Differential growth factor regulation of N-cadherin expression and motility in normal and malignant oral epithelium

Estrogen Receptor β Activation Mitigates Colitis-associated Intestinal Fibrosis via Inhibition of TGF-β/Smad and TLR4/MyD88/NF-κB Signaling Pathways

BACKGROUND

Intestinal fibrosis, a complex complication of colitis, is characterized by excessive extracellular matrix (ECM) deposition. Estrogen receptor (ER) β may play a role in regulating this process.

METHODS

Intestinal tissue samples from stenotic and nonstenotic regions were collected from Crohn's disease (CD) patients. RNA sequencing was conducted on a mouse model to identify differentially expressed mRNAs. Histological, immunohistochemical, and semiquantitative Western blotting analyses were employed to assess ECM deposition and fibrosis. The roles of relevant pathways in fibroblast transdifferentiation, activity, and migration were examined.

RESULTS

Estrogen receptor β expression was found to be downregulated in the stenotic intestinal tissue of CD patients. Histological fibrosis score, collagen deposition, and profibrotic molecules in the colon of an intestinal fibrosis mouse model were significantly decreased after activation of ERβ. In vitro, ERβ activation alleviated transforming growth factor (TGF)-β-induced fibroblast activation and migration, as evidenced by the inhibition of col1α1, fibronectin, α-smooth muscle actin (α-SMA), collagen I, and N-cadherin expression. RNA sequencing showed that ERβ activation affected the expression of genes involved in ECM homeostasis and tissue remodeling. Enrichment analysis of differentially expressed genes highlighted that the downregulated genes were enriched in ECM-receptor interaction, TGF-β signaling, and Toll-like receptor (TLR) signaling. Western blotting confirmed the involvement of TGF-β/Smad and TLR4/MyD88/NF-κB signaling pathways in modulating fibrosis both in vivo and in vitro. The promoter activity of TGF-β1 and TLR4 could be suppressed by ERβ transcription factor.

CONCLUSION

Estrogen receptor β may regulate intestinal fibrosis through modulation of the TGF-β/Smad and TLR4/MyD88/NF-κB signaling pathways. Targeting ERβ activation could be a promising therapeutic strategy for treating intestinal fibrosis.

DIREN mitigates DSS-induced colitis in mice and attenuates collagen deposition via inhibiting the Wnt/β-catenin and focal adhesion pathways

BACKGROUND

DIREN is a SHE ethnic medicine with stasis-resolving, hemostasis, clearing heat, and removing toxin effects. It is clinically used in the treatment of gastrointestinal bleeding, such as ulcerative colitis (UC).

AIM OF THE STUDY

Fibrosis is one of the pathological changes in the progression of UC, which can make it challenging to respond to a treatment. We aimed to illuminate the role of DIREN in DSS-induced UC and tried to unveil its related mechanisms from two perspectives: intestinal inflammation and collagen deposition.

MATERIALS AND METHODS

A 2.5 % dextran sulfate sodium (DSS) water solution was used to induce colitis in mice. The therapeutic effect of DIREN was assessed using the disease activity index, histopathological score, and colon length. Masson and Sirius Red staining was used to observe the fibrosis in the colon. Apoptosis of colonic epithelial cells was observed by TUNEL immunofluorescence staining. RNA-seq observed differential genes and enrichment pathways. Immunohistochemistry and RT-qPCR were used to detect the expression of molecules related to fibrosis and focal adhesion signaling in colon tissue.

RESULTS

The administration of DIREN resulted in a reduction of disease activity index (DAI) in mice with UC while simultaneously promoting an increase in colon length. DIREN mitigated the loss of goblet cells in the colon of UC mice and maintained the integrity of the intestinal mucosa barrier. Masson staining revealed a reduction in colonic fibrosis with DIREN treatment, while Sirius red staining demonstrated a decrease in collagen Ⅰ deposition. DIREN reduced apoptosis of colonic epithelial cells and the expression of genes, such as CDH2, ITGA1, and TGF-β2. Additionally, the results of GSEA analysis of colon tissue transcriptome showed that the differentially expressed genes were enriched in the focal adhesion pathway. DIREN was found to downregulate the protein expression of BAX, N-cadherin, β-catenin, Integrin A1, and Vinculin while upregulating the protein expression of BCL2. Additionally, it led to the co-expression of N-cadherin and α-SMA.

CONCLUSION

DIREN exerts a protective effect against DSS-induced UC by ameliorating colonic fibrosis via regulation of focal adhesion and the WNT/β-catenin signaling pathway, thereby inhibiting fibroblast migration and reducing collagen secretion.

Anti-Metastatic Effects of Lupeol via the Inhibition of MAPK/ERK Pathway in Lung Cancer

BACKGROUND AND OBJECTIVE

ERK pathway is one of the most crucial pathways in lung cancer metastasis. Targeting its pathway is decisive in lung cancer research. Thus, this study demonstrated for the first time for significant and selective anti-metastatic effects of lupeol against lung cancer A549 cells via perturbations in the ERK signaling pathway.

MATERIALS AND METHODS

Human protein targets of lupeol were predicted in silico. Migration and cytotoxicity assays were carried out in vitro. Expression levels of proteins Erk1/2 and pErk1/2 were ensured using Enzyme- Linked Immunosorbent Assay (ELISA). Semi-quantitative RT-PCR technique was used to estimate changes in crucial mesenchymal marker gene expression levels of N-cadherin and vimentin.

RESULTS

Lupeol was found to target ERK and MEK proteins effectively. Despite having no cytotoxic effects, lupeol also significantly inhibited cell migration in A549 cells with decreased expression of the pErk1/2 protein along with N-cadherin and vimentin genes.

CONCLUSION

Lupeol inhibits cell migration, showed no cytotoxic effects on A549 cells, decreased pErk1/2 and EMT gene expression. Thus, it can serve as a potential ERK pathway inhibitor in lung cancer therapeutics.

