Up-regulation of sonic hedgehog contributes to TGF-β1-induced epithelial to mesenchymal transition in NSCLC cells

Regulation of Gene Expression by Sodium Valproate in Epithelial-to-Mesenchymal Transition

PURPOSE

Epithelial-to-mesenchymal transition (EMT) is an important mechanism in cancer metastasis and pulmonary fibrosis. Previous studies demonstrated effect of histone H3 and H4 acetylation in cancer and pulmonary fibrosis, so we hypothesized that histone modification might play a crucial role in gene regulation during EMT. In this study, we investigated the mechanism behind EMT by analyzing comprehensive gene expression and the effect of sodium valproate (VPA), a class I histone deacetylase inhibitory drug, on histone modification.

METHODS

EMT was induced in human alveolar epithelial cells (A549) using 5 ng/mL of transforming growth factor (TGF)-β1. Various concentrations of VPA were then administered, and Western blotting was used to analyze histone acetylation or methylation. Comprehensive gene expression analysis was carried out by RNA sequencing, and chromatin immunoprecipitation was performed with an anti-acetyl histone H3 lysine 27 antibody.

RESULTS

TGF-β1 stimulation led to a decrease in histone acetylation, especially that of histone H3K27, and H3K27ac localization was decreased at particular gene loci. This decrease was recovered by VPA treatment, which also up-regulated the mRNA expression of genes down-regulated by TGF-β1, and correlated with the localization of H3K27ac. However, genes up-regulated by TGF-β1 stimulation were not suppressed by VPA, with the exception of COL1A1.

CONCLUSIONS

Histone acetylation was down-regulated by TGF-β1 stimulation in A549 cells. VPA partially inhibited EMT and the decrease of histone acetylation, which plays an important role in the progression of EMT.

Gli1 promotes transforming growth factor-beta1- and epidermal growth factor-induced epithelial to mesenchymal transition in pancreatic cancer cells

BACKGROUND

The Hedgehog signaling pathway and its key target effector Gli1 are linked closely to the development of the epithelial to mesenchymal transition (EMT) in many cancers. The definite function of Gli1 in regulating the EMT of pancreatic cancer (PC), however, is still unclear.

METHODS

At the cell and tissue levels, we investigated the role of Gli1 in the initiation of EMT in PC with and without external stimulus treatments.

RESULTS

The immunohistochemistry results showed that Gli1 was associated positively with MMP9 but not with E-cad or Vimentin. Gli1 expression was associated positively with tumor T (P = .025) and Union for International Cancer Control stage (P = .032), whereas MMP9 expression was associated positively with lymph node metastasis (P = .017) and Union for International Cancer Control stage (P = .006). Furthermore, patients with Gli1 and MMP9 coexpression had poor overall survival (P = .015). Silencing of Gli1 alone without external stimulus had no effect on EMT but inhibited transforming growth factor-beta1 (TGFβ1)- and epidermal growth factor (EGF)-induced EMT in PANC-1, AsPC-1, and BxPC-3 PC cell lines, along with the inhibition of TGFβ1- and EGF-induced EMT-like cell morphology and invasion, down-regulation of E-cad, and up-regulation of MMP9 and Vimentin in those 3 cell lines, respectively.

CONCLUSION

Gli1 silencing alone has no effect on EMT initiation; however, it exerts a protumor role in the aggressive invasion of PC cells by promoting TGFβ1- and EGF-induced EMT.

[Advances in the molecular mechanisms and prognostic significance of EMT in non-small cell lung cancer]

上皮细胞-间叶细胞转化（epithelial to mesenchymal transition, EMT）不仅在胚胎的发育过程中起着十分重要的作用，还参与非小细胞肺癌（non-small cell lung cancer, NSCLC）的转移过程。近期的研究发现，发生EMT的细胞不仅出现了形态的改变，还出现了相关表型的改变。既往有关EMT发生机制的研究多数是针对其他肿瘤的，因此很有必要研究NSCLC中是否有类似发生机制。随着研究的进展，EMT相关的基础研究逐渐被用于预测NSCLC的预后。本文将对NSCLC中EMT的发生机制及其临床应用的研究进展进行探讨。

SMO Gene Amplification and Activation of the Hedgehog Pathway as Novel Mechanisms of Resistance to Anti-Epidermal Growth Factor Receptor Drugs in Human Lung Cancer

PURPOSE

Resistance to tyrosine kinase inhibitors (TKI) of EGF receptor (EGFR) is often related to activation of other signaling pathways and evolution through a mesenchymal phenotype.

EXPERIMENTAL DESIGN

Because the Hedgehog (Hh) pathway has emerged as an important mediator of epithelial-to-mesenchymal transition (EMT), we studied the activation of Hh signaling in models of EGFR-TKIs intrinsic or acquired resistance from both EGFR-mutated and wild-type (WT) non-small cell lung cancer (NSCLC) cell lines.

RESULTS

Activation of the Hh pathway was found in both models of EGFR-mutated and EGFR-WT NSCLC cell line resistant to EGFR-TKIs. In EGFR-mutated HCC827-GR cells, we found SMO (the Hh receptor) gene amplification, MET activation, and the functional interaction of these two signaling pathways. In HCC827-GR cells, inhibition of SMO or downregulation of GLI1 (the most important Hh-induced transcription factor) expression in combination with MET inhibition exerted significant antitumor activity.In EGFR-WT NSCLC cell lines resistant to EGFR inhibitors, the combined inhibition of SMO and EGFR exerted a strong antiproliferative activity with a complete inhibition of PI3K/Akt and MAPK phosphorylation. In addition, the inhibition of SMO by the use of LDE225 sensitizes EGFR-WT NSCLC cells to standard chemotherapy.

CONCLUSIONS

This result supports the role of the Hh pathway in mediating resistance to anti-EGFR-TKIs through the induction of EMT and suggests new opportunities to design new treatment strategies in lung cancer.

Glioblastoma Circulating Cells: Reality, Trap or Illusion?

Metastases are the hallmark of cancer. This event is in direct relationship with the ability of cancer cells to leave the tumor mass and travel long distances within the bloodstream and/or lymphatic vessels. Glioblastoma multiforme (GBM), the most frequent primary brain neoplasm, is mainly characterized by a dismal prognosis. The usual fatal issue for GBM patients is a consequence of local recurrence that is observed most of the time without any distant metastases. However, it has recently been documented that GBM cells could be isolated from the bloodstream in several studies. This observation raises the question of the possible involvement of glioblastoma-circulating cells in GBM deadly recurrence by a “homing metastasis” process. Therefore, we think it is important to review the already known molecular mechanisms underlying circulating tumor cells (CTC) specific properties, emphasizing their epithelial to mesenchymal transition (EMT) abilities and their possible involvement in tumor initiation. The idea is here to review these mechanisms and speculate on how relevant they could be applied in the forthcoming battles against GBM.

Sonic hedgehog (Shh) signaling promotes tumorigenicity and stemness via activation of epithelial-to-mesenchymal transition (EMT) in bladder cancer

Activation of the sonic hedgehog (Shh) signaling pathway controls tumorigenesis in a variety of cancers. Here, we show a role for Shh signaling in the promotion of epithelial-to-mesenchymal transition (EMT), tumorigenicity, and stemness in the bladder cancer. EMT induction was assessed by the decreased expression of E-cadherin and ZO-1 and increased expression of N-cadherin. The induced EMT was associated with increased cell motility, invasiveness, and clonogenicity. These progression relevant behaviors were attenuated by treatment with Hh inhibitors cyclopamine and GDC-0449, and after knockdown by Shh-siRNA, and led to reversal of the EMT phenotype. The results with HTB-9 were confirmed using a second bladder cancer cell line, BFTC905 (DM). In a xenograft mouse model TGF-β1 treated HTB-9 cells exhibited enhanced tumor growth. Although normal bladder epithelial cells could also undergo EMT and upregulate Shh with TGF-β1 they did not exhibit tumorigenicity. The TGF-β1 treated HTB-9 xenografts showed strong evidence for a switch to a more stem cell like phenotype, with functional activation of CD133, Sox2, Nanog, and Oct4. The bladder cancer specific stem cell markers CK5 and CK14 were upregulated in the TGF-β1 treated xenograft tumor samples, while CD44 remained unchanged in both treated and untreated tumors. Immunohistochemical analysis of 22 primary human bladder tumors indicated that Shh expression was positively correlated with tumor grade and stage. Elevated expression of Ki-67, Shh, Gli2, and N-cadherin were observed in the high grade and stage human bladder tumor samples, and conversely, the downregulation of these genes were observed in the low grade and stage tumor samples. Collectively, this study indicates that TGF-β1-induced Shh may regulate EMT and tumorigenicity in bladder cancer. Our studies reveal that the TGF-β1 induction of EMT and Shh is cell type context dependent. Thus, targeting the Shh pathway could be clinically beneficial in the ability to reverse the EMT phenotype of tumor cells and potentially inhibit bladder cancer progression and metastasis.

