TGF-β signaling promotes desmoid tumor formation via CSRP2 upregulation

Desmoid tumors (DTs), also called desmoid-type fibromatoses, are locally aggressive tumors of mesenchymal origin. In the present study, we developed a novel mouse model of DTs by inducing a local mutation in the Ctnnb1 gene, encoding β-catenin in PDGFRA-positive stromal cells, by subcutaneous injection of 4-hydroxy-tamoxifen. Tumors in this model resembled histologically clinical samples from DT patients and showed strong phosphorylation of nuclear SMAD2. Knockout of SMAD4 in the model significantly suppressed tumor growth. Proteomic analysis revealed that SMAD4 knockout reduced the level of Cysteine-and-Glycine-Rich Protein 2 (CSRP2) in DTs, and treatment of DT-derived cells with a TGF-β receptor inhibitor reduced CSRP2 RNA levels. Knockdown of CSRP2 in DT cells significantly suppressed their proliferation. These results indicate that the TGF-β/CSRP2 axis is a potential therapeutic target for DTs downstream of TGF-β signaling.     

Cathepsin G-mediated enhanced TGF-β signaling promotes angiogenesis via upregulation of VEGF and MCP-1

Transforming growth factor (TGF)-β signaling makes a significant contribution to the pathogenesis of breast cancer bone metastasis. In other tumor types, TGF-β has been shown to promote tumor vascularity. Here, we report that inhibition of TGF-β significantly reduces microvessel density in mammary tumor-induced bone lesions, mediated by decreased expression of both vascular endothelial growth factor (VEGF) and monocyte chemotactic protein (MCP)-1, both known angiogenic factors. Cathepsin G upregulation at the tumor–bone interface has been linked to increased TGF-β signaling, and we also report that inhibition of Cathepsin G reduced tumor vascularity, as well as VEGF and MCP-1 expression.     

Crosstalk between TGF-β signaling and miRNAs in breast cancer metastasis

Transforming growth factor-β (TGF-β) signaling pathway is a key regulator of various cancer biologies, including cancer cell migration, invasion, angiogenesis, proliferation, as well as apoptosis, and it is one of indispensable signaling pathways during cancer metastasis. TGF-β signaling pathway can regulate and be regulated by a series of molecular and signaling pathways where microRNAs (miRNAs) seem to play important roles. miRNAs are small non-coding RNAs that can regulate expressions of their target genes. Emerging evidence suggest that miRNAs participate in various biological and pathologic processes such as cancer cells apoptosis, proliferation, invasion, migration, and metastasis by influencing multiple signaling pathways. In this article, we focus on the interaction between miRNAs and TGF-β in breast cancer (BC) metastasis through modulating invasion-metastasis-related factors, including epithelial-to-mesenchymal transition (EMT), cancer stem cells (CSCs), matrix metalloproteinase (MMP), tissue inhibitors of MMPs (TIMPs), cell adhesion molecules (CAMs), and tumor microenvironment (TME). Through a clear understanding of the complicated links between TGF-β pathway and miRNAs, it may provide a novel and safer therapeutic target to prevent BC metastasis.     

Highly-expressed P2X7 receptor promotes growth and metastasis of human HOS/MNNG osteosarcoma cells via PI3K/Akt/GSK3β/β-catenin and mTOR/HIF1α/VEGF signaling

The P2X7 receptor, an ATP-gated ion channel, is critical for cancer cell growth, invasiveness, and angiogenesis. Previous studies indicate that P2X7 regulates osteoblast proliferation and osteodeposition and that high P2X7 expression has a pro-growth effect in osteosarcoma. However, how it functions in osteosarcoma cell growth and metastasis is not clear. Thus, we elucidated molecular mechanisms of P2X7-dependent positive regulation of osteosarcoma cell proliferation, invasion, migration, epithelial to mesenchymal transition (EMT), and angiogenesis using in vitro and in vivo models. We confirm that P2X7 is highly-expressed in human osteosarcoma tumor tissues and HOS/MNNG, MG63, U2OS, SW1353 and SAOS-2 cell lines. P2X7 receptor stimulation enhanced HOS/MNNG and SAOS-2 cell proliferation, migration and invasion; but knockdown of P2X7 expression or receptor inhibition had opposite effects. P2X7 positively regulated glycogen content, epithelial to mesenchymal transition and stemness of HOS/MNNG cells. P2X7 activation promoted PI3K/Akt/GSK3β/β-catenin and mTOR/HIF1α/VEGF signaling, thereby mediating pro-tumor effects of osteosarcoma cells. Consistent with data from in vitro experiments, systemic administration of P2X7 agonist induced tumor growth, metastasis and tumor-associated bone destruction in osteosarcoma-bearing nude mice, whereas a P2X7 antagonist reversed these effects. Thus, the P2X7 receptor participates in regulation of osteosarcoma growth and metastasis and we offer evidence that P2X7 may be a promising therapeutic target for treating osteosarcoma.     

