Matrix metalloproteinase-induced malignancy in mammary epithelial cells

Current perspectives of mitochondria-targeted antioxidants in cancer prevention and treatment

Oxidative stress nearly always accompanies all stages of cancer development. At the early stages, antioxidants may help to reduce reactive oxygen species (ROS) production and exhibit anticarcinogenic effects. In the later stages, ROS involvement becomes more complex. On the one hand, ROS are necessary for cancer progression and epithelial-mesenchymal transition. On the other hand, antioxidants may promote cancer cell survival and may increase metastatic frequency. The role of mitochondrial ROS in cancer development remains largely unknown. This paper reviews experimental data on the effects of both endogenous and exogenous antioxidants on cancerogenesis focusing on the development and application of mitochondria-targeted antioxidants. We also discuss the prospects for antioxidant cancer therapy, focusing on the use of mitochondria-targeted antioxidants.

RAC1B Suppresses TGF-β-Dependent Chemokinesis and Growth Inhibition through an Autoregulatory Feed-Forward Loop Involving PAR2 and ALK5

The small GTPase RAC1B functions as a powerful inhibitor of transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition, cell motility, and growth arrest in pancreatic epithelial cells. Previous work has shown that RAC1B downregulates the TGF-β type I receptor ALK5, but the molecular details of this process have remained unclear. Here, we hypothesized that RAC1B-mediated suppression of activin receptor-like kinase 5 (ALK5) involves proteinase-activated receptor 2 (PAR2), a G protein-coupled receptor encoded by F2RL1 that is crucial for sustaining ALK5 expression. We found in pancreatic carcinoma Panc1 cells that PAR2 is upregulated by TGF-β1 in an ALK5-dependent manner and that siRNA-mediated knockdown of RAC1B increased both basal and TGF-β1-induced expression of PAR2. Further, the simultaneous knockdown of PAR2 and RAC1B rescued Panc1 cells from a RAC1B knockdown-induced increase in ALK5 abundance and the ALK5-mediated increase in TGF-β1-induced migratory activity. Conversely, Panc1 cells with stable ectopic expression of RAC1B displayed reduced ALK5 expression, an impaired upregulation of PAR2, and a reduced migratory responsiveness to TGF-β1 stimulation. However, these effects could be reversed by ectopic overexpression of PAR2. Moreover, the knockdown of PAR2 alone in Panc1 cells and HaCaT keratinocytes phenocopied RAC1B's ability to suppress ALK5 abundance and TGF-β1-induced chemokinesis and growth inhibition. Lastly, we found that the RAC1B knockdown-induced increase in TGF-β1-induced PAR2 mRNA expression was sensitive to pharmacological inhibition of MEK-ERK signaling. Our data show that in pancreatic and skin epithelial cells, downregulation of ALK5 activity by RAC1B is secondary to suppression of F2RL1/PAR2 expression. Since F2RL1 itself is a TGF-β target gene and its upregulation by TGF-β1 is mediated by ALK5 and MEK-ERK signaling, we suggest the existence of a feed-forward signaling loop involving ALK5 and PAR2 that is efficiently suppressed by RAC1B to restrict TGF-β-driven cell motility and growth inhibition.

Inhibition of Migration and Invasion in Melanoma Cells by β-Escin via the ERK/NF-κB Signaling Pathway

β-Escin, a natural triterpene saponin was extracted from Aesculus hippocastanum seeds, which have been widely used to treat inflammation in traditional medicine. In an effort to study the possible anti-tumor effects of β-escin, we performed wound healing, invasion, and adhesion assays to examine the effects of β-escin on cell migration, invasion, and angiogenesis. Our results revealed that β-escin inhibits cell migration as well as motility in B16F10 and SK-MEL5 cells in a dose-dependent manner. RT-PCR and Western blot analysis showed that β-escin increased TIMP-1, -2 while significantly downregulated phosphorylated extracellular signal-regulated kinase (p-ERK) expression, and suppressing nuclear factor-kappa B (NF-κB) and inhibitor of nuclear factor-kappa B (IκB) expression. Overall, the data from the current study suggest that β-escin has the potential for inhibiting both metastatic and angiogenic activities, and are the earliest evidence for the involvement of the NF-κB/IκB signaling in β-escin-induced anti-tumor effects.

RAC1B: A Rho GTPase with Versatile Functions in Malignant Transformation and Tumor Progression

RAC1B is an alternatively spliced isoform of the monomeric GTPase RAC1. It differs from RAC1 by a 19 amino acid in frame insertion, termed exon 3b, resulting in an accelerated GDP/GTP-exchange and an impaired GTP-hydrolysis. Although RAC1B has been ascribed several protumorigenic functions such as cell cycle progression and apoptosis resistance, its role in malignant transformation, and other functions driving tumor progression like epithelial-mesenchymal transition, migration/invasion and metastasis are less clear. Insertion of exon 3b endows RAC1B with specific biochemical properties that, when compared to RAC1, encompass both loss-of-functions and gain-of-functions with respect to the type of upstream activators, downstream targets, and binding partners. In its extreme, this may result in RAC1B and RAC1 acting in an antagonistic fashion in regulating a specific cellular response with RAC1B behaving as an endogenous inhibitor of RAC1. In this review, we strive to provide the reader with a comprehensive overview, rather than critical discussions, on various aspects of RAC1B biology in eukaryotic cells.

