higher BCAR1 levels were strongly associated with more poorly differentiated NSCLC and predicted poorer prognosis. BCAR1 knockdown caused cell growth arrest, cell migration inhibition and cell cycle arrest of A549 cells. Overexpression of BCAR1 was associated with activation of p38 in NSCLC cases, and BCAR1 knockdown caused reduction of phospho-p38 levels in A549 cells.

Conclusion

Overexpression of BCAR1 is a predictor of poor prognosis in NSCLC and plays important carcinogenic roles in carcinogenesis, probably via activation of p38 MAPK. However, further investigations are required immediately.

Deconstructing the mechanisms and consequences of TGF-β-induced EMT during cancer progression

Transforming growth factor-β (TGF-β) is a potent pleiotropic cytokine that regulates mammalian development, differentiation, and homeostasis in essentially all cell types and tissues. TGF-β normally exerts anticancer activities by prohibiting cell proliferation and by creating cell microenvironments that inhibit cell motility, invasion, and metastasis. However, accumulating evidence indicates that the process of tumorigenesis, particularly that associated with metastatic progression, confers TGF-β with oncogenic activities, a functional switch known as the "TGF-β paradox." The molecular determinants governing the TGF-β paradox are complex and represent an intense area of investigation by researchers in academic and industrial settings. Recent findings link genetic and epigenetic events in mediating the acquisition of oncogenic activity by TGF-β, as do aberrant alterations within tumor microenvironments. These events coalesce to enable TGF-β to direct metastatic progression via the stimulation of epithelial-mesenchymal transition (EMT), which permits carcinoma cells to abandon polarized epithelial phenotypes in favor of apolar mesenchymal-like phenotypes. Attempts to deconstruct the EMT process induced by TGF-β have identified numerous signaling molecules, transcription factors, and microRNAs operant in mediating the initiation and resolution of this complex transdifferentiation event. In addition to its ability to enhance carcinoma cell invasion and metastasis, EMT also endows transitioned cells with stem-like properties, including the acquisition of self-renewal and tumor-initiating capabilities coupled to chemoresistance. Here, we review recent findings that delineate the pathophysiological mechanisms whereby EMT stimulated by TGF-β promotes metastatic progression and disease recurrence in human carcinomas.

Noncanonical TGF-β signaling during mammary tumorigenesis

Breast cancer is a heterogeneous disease comprised of at least five major tumor subtypes that coalesce as the second leading cause of cancer death in women in the United States. Although metastasis clearly represents the most lethal characteristic of breast cancer, our understanding of the molecular mechanisms that govern this event remains inadequate. Clinically, ~30% of breast cancer patients diagnosed with early-stage disease undergo metastatic progression, an event that (a) severely limits treatment options, (b) typically results in chemoresistance and low response rates, and (c) greatly contributes to aggressive relapses and dismal survival rates. Transforming growth factor-β (TGF-β) is a pleiotropic cytokine that regulates all phases of postnatal mammary gland development, including branching morphogenesis, lactation, and involution. TGF-β also plays a prominent role in suppressing mammary tumorigenesis by preventing mammary epithelial cell (MEC) proliferation, or by inducing MEC apoptosis. Genetic and epigenetic events that transpire during mammary tumorigenesis conspire to circumvent the tumor suppressing activities of TGF-β, thereby permitting late-stage breast cancer cells to acquire invasive and metastatic phenotypes in response to TGF-β. Metastatic progression stimulated by TGF-β also relies on its ability to induce epithelial-mesenchymal transition (EMT) and the expansion of chemoresistant breast cancer stem cells. Precisely how this metamorphosis in TGF-β function comes about remains incompletely understood; however, recent findings indicate that the initiation of oncogenic TGF-β activity is contingent upon imbalances between its canonical and noncanonical signaling systems. Here we review the molecular and cellular contributions of noncanonical TGF-β effectors to mammary tumorigenesis and metastatic progression.

