Tumor cell invasion of von Hippel Lindau renal cell carcinoma cells is mediated by membrane type-1 matrix metalloproteinase

Preliminary Study of Whole-Genome Bisulfite Sequencing and Transcriptome Sequencing in VHL Disease-Associated ccRCC

BACKGROUND

Von Hippel-Lindau (VHL) disease is an autosomal dominant hereditary tumor syndrome with an incidence of approximately 1/36,000. VHL disease-associated clear cell renal cell carcinoma (ccRCC) is the most common congenital RCC. Although recent advances in treating RCC have improved the long-term prognosis of patients with VHL disease, kidney cancer is still the leading cause of death in these patients. Therefore, finding new targets for diagnosing and treating VHL disease-associated ccRCC is still essential.

METHODS

In this study, we collected matched tumor tissues and normal samples from 25 patients with VHL disease-associated ccRCC, diagnosed and surgically treated in the Department of Urology, Peking University First Hospital. After screening, we performed whole genome bisulfite sequencing (WGBS) on 23 pairs of tissues and RNA-seq on 6 pairs of tissues. And we also compared the VHL disease-associated ccRCC transcriptome data with the sporadic ccRCC transcriptome data from the The Cancer Genome Atlas (TCGA) public database RESULTS: We found that the methylation level of VHL disease-associated ccRCC tumor tissues was significantly lower than that of normal tissues. The tumor tissues showed a difference in the copy number of 3p loss and 5q and 7q gain compared with normal tissues. We integrated RNA-seq and WGBS data to reveal methylation candidate genes associated with VHL disease-associated ccRCC; our results showed 124 hypermethylated and downregulated genes, and 245 hypomethylated and upregulated genes. By comparing the VHL disease-associated ccRCC transcriptome data with the sporadic ccRCC transcriptome data from the TCGA public database, we found that the major pathways of differential gene enrichment differed between them.

CONCLUSIONS

Our study mapped the multiomics of copy number variation, methylation and mRNA level changes in tumor and normal tissues of clear cell renal cell carcinoma with VHL syndrome, which provides a solid foundation for the mechanistic study, biomarker screening, and therapeutic target discovery of clear cell renal cell carcinoma.

Downstream Targets of VHL/HIF-α Signaling in Renal Clear Cell Carcinoma Progression: Mechanisms and Therapeutic Relevance

The clear cell variant of renal cell carcinoma (ccRCC) is the most common renal epithelial malignancy and responsible for most of the deaths from kidney cancer. Patients carrying inactivating mutations in the Von Hippel-Lindau (VHL) gene have an increased proclivity to develop several types of tumors including ccRCC. Normally, the Hypoxia Inducible Factor alpha (HIF-α) subunits of the HIF heterodimeric transcription factor complex are regulated by oxygen-dependent prolyl-hydroxylation, VHL-mediated ubiquitination and proteasomal degradation. Loss of pVHL function results in elevated levels of HIF-α due to increased stability, leading to RCC progression. While HIF-1α acts as a tumor suppressor, HIF-2α promotes oncogenic potential by driving tumor progression and metastasis through activation of hypoxia-sensitive signaling pathways and overexpression of HIF-2α target genes. One strategy to suppress ccRCC aggressiveness is directed at inhibition of HIF-2α and the associated molecular pathways leading to cell proliferation, angiogenesis, and metastasis. Indeed, clinical and pre-clinical data demonstrated the effectiveness of HIF-2α targeted therapy in attenuating ccRCC progression. This review focuses on the signaling pathways and the involved genes (cyclin D, c-Myc, VEGF-a, EGFR, TGF-α, GLUT-1) that confer oncogenic potential downstream of the VHL-HIF-2α signaling axis in ccRCC. Discussed as well are current treatment options (including receptor tyrosine kinase inhibitors such as sunitinib), the medical challenges (high prevalence of metastasis at the time of diagnosis, refractory nature of advanced disease to current treatment options), scientific challenges and future directions.

The emerging roles of circRNAs in cancer and oncology

Over the past decade, circular RNAs (circRNAs) have emerged as a large class of primarily non-coding RNA molecules, many of which have key roles in cancer development and progression through diverse mechanisms of action. CircRNAs often have tissue-restricted and cancer-specific expression patterns, and accumulating data suggest that these molecules are of potential clinical relevance and utility. In particular, circRNAs have strong potential as diagnostic, prognostic and predictive biomarkers, which is underscored by their detectability in liquid biopsy samples such as in plasma, saliva and urine. However, technical issues in the detection and assessment of circRNAs as well as biological knowledge gaps need to be addressed to move this relatively young field of research forward and bring circRNAs to the forefront of clinical practice. Herein, we review the current knowledge regarding circRNA biogenesis, regulation and functions in cancer as well as their clinical potential as biomarkers, therapeutic agents and drug targets.