Metformin inhibits the migration and invasion of esophageal squamous cell carcinoma cells by downregulating the protein kinase B signaling pathway

Previous studies have suggested that metformin, a biguanide family member widely used as an oral antidiabetic drug, may inhibit proliferation and induce apoptosis in certain types of cancer cell. However, the molecular mechanisms underlying metformin-associated anticancer effects, and in particular antimetastatic effects, remain to be fully understood. The present study assessed the efficacy of metformin in inhibiting the migration and invasion of the esophageal carcinoma cell line EC109, and evaluated the effect of metformin on the protein kinase B (AKT) signaling pathway. EC109 cells were treated with 0, 5, 10 or 20 mM metformin during the logarithmic growth phase. A Transwell assay and western blot analysis revealed that metformin inhibited the migration and invasion of EC109 cells, nuclear factor-κB activation, matrix metallopeptidase 9 and N-cadherin expression in a phosphorylated-AKT dependent manner. These results suggested that metformin inhibits the migration and invasion of human esophageal carcinoma cells by suppressing AKT phosphorylation and regulating the expression of migration- and invasion-associated genes.

Strategic Integration of Multiple Bioinformatics Resources for System Level Analysis of Biological Networks

Recent technological advances in genomics allow the production of biological data at unprecedented tera- and petabyte scales. Efficient mining of these vast and complex datasets for the needs of biomedical research critically depends on a seamless integration of the clinical, genomic, and experimental information with prior knowledge about genotype-phenotype relationships. Such experimental data accumulated in publicly available databases should be accessible to a variety of algorithms and analytical pipelines that drive computational analysis and data mining.We present an integrated computational platform Lynx (Sulakhe et al., Nucleic Acids Res 44:D882-D887, 2016) ( http://lynx.cri.uchicago.edu ), a web-based database and knowledge extraction engine. It provides advanced search capabilities and a variety of algorithms for enrichment analysis and network-based gene prioritization. It gives public access to the Lynx integrated knowledge base (LynxKB) and its analytical tools via user-friendly web services and interfaces. The Lynx service-oriented architecture supports annotation and analysis of high-throughput experimental data. Lynx tools assist the user in extracting meaningful knowledge from LynxKB and experimental data, and in the generation of weighted hypotheses regarding the genes and molecular mechanisms contributing to human phenotypes or conditions of interest. The goal of this integrated platform is to support the end-to-end analytical needs of various translational projects.

Cellular and molecular mechanisms underlying alcohol-induced aggressiveness of breast cancer

Breast cancer is a leading cause of morbidity and mortality in women. Both Epidemiological and experimental studies indicate a positive correlation between alcohol consumption and the risk of breast cancer. While alcohol exposure may promote the carcinogenesis or onset of breast cancer, it may as well enhance the progression and aggressiveness of existing mammary tumors. Recent progress in this line of research suggests that alcohol exposure is associated with invasive breast cancer and promotes the growth and metastasis of mammary tumors. There are multiple potential mechanisms involved in alcohol-stimulated progression and aggressiveness of breast cancer. Alcohol may increase the mobility of cancer cells by inducing cytoskeleton reorganization and enhancing the cancer cell invasion by causing degradation and reconstruction of the extracellular matrix (ECM). Moreover, alcohol may promote the epithelial-mesenchymal transition (EMT), a hallmark of malignancy, and impair endothelial integrity, thereby increasing the dissemination of breast cancer cells and facilitating metastasis. Furthermore, alcohol may stimulate tumor angiogenesis through the activation of cytokines and chemokines which promotes tumor growth. Additionally, alcohol may increase the cancer stem cell population which affects neoplastic cell behavior, aggressiveness, and the therapeutic response. Alcohol can be metabolized in the mammary tissues and breast cancer cells which produces reactive oxygen species (ROS), causing oxidative stress. Recent studies suggest that the epidermal growth factor receptor (EGFR) family, particularly ErbB2 (a member of this family), is involved in alcohol-mediated tumor promotion. Breast cancer cells or mammary epithelial cells over-expressing ErbB2 are more sensitive to alcohol's tumor promoting effects. There is considerable cross-talk between oxidative stress and EGFR/ErbB2 signaling. This review further discusses how the interaction between oxidative stress and EGFR/ErbB2 signaling contributes to the cellular and molecular events associated with breast cancer aggressiveness. We also discuss the potential therapeutic approaches for cancer patients who drink alcoholic beverages.

Paris saponin VII suppresses osteosarcoma cell migration and invasion by inhibiting MMP‑2/9 production via the p38 MAPK signaling pathway

Metastasis is the primary cause of mortality in osteosarcoma. Targeting metastasis is a major strategy in osteosarcoma treatment. As a traditional Chinese medicine, Trillium tschonoskii Maxim has been widely used in the therapy of various diseases, including cancer. However, currently there is no evidence regarding the anti‑metastasic effect of Paris saponin VII (PS VII), which is extracted from Trillium tschonoskii Maxim, on osteosarcoma cells and its underling mechanisms. The present study aimed to examine the effect of PS VII on the migration and invasion of osteosarcoma cells. Viability and proliferation of osteosarcoma cells were examined by MTT assay. Migration and invasion of osteosarcoma cells was then detected using scratch wound healing assays and Transwell assays, respectively. Additionally, the expression of matrix metalloproteinase (MMP)‑2 and ‑9 was determined at the mRNA and protein level following treatment with PS VII. Mitogen‑activated protein kinase (MAPK) expression was also detected by western blot analysis. Finally, an inhibitor of p38 MAPK was used to verify the effect of PS VII on the expression of MMP‑2 and ‑9, as well as the migration and invasion osteosarcoma cells. This demonstrated that the proliferation, migration and invasion of the osteosarcoma cells were suppressed following treatment with PS VII. PS VII downregulated the expression of MMP‑2 and ‑9 in a dose‑ and time‑dependent manner. PS VII also exerted its ability to downregulate the phosphorylation of p38 MAPKs. Furthermore, by using a p38 inhibitor, SB203580, the role of PS VII in MMP‑2 and ‑9 expression and osteosarcoma cell invasion was revealed. Taken together, these results demonstrated that PS VII suppresses the migration and invasion of osteosarcoma cells via the p38 MAPK signaling pathway.