FBW7 upregulation enhances cisplatin cytotoxicity in non- small cell lung cancer cells

INTRODUCTION

Lung cancer is extremely harmful to human health and has one of the highest worldwide incidences of all malignant tumors. Approximately 80% of lung cancers are classified as non-small cell lung cancers (NSCLCs). Cisplatin-based multidrug chemotherapy regimen is standard for such lesions, but drug resistance is an increasing problem. F-box/WD repeat-containing protein 7 (FBW7) is a member of the F-box protein family that regulates cell cycle progression, and cell growth and differentiation. FBW7 also functions as a tumor suppressor.

METHODS

We used cell viability assays, Western blotting, and immunofluorescence combined with siRNA interference or plasmid transfection to investigate the underlying mechanism of cisplatin resistance in NSCLC cells.

RESULTS

We found that FBW7 upregulation significantly increased cisplatin chemosensitivity and that cells expressing low levels of FBW7, such as NCI-H1299 cells, have a mesenchymal phenotype. Furthermore, siRNA-mediated silencing or plasmid-mediated upregulation of FBW7 resulted in altered epithelial-mesenchymal transition (EMT) patterns in NSCLC cells. These data support a role for FBW7 in regulating the EMT in NSCLC cells.

CONCLUSION

FBW7 is a potential drug target for combating drug resistance and regulating the EMT in NSCLC cells.

Role of Shh and TGF in cyclosporine-enhanced expression of collagen and α-SMA by gingival fibroblast

OBJECTIVE

Cyclosporine-A (CsA)-induced gingival overgrowth may arise from an alteration in stoma matrix homeostasis. Sonic hedgehog (Shh) plays a key role during embryogenic development and fibrotic progression, and may be involved in CsA-altered gingival matrix homeostasis.

METHODS

Using the reverse transcription-polymerase chain reaction and Western blot analysis, we investigated the mRNA and protein expressions of Shh, type 1 collagen (COL1), alpha-smooth muscle actin (α-SMA) and transforming growth factor-beta (TGF-β) in human gingival fibroblasts after CsA treatments. The effect of Shh on CsA-induced alterations was further evaluated by the extra-supplement or inhibition of Shh or TGF-β.

RESULTS

Cyclosporine-A enhanced COL1, α-SMA, Shh and TGF-β expressions in human gingival fibroblasts. The exogenous Shh/TGF-β augmented the expression of COL1 and α-SMA, and the Shh/TGF-β inhibition suppressed the CsA-enhanced COL1 and α-SMA expressions. Moreover, Shh mRNA and protein expressions increased if extra-supplementing the exogenous TGF-β, whereas the CsA-upregulated Shh was mitigated by the TGF-β pathway inhibitor. However, neither exogenous Shh nor the Shh pathway inhibitor alters TGF-β expression or CsA-up-regulated TGF-β expression.

CONCLUSIONS

Shh, regulated by TGF-β, mediates CsA-altered gingival matrix homeostasis.

Transcription factor glioma-associated oncogene homolog 1 is required for transforming growth factor-β1-induced epithelial-mesenchymal transition of non-small cell lung cancer cells

Epithelial-mesenchymal transition (EMT) is the process by which epithelial cells depolarize and acquire a mesenchymal phenotype, and is a common early step in the process of metastasis. Patients with lung cancer frequently already have distant metastases when they are diagnosed, highlighting the requirement for early and effective interventions to control metastatic disease. Transforming growth factor-β1 (TGF-β1) is able to induce EMT, however the molecular mechanism of this remains unclear. In the current study, TGF-β1 was reported to induce EMT and promote the migration of non-small cell lung cancer (NSCLC) cells. A notable observation was that EMT induction was accompanied by the upregulation of human glioma-associated oncogene homolog 1 (Gli1) mRNA and protein levels. Furthermore, Gli1 levels were depleted by small interfering RNA, and the Gli1 inhibitor GANT 61 attenuated the TGF-β1-mediated induction of EMT and cell migration. The results of the current study suggest that Gli1 regulates TGF-β1-induced EMT, which may provide a novel therapeutic target to inhibit metastasis in patients with NSCLC.

Non Coding RNA Molecules as Potential Biomarkers in Breast Cancer

The pursuit of minimally invasive biomarkers is a challenging but exciting area of research. Clearly, such markers would need to be sensitive and specific enough to aid in the detection of breast cancer at an early stage, would monitor progression of the disease, and could predict the individual patient's response to treatment. Unfortunately, to date, markers with such characteristics have not made it to the clinic for breast cancer. Past years, many studies indicated that the non-coding part of our genome (the so called 'junk' DNA), may be an ideal source for these biomarkers. In this chapter, the potential use of microRNAs and long non-coding RNAs as biomarkers will be discussed.

Carcinosarcoma of the parotid: investigating its biology with morphoproteomics

Carcinosarcoma of the parotid is a rare biphasic malignant neoplasm comprised of both carcinomatous and sarcomatous components representing approximately 0.4% of all malignant salivary gland neoplasms. We report a case of a 55-year-old Caucasian man who presented with a progressively enlarging left facial mass. Histopathological evaluation of the tumoral tissue revealed a high grade, mixed epithelial and mesenchymal malignant tumor, most consistent with a carcinosarcoma of the parotid. Morphoproteomic analysis was performed and revealed expression of secreted protein acidic and rich in cysteine (SPARC); glioma-associated oncogen protein 2 (Gli2); and phosphorylated signal transducer and activator of transcription (p-STAT3 [Tyr705]) in the carcinomatous and malignant mesenchymal components. These aforementioned markers have been linked to the epithelial-mesenchymal transition in which epithelial cells lose their characteristics and phenotypically become mesenchymal cells. This finding allows us to further understand the biology of the 2 cellular components of the carcinosarcoma as having a monoclonal origin.

Transforming growth factor-β1-induced epithelial to mesenchymal transition increases mitochondrial content in the A549 non-small cell lung cancer cell line

The mitochondrial genome DNA copy number is critical for the functional maintenance of the mitochondria and energy acquisition for cell metabolism. Epithelial to mesenchymal transition (EMT) is an important process during embryonic development and has also been hypothesized to exhibit a significant role in cancer cell invasion and metastasis. In the present study, EMT was induced in the A549 non-small cell lung cancer (NSCLC) cell line, using transforming growth factor-β1 (TGF-β1) and changes in mitochondrial content, mitochondrial DNA (mtDNA) copy number and protein cytochrome c (Cyt c) were determined by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. mtDNA copy number and Cyt c protein levels were observed to increase following the induction of EMT in NSCLC cells. Results of the current study indicate that energy metabolism is adapted to facilitate EMT in NSCLC cells.