The roles of TGF-β signaling in carcinogenesis and breast cancer metastasis

Transforming growth factor-β (TGF-β) ligand is a multifunctional growth factor that regulates various cell behavior, such as cell proliferation, differentiation, migration, and apoptosis. Because TGF-β is a potent growth inhibitor, abnormalities in TGF-β signaling result in carcinogenesis. In addition to tumor suppressor function, TGF-β acts as an oncogenic factor. In particular, TGF-β signaling plays an important role during metastasis of breast cancer. Recently, epithelial-mesenchymal transition (EMT) has been shown to confer malignant properties such as cell motility and invasiveness to cancer cells and plays crucial roles during cancer metastasis. Moreover, breast stem-like cells exhibit EMT properties. Because TGF-β is a potent regulator of EMT as well as cell stemness, TGF-β signaling might play a crucial role in the regulation of breast cancer stem cells.     

TACC3 promotes epithelial–mesenchymal transition (EMT) through the activation of PI3K/Akt and ERK signaling pathways

Transforming acidic coiled-coil protein 3 (TACC3) is a member of the TACC family, essential for mitotic spindle dynamics and centrosome integrity during mitosis. Mounting evidence suggests that deregulation of TACC3 is associated with various types of human cancer. However, the molecular mechanisms by which TACC3 contributes to the development of cancer remain largely unknown. Here, we propose a novel mechanism by which TACC3 regulates epithelial–mesenchymal transition (EMT). By modulating the expression of TACC3, we found that overexpression of TACC3 leads to changes in cell morphology, proliferation, transforming capability, migratory/invasive behavior as well as the expression of EMT-related markers. Moreover, phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated protein kinases (ERKs) signaling pathways are critical for TACC3-mediated EMT process. Notably, depletion of TACC3 is sufficient to suppress EMT phenotype. Collectively, our findings identify TACC3 as a driver of tumorigenesis as well as an inducer of oncogenic EMT and highlight its overexpression as a potential therapeutic target for preventing EMT-associated tumor progression and invasion.     

AnnexinA5 promote glioma cell invasion and migration via the PI3K/Akt/NF-κB signaling pathway

Malignant glioma (MG), the most common primary brain tumor in adults, is extremely aggressive and uniformly fatal. Several treatment strategies have shown significant preclinical promise in murine models of glioma; however, none have produced meaningful clinical responses in human patients. We hypothesize that introduction of an additional preclinical animal model better approximating the complexity of human MG, particularly in interactions with host immune responses, will bridge the existing gap between these two stages of testing. Here, we characterize the immunologic landscape and gene expression profiles of spontaneous canine glioma and evaluate its potential for serving as such a translational model. RNA in situ hybridization, flowcytometry, and RNA sequencing were used to evaluate immune cell presence and gene expression in healthy and glioma-bearing canines. Similar to human MGs, canine gliomas demonstrated increased intratumoral immune cell infiltration (CD4+, CD8+ and CD4+Foxp3+ T cells). The peripheral blood of glioma-bearing dogs also contained a relatively greater proportion of CD4+Foxp3+ regulatory T cells and plasmacytoid dendritic cells. Tumors were strongly positive for PD-L1 expression and glioma-bearing animals also possessed a greater proportion of immune cells expressing the immune checkpoint receptors CTLA-4 and PD-1. Analysis of differentially expressed genes in our canine populations revealed several genetic changes paralleling those known to occur in human disease. Naturally occurring canine glioma has many characteristics closely resembling human disease, particularly with respect to genetic dysregulation and host immune responses to tumors, supporting its use as a translational model in the preclinical testing of prospective anti-glioma therapies proven successful in murine studies.     