Tumor cell expression of MMP3 as a prognostic factor for poor survival in pancreatic, pulmonary, and mammary carcinoma

Breast, lung, and pancreatic cancers collectively represent one third of all diagnosed tumors and are responsible for almost 40% of overall cancer mortality. Despite improvements in current treatments, efforts to develop more specific therapeutic options are warranted. Here we identify matrix metalloproteinase 3 (MMP3) as a potential target within all three of these tumor types. MMP3 has previously been shown to induce expression of Rac1b, a tumorigenic splice isoform of Rac1. In this study we find that MMP3 and Rac1b proteins are both strongly expressed by the tumor cells of all three tumor types and that expression of MMP3 protein is prognostic of poor survival in pancreatic cancer patients. We also find that MMP3 gene expression can serve as a prognostic marker for patient survival in breast and lung cancer. These results suggest an oncogenic MMP3-Rac1b signaling axis as a driver of tumor progression in three common poor prognosis tumor types, further suggesting that new therapies to target these pathways could have substantial therapeutic benefit.

Inhibition of metastasis and invasion of ovarian cancer cells by crude polysaccharides from rosa roxburghii tratt in vitro

BACKGROUND

Rosa Roxburghii Tratt is a promising wild fruit crop in Southwest China. Its extracts have been used as traditional Chinese medicine, which benefit immune responses and cure various health disorders. However, whether Rosa Roxburghii Tratt polysaccharides could inhibit metastasis and invasion of ovarian cancer cells remains unknown.

MATERIALS AND METHODS

Effects of crude polysaccharides from Rosa Roxburghii Tratt on the viability of ovarian cancer A2780 cells were detected by MTT assay. Ovarian carcinoma cell migration and invasion after exposure to Rosa Roxburghii Tratt polysaccharides were quantified by wound healing and Transwell assays, respectively. Western blotting was applied to assess protein levels of MMP-9.

RESULTS

The results indicated that Rosa Roxburghii Tratt polysaccharides significantly reduced wound closure rate of A2780 cells, inhibited their migration and invasion, and suppressed the expression of MMP-9.

CONCLUSIONS

Our findings indicated that Rosa Roxburghii Tratt polysaccharides have potential for develop as anti-metastatic cancer drug preparations for ovarian cancer patients.

Sanguinarine inhibits Rac1b-rendered cell survival enhancement by promoting apoptosis and blocking proliferation

AIM

Small GTPase Rac1 is a member of the Ras superfamily, which plays important roles in regulation of cytoskeleton reorganization, cell growth, proliferation, migration, etc. The aim of this study was to determine how a constitutively active Rac1b regulated cell proliferation and to investigate the effects of the Rac1b inhibitor sanguinarine.

METHODS

Three HEK293T cell lines stably overexpressing GFP, Rac1-GFP or Rac1b-GFP were constructed by lentiviral infection. The cells were treated with sanguinarine (1 μmol/L) or its analogue berberine (1 μmol/L) for 4 d. Cell proliferation was evaluated by counting cell numbers and with a BrdU incorporation assay. The levels of cleaved PARP-89 (an apoptosis marker) and cyclin-D1 (a proliferative index) were measured using Western blotting.

RESULTS

In 10% serum-containing media, overexpressing either Rac1 or Rac1b did not significantly change the cell proliferation. In the serum-starved media, however, the survival rate of Rac1b cells was significantly increased, whereas that of Rac1 cells was moderately increased. The level of cleaved PARP-89 was significantly increased in serum-starved Rac1 cells, but markedly reduced in serum-starved Rac1b cells. The level of cyclin-D1 was significantly increased in both serum-starved Rac1 and Rac1b cells. Treatment with sanguinarine, but not berberine, inhibited the proliferation of Rac1b cells, which was accompanied by significantly increased the level of PARP-89, and decreased both the level of cyclin-D1 and the percentage of BrdU positive cells.

CONCLUSION

Rac1b enhances the cell proliferation under a growth-limiting condition via both anti-apoptotic and pro-proliferative mechanisms. Sanguinarine, as the specific inhibitor of Rac1b, is a potential therapeutic agent for malignant tumors with up-regulated Rac1b.

CrkL regulates SDF-1-induced breast cancer biology through balancing Erk1/2 and PI3K/Akt pathways

The adapter protein CrkL is required for regulating the malignant potential of human cancers. However, the regulatory mechanisms of CrkL on the stromal cell-derived factor 1 (SDF-1)/CXCR4 signaling pathways in breast cancer are not well characterized. Here, CXCR4 and CrkL proteins were tested in breast cancer cell lines and 60 primary breast cancer tissues. In vitro, the roles of CrkL in SDF-1-induced MDA-MB-231 cell cycle, invasion and migration were investigated. In the present study, CXCR4 and CrkL were highly expressed in MCF-7, MDA-MB-231, MDA-MB-231HM MDA-MB-468 and tumor tissues (80 and 60 %, respectively) and closely correlated with lymph node metastasis. In vitro studies revealed that SDF-1 induced the activation of CrkL, Erk1/2, Akt and matrix metallopeptidase 9 (MMP9) in MDA-MB-231 cells. The si-CrkL treatment significantly down-regulated the phosphorylated Erk1/2 (p-Erk1/2) and MMP9, but up-regulated p-Akt, compared with control. Importantly, wound-healing and transwell invasion assays showed that si-CrkL significantly impaired the wound closure and inhibited the SDF-1-induced invasion; similarly, flow cytometry showed that si-CrkL affected cell cycle. In conclusion, these results suggest that CrkL plays a regulatory role in the SDF-1-induced Erk1/2 and PI3K/Akt pathways and further managed the invasion and migration of breast cancer cells. Thus, CrkL may be recommended as an interesting therapeutic target for breast cancer.

Prognostic value of MMP-9 in ovarian cancer: a meta-analysis

OBJECTIVE

Matrix metalloproteinase-9(MMP-9) plays an important role in tumor cell invasion. Although it has been studied frequently in ovarian cancer, its prognostic impact is still equivocal. The aim of this study was to more precisely estimate its prognostic significance.