MRC2 expression correlates with TGFβ1 and survival in hepatocellular carcinoma

MRC2 (Mannose Receptor C Type 2) is a constitutively recycling endocytic receptor belonging to the mannose receptor family, which has been found to be closely involved with cancer metastasis. This study attempted to determine MRC2 expression on hepatocellular carcinoma (HCC) and its significance on postsurgical prognosis of HCCs. The expression of both MRC2 and transforming growth factor (TGFβ1) was detected in tumor tissues and adjacent liver tissues from 96 HCCs by immunohistochemistry staining, and it was found that MRC2 expression in HCC tissues was significantly higher than in adjacent liver tissues. HCCs with higher MRC2 expression had worse prognosis after liver resection. Univariate analysis showed that advanced TNM staging of HCC, higher Edmonson-Steiner classification, intrahepatic metastases, portal vein invasion, higher MRC2 and higher TGFβ1 were the poor prognostic factors. Furthermore, multivariate analysis revealed that intrahepatic metastases, higher MRC2 and higher TGFβ1 were the independent prognostic factors. TGFβ1 treatment up-regulated MRC2 expression, cell migration and invasion of Huh7 cells notably. In addition, knockdown of MRC2 repressed the effect of TGFβ1 on cell migration and invasion. These data suggest that MRC2 overexpression predicts poor prognosis of HCCs after liver resection and MRC2 potentially contributed to TGFβ1-driven up-regulation of cell migration and invasion in HCC.

Emerging role of mucins in epithelial to mesenchymal transition

Epithelial to mesenchymal transition (EMT) is an important and complex phenomenon that determines the aggressiveness of cancer cells. The morphological transformation of cancerous cells is accompanied by various cellular processes such as alterations in cell-cell adhesion, cell matrix degradation, down regulation of epithelial marker Ecadherin and upregulation of mesenchymal markers N-cadherin and Vimentin. Besides these markers several other important tumor antigens/mucins are also involved in the EMT process. Mainly high molecular weight glycoproteins such as mucin molecules (MUC1, MUC4 and MUC16) play a major role in the cellular transformation and signaling alteration in EMT process. In addition to these factors, EMT may be an essential process triggering the emergence or expansion of the CSC population, which slowly results in the initiation of tumor at metastatic sites. Furthermore, mucins have been demonstrated to be involved in the EMT process and also in the enrichment of cancer stem cell population. Mucin mediated EMT is very complex since the key components of tumor microenvironment are also regulating mucin molecules. In this review, we have discussed all the aforementioned factors and their mechanistic involvement for EMT process.

Inhibition of Hedgehog signalling by NVP-LDE225 (Erismodegib) interferes with growth and invasion of human renal cell carcinoma cells

Background:

Multiple lines of evidence support that the Hedgehog (Hh) signalling has a role in the maintenance and progression of different human cancers. Therefore, inhibition of the Hh pathway represents a valid anticancer therapeutic approach for renal cell carcinoma (RCC) patients. NVP-LDE225 is a Smoothened (Smo) antagonist that induces dose-related inhibition of Hh and Smo-dependent tumour growth.

Methods:

We assayed the effects of NVP-LDE225 alone or in combination with everolimus or sunitinib on the growth and invasion of human RCC models both in vitro and in vivo. To this aim, we used a panel of human RCC models, comprising cells with acquired resistance to sunitinib – a multiple tyrosine kinase inhibitor approved as a first-line treatment for RCC.

Results:

NVP-LDE225 cooperated with either everolimus or sunitinib to inhibit proliferation, migration, and invasion of RCC cells even in sunitinib-resistant (SuR) cells. Some major transducers involved in tumour cell motility, including paxillin, were also efficiently inhibited by the combination therapy, as demonstrated by western blot and confocal microscopy assays. Moreover, these combined treatments inhibited tumour growth and increased animal survival in nude mice xenografted with SuR RCC cells. Finally, lung micrometastasis formation was reduced when mice were treated with NVP-LDE225 plus everolimus or sunitinib, as evidenced by artificial metastatic assays.

Conclusions:

Hedgehog inhibition by NVP-LDE225 plus sunitinib or everolimus bolsters antitumour activity by interfering with tumour growth and metastatic spread, even in SuR cells. Thus, this new evidence puts forward a new promising therapeutic approach for RCC patients.

IQGAP3 promotes EGFR-ERK signaling and the growth and metastasis of lung cancer cells

Proteins of the IQGAP family display complicated and often contradictory activities in tumorigenesis. IQGAP1 has well documented oncogenic potential and IQGAP2 has putative tumor-suppressive function. IQGAP3 is the latest addition to this family and its role in cancer development remains to be defined. Here we demonstrate IQGAP3 expression is markedly increased in lung cancer tissues at both mRNA and protein levels. Overexpression of IQGAP3 promoted tumor cell growth, and migration and invasion, whereas knockdown of IQGAP3 exhibited opposite effects. Moreover, suppression of IQGAP3 in a lung cancer cell line caused a reduction in the tumorigenicity of these cells in lung tissue after intravenous injection. Furthermore, we showed that IQGAP3 is able to interact with ERK1 and enhance its phosphorylation following treatment with EGF. These data suggest that IQGAP3 may contribute to the pathogenesis of lung cancer by modulating EGFR-ERK signaling.

Cyclosporine A up-regulates Sonic hedgehog in gingiva: role of the up-regulation on gingival cell proliferation

BACKGROUND AND OBJECTIVE

Sonic hedgehog protein (SHH) is a mitogen that stimulates cell proliferation. Cyclosporine A enhances the proliferation of gingival cells; however, the relationships of SHH to cyclosporine A or to cyclosporine A-enhanced gingival cell proliferation have not been described.

MATERIAL AND METHODS

Here, we investigated SHH expression in gingiva in vitro and in vivo after cyclosporine A treatment and tested the effect of SHH inhibition on cyclosporine A-enhanced gingival fibroblast proliferation in vitro.

RESULTS

In human gingival fibroblasts, cyclosporine A treatment increased the expression of SHH transcripts and SHH protein, and stimulated cell proliferation; the addition of cyclopamine, an SHH signaling inhibitor, suppressed cyclosporine A-enhanced cell proliferation. Up-regulated expression of SHH and up-regulation of proliferating cell nuclear antigen transcripts and protein were observed in the edentulous gingiva of cyclosporine A-treated rats.

CONCLUSION

Cyclosporine A up-regulates gingival SHH expression in vitro and in vivo, and the inhibition of the SHH pathway counteracts the stimulatory effect of cyclosporine A on gingival fibroblast proliferation. Therefore, we suggest that SHH mediates a novel molecular mechanism for cyclosporine A-induced gingival complications.

P130cas is required for TGF-β1-mediated epithelial-mesenchymal transition in lung cancer

In lung cancer A549 cells, the present study evaluated the associations between p130cas expression and the activation of p38 or Smad2, which are components of two of the main signaling pathways of transforming growth factor-β1 (TGF-β1), i.e., epithelial-mesenchymal transition (EMT) and apoptosis, respectively. TGF-β1-induced EMT was investigated by inspecting cell shape and cell migration, and by testing E-Cadherin, N-Cadherin and Vimentin biomarkers in p130cas-RNA interference (RNAi)-A549 cells. The changes in TGF-β1-induced apoptosis, i.e., cleaved Caspase-3 levels, were additionally analyzed following p130cas-RNAi. p130cas-knockdown decreased the phosphorylated (p)-p38 expression level, and blockaded the TGF-β1-induced activation of p-p38 in the A549 cells. p130cas-knockdown arrested cell migration and impaired TGF-β1-induced EMT in the A549 cells, characterized by changes in cell morphology and biomarker levels. However, p130cas-knockdown had no impact on the activation of Smad2 and the cleavage of Caspase-3. These results indicate that p130cas is a novel molecular ‘rheostat’ that alters the function of the TGF-β1 signaling pathway from tumor suppression to tumor promotion in lung cancer cells. The underlying mechanism warrants further study.

The therapeutic potential of targeting the epithelial-mesenchymal transition in cancer

INTRODUCTION

The process of epithelial-to-mesenchymal transition (EMT) has long been advocated as a process during tumor progression and the acquisition of metastatic potential of human cancers. EMT has also been linked with resistance to cancer therapies.