Smad linker region phosphorylation is a signalling pathway in its own right and not only a modulator of canonical TGF-β signalling

Transforming growth factor (TGF)-β signalling pathways are intensively investigated because of their diverse association with physiological and pathophysiological states. Smad transcription factors are the key mediators of TGF-β signalling. Smads can be directly phosphorylated in the carboxy terminal by the TGF-β receptor or in the linker region via multiple intermediate serine/threonine kinases. Growth factors in addition to hormones and TGF-β can activate many of the same kinases which can phosphorylate the Smad linker region. Historically, Smad linker region phosphorylation was shown to prevent nuclear translocation of Smads and inhibit TGF-β signalling pathways; however, it was subsequently shown that Smad linker region phosphorylation can be a driver of gene expression. This review will cover the signalling pathways of Smad linker region phosphorylation that drive the expression of genes involved in pathology and pathophysiology. The role of Smad signalling in cell biology is expanding rapidly beyond its role in TGF-β signalling and many signalling paradigms need to be re-evaluated in terms of Smad involvement.

Unconventional Ways to Live and Die: Cell Death and Survival in Development, Homeostasis, and Disease

Balancing cell death and survival is essential for normal development and homeostasis and for preventing diseases, especially cancer. Conventional cell death pathways include apoptosis, a form of programmed cell death controlled by a well-defined biochemical pathway, and necrosis, the lysis of acutely injured cells. New types of regulated cell death include necroptosis, pyroptosis, ferroptosis, phagoptosis, and entosis. Autophagy can promote survival or can cause death. Newly described processes of anastasis and resuscitation show that, remarkably, cells can recover from the brink of apoptosis or necroptosis. Important new work shows that epithelia achieve homeostasis by extruding excess cells, which then die by anoikis due to loss of survival signals. This mechanically regulated process both maintains barrier function as cells die and matches rates of proliferation and death. In this review, we describe these unconventional ways in which cells have evolved to die or survive, as well as the contributions that these processes make to homeostasis and cancer.

Interaction between N-cadherin and decoy receptor-2 regulates apoptosis in head and neck cancer

N-cadherin is a neural cell adhesion molecule that aberrantly occurs in head and neck cancers to promote cancer cell growth. However, the underlying mechanisms remain unclear. Here we report that N-cadherin increases cancer cell growth by inhibiting apoptosis. Apoptosis eliminates old, unnecessary, and unhealthy cells. However, tumor cells have the ability of avoiding apoptosis that increases cancer cell growth. Recent studies have found that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis in tumor cells by reacting with four distinct cell surface receptors: TRAIL-R1 (DR-4), TRAIL-R2 (DR-5), TRAIL-R3 (DcR-1), and TRAIL-R4 (DcR-2). Among these TRAIL receptors, the death receptors DR-4 and DR-5 transmit apoptotic signals owing to the death domain in the intracellular portion. Conversely, the decoy receptors DcR-1 and DcR-2 lack a complete intracellular portion, so neither can transmit apoptotic signals. DcR-1 or DcR-2 overexpression suppresses TRAIL-induced apoptosis.

In this study, N-cadherin overexpression increased DcR-2 expression and decreased DR-5 expression. In contrast, knockdown of N-cadherin expression upregulated DR-5 expression and downregulated DcR-2 expression. A significantly positive relationship between N-cadherin and DcR-2 expression was also found in HNSCC specimens. Those specimens with a lower apoptotic index showed a higher expression of N-cadherin and/or DcR-2. In addition, we demonstrated that N-cadherin interacts directly with DcR-2. Notably, DcR-2 induces cancer cell survival through the cleavage of caspases and PARP by activating MAPK/ERK pathway and suppressing NF-kB/ p65 phosphorylation, which has a very important role in resistance to chemotherapy.

Thrombin promotes PAI-1 expression and migration in keratinocytes via ERK dependent Smad linker region phosphorylation

Keratinocyte proliferation and migration is essential during re-epithelialisation for the restoration of the epithelial barrier during skin wound healing. Numerous growth factors are involved in the stimulation of keratinocyte proliferation and migration. The signalling pathways that drive these processes during wound healing are not well defined. This study investigated thrombin-mediated signalling in keratinocytes. The thrombin receptor, protease-activated receptor 1 (PAR-1) is a seven transmembrane G-protein coupled receptor that is known to transactivate the epidermal growth factor receptor (EGFR). Immortalized human keratinocytes (HaCaT cells) were treated with thrombin and selective inhibitors to EGFR and MAP kinases. Whole cell lysates were separated on SDS-PAGE and analysed by Western blot using antibodies against transcription factor Smad2. Quantitative real-time polymerase chain reaction was used to measure the mRNA expression of PAI-1 while scratch wound assays were used to measure keratinocyte migration. Western blot data showed that thrombin mediates PAR-1 transactivation of EGFR and the downstream phosphorylation of the transcription factor Smad2 linker (Smad2L) region. ERK1/2 inhibition by UO126 caused a decrease in Smad2L phosphorylation while the p38 inhibitor SB202190 and JNK inhibitor SP600125 did not. Smad2L Ser250 was specifically phosphorylated by this thrombin mediated pathway while Ser245 and Ser255 were not. Thrombin increased PAI-1 mRNA expression and keratinocyte migration and this was reduced when either EGFR or ERK1/2 were blocked. Taken together these results show that thrombin mediated mRNA expression of PAI-1 in keratinocytes and migration occurs via EGFR transactivation and involves signalling intermediates ERK1/2 and Smad2 and may be a key pathway in skin wound healing.