METHOD

We searched Pubmed, Embase, OVID, Sciencedirect and CBM databases to identify eligible studies. Hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (95% CIs) were pooled across studies using fixed-effects or random-effects models. We also performed subgroup analysis.

RESULTS

30 studies (n=2552 patients) focusing on prognosis or expression of MM-9 were included. Increased expression of MMP-9 was associated with poor prognosis in ovarian cancer patients (HR=1.68, 95%CI 1.09-2.59, p=0.02). Besides, MMP-9 expression in ovarian cancer was significantly higher than non-malignant tumors (OR=11.46, 95%CI 8.47-15.50, P<0.00001). Moreover, increased expression of MMP-9 was significantly associated with FIGO stage (OR=4.85, 95%CI 2.60-9.04, P<0.00001), grade of differentiation (OR=3.34, 95%CI 2.46-4.54, P<0.00001), lymph node metastasis (OR=5.75, 95%CI 3.71-8.92, P<0.00001) and there was no association with histological type of ovarian cancer.

CONCLUSIONS

Increased expression of MMP- 9 was associated with poor prognosis in ovarian cancer patients. Down-regulation of MMP-9 is an attractive therapeutic approach which might improve outcome of ovarian cancer.

Clinical significance of serum COL6A3 in pancreatic ductal adenocarcinoma

Type VI collagen (COL6) forms a microfibrillar network often associated with type I collagen and constitutes a major component of the desmoplastic reaction in pancreatic ductal adenocarcinoma (PDA). We have demonstrated recently that the α3 chain of COL6, COL6A3, is highly expressed in PDA tissue and undergoes tumor-specific alternative splicing. In this study, we investigated the diagnostic value and clinical significance of circulating COL6A3 protein and mRNA in PDA. COL6A3 levels in sera from patients with PDA (n = 44), benign lesions (n = 46) and age-matched healthy volunteers (n = 30) were analyzed by enzyme-linked immunosorbent assays (ELISA). Predictive abilities of COL6A3 were examined using receiver operating characteristic (ROC) curves from logistic regression models for PDA versus normal or benign serum levels. Expression levels were correlated with clinicopathological parameters. Real-time PCR was used to analyze the presence of COL6A3 mRNA containing alternative spliced exons E3, E4, and E6. Circulating COL6A3 protein levels were significantly elevated in PDA patients when compared to healthy sera (p = 0.0001) and benign lesions (p = 0.0035). The overall area under the ROC was 0.975. Log(COL6A3) alone provided good discrimination between PDA and benign lesions (area under the curve (AUC) = 0.817), but combined with CA19-9 provided excellent discrimination (AUC = 0.904). Interestingly, high COL6A3 serum levels were significantly associated with perineural invasion and cigarette smoking. Combined E3, E4, and E6 serum RNA values provided good sensitivity but low specificity. Our data demonstrate for the first time the potential clinical significance of circulating COL6A3 in the diagnosis of pancreatic malignancy.

Development of EHop-016: a small molecule inhibitor of Rac

The Rac inhibitor EHop-016 was developed as a compound with the potential to inhibit cancer metastasis. Inhibition of the first step of metastasis, migration, is an important strategy for metastasis prevention. The small GTPase Rac acts as a pivotal binary switch that is turned "on" by guanine nucleotide exchange factors (GEFs) via a myriad of cell surface receptors, to regulate cancer cell migration, survival, and proliferation. Unlike the related GTPase Ras, Racs are not usually mutated, but overexpressed or overactivated in cancer. Therefore, a rational Rac inhibitor should block the activation of Rac by its upstream effectors, GEFs, and the Rac inhibitor NSC23766 was developed using this rationale. However, this compound is ineffective at inhibiting the elevated Rac activity of metastatic breast cancer cells. Therefore, a panel of small molecule compounds were derived from NSC23766 and screened for Rac activity inhibition in metastatic cancer cells. EHop-016 was identified as a compound that blocks the interaction of Rac with the GEF Vav in metastatic human breast cancer cells with an IC50 of ~1μM. At higher concentrations (10μM), EHop-016 inhibits the related Rho GTPase Cdc42, but not Rho, and also reduces cell viability. Moreover, EHop-016 inhibits the activation of the Rac downstream effector p21-activated kinase, extension of motile actin-based structures, and cell migration. Future goals are to develop EHop-016 as a therapeutic to inhibit cancer metastasis, either individually or in combination with current anticancer compounds. The next generation of EHop-016-based Rac inhibitors is also being developed.

RAC1b overexpression in papillary thyroid carcinoma: a role to unravel

CONTEXT

The BRAF V600E mutation is the most frequent genetic alteration in papillary thyroid carcinoma (PTC). In colorectal cancer, BRAF V600E was described to functionally cooperate with RAC1b, a hyperactive splice variant of the small GTPase RAC1, to sustain cell survival. This interplay has never been investigated in PTCs.

OBJECTIVE

We aimed to analyze the expression of RAC1b in PTC and correlate its expression with BRAF V600E mutational status, histopathological features, and clinical outcome.

PATIENTS AND METHODS

Sixty-one patients and 87 samples (61 PTCs and 26 normal thyroid tissues) were included. Patients were divided into two groups based on longitudinal evolution and final outcome. RAC1b expression levels were determined by quantitative RT-PCR and western blotting.

RESULTS

RAC1b was expressed in thyroid and overexpressed in 46% of PTCs. Neither RAC1b overexpression nor V600E mutation correlated with histopathological features classically associated with worse prognosis. RAC1b overexpression was significantly associated with both V600E mutation (P=0.0008) and poor clinical outcome (P=0.0029). Whereas BRAF V600E alone did not associate with patient outcome (P=0.2865), the association of RAC1b overexpression with BRAF V600E was overrepresented in the group with poorer clinical outcome (P=0.0044).