Loss of RAB1B promotes triple-negative breast cancer metastasis by activating TGF-β/SMAD signaling

Triple-negative breast cancer (TNBC) is a highly aggressive tumor subtype associated with a poor prognosis. The mechanism involved in TNBC progression remains largely unknown. To date, there are no effective therapeutic targets for this tumor subtype. In this study, by performing quantitative proteomic analyses in highly metastatic and parental breast cancer cell line, we found that RAB1B, a member of the RAS oncogene family, was significantly down-regulated in highly metastatic breast cancer cells. Moreover, down-regulation of RAB1B was also found to promote the proliferation and migration of TNBC cells in vitro and in vivo. Mechanistically, loss of RAB1B resulted in elevated expression of TGF-β receptor 1 (TβR1) through decreased degradation of ubiquitin, increased levels of phosphorylated SMAD3 and TGF-β-induced epithelial-mesenchymal transition (EMT). Furthermore, low RAB1B expression correlated with poor prognosis in breast cancer patients. Taken together, our findings reveal that RAB1B acts as a metastasis suppressor in TNBC by regulating the TGF-β/SMAD signaling pathway and RAB1B may serve as a novel biomarker of prognosis and the response to anti-tumor therapeutics for patients with TNBC.     

Therapeutic targeting of the focal adhesion complex prevents oncogenic TGF-β signaling and metastasis

Introduction  

Mammary tumorigenesis is associated with the increased expression of several proteins in the focal adhesion complex, including focal adhesion kinase (FAK) and various integrins. Aberrant expression of these molecules occurs concomitant with the conversion of TGF-β function from a tumor suppressor to a tumor promoter. We previously showed that interaction between β₃ integrin and TβR-II facilitates TGF-β-mediated oncogenic signaling, epithelial-mesenchymal transition (EMT), and metastasis. However, the molecular mechanisms by which the focal adhesion complex contributes to β₃ integrin:TβR-II signaling and the oncogenic conversion of TGF-β remain poorly understood.     

IL-13 receptor α2 stimulates human glioma cell growth and metastasis through the Src/PI3K/Akt/mTOR signaling pathway

Tumor Biology - Glioma is a malignant tumor that affects all kinds of people all over the world. It demonstrates remarkable infiltrative and invasive features. The high expression of interleukin-13...     

Circ-E-Cad encodes a protein that promotes the proliferation and migration of gastric cancer via the TGF-β/Smad/C-E-Cad/PI3K/AKT pathway

Accumulating studies indicate that circular RNAs (circRNAs) play critical roles in cancer progression. Most of them have been reported to act as microRNA sponges or interact with RNA-binding proteins; however, their full range of functions remains largely unclear. Recently, an increasing number of circRNAs have been found to encode proteins. C-E-Cad, a protein encoded by circular E-cadherin (circ-E-Cad), has been shown to have a great influence in the progression of glioblastoma, but its specific role in gastric cancer (GC) is unclear. Here, we found that both circ-E-Cad and C-E-Cad were upregulated in GC cell lines and GC tissues compared with a human gastric epithelial cell line (GES-1) and normal tissues. Knockdown of circ-E-Cad suppressed GC cell line proliferation and metastasis in vitro and in vivo, whereas overexpression of C-E-Cad had the opposite effects. Immunoblotting revealed that C-E-Cad exerted tumor-promoting functions by regulating the PI3K/AKT pathway. A rescue experiment showed that C-E-Cad but not circ-E-Cad was the executor of protumor biological functions. In addition, we demonstrated that the C-E-Cad expression level could have been increased by the TGF-β/Smad pathway. In summary, our results indicated that the TGF-β/Smad pathway could increase the expression of C-E-Cad to regulate GC cell proliferation, migration, and epithelial-mesenchymal transition by affecting PI3K/AKT signaling.     