Phosphorylation-dependent stabilization of MZF1 upregulates N-cadherin expression during protein kinase CK2-mediated epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a critical process in invasion and metastasis of cancer cells. E-cadherin to N-cadherin switching is considered a molecular hallmark of EMT. Recently, we reported that increased CK2 activity fully induces E-cadherin to N-cadherin switching, but the molecular mechanisms of N-cadherin upregulation are unknown. In this study, we examined how N-cadherin is upregulated by CK2. N-cadherin promoter analysis and ChIP analysis identified and confirmed myeloid zinc finger 1 (MZF1) as an N-cadherin transcription factor. Molecular analysis showed that MZF1 directly interacts with CK2 and is phosphorylated at serine 27. Phosphorylation stabilizes MZF1 and induces transcription of N-cadherin. MZF1 knockdown (MKD) in N-cadherin-expressing cancer cells downregulates N-cadherin expression and reverts the morphology from spindle and fibroblast-like to a rounded, epithelial shape. In addition, we showed that that MKD reduced the motility and invasiveness of N-cadherin-expressing cancer cells. Collectively, these data indicate that N-cadherin upregulation in CK2-mediated E-cadherin to N-cadherin switching is dependent on phosphorylation-mediated MZF1 stabilization. CK2 could be a good therapeutic target for the prevention of metastasis.

A Phosphatidic Acid (PA) conveyor system of continuous intracellular transport from cell membrane to nucleus maintains EGF receptor homeostasis

The intracellular concentration of the mitogen phosphatidic acid (PA) must be maintained at low levels until the need arises for cell proliferation. How temporal and spatial trafficking of PA affects its target proteins in the different cellular compartments is not fully understood. We report that in cancer cells, PA cycles back and forth from the cellular membrane to the nucleus, affecting the function of epidermal growth factor (EGF), in a process that involves PPARα/LXRα signaling. Upon binding to its ligand, EGF receptor (EGFR)-initiated activation of phospholipase D (PLD) causes a spike in intracellular PA production that forms vesicles transporting EGFR from early endosomes (EEA1 marker) and prolonged internalization in late endosomes and Golgi (RCAS marker). Cells incubated with fluorescent-labeled PA (NBD-PA) show PA in “diffuse” locations throughout the cytoplasm, punctae (small, <0.1 μm) vesicles) and large (>0.5 μm) vesicles that co-localize with EGFR. We also report that PPARα/LXRα form heterodimers that bind to new Responsive Elements (RE) in the EGFR promoter. Nuclear PA enhances EGFR expression, a role compatible with the mitogenic ability of the phospholipid. Newly made EGFR is packaged into PA recycling vesicles (Rab11 marker) and transported back to the cytoplasm and plasma membrane. However, a PLD+PA combination impedes binding of PPARα/LXRα to the EGFR promoter. Thus, if PA levels inside the nucleus reach a certain threshold (>100 nM) PA outcompetes the nuclear receptors and transcription is inhibited. This new signaling function of PLD-PA targeting EGFR trafficking and biphasically modulating its transcription, could explain cell proliferation initiation and its maintenance in cancer cells.

ANXA1 affects cell proliferation, invasion and epithelial-mesenchymal transition of oral squamous cell carcinoma

Annexin A1 (ANXA1) acts either as a tumor suppressor or an oncogene in different tumor types. Several clinical studies revealed that the expression of ANXA1 is associated with the pathologic differentiation grade in oral squamous cell carcinoma (OSCC) patients. However, the direct function of ANXA1 in OSCC progression has remained to be fully clarified. The present study was designed to investigate the role of ANXA1 in OSCC cell proliferation and invasion in vitro. Furthermore, whether ANXA1 was involved in transforming growth factor β1 (TGFβ1)/epidermal growth factor (EGF)-induced epithelial-mesenchymal transition (EMT) in OSCC was explored. Tca-8113 and SCC-9 cells were transfected with ANXA1-pcDNA3.1 plasmid to overexpress ANXA1. Subsequently, cell proliferation and invasion were examined using MTT and Transwell-Matrigel invasion assays. TGFβ1 and EGF were used to induce EMT in Tca-8113 and SCC-9 cells, and the expression of epithelial (E)-cadherin, neural (N)-cadherin and vimentin was determined by western blot analysis. The results demonstrated that ANXA1 overexpression induced a significant decrease of cell growth and invasiveness in Tca-8113 and SCC-9 cells. The expression of E-cadherin was significantly increased, while the expression of vimentin and N-cadherin was significantly decreased in ANXA1-overexpressing Tca-8113 and SCC-9 cells. ANXA1 expression was significantly decreased in TGFβ1/EGF-treated cells. Furthermore TGFβ1/EGF-induced EMT in OSCC cell lines was attenuated by ANXA1 overexpression. In conclusion, to the best of our knowledge, the present study was the first to evidence that ANXA1 inhibits OSCC cell proliferation and invasion in vitro. TGFβ1/EGF-induced EMT was reversed by ANXA1 in OSCC. ANXA1 was suggested to be a potential marker for OSCC as well as a novel treatment.

Upregulation of annexin A1 expression by butyrate in human melanoma cells induces invasion by inhibiting E-cadherin expression

Epithelial to mesenchymal transition (EMT) is a critical step in the metastasis of epithelial cancer cells. Butyrate, which is produced from dietary fiber by colonic bacterial fermentation, has been reported to influence EMT. However, some studies have reported that butyrate promotes EMT, while others have reported an inhibitory effect. To clarify these controversial results, it is necessary to elucidate the mechanism by which butyrate can influence EMT. In this study, we examined the potential role of annexin A1 (ANXA1), which was previously reported to promote EMT in breast cancer cells, as a mediator of EMT regulation by butyrate. We found that ANXA1 mRNA and protein were expressed in highly invasive melanoma cell lines (A2058 and A375), but not in SK-MEL-5 cells, which are less invasive. We also showed that butyrate induced ANXA1 mRNA and protein expression and promoted EMT-related cell invasion in SK-MEL-5 cells. Downregulation of ANXA1 expression using specific small interfering RNAs in butyrate-treated SK-MEL-5 cells resulted in increased expression of the epithelial marker E-cadherin and decreased cell invasion. Moreover, overexpressing ANXA1 decreased the expression of the E-cadherin. Collectively, these results indicate that butyrate induces the expression of ANXA1 in human melanoma cells, which then promotes invasion through activating the EMT signaling pathway.