AREAS COVERED

Basic research has provided evidence connecting EMT to increased invasion, angiogenesis and metastasis of cancer cells. A number of signaling pathways such as notch, wnt, hedgehog and PI3K-AKT, and various other individual factors therein, have been intricately connected to the onset of EMT. Here, we provide latest updates on the evidences that further highlight an association between various signaling pathways and EMT, with a focus on therapeutic targets that may have the potential to reverse EMT.

EXPERT OPINION

Our understanding of EMT and its underlying causes is rapidly evolving and a number of putative targets have been identified. It is crucial, now than ever before, to design novel translational and clinical studies for the benefit of advanced stage cancer patients with metastatic disease.

Sonic hedgehog and androgen signaling in tumor and stromal compartments drives epithelial-mesenchymal transition in prostate cancer

OBJECTIVE

Sonic hedgehog (Shh) signaling, androgens and epithelial-mesenchymal transition (EMT) are related to prostate cancer (PCa) progression. The aim of this study was to investigate how Shh and androgen [dihydrotestosterone (DHT)] signaling act in prostate epithelial and stromal compartments and whether this signaling pathway drives EMT and promotes PCa progression.

MATERIAL AND METHODS

LNCaP, normal prostate fibroblast (NPF) and cancer-associated prostate fibroblast (CPF) cells were studied with DHT and/or the Shh signaling inhibitor cyclopamine. Real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed to evaluate the expressions of a potential Shh target gene, osteonectin (ON) and EMT-associated markers (E-cadherin, N-cadherin and vimentin). Immunohistochemical studies using PCa prostatectomy samples were performed to assess the expression levels of ON, Gli-1, androgen receptor, Shh, E-cadherin, N-cadherin and vimentin.

RESULTS

While DHT enhanced cell proliferation in CPF more than LNCaP or NPF, cyclopamine inhibited cell proliferation enhanced by DHT in CPF. Real-time RT-PCR showed whereas both Shh and DHT induced N-cadherin and vimentin, DHT also induced the expression of osteonectin in LNCaP and cyclopamine blocked these expressions in osteonectin, N-cadherin and vimentin (p = 0.0084, 0.0002 and 0.0373, respectively). Immunohistochemistry showed that high expression of stromal, but, not epithelial, ON was significantly correlated with serum prostate-specific antigen (PSA) (p = 0.031), and high expression of Gli-1 and low expression of stromal ON with PSA recurrence (p = 0.0114 and p = 0.0005, respectively).

CONCLUSIONS

Shh and androgen signaling in prostate tumor and stromal compartments drives EMT, and thus may play some role in PCa progression. Cyclopamine may be one therapeutic strategy for PCa.

Development of the external genitalia and their sexual dimorphic regulation in mice

The study of the external genitalia is divided into 2 developmental stages: the formation and growth of a bipotential genital tubercle (GT) and the sexual differentiation of the male and female GT. The sexually dimorphic processes, which occur during the second part of GT differentiation, are suggested to be governed by androgen signaling and more recently crosstalk with other signaling factors. The process of elucidating the regulatory mechanisms of hormone signaling towards other signaling networks in the GT is still in its early stages. Nevertheless, it is becoming a productive area of research. This review summarizes various studies on the development of the murine GT and the defining characteristics of a masculinized GT and presents the different signaling pathways possibly involved during masculinization.

The emerging role of insulin and insulin-like growth factor signaling in cancer stem cells

Cancer cells frequently exploit the IGF signaling, a fundamental pathway mediating development, cell growth, and survival. As a consequence, several components of the IGF signaling are deregulated in cancer and sustain cancer progression. However, specific targeting of IGF-IR in humans has resulted efficacious only in small subsets of cancers, making researches wondering whether IGF system targeting is still worth pursuing in the clinical setting. Although no definite answer is yet available, it has become increasingly clear that other components of the IGF signaling pathway, such as IR-A, may substitute for the lack of IGF-IR, and induce cancer resistance and/or clonal selection. Moreover, accumulating evidence now indicates that IGF signaling is a central player in the induction/maintenance of epithelial mesenchymal transition (EMT) and cell stemness, two strictly related programs, which play a key role in metastatic spread and resistance to cancer treatments. Here we review the evidences indicating that IGF signaling enhances the expression of transcription factors implicated in the EMT program and has extensive cross-talk with specific pathways involved in cell pluripotency and stemness maintenance. In turn, EMT and cell stemness activate positive feed-back mechanisms causing up-regulation of various IGF signaling components. These findings may have novel translational implications.

Epithelial-to-mesenchymal transition predicts prognosis in clinical gastric cancer

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is considered to play an important role in cancer invasion and metastasis.

METHODS

The mRNA levels of an epithelial marker (E-cadherin), mesenchymal marker (vimentin), and Zeb-1 were measured in 11 gastric cancer cell lines. Functional analysis was performed using Zeb-1 knockdown. EMT status of 116 gastric cancer patients was determined by calculating the vimentin/E-cadherin mRNA expression ratio in cancerous tissue and the correlation between EMT status, clinicopathological factors, prognosis, and Zeb-1 were analyzed.

RESULTS

Cell lines were classified as epithelial or mesenchymal. Zeb-1 expression was significantly correlated with the mesenchymal phenotype. Treatment with Zeb-1 siRNA also reduced the capacity to proliferate, migrate, and invade. Patients were classified as epithelial or mesenchymal by V/E ratio (vimentin/E-cadherin ratio) and as Zeb-1 low or high expression group. The mesenchymal group was significantly associated with diffuse type cancer and stage IV. On multivariate analysis, the EMT status (mesenchymal group) was an independent prognostic factor (P = 0.022). There was a significant correlation between the V/E ratio and Zeb-1 expression (r = 0.73). Patients in Zeb-1 high group had significantly poorer survival than those in low group (P = 0.0071).

CONCLUSIONS

EMT is a critical prognostic factor for gastric cancer. Zeb-1 might be a promising therapeutic target.

Gefitinib inhibits invasive phenotype and epithelial-mesenchymal transition in drug-resistant NSCLC cells with MET amplification

Despite the initial response, all patients with epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) eventually develop acquired resistance to EGFR tyrosine kinase inhibitors (TKIs). The EGFR-T790M secondary mutation is responsible for half of acquired resistance cases, while MET amplification has been associated with acquired resistance in about 5-15% of NSCLCs. Clinical findings indicate the retained addiction of resistant tumors on EGFR signaling. Therefore, we evaluated the molecular mechanisms supporting the therapeutic potential of gefitinib maintenance in the HCC827 GR5 NSCLC cell line harbouring MET amplification as acquired resistance mechanism. We demonstrated that resistant cells can proliferate and survive regardless of the presence of gefitinib, whereas the absence of the drug significantly enhanced cell migration and invasion. Moreover, the continuous exposure to gefitinib prevented the epithelial-mesenchymal transition (EMT) with increased E-cadherin expression and down-regulation of vimentin and N-cadherin. Importantly, the inhibition of cellular migration was correlated with the suppression of EGFR-dependent Src, STAT5 and p38 signaling as assessed by a specific kinase array, western blot analysis and silencing functional studies. On the contrary, the lack of effect of gefitinib on EGFR phosphorylation in the H1975 cells (EGFR-T790M) correlated with the absence of effects on cell migration and invasion. In conclusion, our findings suggest that certain EGFR-mutated patients may still benefit from a second-line therapy including gefitinib based on the specific mechanism underlying tumor cell resistance.

Inhibition of Hedgehog signaling sensitizes NSCLC cells to standard therapies through modulation of EMT-regulating miRNAs

Background

Epidermal growth factor receptor- tyrosine kinase inhibitors (EGFR-TKIs) benefit Non-small cell lung cancer (NSCLC) patients, and an EGFR-TKIi erlotinib, is approved for patients with recurrent NSCLC. However, resistance to erlotinib is a major clinical problem. Earlier we have demonstrated the role of Hedgehog (Hh) signaling in Epithelial-to-Mesenchymal transition (EMT) of NSCLC cells, leading to increased proliferation and invasion. Here, we investigated the role of Hh signaling in erlotinib resistance of TGF-β1-induced NSCLC cells that are reminiscent of EMT cells.