CONCLUSIONS

Present results document, for the first time, expression of RAC1b in normal thyroid cells as well as overexpression in a subset of PTCs. Furthermore, they suggest a possible interplay between BRAF V600E and RAC1b contributing to poor clinical outcome. Future studies are needed to clarify the oncogenic potential of RAC1b in thyroid carcinogenesis.

Analysis of constant tissue remodeling in Syrian hamster Harderian gland: intra-tubular and inter-tubular syncytial masses

The Syrian hamster Harderian gland (HG) has a marked sexual dimorphism and exhibits an extraordinary rate of porphyrinogenesis. The physiological oxidative stress, derived from constant porphyrin production, is so high that the HG needs additional survival autophagic mechanisms to fight against this chronic exposure, provoking the triggering of a holocrine secretion in female glands that forms two types of secretory masses: intra-tubular-syncytial and inter-tubular-syncytial masses. The aim of this work was to study the development of this inter-tubular holocrine secretion. To approach this task, we have considered that the steps developed during the formation of the so-called invasive masses consist of the growth of epithelial cells, cell detachment from the basal lamina and invasion of surrounding tissues. The presence of these masses, particularly in the female HG, are closely linked to sexual dimorphism in redox balance and to alterations in the expression of certain factors such as cytokeratins, P-cadherin, matrix metalloproteinases, cathepsin H, proliferating cell nuclear antigen, p53, CD-31 and vascular endothelial growth factor, which seem to be involved in tissue remodeling. The results document unusual mechanisms of secretion in Syrian hamster HG: an extraordinary system of massive secretion through the conjunctive tissue, disrupting the branched structure of the gland.

Matrix metalloproteinase induction of Rac1b, a key effector of lung cancer progression

Lung cancer is more deadly than colon, breast, and prostate cancers combined, and treatment improvements have failed to improve prognosis significantly. Here, we identify a critical mediator of lung cancer progression, Rac1b, a tumor-associated protein with cell-transforming properties that are linked to the matrix metalloproteinase (MMP)-induced epithelial-mesenchymal transition (EMT) in lung epithelial cells. We show that expression of mouse Rac1b in lung epithelial cells of transgenic mice stimulated EMT and spontaneous tumor development and that activation of EMT by MMP-induced expression of Rac1b gave rise to lung adenocarcinoma in the transgenic mice through bypassing oncogene-induced senescence. Rac1b is expressed abundantly in stages 1 and 2 of human lung adenocarcinomas and, hence, is an attractive molecular target for the development of new therapies that prevent progression to later-stage lung cancers.

Micro- and nanoscale engineering of cell signaling

It is increasingly recognized that cell signaling, as a chemical process, must be considered at the local, micrometer scale. Micro- and nanofabrication techniques provide access to these dimensions, with the potential to capture and manipulate the spatial complexity of intracellular signaling in experimental models. This review focuses on recent advances in adapting surface engineering for use with biomolecular systems that interface with cell signaling, particularly with respect to surfaces that interact with multiple receptor systems on individual cells. The utility of this conceptual and experimental approach is demonstrated in the context of epithelial cells and T lymphocytes, two systems whose ability to perform their physiological function is dramatically impacted by the convergence and balance of multiple signaling pathways.

Matrix metalloproteinase-9 expression correlates with prognosis and involved in ovarian cancer cell invasion

PURPOSE

One of the most important characteristics of ovarian cancer is invasion and metastasis. Matrix metalloproteinases (MMPs) are known to play an important role in cancer cell invasion by mediating the degradation of extracellular matrix (ECM). The activities of MMPs are regulated by tissue inhibitors of metalloproteinases (TIMPs). In this study, we investigated the clinical significance of MMP-2, -7 and -9 and TIMP-1, -2 and -3 expression and MMP-9 functional role in cell invasion and adhesion in ovarian cancer.

METHODS

RT-PCR was used to determine mRNA expression of MMP-2, -7 and -9 and TIMP-1, -2 and -3 in ovarian tissues; ELISA was used to detect the serum level of MMP-9; RNA interference (RNAi) was performed to determine the function of MMP-9 in cell invasion and adhesion in ovarian cancer cells.

RESULTS

mRNA expression of MMP-2, MMP-7, MMP-9, TIMP-2 and TIMP-3 and serum level of MMP-9 were significantly high in patients with ovarian cancer. MMP-9 expression was significantly high in patients with advanced ovarian cancer and correlated with poor prognosis. The ability of cells for invasion and adhesion was significantly reduced by treatment of cells with MMP-9 siRNA.

CONCLUSIONS

Our results suggest that MMP-9 is a potential prognostic factor for ovarian cancer and could be a novel treatment target in ovarian cancer patients.

Involvement of hnRNP A1 in the matrix metalloprotease-3-dependent regulation of Rac1 pre-mRNA splicing

Rac1b is an alternatively spliced isoform of the small GTPase Rac1 that includes the 57-nucleotide exon 3b. Rac1b was originally identified through its over-expression in breast and colorectal cancer cells, and has subsequently been implicated as a key player in a number of different oncogenic signaling pathways, including tumorigenic transformation of mammary epithelial cells exposed to matrix metalloproteinase-3 (MMP-3). Although many of the cellular consequences of Rac1b activity have been recently described, the molecular mechanism by which MMP-3 treatment leads to Rac1b induction has not been defined. Here we use proteomic methods to identify heterogeneous nuclear ribonucleoprotein (hnRNP) A1 as a factor involved in Rac1 splicing regulation. We find that hnRNP A1 binds to Rac1 exon 3b in mouse mammary epithelial cells, repressing its inclusion into mature mRNA. We also find that exposure of cells to MMP-3 leads to release of hnRNP A1 from exon 3b and the consequent generation of Rac1b. Finally, we analyze normal breast tissue and breast cancer biopsies, and identify an inverse correlation between expression of hnRNP A1 and Rac1b, suggesting the existence of this regulatory axis in vivo. These results provide new insights on how extracellular signals regulate alternative splicing, contributing to cellular transformation and development of breast cancer.