High expression of CTHRC1 promotes EMT of epithelial ovarian cancer (EOC) and is associated with poor prognosis

Collagen triple helix repeat-containing 1 (CTHRC1) is aberrantly overexpressed in multiple malignant tumors. However, the expression characteristics and function of CTHRC1 in epithelial ovarian cancer (EOC) remain unclear. We found that CTHRC1 expression was up-regulated in the paraffin-embedded EOC tissues compared to borderline or benign tumor tissues. CTHRC1 expression was positively correlated with tumor size (p = 0.008), menopause (p = 0.037), clinical stage (p = 0.002) and lymph node metastasis (p < 0.001) and was also an important prognostic factor for the overall survival of EOC patients, as revealed by Kaplan-Meier analysis. CTHRC1 increased the invasive capabilities of EOC cells in vitro by activating the Wnt/β-catenin signaling pathway. We showed that ectopic transfection of CTHRC1 in EOC cells up-regulated the expression of EMT markers such as N-cadherin and vimentin, and EMT-associated transcriptional factor Snail. Knockdown of CTHRC1 expression in EOC cells resulted in down-regulation of N-cadherin, vimentin, Snail and translocation of β-catenin. Collectively, CTHRC1 may promote EOC metastasis through the induction of EMT process and serve as a potential biomarker for prognosis as well as a target for therapy.

The bone marrow metastasis niche in retinoblastoma

BACKGROUND

Retinoblastoma (Rb) is a progressive cancer which mainly occurs in children, and which is caused by different genetic or epigenetic alterations that lead to inactivation of both alleles of the RB1 gene. Hereditary and non-hereditary forms of Rb do exist, and the hereditary form is associated with an increased risk of secondary malignancies. Metastasis to distant organs is a critical feature of many tumors, and may be caused by various molecular alterations at different stages. Recognition of these alterations and, thus, insight into the processes underlying the development of metastases may result in novel preventive as well as effective targeted treatment options. Rb is associated with metastases to various organs and tissues, including the bone marrow (BM).

METHODS

Here, we provide an overview of mutations and other molecular changes known to be involved in Rb development and metastasis to the BM. This overview is based on a literature search ranging from 1990 to 2015.

CONCLUSIONS

The various BM metastasis-related molecular changes identified to date may be instrumental for a better diagnosis, prognosis and classification of Rb patients, as well as for the development of novel comprehensive (targeted) therapies.

CDH2 and CDH11 act as regulators of stem cell fate decisions

Accumulating evidence suggests that the mechanical and biochemical signals originating from cell-cell adhesion are critical for stem cell lineage specification. In this review, we focus on the role of cadherin mediated signaling in development and stem cell differentiation, with emphasis on two well-known cadherins, cadherin-2 (CDH2) (N-cadherin) and cadherin-11 (CDH11) (OB-cadherin). We summarize the existing knowledge regarding the role of CDH2 and CDH11 during development and differentiation in vivo and in vitro. We also discuss engineering strategies to control stem cell fate decisions by fine-tuning the extent of cell-cell adhesion through surface chemistry and microtopology. These studies may be greatly facilitated by novel strategies that enable monitoring of stem cell specification in real time. We expect that better understanding of how intercellular adhesion signaling affects lineage specification may impact biomaterial and scaffold design to control stem cell fate decisions in three-dimensional context with potential implications for tissue engineering and regenerative medicine.

TGF-β1 induces EMT reprogramming of porcine bladder urothelial cells into collagen producing fibroblasts-like cells in a Smad2/Smad3-dependent manner

Activation of fibroblasts and their differentiation into myofibroblasts, excessive collagen production and fibrosis occurs in a number of bladder diseases. Similarly, conversion of epithelial cells into mesenchymal cells (EMT) has been shown to increase fibroblasts like cells. TGF-β1 can induce the EMT and the role of TGF-β1-induced EMT during bladder injury leading to fibrosis and possible organ failure is gaining increasing interest. Here we show that EMT and fibrosis in porcine bladder urothelial (UC) cells are Smad dependent. Fresh normal porcine bladder urothelial cells were grown in culture with or without TGF-β1 and EMT markers were assessed. TGF-β1 treatment induced changes in cellular morphology as depicted by a significant decrease in the expression of E-cadherin and corresponding increase in N-cadherin and α-SMA. We knocked down Smad2 and Smad3 by Smad specific siRNA. Downregulation of E-cadherin expression by TGF-β1 was Smad3-dependent, whereas N-cadherin and α-SMA were dependent on both Smad2 and Smad3. Connective tissue growth factor (CTGF/CCN2), matrix metalloproteinase-2 and -9 (MMP-2, MMP-9) has been shown to play important roles in the pathogenesis of fibrosis. Induction of these genes by TGF-β1 was found to be time dependent. Upregulation of CTGF/CCN2 by TGF-β1 was Smad3 dependent; whereas MMP-2 was Smad2 dependent. Smad2 and Smad3 both participated in MMP-9 expression. TGF-β1 reprogrammed mesenchymal fibroblast like cells robustly expressed collagen I and III and these was inhibited by SB-431542, a TGF-β receptor inhibitor. Our results indicate that EMT of porcine bladder UC cells is TGF-β1 dependent and is mediated through Smad2 and Smad3. TGF-β1 may be an important factor in the development of bladder fibrosis via an EMT mechanism. This identifies a potential amenable therapeutic target.

α-Smooth muscle actin-positive myofibroblasts, in association with epithelial-mesenchymal transition and lymphogenesis, is a critical prognostic parameter in patients with oral tongue squamous cell carcinoma

BACKGROUND

α-Smooth muscle actin (α-SMA)-positive myofibroblasts play a pivotal role in progression and metastasis of solid carcinomas. Epithelial-mesenchymal transition (EMT) of cancer cells and lymphogenesis of tumor microenvironment are the important events in tumor metastasis. This study aimed to investigate the relationship between the expression of myofibroblasts marker, α-SMA, and clinicopathological features, EMT, lymphogenesis, and prognostic status in oral tongue squamous cell carcinoma (OTSCC).

METHODS

Immunohistochemisty was used to detect α-SMA expression in 50 OTSCCs. EMT and lymphogenesis were also identified by immunostaining with N-cadherin, vimentin, and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1).