Methods

Hh signaling was inhibited by specific siRNA and by GDC-0449, a small molecule antagonist of G protein coupled receptor smoothened in the Hh pathway. Not all NSCLC patients are likely to benefit from EGFR-TKIs and, therefore, cisplatin was used to further demonstrate a role of inhibition of Hh signaling in sensitization of resistant EMT cells. Specific pre- and anti-miRNA preparations were used to study the mechanistic involvement of miRNAs in drug resistance mechanism.

Results

siRNA-mediated inhibition as well as pharmacological inhibition of Hh signaling abrogated resistance of NSCLC cells to erlotinib and cisplatin. It also resulted in re-sensitization of TGF-β1-induced A549 (A549M) cells as well the mesenchymal phenotypic H1299 cells to erlotinib and cisplatin treatment with concomitant up-regulation of cancer stem cell (CSC) markers (Sox2, Nanog and EpCAM) and down-regulation of miR-200 and let-7 family miRNAs. Ectopic up-regulation of miRNAs, especially miR-200b and let-7c, significantly diminished the erlotinib resistance of A549M cells. Inhibition of Hh signaling by GDC-0449 in EMT cells resulted in the attenuation of CSC markers and up-regulation of miR-200b and let-7c, leading to sensitization of EMT cells to drug treatment, thus, confirming a connection between Hh signaling, miRNAs and drug resistance.

Conclusions

We demonstrate that Hh pathway, through EMT-induction, leads to reduced sensitivity to EGFR-TKIs in NSCLCs. Therefore, targeting Hh pathway may lead to the reversal of EMT phenotype and improve the therapeutic efficacy of EGFR-TKIs in NSCLC patients.

Crosstalk between Shh and TGF-β signaling in cyclosporine-enhanced cell proliferation in human gingival fibroblasts

BACKGROUND

Immunosuppressant cyclosporine-A induces gingival hyperplasia, which is characterized by increased fibroblast proliferation and overproduction of extracellular matrix components and regulated by transforming growth factor-beta (TGF-β). The TGF-β and Sonic hedgehog (Shh) pathways both mediate cell proliferation. Crosstalk between these pathways in cancer has recently been proposed, but the hierarchical pattern of this crosstalk remains unclear. In normal fibroblasts, a TGF-β-stimulating Shh pattern was observed in induced fibrosis. However, Shh pathway involvement in cyclosporine-enhanced gingival proliferation and the existence of crosstalk with the TGF-β pathway remain unclear.

METHODOLOGY/PRINCIPAL FINDINGS

Cyclosporine enhanced mRNA and protein levels of TGF-β and Shh in human gingival fibroblasts (RT-PCR and western blotting). A TGF-β pathway inhibitor mitigated cyclosporine-enhanced cell proliferation and an Shh pathway inhibitor attenuated cyclosporine-enhanced proliferation in fibroblasts (MTS assay and/or RT-PCR of PCNA). Exogenous TGF-β increased Shh expression; however, exogenous Shh did not alter TGF-β expression. The TGF-β pathway inhibitor mitigated cyclosporine-upregulated Shh expression, but the Shh pathway inhibitor did not alter cyclosporine-upregulated TGF-β expression.

CONCLUSIONS/SIGNIFICANCE

The TGF-β and Shh pathways mediate cyclosporine-enhanced gingival fibroblast proliferation. Exogenous TGF-β increased Shh expression, and inhibition of TGF-β signaling abrogated the cyclosporine-induced upregulation of Shh expression; however, TGF-β expression appeared unchanged by enhanced or inhibited Shh signaling. This is the first study demonstrating the role of Shh in cyclosporine-enhanced gingival cell proliferation; moreover, it defines a hierarchical crosstalk pattern in which TGF-β regulates Shh in gingival fibroblasts. Understanding the regulation of cyclosporine-related Shh and TGF-β signaling and crosstalk in gingival overgrowth will clarify the mechanism of cyclosporine-induced gingival enlargement and help develop targeted therapeutics for blocking these pathways, which can be applied in pre-clinical and clinical settings.

Fibrosis of two: Epithelial cell-fibroblast interactions in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by the progressive and ultimately fatal accumulation of fibroblasts and extracellular matrix in the lung that distorts its architecture and compromises its function. IPF is now thought to result from wound-healing processes that, although initiated to protect the host from injurious environmental stimuli, lead to pathological fibrosis due to these processes becoming aberrant or over-exuberant. Although the environmental stimuli that trigger IPF remain to be identified, recent evidence suggests that they initially injure the alveolar epithelium. Repetitive cycles of epithelial injury and resultant alveolar epithelial cell death provoke the migration, proliferation, activation and myofibroblast differentiation of fibroblasts, causing the accumulation of these cells and the extracellular matrix that they synthesize. In turn, these activated fibroblasts induce further alveolar epithelial cell injury and death, thereby creating a vicious cycle of pro-fibrotic epithelial cell-fibroblast interactions. Though other cell types certainly make important contributions, we focus here on the "pas de deux" (steps of two), or perhaps more appropriate to IPF pathogenesis, the "folie à deux" (madness of two) of epithelial cells and fibroblasts that drives the progression of pulmonary fibrosis. We describe the signaling molecules that mediate the interactions of these cell types in their "fibrosis of two", including transforming growth factor-β, connective tissue growth factor, sonic hedgehog, prostaglandin E2, angiotensin II and reactive oxygen species. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Down-regulation of eIF5A-2 prevents epithelial-mesenchymal transition in non-small-cell lung cancer cells

BACKGROUND

Epithelial-mesenchymal transition (EMT) is believed to be the critical process in malignant tumor invasion and metastases, and has a great influence on improving the survival rate in non-small-cell lung cancer (NSCLC) patients. Recent studies suggested that eukaryotic initiation factor 5A-2 (eIF5A-2) might serve as an adverse prognostic marker of survival. We detected eIF5A-2 in NSCLC A549 cells, and found that the invasive capability correlates with the eIF5A-2 expression.

METHODS

Transforming growth factor (TGF)-β1 was used to induce EMT in A549 cells. Western blotting, immunofluorescence, wound healing assay, and transwell-matrigel invasion chambers were used to identify phenotype changes. Western blotting was also used to observe changes of the expression of eIF5A-2. We down-regulated the eIF5A-2 expression using an eIF5A-2 siRNA and identified the phenotype changes by western blotting and immunofluorescence. We tested the change of migration and invasion capabilities of A549 cells by the wound healing assay and transwell-matrigel invasion chambers.

RESULTS

After stimulating with TGF-β1, almost all A549 cells changed to the mesenchymal phenotype and acquired more migration and invasion capabilities. These cells also had higher eIF5A-2 protein expression. Down-regulation of eIF5A-2 expression with eIF5A-2 siRNA transfection could change the cells from mesenchymal to epithelial phenotype and decrease tumor cell migration and invasive capabilities significantly.

CONCLUSIONS

The expression of eIF5A-2 was up-regulated following EMT phenotype changes in A549 cells, which correlated with enhanced tumor invasion and metastatic capabilities. Furthermore, in the A549 cell line, the process of EMT phenotype change could be reversed by eIF5A-2 siRNA, with a consequent weakening of both invasive and metastatic capabilities.