P130Cas attenuates epidermal growth factor (EGF) receptor internalization by modulating EGF-triggered dynamin phosphorylation

Background

Endocytosis controls localization-specific signal transduction via epidermal growth factor receptor (EGFR), as well as downregulation of that receptor. Extracellular matrix (ECM)-integrin coupling induces formation of macromolecular complexes that include EGFR, integrin, Src kinase and p130Cas, resulting in EGFR activation. In addition, cell adhesion to ECM increases EGFR localization at the cell surface and reduces EGFR internalization. The molecular mechanisms involved are not yet well understood.

Methodology/Principal Findings

We investigated the molecular mechanism by which p130Cas affects the endocytic regulation of EGFR. Biochemical quantification revealed that cell adhesion to fibronectin (FN) increases total EGFR levels and its phosphorylation, and that p130Cas is required for this process. Measurements of Texas Red-labeled EGF uptake and cell surface EGFR revealed that p130Cas overexpression reduces EGF-induced EGFR internalization, while p130Cas depletion enhances it. In addition, both FN-mediated cell adhesion and p130Cas overexpression reduce EGF-stimulated dynamin phosphorylation, which is necessary for EGF-induced EGFR internalization. Coimmunoprecipitation and GST pull-down assays confirmed the interaction between p130Cas and dynamin. Moreover, a SH3-domain-deleted form of p130Cas, which shows diminished binding to dynamin, inhibits dynamin phosphorylation and EGF uptake less effectively than wild-type p130Cas.

Conclusions/Significance

Our results show that p130Cas plays an inhibitory role in EGFR internalization via its interaction with dynamin. Given that the EGFR internalization process determines signaling density and specificity in the EGFR pathway, these findings suggest that the interaction between p130Cas and dynamin may regulate EGFR trafficking and signaling in the same manner as other endocytic regulatory proteins related to EGFR endocytosis.

Integrin signalling adaptors: not only figurants in the cancer story

Current evidence highlights the ability of adaptor (or scaffold) proteins to create signalling platforms that drive cellular transformation upon integrin-dependent adhesion and growth factor receptor activation. The understanding of the biological effects that are regulated by these adaptors in tumours might be crucial for the identification of new targets and the development of innovative therapeutic strategies for human cancer. In this Review we discuss the relevance of adaptor proteins in signalling that originates from integrin-mediated cell-extracellular matrix (ECM) adhesion and growth factor stimulation in the context of cell transformation and tumour progression. We specifically underline the contribution of p130 Crk-associated substrate (p130CAS; also known as BCAR1), neural precursor cell expressed, developmentally down-regulated 9 (NEDD9; also known as HEF1), CRK and the integrin-linked kinase (ILK)-pinch-parvin (IPP) complex to cancer, along with the more recently identified p140 Cas-associated protein (p140CAP; also known as SRCIN1).

The pathophysiology of epithelial-mesenchymal transition induced by transforming growth factor-beta in normal and malignant mammary epithelial cells

Epithelial-mesenchymal transition (EMT) is an essential process that drives polarized, immotile mammary epithelial cells (MECs) to acquire apolar, highly migratory fibroblastoid-like features. EMT is an indispensable process that is associated with normal tissue development and organogenesis, as well as with tissue remodeling and wound healing. In stark contrast, inappropriate reactivation of EMT readily contributes to the development of a variety of human pathologies, particularly those associated with tissue fibrosis and cancer cell invasion and metastasis, including that by breast cancer cells. Although metastasis is unequivocally the most lethal aspect of breast cancer and the most prominent feature associated with disease recurrence, the molecular mechanisms whereby EMT mediates the initiation and resolution of breast cancer metastasis remains poorly understood. Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that is intimately involved in regulating numerous physiological processes, including cellular differentiation, homeostasis, and EMT. In addition, TGF-beta also functions as a powerful tumor suppressor in MECs, whose neoplastic development ultimately converts TGF-beta into an oncogenic cytokine in aggressive late-stage mammary tumors. Recent findings have implicated the process of EMT in mediating the functional conversion of TGF-beta during breast cancer progression, suggesting that the chemotherapeutic targeting of EMT induced by TGF-beta may offer new inroads in ameliorating metastatic disease in breast cancer patients. Here we review the molecular, cellular, and microenvironmental factors that contribute to the pathophysiological activities of TGF-beta during its regulation of EMT in normal and malignant MECs.