RESULTS

There was a significant correlation respectively between the α-SMA (P = 0.002), vimentin (P < 0.001), N-cadherin (P = 0.025) expression and cervical lymph node metastasis of OTSCC. Carcinomas with α-SMA (P = 0.001), vimentin (P = 0.003), and N-cadherin (P = 0.012) expression were more advanced in terms of tumor-node-metastases status. Univariate analysis showed that pathologic node status (P < 0.001), α-SMA (P = 0.001), and vimentin expression (P = 0.044) was significantly associated with overall survival time, but multivariate analysis just showed the α-SMA expression (P = 0.008) and pathologic node status (P = 0.003) was independently predictive of prognosis. Furthermore, statistical analysis showed significant correlation between α-SMA expression and vimentin (P = 0.037), N-cadherin (P = 0.019), or LYVE-1 positive vessel count (P = 0.041).

CONCLUSION

Our results indicate that α-SMA-positive myofibroblasts have important impacts on cancer progression, metastasis, and survival prognosis of patients with OTSCC. The functions of α-SMA-positive myofibroblasts in OTSCC may be associated with promoting EMT of tumor cells and lymphogenesis of metastasis microenvironment.

Glutamine synthetase functions as a negative growth regulator in glioma

Our recent study demonstrated that glutamine synthetase (GS) may not only serve as a glutamate-converting enzyme in glial cells, but may also function as a regulator of astrocyte migration after injury. In this report, we showed that GS expression increased in cultured rat C6 glioma cells that underwent long-term serially propagation. The stable overexpression of GS in C6 glioma cells resulted in growth arrest and motility suppression; however the stable knockdown of GS resulted in motility enhancement. In correlation with cell aggregation, N-cadherin levels increased at sites of cell-cell contact in C6 cells overexpressing GS, and decreased in C6 cells with stable GS knockdown; total N-cadherin expression levels remained unchanged in these cells. In addition, levels of p21, a potent cyclin-dependent kinase inhibitor, increased, while cyclin D1 levels decreased in C6 cells overexpressing GS. Our additional studies showed that N-cadherin-mediated cell-cell contacts were implicated in GS-induced cell growth arrest and impairment of cell migration, as evidenced by the inhibition of GS on cell growth and motility by the neutralizing anti-N-cadherin monoclonal antibody (GC-4 mAb). Collectively, these observations suggest a novel mechanism of growth regulation by GS that involves N-cadherin mediated cell-cell contact.

Transforming growth factor-β signalling: role and consequences of Smad linker region phosphorylation

Transforming growth factor-β (TGF-β) is a secreted homodimeric protein that plays an important role in regulating various cellular responses including cell proliferation and differentiation, extracellular matrix production, embryonic development and apoptosis. Disruption of the TGF-β signalling pathway is associated with diverse disease states including cancer, renal and cardiac fibrosis and atherosclerosis. At the cell surface TGF-β complex consists of two type I and two type II transmembrane receptors (TβRI and TβRII respectively) which have serine/threonine kinase activity. Upon TGF-β engagement TβRII phosphorylates TβRI which in turn phosphorylates Smad2/3 on two serine residues at their C-terminus which enables binding to Smad4 to form heteromeric Smad complexes that enter the nucleus to initiate gene transcription including for extracellular matrix proteins. TGF-β signalling is also known to activate other serine/threonine kinase signalling that results in the phosphorylation of the linker region of Smad2. The Smad linker region is defined as the domain which lies between the MH1 and MH2 domains of a Smad protein. Serine/threonine kinases that are known to phosphorylate the Smad linker region include mitogen-activated protein kinases, extracellular-signal regulated kinase, Jun N-terminal kinase and p38 kinase, the tyrosine kinase Src, phosphatidylinositol 3'-kinase, cyclin-dependent kinases, rho-associated protein kinase, calcium calmodulin-dependent kinase and glycogen synthase kinase-3. This review will cover the role of Smad linker region phosphorylation downstream of TGF-β signalling in vascular cells. Key factors including the identification of the kinases that phosphorylate individual Smad residues, the upstream agents that activate these kinases, the cellular location of the phosphorylation event and the importance of the linker region in regulation and expression of genes induced by TGF-β are covered.

New approaches in the development of a vaccine for mucosal candidiasis: progress and challenges

The commensal fungus Candida albicans causes mucosal candidiasis in the rapidly expanding number of immunocompromised patients. Mucosal candidiasis includes oropharyngeal, esophageal, gastrointestinal, and vaginal infections. Vulvovaginal candidiasis (VVC) and antimycotic-refractory recurrent VVC is a frequent problem in healthy childbearing women. Both these mucosal infections can affect the quality of life and finding new therapeutical and preventive approaches is a challenge. A vaccine against candidal infections would be a new important tool to prevent and/or cure mucosal candidiasis and would be of benefit to many patients. Several Candida antigens have been proposed as vaccine candidates including cell wall components and virulence factors. Here we discuss the recent progress and problems associated with vaccination against mucosal candidiasis.

Anoikis resistance: an essential prerequisite for tumor metastasis

Metastasis is a multistep process including dissociation of cancer cells from primary sites, survival in the vascular system, and proliferation in distant target organs. As a barrier to metastasis, cells normally undergo an apoptotic process known as “anoikis,” a form of cell death due to loss of contact with the extracellular matrix or neighboring cells. Cancer cells acquire anoikis resistance to survive after detachment from the primary sites and travel through the circulatory and lymphatic systems to disseminate throughout the body. Because recent technological advances enable us to detect rare circulating tumor cells, which are anoikis resistant, currently, anoikis resistance becomes a hot topic in cancer research. Detailed molecular and functional analyses of anoikis resistant cells may provide insight into the biology of cancer metastasis and identify novel therapeutic targets for prevention of cancer dissemination. This paper comprehensively describes recent investigations of the molecular and cellular mechanisms underlying anoikis and anoikis resistance in relation to intrinsic and extrinsic death signaling, epithelial-mesenchymal transition, growth factor receptors, energy metabolism, reactive oxygen species, membrane microdomains, and lipid rafts.