TGF-β induces fascin expression in gastric cancer via phosphorylation of smad3 linker area

Background: Fascin is an actin-bundling protein critical for tumor invasion. TGF-β could induce fascin expression in gastric cancer cells. In this study, we attempted to explore the role of p-smad3L in the expression of fascin induced by TGF-β in gastric cancer cells. Methods: Pseudopodia were evaluated by immunofluorescence. Fascin expression was detected by RT-PCR and western blot. Smad3 siRNA was used to repress the endogenous smad3. The phosphorylations of smad3 linker region at sites s204, s208 and s213 were detected by western blot. The fascin promoter reporter activity was measured by dual luciferase assay. Results: TGF-β could increase the formation of pseudopodia and the expression of fascin in gastric cancer cells. Smad3 depletion abrogated the expression of fascin induced by TGF-β. The phosphorylation of smad3 linker region at serine 204, 208 and 213 was enhanced in gastric cancer cells after TGF-β treatment. The fascin promoter reporter activity was significantly enhanced with TGF-β treatment in both wild-type Smad3 group and Smad3EPSM group (P<0.05). Furthermore, the fascin promoter reporter activity in the wild-type Smad3 transfectant cells was significantly higher than that in Smad3EPSM cells (P<0.05). Conclusions: fascin expression induced by TGF-β depends on smad3, at least in part, depends on smad3 linker phosphorylation.     

Insulin-like growth factor-binding protein-3 suppresses tumor growth via activation of caspase-dependent apoptosis and cross-talk with NF-κB signaling

Nuclear factor-kappaB (NF-κB) is constitutively activated in a variety of human cancers including prostate cancer and involved in tumorigenesis, tumor progression and chemo-resistance. Insulin-like growth factor-binding protein-3 (IGFBP-3) is a potent tumor suppressor and is significantly suppressed in a variety of cancers. Diverse biological effects of IGFBP-3 have been reported to be both dependent and independent of the IGF/IGF-I receptor (IGF-IR) axis. The precise underlying mechanisms of IGF/IGF-IR-independent, antiproliferative actions of IGFBP-3 are yet to be elucidated. We found an inverse correlation between NF-κB activity and IGFBP-3 expression during prostate cancer progression using an in vitro prostate cancer progression model. Restoration of IGFBP-3 resulted in significant inhibition of constitutively elevated NF-κB activity in prostate cancer cells. IGFBP-3 further inhibited the expression of NF-κB-regulated angiogenic factors such as VEGF and IL-8, and cell adhesion molecules, ICAM-1 and VCAM-1. This inhibitory action of IGFBP-3 was IGF/IGF-IR-independent since IGFBP-3 mutant devoid of IGF binding affinity had a similar inhibitory effect. We identified that IGFBP-3 degrades the key NF-κB regulatory molecules-IκBα and p65-NF-κB proteins through activation of caspase-8 and -3/-7, thereby inhibiting elevated NF-κB activity in prostate cancer. Finally intratumoral administration of IGFBP-3 resulted in significant tumor suppression as well as sensitization of antitumor effect of doxorubicin. Our findings indicate that IGFBP-3 exerts antitumor effects via IGF-independent mechanisms which involve activation of caspase-dependent apoptosis and cross-talk with NF-κB signaling. The use of IGFBP-3 as a cancer therapeutic with this distinctive suppression mechanism may offer alternate means to treat chemotherapy resistant tumors.     

Activation of Akt/GSK3β and Akt/Bcl-2 signaling pathways in nickel-transformed BEAS-2B cells