Nmp4/CIZ inhibits mechanically induced beta-catenin signaling activity in osteoblasts

Cellular mechanotransduction, the process of converting mechanical signals into biochemical responses within cells, is a critical aspect of bone health. While the effects of mechanical loading on bone are well recognized, elucidating the specific molecular pathways involved in the processing of mechanical signals by bone cells represents a challenge and an opportunity to identify therapeutic strategies to combat bone loss. In this study we have for the first time examined the relationship between the nucleocytoplasmic shuttling transcription factor nuclear matrix protein-4/cas interacting zinc finger protein (Nmp4/CIZ) and beta-catenin signaling in response to a physiologic mechanical stimulation (oscillatory fluid shear stress, OFSS) in osteoblasts. Using calvaria-derived osteoblasts from Nmp4-deficient and wild-type mice, we found that the normal translocation of beta-catenin to the nucleus in osteoblasts that is induced by OFSS is enhanced when Nmp4/CIZ is absent. Furthermore, we found that other aspects of OFSS-induced mechanotransduction generally associated with the beta-catenin signaling pathway, including ERK, Akt, and GSK3beta activity, as well as expression of the beta-catenin-responsive protein cyclin D1 are also enhanced in cells lacking Nmp4/CIZ. Finally, we found that in the absence of Nmp4/CIZ, OFSS-induced cytoskeletal reorganization and the formation of focal adhesions between osteoblasts and the extracellular substrate is qualitatively enhanced, suggesting that Nmp4/CIZ may reduce the sensitivity of bone cells to mechanical stimuli. Together these results provide experimental support for the concept that Nmp4/CIZ plays an inhibitory role in the response of bone cells to mechanical stimulation induced by OFSS.

CAS proteins in normal and pathological cell growth control

Proteins of the CAS (Crk-associated substrate) family (BCAR1/p130Cas, NEDD9/HEF1/Cas-L, EFS/SIN and CASS4/HEPL) are integral players in normal and pathological cell biology. CAS proteins act as scaffolds to regulate protein complexes controlling migration and chemotaxis, apoptosis, cell cycle, and differentiation, and have more recently been linked to a role in progenitor cell function. Reflecting these complex functions, over-expression of CAS proteins has now been strongly linked to poor prognosis and increased metastasis in cancer, as well as resistance to first-line chemotherapeutics in multiple tumor types including breast and lung cancers, glioblastoma, and melanoma. Further, CAS proteins have also been linked to additional pathological conditions including inflammatory disorders, Alzheimer's and Parkinson's disease, as well as developmental defects. This review will explore the roles of the CAS proteins in normal and pathological states in the context of the many mechanistic insights into CAS protein function that have emerged in the past decade.

Mechanisms of the epithelial-mesenchymal transition by TGF-beta

The formation of epithelial cell barriers results from the defined spatiotemporal differentiation of stem cells into a specialized and polarized epithelium, a process termed mesenchymal-epithelial transition. The reverse process, epithelial-mesenchymal transition (EMT), is a metastable process that enables polarized epithelial cells to acquire a motile fibroblastoid phenotype. Physiological EMT also plays an essential role in promoting tissue healing, remodeling or repair in response to a variety of pathological insults. On the other hand, pathophysiological EMT is a critical step in mediating the acquisition of metastatic phenotypes by localized carcinomas. Although metastasis clearly is the most lethal aspect of cancer, our knowledge of the molecular events that govern its development, including those underlying EMT, remain relatively undefined. Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that oversees and directs all aspects of cell development, differentiation and homeostasis, as well as suppresses their uncontrolled proliferation and transformation. Quite dichotomously, tumorigenesis subverts the tumor suppressing function of TGF-beta, and in doing so, converts TGF-beta to a tumor promoter that stimulates pathophysiological EMT and metastasis. It therefore stands to reason that determining how TGF-beta induces EMT in developing neoplasms will enable science and medicine to produce novel pharmacological agents capable of preventing its ability to do so, thereby improving the clinical course of cancer patients. Here we review the cellular, molecular and microenvironmental mechanisms used by TGF-beta to mediate its stimulation of EMT in normal and malignant cells.