Interplay between β1-integrin and Rho signaling regulates differential scattering and motility of pancreatic cancer cells by snail and Slug proteins

The Snail family of transcription factors has been implicated in pancreatic cancer progression. We recently showed that Snail (Snai1) promotes membrane-type 1 matrix metalloproteinase (MT1-MMP)- and ERK1/2-dependent scattering of pancreatic cancer cells in three-dimensional type I collagen. In this study, we examine the role of Slug (Snai2) in regulating pancreatic cancer cell scattering in three-dimensional type I collagen. Although Slug increased MT1-MMP expression and ERK1/2 activity, Slug-expressing cells failed to scatter in three-dimensional collagen. Moreover, in contrast to Snail-expressing cells, Slug-expressing cells did not demonstrate increased collagen I binding, collagen I-driven motility, or α2β1-integrin expression. Significantly, inhibiting β1-integrin function decreased migration and scattering of Snail-expressing cells in three-dimensional collagen. As Rho GTPases have been implicated in invasion and migration, we also analyzed the contribution of Rac1 and Rho signaling to the differential migration and scattering of pancreatic cancer cells. Snail-induced migration and scattering were attenuated by Rac1 inhibition. In contrast, inhibiting Rho-associated kinase ROCK1/2 increased migration and scattering of Slug-expressing cells in three-dimensional collagen and thus phenocopied the effects of Snail in pancreatic cancer cells. Additionally, the increased migration and scattering in three-dimensional collagen of Slug-expressing cells following ROCK1/2 inhibition was dependent on β1-integrin function. Overall, these results demonstrate differential effects of Snail and Slug in pancreatic cancer and identify the interplay between Rho signaling and β1-integrin that functions to regulate the differential scattering and migration of Snail- and Slug-expressing pancreatic cancer cells.

MicroRNA-138 suppresses epithelial-mesenchymal transition in squamous cell carcinoma cell lines

Down-regulation of miR-138 (microRNA-138) has been frequently observed in various cancers, including HNSCC (head and neck squamous cell carcinoma). Our previous studies suggest that down-regulation of miR-138 is associated with mesenchymal-like cell morphology and enhanced cell migration and invasion. In the present study, we demonstrated that these miR-138-induced changes were accompanied by marked reduction in E-cad (E-cadherin) expression and enhanced Vim (vimentin) expression, characteristics of EMT (epithelial-mesenchymal transition). On the basis of a combined experimental and bioinformatics analysis, we identified a number of miR-138 target genes that are associated with EMT, including VIM, ZEB2 (zinc finger E-box-binding homeobox 2) and EZH2 (enhancer of zeste homologue 2). Direct targeting of miR-138 to specific sequences located in the mRNAs of the VIM, ZEB2 and EZH2 genes was confirmed using luciferase reporter gene assays. Our functional analyses (knock-in and knock-down) demonstrated that miR-138 regulates the EMT via three distinct pathways: (i) direct targeting of VIM mRNA and controlling the expression of VIM at a post-transcriptional level, (ii) targeting the transcriptional repressors (ZEB2) which in turn regulating the transcription activity of the E-cad gene, and (iii) targeting the epigenetic regulator EZH2 which in turn modulates its gene silencing effects on the downstream genes including E-cad. These results, together with our previously observed miR-138 effects on cell migration and invasion through targeting RhoC (Rho-related GTP-binding protein C) and ROCK2 (Rho-associated, coiled-coil-containing protein kinase 2) concurrently, suggest that miR-138 is a multi-functional molecular regulator and plays major roles in EMT and in HNSCC progression.

Crosstalk between Smad and Mitogen-Activated Protein Kinases for the Regulation of Apoptosis in Cyclosporine A- Induced Renal Tubular Injury

Background/Aims

It remains elusive whether there is a crosstalk between Smad and mitogen-activated protein kinases (MAPKs) and whether it regulates cyclosporine A (CyA)-induced apoptosis in renal proximal tubular cells (RPTCs).

Methods

The effect of CyA on nuclear translocation of Smad2/3 and MAPKs (measured by Western blotting or immunofluorescence) and apoptosis (determined by Hoechst 33258 staining) was examined in HK-2 cells.

Results

CyA induced apoptosis at 24 h and nuclear translocation of phosphorylated (p)-Smad2/3 at 3 h, which was continued till 24 h. CyA enhanced the expression of p-ERK at 1 h, which was continued till 24 h, and of p-p38MAPK at 1–6 h, which returned to control level at 12 h. CyA did not affect JNK. An inhibitor of ERK, PD98059, prevented CyA-induced nuclear translocation of Smad2/3 and apoptosis. An inhibitor of p38MAPK, SB202190, deteriorated CyA-induced nuclear translocation of p-Smad2/3. Epidermal growth factor (EGF) activated ERK and p38MAPK but not JNK. EGF-induced activation of MAPKs ameliorated CyA-induced nuclear translocation of p-Smad2/3 and apoptosis. Inhibition of p38MAPK but not of ERK abolished the protective effect of EGF on CyA-induced nuclear translocation of p-Smad2/3 and apoptosis.

Conclusion

Crosstalk between R-Smad and p38MAPK/ERK, but not JNK differentially regulates apoptosis in CyA-induced RPTC injury.