Curcumin reverses the epithelial-mesenchymal transition of pancreatic cancer cells by inhibiting the Hedgehog signaling pathway

Curcumin, a phenolic compound extracted from Zingiberaceae turmeric, has strong anti-inflammatory, antioxidant and antitumor properties. However, the anticarcinogenic mechanism of curcumin has yet to be fully elucidated. Epithelial-mesenchymal transition (EMT) induced by transforming growth factor-β1 (TGF-β1) is involved in the promotion of tumor invasion and metastasis, and is closely related to the drug resistance of tumor cells. The abnormal activation of Hedgehog signaling also plays an important role in tumorigenesis and metastasis. In order to investigate whether curcumin can reverse the TGF-β1-stimulated EMT of pancreatic cancer PANC-1 cells, and its possible mechanism, the pancreatic cancer cell line PANC-1 was stimulated with TGF-β1 (5 ng/ml) for 7 days to induce formation of EMT, and the TGF-β1-stimulated PANC-1 cells were treated with different concentrations of curcumin (10, 20 and 30 µmol/ml) for 48 h. The growth inhibition rate of the cells was measured by MTT assay, apoptosis was detected by flow cytometry, the expression levels of Shh, GLI1, E-cadherin and vimentin were detected by western blot analysis, and cell invasion and migration ability were examined by transwell cell invasion assay and wound healing assay. Following stimulation with TGF-β1, the expression levels of Shh, GLI1 and vimentin in the TGF-β1-stimulated group were significantly increased, compared with those in the control group (P<0.01, respectively). The expression levels of E-cadherin in the TGF-β1-stimulated group were significantly decreased, compared with those in the control group (P<0.01). The TGF-β1-stimulated PANC-1 cells were treated with curcumin and the results showed that curcumin significantly inhibited TGF-β1-stimulated PANC-1 cell proliferation and induced apoptosis, compared with other groups (P<0.01), and the expression levels of Shh, GLI1 and vimentin in the curcumin-treated group were significantly decreased compared with those in the control group (P<0.01, respectively). The expression level of E-cadherin in the curcumin-treated group was significantly increased compared with that in the control group (P<0.01). Cell invasion in the curcumin-treated group (30 µmol/ml) was significantly decreased compared with that in the control group (P<0.01). The scratch wounds in the curcumin-treated group healed slower compared with those in the control group (P<0.01). Curcumin significantly inhibited the invasion and migration of TGF-β1-stimulated PANC-1 cells. These results indicate that curcumin can inhibit the proliferation of TGF-β1-stimulated PANC-1 cells, it can induce apoptosis, and reverse the EMT. The possible underlying molecular mechanisms are through inhibition of the Shh-GLI1 signaling pathway.

Emerging evidence of epithelial-to-mesenchymal transition in lung carcinogenesis

The epithelial-to-mesenchymal transition (EMT) is a developmental programme that regulates embryonic morphogenesis and involves significant morphological and molecular changes in cells. Experimental models have revealed that EMT also contributes to various malignant features of cancer cells, including motile, invasive, anti-apoptotic and stem-like phenotypes. Clinically, correlative studies have indicated that mesenchymal-like features of tumour cells are associated with poor tumour differentiation as well as worse patient prognosis. Nevertheless, due to its transitory nature, demonstration of an actual occurrence of EMT during human carcinogenesis is challenging, and most of the evidence to date has been limited to breast and colorectal cancers. However, recent studies suggest that EMT may occur during lung cancer development, although such evidence is still limited. We propose three approaches for obtaining direct evidence of EMT in human cancers and use these criteria to review the available data. We suggest that multiple intrinsic and extrinsic factors cooperatively induce EMT in lung cancer. Intrinsic factors include oncogenic genetic changes such as mutant K-RAS. Extrinsic factors are associated with a tumour microenvironment that is inflammatory and hypoxic. The induction of EMT is primarily mediated by various EMT-inducing transcription factors that suppress E-cadherin expression, including SLUG and ZEB1. miR-200 family expression can reverse EMT by suppressing EMT- inducing transcription factors. Obviously, more data demonstrating the clinical relevance of EMT in lung cancer are required, and further elucidation of how EMT is regulated in lung cancer will enable us to develop novel therapeutics that specifically target molecules with critical roles in EMT.

Erlotinib resistance in lung cancer: current progress and future perspectives

Lung cancer is the most common cancer in the world. Despite modern advancements in surgeries, chemotherapies, and radiotherapies over the past few years, lung cancer still remains a very difficult disease to treat. This has left the death rate from lung cancer victims largely unchanged throughout the past few decades. A key cause for the high mortality rate is the drug resistance that builds up for patients being currently treated with the chemotherapeutic agents. Although certain chemotherapeutic agents may initially effectively treat lung cancer patients, there is a high probability that there will be a reoccurrence of the cancer after the patient develops resistance to the drug. Erlotinib, the epidermal growth factor receptor (EGFR)-targeting tyrosine kinase inhibitor, has been approved for localized as well as metastatic non-small cell lung cancer where it seems to be more effective in patients with EGFR mutations. Resistance to erlotinib is a common observation in clinics and this review details our current knowledge on the subject. We discuss the causes of such resistance as well as innovative research to overcome it. Evidently, new chemotherapy strategies are desperately needed in order to better treat lung cancer patients. Current research is investigating alternative treatment plans to enhance the chemotherapy that is already offered. Better insight into the molecular mechanisms behind combination therapy pathways and even single molecular pathways may help improve the efficacy of the current treatment options.

Activation of uPAR is required for cigarette smoke extract-induced epithelial-mesenchymal transition in lung epithelial cells

Cigarette smoke is a major risk factor for lung cancer, which may contribute to lung cancer invasion and metastasis. However, the mechanism remains unclear. Epithelial-mesenchymal transition (EMT) is a critical phenotypic alteration of cells that triggers invasion and metastasis. The urokinase-type plasminogen activator receptor (uPAR) is originally thought to assist the directional invasion of migrating cells, and increasing evidences show that overexpression of uPAR in cancer cells promotes EMT. Therefore, we intend to study the role of uPAR in cigarette smoke extract (CSE)-induced EMT in lung epithelial cells. In this study, we showed that lung epithelial cells cultured after CSE treatment demonstrated changes consistent with EMT. E-cadherin was decreased, while vimentin, N-cadherin, and α-SMA expression was increased in both A549 and BEAS-2B cells. Cells acquired a mesenchymal-like morphology and increased cell motility and invasion. In addition, CSE-induced EMT was accompanied by increased expression of uPAR and activation of AKT downstream of uPAR. CSE-induced EMT and activation of AKT were blocked by uPAR gene silencing. Antagonizing PI3K also inhibits development of CSE-induced EMT. We conclude that CSE can induce EMT, and the activity of uPAR-dependent signal pathway in EMT is recapitulated in lung epithelial cells in vitro.

Hedgehog signaling pathway regulates human pancreatic cancer cell proliferation and metastasis

Pancreatic cancer is one of the most aggressive and devastating malignancies. The Hedgehog (Hh) pathway has been reported to play an important role in pancreatic cancer development and progression. The aim of this study was to examine the activation of the Hh pathway in human pancreatic cancer tissue samples and pancreatic cancer cell lines, and the molecular mechanisms involved in the Hh pathway mediated effects on pancreatic cancer cell proliferation and invasion. The expression levels of Hh molecules in human pancreatic cancer tissue samples and pancreatic cancer cell lines were evaluated using RT-PCR. The role of the Hh pathway in cell proliferation and invasion was evaluated using flow cytometry, MTT, colony formation assays and transwell invasion assays, and the expression of cancer stem cell markers and epithelial-mesenchymal transition (EMT) were evaluated using flow cytometry and RT-PCR. Tumorigenicity assays were used to further investigate the role of the Hh pathway in vivo. Hh molecules were highly expressed in human pancreatic cancer tissue samples and pancreatic cancer cell lines. Inhibition of the Hh pathway notably decreased cell proliferation and induced apoptosis through inhibition of the PI3K/AKT pathway and cancer stem cells. Furthermore, inhibition of the Hh signaling pathway significantly inhibited EMT by suppressing the activation of transcription factors Snail and Slug, which are correlated with significantly reduced pancreatic cancer cell invasion, suggesting that the Hh signaling pathway is involved in early metastasis. These results indicate that activation of the Hh pathway is a common event. Inhibition of the Hh pathway may be a potential molecular target of new therapeutic strategies for pancreatic cancer.