Characterization of EHop-016, novel small molecule inhibitor of Rac GTPase

The Rho GTPase Rac regulates actin cytoskeleton reorganization to form cell surface extensions (lamellipodia) required for cell migration/invasion during cancer metastasis. Rac hyperactivation and overexpression are associated with aggressive cancers; thus, interference of the interaction of Rac with its direct upstream activators, guanine nucleotide exchange factors (GEFs), is a viable strategy for inhibiting Rac activity. We synthesized EHop-016, a novel inhibitor of Rac activity, based on the structure of the established Rac/Rac GEF inhibitor NSC23766. Herein, we demonstrate that EHop-016 inhibits Rac activity in the MDA-MB-435 metastatic cancer cells that overexpress Rac and exhibits high endogenous Rac activity. The IC(50) of 1.1 μM for Rac inhibition by EHop-016 is ∼100-fold lower than for NSC23766. EHop-016 is specific for Rac1 and Rac3 at concentrations of ≤5 μM. At higher concentrations, EHop-016 inhibits the close homolog Cdc42. In MDA-MB-435 cells that demonstrate high active levels of the Rac GEF Vav2, EHop-016 inhibits the association of Vav2 with a nucleotide-free Rac1(G15A), which has a high affinity for activated GEFs. EHop-016 also inhibits the Rac activity of MDA-MB-231 metastatic breast cancer cells and reduces Rac-directed lamellipodia formation in both cell lines. EHop-016 decreases Rac downstream effects of PAK1 (p21-activated kinase 1) activity and directed migration of metastatic cancer cells. Moreover, at effective concentrations (<5 μM), EHop-016 does not affect the viability of transformed mammary epithelial cells (MCF-10A) and reduces viability of MDA-MB-435 cells by only 20%. Therefore, EHop-016 holds promise as a targeted therapeutic agent for the treatment of metastatic cancers with high Rac activity.

The tumor microenvironment: part 1

For years the mutated, highly proliferating neoplastic cells were presented as the only important agent in tumors; however, during the last 3–4 decades it has become clear that the microenvironment of the cancer cells plays a determinative role in the malignant evolution of neoplasia. Cancers are in fact heterogeneous entities containing, in addition to the neoplastic cell component, cells derived of multiple lineages (fibroblasts, endothelial cells lining blood and lymphatic vessels, pericytes, adipocytes and immune system cells belonging to both innate and adaptive responses), as well as the extracellular matrix, with a large variety of soluble molecules of biological importance, constituting a complex organ-like structure. The tumor microenvironment consists in a tissue that may have a predictive significance for tumor behavior and response to therapy.

What does matrix metalloproteinase-1 expression in patients with breast cancer really tell us?

Molecular and biochemical expressions of matrix metalloproteinases in breast cancer tissue and cells offers promise in helping us understand the breast cancer microenvironment, and also in the future it is hoped this will improve its detection, treatment and prognosis. In a retrospective study recently published in BMC Cancer, microenvironment predisposing to breast cancer progression, metastatic behavior and the expression of matrix metalloproteinase-1 (MMP-1) and its correlation with well-known biochemical, molecular and clinicopathologic factors in breast cancer cells and cancer-associated stromal cells was examined; this study also analyzed patient survival in different breast cancer subtypes. The positive correlation in breast tumor and stromal cells between MMP-1 expression and several markers of tumor grade and stage provide us with some useful new insights into important questions about the molecular profiling of the stromal microenvironment in metastatic breast cancer. The study showed that MMP-1 expression is strongly associated with poor clinical outcome, so now we look forward to future larger studies in breast cancer patients in which we can relate wider MMP molecular profiling to identify lethal tumor and stromal microenvironments predisposing to breast cancer progression, metastatic behavior and poor prognosis. Please see related article http://www.biomedcentral.com/1471-2407/11/348.

PPARgamma and Proline Oxidase in Cancer

Proline is metabolized by its own specialized enzymes with their own tissue and subcellular localizations and mechanisms of regulation. The central enzyme in this metabolic system is proline oxidase, a flavin adenine dinucleotide-containing enzyme which is tightly bound to mitochondrial inner membranes. The electrons from proline can be used to generate ATP or can directly reduce oxygen to form superoxide. Although proline may be derived from the diet and biosynthesized endogenously, an important source in the microenvironment is from degradation of extracellular matrix by matrix metalloproteinases. Previous studies showed that proline oxidase is a p53-induced gene and its overexpression can initiate proline-dependent apoptosis by both intrinsic and extrinsic pathways. Another important factor regulating proline oxidase is peroxisome proliferator activated receptor gamma (PPARγ). Importantly, in several cancer cells, proline oxidase may be an important mediator of the PPARγ-stimulated generation of ROS and induction of apoptosis. Knockdown of proline oxidase expression by antisense RNA markedly decreased these PPARγ-stimulated effects. These findings suggest an important role in the proposed antitumor effects of PPARγ. Moreover, it is possible that proline oxidase may contribute to the other metabolic effects of PPARγ.

BMP-6 inhibits MMP-9 expression by regulating heme oxygenase-1 in MCF-7 breast cancer cells

PURPOSE

BMP-6, which belongs to the TGF-β superfamily, is a multifunctional molecule with distinct abilities in embryogenesis and organogenesis. Our recent research has implied that BMP-6 may suppress breast cancer metastasis. In the present study, we extended to elucidate the molecular mechanism by which BMP-6 exerts its anti-tumorigenic effect.