MT1-MMP cooperates with Kras(G12D) to promote pancreatic fibrosis through increased TGF-β signaling

Pancreatic cancer is associated with a pronounced fibrotic reaction that was recently shown to limit delivery of chemotherapy. To identify potential therapeutic targets to overcome this fibrosis, we examined the interplay between fibrosis and the key proteinase membrane type 1-matrix metalloproteinase (MT1-MMP, MMP-14), which is required for growth and invasion in the collagen-rich microenvironment. In this article, we show that compared with control mice (Kras(+)/MT1-MMP(-)) that express an activating Kras(G12D) mutation necessary for pancreatic cancer development, littermate mice that express both MT1-MMP and Kras(G12D) (Kras(+)/MT1-MMP(+)) developed a greater number of large, dysplastic mucin-containing papillary lesions. These lesions were associated with a significant amount of surrounding fibrosis, increased α-smooth muscle actin (+) cells in the stroma, indicative of activated myofibroblasts, and increased Smad2 phosphorylation. To further understand how MT1-MMP promotes fibrosis, we established an in vitro model to examine the effect of expressing MT1-MMP in pancreatic ductal adenocarcinoma (PDAC) cells on stellate cell collagen deposition. Conditioned media from MT1-MMP-expressing PDAC cells grown in three-dimensional collagen enhanced Smad2 nuclear translocation, promoted Smad2 phosphorylation, and increased collagen production by stellate cells. Inhibiting the activity or expression of the TGF-β type I receptor in stellate cells attenuated MT1-MMP conditioned medium-induced collagen expression by stellate cells. In addition, a function-blocking anti-TGF-β antibody also inhibited MT1-MMP conditioned medium-induced collagen expression in stellate cells. Overall, we show that the bona fide collagenase MT1-MMP paradoxically contributes to fibrosis by increasing TGF-β signaling and that targeting MT1-MMP may thus help to mitigate fibrosis.

Deregulation of Snai2 is associated with metastasis and poor prognosis in tongue squamous cell carcinoma

The members of the Snail superfamily of zinc-finger transcription factors, including Snai1 and Snai2, are involved in essential biological processes, such as epithelial-mesenchymal transition (EMT). Although Snai1 has been investigated in a number of cancers, our knowledge on Snai2 and its role(s) in squamous cell carcinoma of oral tongue (SCCOT) is limited. In this study, we confirmed the previous observation that over-expression of Snai2 is a frequent event in SCCOT. We further demonstrated that Snai2 over-expression is associated with lymph node metastasis in two independent SCCOT patient cohorts (total n = 129). Statistical analysis revealed that Snai2 over-expression was correlated with reduced overall survival. Furthermore, over-expression of Snai2 was correlated with reduced E-cadherin expression and enhanced Vimentin expression, suggesting a functional role of Snai2 in EMT. These observations were confirmed in vitro, in which knockdown of Snai2 induced a switch from a mesenchymal-like morphology to an epithelial-like morphology in SCCOT cell lines, and suppressed the cell invasion and migration. In contrast, ectopic transfection of Snai2 led to enhanced cell invasion and migration. Furthermore, Snai2 knockdown attenuated TGFβ1-induced EMT in SCCOT cell lines. Taken together, these data suggest that Snai2 plays major roles in EMT and the progression of SCCOT and may serve as a therapeutic target for patients at risk of metastasis.

Endothelial Smad4 maintains cerebrovascular integrity by activating N-cadherin through cooperation with Notch

Cerebrovascular dysfunction is strongly associated with neonatal intracranial hemorrhage (ICH) and stroke in adults. Cerebrovascular endothelial cells (ECs) play important roles in maintaining a stable cerebral circulation in the central nervous system by interacting with pericytes. However, the genetic mechanisms controlling the functions of cerebral ECs are still largely unknown. Here, we report that disruption of Smad4, the central intracellular mediator of transforming growth factor-β (TGF-β) signaling, specifically in the cerebral ECs, results in perinatal ICH and blood-brain barrier breakdown. Furthermore, the mutant vessels exhibit defective mural cell coverage. Smad4 stabilizes cerebrovascular EC-pericyte interactions by regulating the transcription of N-cadherin through associating with the Notch intracellular complex at the RBP-J binding site of the N-cadherin promoter. These findings uncover a distinct role of endothelial Smad4 in maintaining cerebrovascular integrity and suggest important implications for genetic or functional deficiencies in TGF-β/Smad signaling in the pathogenesis of cerebrovascular dysfunction.

Search for the tumor-associated proteins of oral squamous cell carcinoma collected in Taiwan using proteomics strategy

Squamous cell carcinoma (SCC) accounts for more than 90% of malignant tumors of the oral cavity. In Taiwan, oral squamous cell carcinoma (OSCC) is among the most frequent malignancies, largely due to betal quid chewing. Despite the recent improvement in treatment results, the long-term outcome of OSCC generally remains poor, especially for those with advanced diseases. It is therefore desirable to identify potential biomarkers that may aid in risk stratification and perhaps the development of therapeutic targets. In this study, we exploited two-dimensional gel electrophoresis (2-DE) coupled with mass spectrometry to compare the proteome maps of 10 OSCC specimens with their adjacent nontumorous epithelia to identify differentially expressed proteins. Comparative proteomics indicated that 17 proteins were differentially expressed in OSCC with 11 up-regulated and 6 down-regulated proteins. These deregulated proteins participated in cytoskeletal functions, cell signaling, antiapoptosis, angiogenesis, lipid metabolism, drug metabolism, and protein translation/turnover. They were all associated with tumor development in various cancers. Among the dys-regulated proteins, the immunoexpression of three proteins including nicotinamide N-methyltransferase, apolipoprotein AI, and 14-3-3 zeta were evaluated in 38 OSCCs of testing cohort to confirm the proteomics data. Subsequently, the expression of 14-3-3 zeta, as the most relevant to OSCC progression determined by testing cohort, was further assessed in 80 OSCCs of independent validation cohort to identify the clinical relevance of its expression. By this comprehensive study, we identified 14-3-3 zeta as the only prognosticator of local recurrence-free survival (LRFS) and also an independently predicted factor of disease-specific survival (DSS).