The Akt signaling pathway has been implicated in a wide range of cellular functions involving cell survival and proliferation, angiogenesis, metabolism and cell migration. Accumulating evidence suggests that Akt perturbations play an important role in human malignancy. Here, we investigated Akt perturbation in nickel-transformed cells. Chronic treatment of human bronchial epithelial BEAS-2B cells with low doses of nickel chloride resulted in cell transformation demonstrated by anchorage-independent (AI) growth, increased cell growth and alterations of cell growth pattern. Western blot assays show that phosphorylation of Akt at Ser473, but not that of p38, JNK and ERK, was increased in nickel-transformed cells compared with controls. Inhibition of Akt or PI3K by pharmacological or biochemical interference suppressed nickel AI growth and cell growth of transformed cells. Activation of Akt led to inhibition of GSK3β by phosphorylation at Ser9 in nickel-transformed cells. In addition, two major anti-apoptotic proteins of the Bcl family, Bcl-2 and Bcl-XL, were increased in nickel-transformed cells. By employing the small interfering RNA technique (siRNA), our results showed that siRNA Akt attenuated the expression of Bcl-2 and Bcl-XL in nickel-transformed cells, indicating that induction of Bcl-2 and Bcl-XL was likely mediated through Akt. ROS generation was decreased in nickel-transformed cells compared with controls. Moreover, down-regulation of retinoblastoma protein (Rb) was observed in nickel-transformed cells. Taken together, these findings demonstrate that activation of Akt, followed by GSK3β inhibition and Bcl-2, Bcl-XL up-regulation and decrease of ROS generation, along with a synergistic effect of Rb down-regulation may cause apoptosis resistance, contributing to the overall mechanism of nickel carcinogenesis.     

CHC promotes tumor growth and angiogenesis through regulation of HIF-1α and VEGF signaling

Pancreatic adenocarcinoma is an aggressive disease with a high mortality rate. In this study, we have newly generated a monoclonal antibody (mAb), Pa65-2, which specifically binds to pancreatic cancer cells and tumor blood vessels. The target protein of Pa65-2 is identified as human clathrin heavy chain (CHC). In vitro and In vivo study showed that suppression of CHC either by shRNA or by Pa65-2 inhibited tumor growth and angiogenesis. One of the key functions of CHC was to bind with the hypoxia-inducing factor (HIF)-1α protein, increasing the stability of this protein and facilitating its nuclear translocation, thereby regulating the expression of VEGF. Taken together, our findings indicate that CHC plays a role in the processes of tumorigenesis and angiogenesis. Pa65-2 antibody or CHC shRNA can potentially be used for pancreatic cancer therapy.     

Differential roles for the p101 and p84 regulatory subunits of PI3Kγ in tumor growth and metastasis

Phosphoinositide 3-kinase γ (PI3Kγ) consists of a catalytic subunit p110γ, which forms mutually exclusive dimers with one of the regulatory subunits called p101 and p84/p87(PIKAP). Recently, PI3Kγ emerged as being a potential oncogene because overexpression of the catalytic subunit p110γ or the regulatory subunit p101 leads to oncogenic cellular transformation and malignancy. However, the contribution of the individual subunits to tumor growth and metastasis and the mechanisms involved are not understood. We therefore individually knocked down the PI3Kγ subunits (p84, p101 and p110γ) in MDA-MB-231 cells, which reduced in vitro migration of the cell lines. Knockdown of p110γ or p101 inhibited apoptosis, Akt phosphorylation and lung colonization in SCID mice. Similarly, the knockdown of p110γ and p101 in murine epithelial carcinoma 4T1.2 cells inhibited primary tumor growth and spontaneous metastasis, as well as lung colonization. In contrast, knockdown of p84 in MDA-MB-231 cells enhanced Akt phosphorylation and lung colonization. These findings are the first to implicate differential functions of the two PI3Kγ regulatory subunits in the process of oncogenesis, and indicate that loss of p101 is sufficient to reduce in vivo tumor growth and metastasis to the same extent as that of p110γ.     

SOX2 promotes tumor metastasis by stimulating epithelial-to-mesenchymal transition via regulation of WNT/β-catenin signal network

SOX2 was reported to promote metastasis in various tumor tissues; however the underlying mechanisms remain elusive. Here, we disclosed that SOX2 improves metastasis of breast and prostate cancer cells by promoting epithelial-to-mesenchymal transition (EMT) through WNT/β-catenin, but not TGF-β or Snail1 signaling. Dual luciferase assay and chromatin immunoprecipitation revealed activation and binding of SOX2 on promoter region of β-catenin. In addition, SOX2 affects the protein expression levels of DKK3, DVL1 and DVL3, which are regulators or downstream molecules of WNT signaling. Taken together, our findings demonstrated β-catenin as one of vital downstream molecules that mediate the EMT induced by SOX2.