METHODS

The Boyden chamber assay was used to examine the ability of BMP-6 and HO-1 in MCF-7 malignant progress. RT-PCR, western blot, luciferase assay, and quantitative CHIP were used to determine the potential mechanism and signaling pathways by which BMP-6 and HO-1 function as anti-metastatic factors in MCF-7 cells.

RESULTS

The Boyden chamber assay showed that BMP-6 inhibited the migration and invasion of MCF-7 cells, which effect was significantly deprived by knockdown of HO-1. We further demonstrated that BMP-6 treatment resulted in an activation of HO-1 transcription through the recruitment of Smad1/5 to the Smad-responsive element on its promoter. In addition, BMP-6-induced up-regulation of HO-1 exhibited an inhibitory effect on MMP-9 secretion in a paracrine action in MCF-7 cells. Overexpression of BMP-6 and HO-1 synergistically suppressed MMP-9 transcription, which effect was specifically mediated via the MAPK/p38/AP-1 signaling. However, blockade of HO-1 using ZnPPIX totally abolished BMP-6-regulated MMP-9 activation in MCF-7 cells.

CONCLUSIONS

These observations suggest a novel role of BMP-6/HO-1 cascade to relieve breast cancer metastasis by regulating the secretion of growth factors in tumor microenvironment.

The 19-amino acid insertion in the tumor-associated splice isoform Rac1b confers specific binding to p120 catenin

The Rac1b splice isoform contains a 19-amino acid insertion not found in Rac1; this insertion leads to decreased GTPase activity and reduced affinity for GDP, resulting in the intracellular predominance of GTP-bound Rac1b. Here, using co-precipitation and proteomic methods, we find that Rac1b does not bind to many common regulators of Rho family GTPases but that it does display enhanced binding to SmgGDS, RACK1, and p120 catenin (p120(ctn)), proteins involved in cell-cell adhesion, motility, and transcriptional regulation. We use molecular modeling and structure analysis approaches to determine that the interaction between Rac1b and p120(ctn) is dependent upon protein regions that are predicted to be unstructured in the absence of molecular complex formation, suggesting that the interaction between these two proteins involves coupled folding and binding. We also find that directed cell movement initiated by Rac1b is dependent upon p120. These results define a distinct binding functionality of Rac1b and provide insight into how the distinct phenotypic program activated by this protein may be implemented through molecular recognition of effectors distinct from those of Rac1.

A cell active chemical GEF inhibitor selectively targets the Trio/RhoG/Rac1 signaling pathway

RhoGEFs (guanine nucleotide exchange factors of the Rho GTPase family) are upstream regulators of cell adhesion and migration pathways, thus representing attractive yet relatively unexplored targets for the development of anti-invasive drugs. We screened for chemical inhibitors of TrioN, the N-terminal GEF domain of the multidomain Trio protein, and identified ITX3 as a nontoxic inhibitor. In transfected mammalian cells, ITX3 blocked TrioN-mediated dorsal membrane ruffling and Rac1 activation while having no effect on GEF337-, Tiam1-, or Vav2-mediated RhoA or Rac1 activation. ITX3 specifically inhibited endogenous TrioN activity, as evidenced by its ability to inhibit neurite outgrowth in nerve growth factor (NGF)-stimulated PC12 cells or C2C12 differentiation into myotubes. This study introduces a selective cell active inhibitor of the Trio/RhoG/Rac1 pathway and validates RhoGEFs as druggable targets.

Type IV collagen is a tumour stroma-derived biomarker for pancreas cancer

BACKGROUND

Pancreas cancer is a dreaded disease with high mortality, despite progress in surgical and oncological treatments in recent years. The field is hampered by a lack of good prognostic and predictive tumour biomarkers to be used during follow-up of patients.

METHODS

The circulating level of type IV collagen was measured by ELISA in pancreas cancer patients and controls. The expression pattern of type IV collagen in normal pancreas, pancreas cancer tissue and in pancreas cancer cell lines was studied by immunofluorescence and Western blot techniques.

RESULTS

Patients with pancreas cancer have significantly increased circulating levels of type IV collagen. In pancreas cancer tissue high levels of type IV collagen expression was found in close proximity to cancer cells in the tumour stroma. Furthermore, pancreas cancer cells were found to produce and secrete type IV collagen in vitro, which in part can explain the high type IV collagen expression observed in pancreas cancer tissue, and the increased circulating levels in pancreas cancer patients. Of clinical importance, our results show that the circulating level of type IV collagen after surgery is strongly related to prognosis in patients treated for pancreas cancer by pancreatico-duodenectomy with curative intent. Persisting high levels of circulating type IV collagen after surgery indicates a quick relapse in disease and poor survival.

CONCLUSION

Our results most importantly show that stroma related substances can be evaluated as potential cancer biomarkers, and thereby underline the importance of the tumour microenvironment also in this context.

Change in cell shape is required for matrix metalloproteinase-induced epithelial-mesenchymal transition of mammary epithelial cells

Cell morphology dictates response to a wide variety of stimuli, controlling cell metabolism, differentiation, proliferation, and death. Epithelial-mesenchymal transition (EMT) is a developmental process in which epithelial cells acquire migratory characteristics, and in the process convert from a "cuboidal" epithelial structure into an elongated mesenchymal shape. We had shown previously that matrix metalloproteinase-3 (MMP3) can stimulate EMT of cultured mouse mammary epithelial cells through a process that involves increased expression of Rac1b, a protein that stimulates alterations in cytoskeletal structure. We show here that cells treated with MMP-3 or induced to express Rac1b spread to cover a larger surface, and that this induction of cell spreading is a requirement of MMP-3/Rac1b-induced EMT. We find that limiting cell spreading, either by increasing cell density or by culturing cells on precisely defined micropatterned substrata, blocks expression of characteristic markers of EMT in cells treated with MMP-3. These effects are not caused by general disruptions in cell signaling pathways, as TGF-beta-induced EMT is not affected by similar limitations on cell spreading. Our data reveal a previously unanticipated cell shape-dependent mechanism that controls this key phenotypic alteration and provide insight into the distinct mechanisms activated by different EMT-inducing agents.