Cell invasion of highly metastatic MTLn3 cancer cells is dependent on phospholipase D2 (PLD2) and Janus kinase 3 (JAK3)

MTLn3 cells are highly invasive breast adenoacarcinoma cells. The relative level of the epidermal-growth-factor-stimulated invasion of this cell line is greater than two other breast cancer cell lines (MDA-MB-231 and MCF-7) and one non-small cell lung cancer cell line (H1299). We have determined that the mechanism of cancer cell invasion involves the presence of an enzymatically active phospholipase D (PLD), with the PLD2 isoform being more relevant than PLD1. PLD2 silencing abrogated invasion, whereas ectopic expression of PLD2 augmented cell invasion in all four cell lines, with an efficacy (MTLn3±MDA-MB-231>H1299±MCF-7) that correlated well with their abilities to invade Matrigel in vitro. We also report that PLD2 is under the control of Janus kinase 3 (JAK3), with the kinase phosphorylating PLD2 at the Y415 residue, thus enabling its activation. Y415 is located downstream of a PH domain and upstream of the catalytic HKD-1 domain of PLD2. JAK3 knockdown abrogated lipase activity and epidermal-growth-factor-stimulated cell invasion directly. For the purposes of activating PLD2 for cell invasion, JAK3 operates via an alternative pathway that is independent of STAT, at least in MTLn3 cells. We also consistently found that JAK3 and PLD2 pathways are utilized at the maximum efficiency (phosphorylation and activity) in highly invasive MTLn3 cells versus a relatively low utilization in the less invasive MCF-7 cell line. In summary, a high level of cell invasiveness of cancer cells can be explained for the first time by combined high JAK3/PLD2 phosphorylation and activity involving PLD2's Y415 residue, which might constitute a novel target to inhibit cancer cell invasion.

Pancreatic cancer cells respond to type I collagen by inducing snail expression to promote membrane type 1 matrix metalloproteinase-dependent collagen invasion

Pancreatic ductal adenocarcinoma (PDAC) is characterized by pronounced fibrotic reaction composed primarily of type I collagen. Although type I collagen functions as a barrier to invasion, pancreatic cancer cells have been shown to respond to type I collagen by becoming more motile and invasive. Because epithelial-mesenchymal transition is also associated with cancer invasion, we examined the extent to which collagen modulated the expression of Snail, a well known regulator of epithelial-mesenchymal transition. Relative to cells grown on tissue culture plastic, PDAC cells grown in three-dimensional collagen gels induced Snail. Inhibiting the activity or expression of the TGF-β type I receptor abrogated collagen-induced Snail. Downstream of the receptor, we showed that Smad3 and Smad4 were critical for the induction of Snail by collagen. In contrast, Smad2 or ERK1/2 was not involved in collagen-mediated Snail expression. Overexpression of Snail in PDAC cells resulted in a robust membrane type 1-matrix metalloproteinase (MT1-MMP, MMP-14)-dependent invasion through collagen-coated transwell chambers. Snail-expressing PDAC cells also demonstrated MT1-MMP-dependent scattering in three-dimensional collagen gels. Mechanistically, Snail increased the expression of MT1-MMP through activation of ERK-MAPK signaling, and inhibiting ERK signaling in Snail-expressing cells blocked two-dimensional collagen invasion and attenuated scattering in three-dimensional collagen. To provide in vivo support for our findings that Snail can regulate MT1-MMP, we examined the expression of Snail and MT1-MMP in human PDAC tumors and found a statistically significant positive correlation between MT1-MMP and Snail in these tumors. Overall, our data demonstrate that pancreatic cancer cells increase Snail on encountering collagen-rich milieu and suggest that the desmoplastic reaction actively contributes to PDAC progression.

N-cadherin expression is correlated with metastasis of spindle cell carcinoma of head and neck region

Spindle cell carcinoma (SpCC) is a biphasic tumor composed of conventional squamous cell carcinoma and a malignant spindle cell component. SpCC expresses both epithelial and mesenchymal markers by immunohistochemical analysis. There is mounting evidence for sarcomatoid transformation from the epithelial component, supporting the theory that SpCC is a monoclonal neoplasm originating from a stem cell giving rise to both components. The loss of E-cadherin and the gain of N-cadherin expression are known as the "cadherin switching". Cadherin switching is a major hallmark of epithelial-mesenchymal transition (EMT). EMT is a crucial process in cancer progression providing cancer cells with the ability to escape from the primary focus, to invade stromal tissues, and to migrate to distant regions. Although E-cadherin down-regulation is well known in various cancers, there are a few studies on N-cadherin expression in cancer. Here, therefore, we investigated N-cadherin expression in the progression of head and neck SpCC. First, we examined cadherin switching in our established SpCC cell lines, SpCC-1 and SpCC-2. SpCC-1 and SpCC-2 cells were spindle in shape and showed cadherin switching. Moreover, we examined N-cadherin expression in 15 SpCC cases by immunohistochemistry. Although N-cadherin expression was not observed in non-neoplastic squamous epithelium, high expression of N-cadherin was observed in 10 of 15 SpCC cases. Interestingly, 6 of 7 SpCC cases with metastasis showed high expression of N-cadherin. In conclusion, our findings suggest that N-cadherin may play an important role in metastasis of SpCC in addition to the pathogenesis of SpCC of the head and neck.

Rho-ROCK-myosin signaling mediates membrane type 1 matrix metalloproteinase-induced cellular aggregation of keratinocytes

Membrane type 1-matrix metalloproteinase (MT1-MMP, MMP14), which is associated with extracellular matrix (ECM) breakdown in squamous cell carcinoma (SCC), promotes tumor formation and epithelial-mesenchymal transition. However, in this report we demonstrate that MT1-MMP, by cleaving the underlying ECM, causes cellular aggregation of keratinocytes and SCC cells. Treatment with an MMP inhibitor abrogated MT1-MMP-induced phenotypic changes, but decreasing E-cadherin expression did not affect MT1-MMP-induced cellular aggregation. As ROCK1/2 can regulate cell-cell and cell-ECM interaction, we examined its role in mediating MT1-MMP-induced phenotypic changes. Blocking ROCK1/2 expression or activity abrogated the cellular aggregation resulting from MT1-MMP expression. Additionally, blocking Rho and non-muscle myosin attenuated MT1-MMP-induced phenotypic changes. Moreover, SCC cells expressing only the catalytically active MT1-MMP protein demonstrated increased cellular aggregation and increased myosin II activity in vivo when injected subcutaneously into nude mice. Together, these results demonstrate that expression of MT1-MMP may be anti-tumorigenic in keratinocytes by promoting cellular aggregation.