Fucosyltransferase 8 as a functional regulator of nonsmall cell lung cancer

The up-regulation of fucosyltransferase 8 (FUT8), the only enzyme catalyzing α1,6-fucosylation in mammals, has been observed in several malignant cancers including liver, ovarian, thyroid, and colorectal cancers. However, the pathological role and the regulatory mechanism of FUT8 in cancers remain largely unknown. In the current study, we report that the expression of FUT8 is up-regulated in nonsmall cell lung cancer (NSCLC) and correlates with tumor metastasis, disease recurrence, and poor survival in patients with NSCLC. Knocking down FUT8 in aggressive lung cancer cell lines significantly inhibits their malignant behaviors including in vitro invasion and cell proliferation, as well as in vivo metastasis and tumor growth. The results of glycoproteomic and microarray analyses show that FUT8 globally modifies surface antigens, receptors, and adhesion molecules and is involved in the regulation of dozens of genes associated with malignancy, suggesting that FUT8 contributes to tumor progression through multiple mechanisms. Moreover, we show that FUT8 is up-regulated during epithelial-mesenchymal transition (EMT), a critical process for malignant transformation of tumor, via the transactivation of β-catenin/lymphoid enhancer-binding factor-1 (LEF-1). These results provide a model to illustrate the relation between FUT8 expression and lung cancer progression and point to a promising direction for the prognosis and therapy of lung cancer.

Emerging roles of PDGF-D in EMT progression during tumorigenesis

Platelet-derived growth factor-D (PDGF-D) signaling pathway has been reported to be involved in regulating various cellular processes, such as cell growth, apoptotic cell death, migration, invasion, angiogenesis and metastasis. Recently, multiple studies have shown that PDGF-D plays a critical role in governing epithelial-to-mesenchymal transition (EMT), although the underlying mechanism of PDGF-D-mediated acquisition of EMT is largely unclear. Therefore, this mini review will discuss recent advances in our understanding of the role of PDGF-D in the acquisition of EMT during tumorigenesis. Furthermore, we will summarize the function of chemical inhibitors and natural compounds that are known to inactivate PDGF-D signaling pathway, which leads to the reversal of EMT. In summary, inactivation of PDGF-D could be a novel strategy for achieving better treatment outcome of patients inflicted with cancers.

The role of microRNAs in breast cancer migration, invasion and metastasis

MicroRNAs (miRNAs) are a major class of small, noncoding RNA molecules that regulate gene expression by targeting mRNAs to trigger either translational repression or mRNA degradation. They have recently been more widely investigated due to their potential role as targets for cancer therapy. Many miRNAs have been implicated in several human cancers, including breast cancer. miRNAs are known to regulate cell cycle and development, and thus may serve as useful targets for exploration in anticancer therapeutics. The link between altered miRNA signatures and breast cancer development and metastasis can be observed either through the loss of tumor suppressor miRNAs, such as let-7s, miR-30a/31/34a/125s/200s/203/205/206/342 or the overexpression of oncogenic miRNAs, such as miR-10b/21/135a/155/221/222/224/373/520c in breast cancer cells. Some of these miRNAs have also been validated in tumor specimens of breast cancer patients, underscoring their potential roles in diagnostics, as well as targets for novel therapeutics for breast cancer. In this review article, we will provide an overview and update of our current understanding of the mode of action of several of these well characterized miRNAs in breast cancer models. Therefore, better understanding of the gene networks orchestrated by these miRNAs may help exploit the full potential of miRNAs in regards to cancer diagnosis, treatment, and therapeutics.

Overlapping activities of TGF-β and Hedgehog signaling in cancer: therapeutic targets for cancer treatment

Recent advances in the field of cancer therapeutics come from the development of drugs that specifically recognize validated oncogenic or pro-metastatic targets. The latter may be mutated proteins with altered function, such as kinases that become constitutively active, or critical components of growth factor signaling pathways, whose deregulation leads to aberrant malignant cell proliferation and dissemination to metastatic sites. We herein focus on the description of the overlapping activities of two important developmental pathways often exacerbated in cancer, namely Transforming Growth Factor-β (TGF-β) and Hedgehog (HH) signaling, with a special emphasis on the unifying oncogenic role played by GLI1/2 transcription factors. The latter are the main effectors of the canonical HH pathway, yet are direct target genes of TGF-β/SMAD signal transduction. While tumor-suppressor in healthy and pre-malignant tissues, TGF-β is often expressed at high levels in tumors and contributes to tumor growth, escape from immune surveillance, invasion and metastasis. HH signaling regulates cell proliferation, differentiation and apoptosis, and aberrant HH signaling is found in a variety of cancers. We discuss the current knowledge on HH and TGF-β implication in cancer including cancer stem cell biology, as well as the current state, both successes and failures, of targeted therapeutics aimed at blocking either of these pathways in the pre-clinical and clinical settings.

Role of Sonic Hedgehog in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and lethal disease of unknown etiology and uncertain pathogenic mechanisms. Recent studies indicate that the pathogenesis of the disease may involve the abnormal expression of certain developmental pathways. Here we evaluated the expression of Sonic Hedgehog (SHH), Patched-1, Smoothened, and transcription factors glioma-associated oncogene homolog (GLI)1 and GLI2 by RT-PCR, as well as their localization in IPF and normal lungs by immunohistochemistry. The effects of SHH on fibroblast proliferation, migration, collagen and fibronectin production, and apoptosis were analyzed by WST-1, Boyden chamber chemotaxis, RT-PCR, Sircol, and annexin V-propidium iodide binding assays, respectively. Our results showed that all the main components of the Sonic signaling pathway were overexpressed in IPF lungs. With the exception of Smoothened, they were also upregulated in IPF fibroblasts. SHH and GLI2 localized to epithelial cells, whereas Patched-1, Smoothened, and GLI1 were observed mainly in fibroblasts and inflammatory cells. No staining was detected in normal lungs. Recombinant SHH increased fibroblast proliferation (P < 0.05), collagen synthesis, (2.5 ± 0.2 vs. 4.5 ± 1.0 μg of collagen/ml; P < 0.05), fibronectin expression (2-3-fold over control), and migration (190.3 ± 12.4% over control, P < 0.05). No effect was observed on α-smooth muscle actin expression. SHH protected lung fibroblasts from TNF-α/IFN-γ/Fas-induced apoptosis (14.5 ± 3.2% vs. 37.3 ± 7.2%, P < 0.0001). This protection was accompanied by modifications in several apoptosis-related proteins, including increased expression of X-linked inhibitor of apoptosis. These findings indicate that the SHH pathway is activated in IPF lungs and that SHH may contribute to IPF pathogenesis by increasing the proliferation, migration, extracellular matrix production, and survival of fibroblasts.

Hedgehog signaling blockade delays hepatocarcinogenesis induced by hepatitis B virus X protein

The hepatitis B virus (HBV) encoded X protein (HBx) contributes centrally to the pathogenesis of hepatocellular carcinoma (HCC). Aberrant activation of the Hedgehog (Hh) pathway has been linked to many tumor types including HCC. Thus, experiments were designed to test the hypothesis that HBx promotes HCC via activation of Hh signaling. HBx expression correlated with an upregulation of Hh markers in human liver cancer cell lines, in liver samples from HBV infected patients with HCC, and in the livers of HBx transgenic mice (HBxTg) that develop hepatitis, steatosis, and dysplasia, culminating in the appearance of HCC. The findings in human samples provide clinical validation for the in vitro results and those in the HBxTg. Blockade of Hh signaling inhibited HBx stimulation of cell migration, anchorage-independent growth, tumor development in HBxTg, and xenograft growth in nude mice. Results suggest that the ability of HBx to promote cancer is at least partially dependent upon the activation of the Hh pathway. This study provides biologic evidence for the role of Hh signaling in the pathogenesis of HBV-mediated HCC and suggests cause and effect for the first time. The observation that inhibition of Hh signaling partially blocked the ability of HBx to promote growth and migration in vitro and tumorigenesis in two animal models implies that Hh signaling may represent an "oncogene addiction" pathway for HBV-associated HCC. This work could be central to designing specific treatments that target early development and progression of HBx-mediated HCC.