The metabolism of proline as microenvironmental stress substrate

Proline, a unique proteogenic secondary amino acid, has its own metabolic system with special features. Recent findings defining the regulation of this system led us to propose that proline is a stress substrate in the microenvironment of inflammation and tumorigenesis. The criteria for proline as a stress substrate are: 1) the enzymes utilizing proline respond to stress signaling; 2) there is a large, mobilizable pool of proline; and 3) the metabolism of proline serves special stress functions. Studies show that the proline-utilizing enzyme, proline oxidase (POX)/proline dehydrogenase (PRODH), responds to genotoxic, inflammatory, and nutrient stress. Proline as substrate is stored as collagen in extracellular matrix, connective tissue, and bone and it is rapidly released from this reservoir by the sequential action of matrix metalloproteinases, peptidases, and prolidase. Special functions include the use of proline by POX/PRODH to generate superoxide radicals that initiate apoptosis by intrinsic and extrinsic pathways. Under conditions of nutrient stress, proline is an energy source. It provides carbons for the tricarboxylic acid cycle and also participates in the proline cycle. The latter, catalyzed by mitochondrial POX and cytosolic pyrroline-5-carboxylate reductase, shuttles reducing potential from the pentose phosphate pathway into mitochondria to generate ATP and oxidizing potential to activate the cytosolic pentose phosphate pathway.

A novel anticancer effect of butein: inhibition of invasion through the ERK1/2 and NF-kappa B signaling pathways in bladder cancer cells

There is increasing evidence that epithelial-mesenchymal transition (EMT) plays a critical role in cancer metastasis. Butein is a polyphenolic compound, which has been found to exhibit anti-proliferation effects on cancer cells. Here, we report that in addition to its function as an anti-proliferation agent, butein can inhibit migration and invasion through the ERK1/2 and NF-kappaB signaling pathways in human bladder cancer cells, and this inhibitory effect may be associated with reversal of EMT. These results were further confirmed by RNAi-mediated suppression of NF-kappaB, which partly reverses EMT and inhibits cell invasive ability in vitro. These results suggest a novel function of butein as an invasion inhibitor in bladder cancer.

The metabolism of proline, a stress substrate, modulates carcinogenic pathways

The resurgence of interest in tumor metabolism has led investigators to emphasize the metabolism of proline as a "stress substrate" and to suggest this pathway as a potential anti-tumor target. Proline oxidase, a.k.a. proline dehydrogenase (POX/PRODH), catalyzes the first step in proline degradation and uses proline to generate ATP for survival or reactive oxygen species for programmed cell death. POX/PRODH is induced by p53 under genotoxic stress and initiates apoptosis by both mitochondrial and death receptor pathways. Furthermore, POX/PRODH is induced by PPARgamma and its pharmacologic ligands, the thiazolidinediones. The anti-tumor effects of PPARgamma may be critically dependent on POX/PRODH. In addition, it is upregulated by nutrient stress through the mTOR pathway to maintain ATP levels. We propose that proline is made available as a stress substrate by the degradation of collagen in the microenvironmental extracellular matrix by matrix metalloproteinases. In a manner analogous to autophagy, this proline-dependent process for bioenergetics from collagen in extracellular matrix can be designated "ecophagy".

Possible role of NFkappaB in the embryonic vascular remodeling and the endothelial mesenchymal transition process

The NFkappaB family of transcription factors, particularly the activated p50/p65 heterodimer, is expressed in vascular cells during intimal thickening formation when hemodynamic conditions are altered. Here, we report that p50, p65, IkappaBalpha and IKKalpha display different spatial and temporal patterns of expression and distribution during both chicken embryo aortic wall remodeling and intimal thickening development. Additionally, we show that both p50 and p65 were located in the nucleus of some mesenchymal cells expressing alpha-smooth muscle actin which are present in the spontaneous intimal thickening observed at embryonic days 12-14 of development. We also demonstrated that both NFkappaB subunits are present in monolayers of primary embryonic aortic endothelial cells attached to fibronectin and stimulated with complete medium. This study demonstrates for the first time the presence of activated NFkappaB during the remodeling of the embryonic aortic wall and the formation of intimal thickening, providing evidence that suggest a possible role for this transcription factor in the EndoMT process.

Laminin-332-integrin interaction: a target for cancer therapy?

For many years, extracellular matrix (ECM) was considered to function as a tissue support and filler. However, we now know that ECM proteins control many cellular events through their interaction with cell-surface receptors and cytoplasmic signaling pathways. For example, they regulate cell proliferation, cell division, cell adhesion, cell migration, and apoptosis. We focus in this review on a laminin isoform, laminin-332 (formerly termed laminin-5), a major component of the basement membrane (BM) of skin and other epithelial tissues. It is composed of 3 subunits (alpha3beta3 and gamma3 and interacts with at least two integrin receptors expressed by epithelial cells (alpha3beta1 and alpha6beta4 integrin. Mutations in either laminin-332 or integrin alpha6beta4 result in junctional epidermolysis bullosa, a blistering skin disease, while targeting of laminin-332 by autoantibodies in cicatricial pemphigoid leads to dysadhesion of epithelial cells from their underlying connective tissue. Abnormal expression of laminin-332 and its integrin receptors is also a hallmark of certain tumor types and is believed to promote invasion of colon, breast and skin cancer cells. Moreover, there is emerging evidence that laminin-332 and its protease degradation products are not only found at the leading front of several tumors but also likely induce and/or promote tumor cell migration. Thus, in this review, we focus specifically on the role of laminin-332 and its integrin receptors in adhesion, proliferation, and migration/invasion of cancer cells. Finally, we discuss strategies for the development of laminin-332-based antagonists for the treatment of malignant tumors.