Nmp4/CIZ: road block at the intersection of PTH and load

Teriparatide (parathyroid hormone, [PTH]) is the only FDA-approved drug that replaces bone lost to osteoporosis. Enhancing PTH efficacy will improve cost-effectiveness and ameliorate contraindications. Combining this hormone with load-bearing exercise may enhance therapeutic potential consistent with a growing body of evidence that these agonists are synergistic and share common signaling pathways. Additionally, neutralizing molecules that naturally suppress the anabolic response to PTH may also improve the efficacy of treatment with this hormone. Nmp4/CIZ (nuclear matrix protein 4/cas interacting zinc finger)-null mice have enhanced responses to intermittent PTH with respect to increasing trabecular bone mass and are also immune to disuse-induced bone loss likely by the removal of Nmp4/CIZ suppressive action on osteoblast function. Nmp4/CIZ activity may be sensitive to changes in the mechanical environment of the bone cell brought about by hormone- or mechanical load-induced changes in cell shape and adhesion. Nmp4 was identified in a screen for PTH-responsive nuclear matrix architectural transcription factors (ATFs) that we proposed translate hormone-induced changes in cell shape and adhesion into changes in target gene DNA conformation. CIZ was independently identified as a nucleocytoplasmic shuttling transcription factor associating with the mechano-sensitive focal adhesion proteins p130Cas and zxyin. The p130Cas/zyxin/Nmp4/CIZ pathway resembles the beta-catenin/TCF/LEF1 mechanotransduction response limb and both share features with the HMGB1 (high mobility group box 1)/RAGE (receptor for advanced glycation end products) signaling axis. Here we describe Nmp4/CIZ within the context of the PTH-induced anabolic response and consider the place of this molecule in the hierarchy of the PTH-load response network.

p130Cas is required for mammary tumor growth and transforming growth factor-beta-mediated metastasis through regulation of Smad2/3 activity

During breast cancer progression, transforming growth factor-beta (TGF-beta) switches from a tumor suppressor to a pro-metastatic molecule. Several recent studies suggest that this conversion in TGF-beta function depends upon fundamental changes in the TGF-beta signaling system. We show here that these changes in TGF-beta signaling are concomitant with aberrant expression of the focal adhesion protein, p130Cas. Indeed, elevating expression of either the full-length (FL) or just the carboxyl terminus (CT) of p130Cas in mammary epithelial cells (MECs) diminished the ability of TGF-beta1 to activate Smad2/3, but increased its coupling to p38 MAPK. This shift in TGF-beta signaling evoked (i) resistance to TGF-beta-induced growth arrest, and (ii) acinar filling upon three-dimensional organotypic cultures of p130Cas-FL or -CT expressing MECs. Furthermore, rendering metastatic MECs deficient in p130Cas enhanced TGF-beta-stimulated Smad2/3 activity, which restored TGF-beta-induced growth inhibition both in vitro and in mammary tumors produced in mice. Additionally, whereas elevating TbetaR-II expression in metastatic MECs had no affect on their phosphorylation of Smad2/3, this event markedly enhanced their activation of p38 MAPK, leading to increased MEC invasion and metastasis. Importantly, depleting p130Cas expression in TbetaR-II-expressing metastatic MECs significantly increased their activation of Smad2/3, which (i) reestablished the physiologic balance between canonical and noncanonical TGF-beta signaling, and (ii) reversed cellular invasion and early mammary tumor cell dissemination stimulated by TGF-beta. Collectively, our findings identify p130Cas as a molecular rheostat that regulates the delicate balance between canonical and noncanonical TGF-beta signaling, a balance that is critical to maintaining the tumor suppressor function of TGF-beta during breast cancer progression.