Progress in understanding the role of epithelial-mesenchymal transition in the pathogenesis of colorectal tumors

Epithelial-mesenchymal transition is a well established biological event that plays an important role not only in the normal development of tissues and organs but also in the pathogenesis of many diseases. Increasing evidence has established its presence in the human colon during colorectal carcinogenesis and cancer invasion, chronic inflammation-related fibrosis, and mucosal healing. A large body of evidence supports the role of transforming growth factor-β and its downstream Smad signaling, the phosphatidylinositol 3'-kinase/Akt/mTOR axis, the Ras-mitogen-activated protein kinase/Snail/Slug and FOXC2 pathway, and Hedgehog signaling and microRNAs in epithelial-mesenchymal transition in the development of colorectal cancers. Here we discuss the role of these pathways in the initiation and development of the transition events. A better understanding of their induction and regulation may lead to the identification of pathways and factors that could be potent therapeutic targets.

The ubiquitin-proteasome system and signal transduction pathways regulating Epithelial Mesenchymal transition of cancer

Epithelial to Mesenchymal transition (EMT) in cancer, a process permitting cancer cells to become mobile and metastatic, has a signaling hardwire forged from development. Multiple signaling pathways that regulate carcinogenesis enabling characteristics in neoplastic cells such as proliferation, resistance to apoptosis and angiogenesis are also the main players in EMT. These pathways, as almost all cellular processes, are in their turn regulated by ubiquitination and the Ubiquitin-Proteasome System (UPS). Ubiquitination is the covalent link of target proteins with the small protein ubiquitin and serves as a signal to target protein degradation by the proteasome or to other outcomes such as endocytosis, degradation by the lysosome or specification of cellular localization. This paper reviews signal transduction pathways regulating EMT and being regulated by ubiquitination.

Study on the skip metastasis of axillary lymph nodes in breast cancer and their relation with Gli1 expression

The skip metastasis (SM) of axillary lymph nodes (ALN) in breast cancer is an important phenomenon which is crucial to determine the correct choice of surgical resection. The mechanism of SM of ALN is unclear. Gli1 protein is a core epithelial-to-mesenchymal transition (EMT) regulatory factor that plays essential roles in both development and disease processes and has been associated with metastasis in carcinomas. The aim of this study was to investigate the clinicopathological characteristics of SM and evaluate the significance of Gli1 expression in breast cancer patients with metastasis of ALN. Clinicopathological data from 1,037 female breast cancer patients who underwent radical mastectomy were retrospectively reviewed. In this study, an SM was defined as level I absence but level II and/or level III involvement. The expression of Gli1 was evaluated by immunohistochemistry in 102 non-SM cases with positive nodes and 33 SM cases. In univariate analysis, we found that pN category, TNM stage, intrinsic subtypes and Gli1 expression was significant risk factor of SM. Further logistic regression analysis revealed that luminal A cases had a lower risk of SM relative to luminal B 1 (HER2 negative) cases. Further multivariate analysis revealed that Gli1 expression and numbers of positive lymph nodes were the independent factors which associated with SM. Collectively, Breast cancer with SM of ALN associated with the intrinsic subtype of the luminal B1. Gli1 expression related with the procession of breast cancer with SM, which can be used as a predictor of SM of ALN in breast cancer.

EMT and oxidative stress: a bidirectional interplay affecting tumor malignancy

SIGNIFICANCE

Epithelial-mesenchymal transition (EMT) is emerging as a driving force in tumor progression, enabling cancer cells to evade their "homeland" and to colonize remote locations. In this review, we focus on the emerging views dealing with a redox control of EMT and with the importance of a pro-oxidant environment, both in cancer and stromal cells, to attain an improvement in tumor malignancy.

RECENT ADVANCES

The variety of signals able to promote EMT is large and continuously growing, ranging from soluble factors to components of the extracellular matrix. Compelling evidence highlights reactive oxygen species (ROS) as crucial conspirators in EMT engagement.

CRITICAL ISSUES

Tumor microenvironment exploits a fascinating role in ensuring EMT outcome within the primary tumor, granting for the achievement of an essential selective advantage for cancer cells. Cancer-associated fibroblasts, macrophages, and hypoxia are major players in this scenario, exerting a propelling role for EMT, as well as for invasiveness, stemness, and dissemination of metastatic cells.

FUTURE DIRECTIONS

Future research focused on EMT should address some key points that are still unclear. They include: i) the role of the reverse phenomenon (i.e., mesenchymal-epithelial transition) that is likely regulated in the final stages of tumor progression, or that of mesenchymal-amoeboid transition, a plasticity program of cancer cells, which often follows EMT and offers a further metastatic advantage, and ii) the molecular basis of the correlation between stemness, EMT and ROS content.

TGF-β-induced epithelial-mesenchymal transition: a link between cancer and inflammation

Metastatic spread of tumor cells to vital organs is the major cause of death in cancer. Accumulating data support an important role of infiltrating immune cells in promoting carcinoma progression into metastatic disease. Tumor-infiltrating immune cells produce and secrete cytokines, growth factors and proteases that re-activate latent developmental processes including epithelial-mesenchymal transition (EMT). EMT provides tumor cells with invasive, migratory and stem cell properties allowing them to disseminate and propagate at distant sites. Induction of EMT requires two criteria to be fulfilled: (i) cells are competent to undergo EMT (ii) an EMT-permissive microenvironment exists. The cytokine TGF-β, which is expressed by tumor-infiltrating immune cells, stands out as a master regulator of the pro-invasive tumor microenvironment. TGF-β cooperates with stem cell pathways, such as Wnt and Ras signaling, to induce EMT. In addition, TGF-β contributes to an EMT-permissive microenvironment by switching the phenotypes of tumor-infiltrating immune cells, which thereby mount pro-invasive and pro-metastatic immune responses. In this review, we discuss the role of TGF-β-induced EMT as a link between cancer and inflammation in the context of questions, which from our point of view are key to answer in order to understand the functionality of EMT in tumors.

Epithelial-mesenchymal transition, the tumor microenvironment, and metastatic behavior of epithelial malignancies

OBJECTIVE

The mechanisms of cancer metastasis have been intensely studied recently and may provide vital therapeutic targets for metastasis prevention. We sought to review the contribution of epithelial-mesenchymal transition and the tumor microenvironment to cancer metastasis.

SUMMARY BACKGROUND DATA

Epithelial-mesenchymal transition is the process by which epithelial cells lose cell-cell junctions and baso-apical polarity and acquire plasticity, mobility, invasive capacity, stemlike characteristics, and resistance to apoptosis. This cell biology program is active in embryology, wound healing, and pathologically in cancer metastasis, and along with the mechanical and cellular components of the tumor microenvironment, provides critical impetus for epithelial malignancies to acquire metastatic capability.

METHODS

A literature review was performed using PubMed for "epithelial-mesenchymal transition", "tumor microenvironment", "TGF-β and cancer", "Wnt and epithelial-mesenchymal transition", "Notch and epithelial-mesenchymal transition", "Hedgehog and epithelial-mesenchymal transition" and "hypoxia and metastasis". Relevant primary studies and review articles were assessed.

RESULTS

Major signaling pathways involved in epithelial-mesenchymal transition include TGF-β, Wnt, Notch, Hedgehog, and others. These pathways converge on several transcription factors, including zinc finger proteins Snail and Slug, Twist, ZEB 1/2, and Smads. These factors interact with one another and others to provide crosstalk between the relevant signaling pathways. MicroRNA suppression and epigenetic changes also influence the changes involved in epithelial-mesenchymal transition. Cellular and mechanical components of the tumor microenvironment are also critical in determining metastatic potential.

CONCLUSIONS

While the mechanisms promoting metastasis are extremely wide ranging and still under intense investigation, the epithelial-mesenchymal transition program and the tumor microenvironment are both critically involved in the acquisition of metastatic potential. As our understanding of these complexities increases, the ability to target these processes for therapy will offer new promise in the treatment of epithelial malignancy and metastasis.