Qualitative and Quantitative Analysis of Tumor Cell Invasion Using Au Clusters

Tumor invasion/metastasis is still the major cause of death in cancer patients. Membrane type-1 matrix metalloproteinase (MT1-MMP) is directly related to tumor invasion/metastasis. To accurately and quickly distinguish the risk of invasion/metastasis of primary tumor cells, it is urgent to develop a simple and precise quantitative method to distinguish the expression level of MT1-MMP. In this work, we have constructed red fluorescent Au clusters with peroxidase-like properties that could specifically bind to MT1-MMP on human cervical cancer cells. After MT1-MMP was labelled with Au clusters, we could visually see red fluorescence of MT1-MMP on cervical cancer cells via fluorescence microscopy and catalytic color imaging using an ordinary optical microscope. The constructed Au clusters contained 26 Au atoms; thus, the amount of MT1-MMP on cervical cancer cells could be accurately quantified using inductively coupled plasma mass spectrometry (ICP-MS). More importantly, the invasion/metastasis capabilities of the cervical cancer Siha, Caski and Hela cells with different MT1-MMP amounts could be accurately distinguished by fluorescence/catalysis qualitative imaging and ICP-MS quantitative analysis. This method of qualitative/quantitative analysis of tumor-associated proteins on cancer cells has great potential for accurately diagnosing aggressive tumor cells and assessment of their invasion/metastasis risk.

Impact of inflammation and immunotherapy in renal cell carcinoma

Substantial research attention has been directed at exploring the mechanisms and treatment of renal cell carcinoma (RCC). Indeed, the association between inflammation and tumor phenotypes has been at the center of cancer research. Concomitant with research on the inflammation response and inflammatory molecules involved in RCC, new breakthroughs have emerged. A large body of knowledge now shows that treatments targeting inflammation and immunity in RCC provide substantial clinical benefits. Adequate analysis and a better understanding of the mechanisms of inflammatory factors in the occurrence and progression of RCC are highly desirable. Currently, numerous RCC treatments targeted at inflammation and immunotherapy are available. The current review describes in detail the link between inflammation and RCC.

circPTCH1 promotes invasion and metastasis in renal cell carcinoma via regulating miR-485-5p/MMP14 axis

Background: Circular RNAs (circRNAs) are a new class of non-coding RNAs (ncRNAs) that are derived from exons or introns by special selective shearing. circRNAs have been shown to play critical roles in various human cancers. However, their roles in renal cell carcinoma (RCC) and the underlying mechanisms remain largely unknown.

Methods: A novel circRNA-circPTCH1, was identified from a microarray analysis of five paired RCC tissues. Then, we validated its expression and characterization through qRT-PCR, gel electrophoresis, RNase R digestion assays and Sanger sequencing. Functional experiments were performed to determine the effect of circPTCH1 on RCC progression both in vitro and in vivo. The interactions between circPTCH1 and miR-485-5p were clarified by RNA pull-down, luciferase reporter and RNA immunoprecipitation (RIP) assays.

Results: We observed that circPTCH1 was up-regulated in RCC cell lines and tumor samples, and higher levels of circPTCH1 were significantly correlated with worse patient survival, advanced Fuhrman grade and greater risk of metastases. Elevated circPTCH1 expression led to increased migration and invasion of RCC cells both in vitro and in vivo whereas silencing circPTCH1 decreased migration and invasion and impeded the epithelial-mesenchymal transition (EMT) of RCC cells. Mechanistically, we elucidated that circPTCH1 could directly bind miR-485-5p and subsequently suppress expression of the target gene MMP14.

Conclusion: circPTCH1 promotes RCC metastasis via the miR-485-5p/MMP14 axis and activation of the EMT process. Targeting circPTCH1 may represent a promising therapeutic strategy for metastatic RCC.

Translocating a High-Affinity Designer TIMP-1 to the Cell Membrane for Total Renal Carcinoma Inhibition: Putting the Prion Protein to Good Use

Membrane type 1-matrix metalloproteinase (MT1-MMP) and tumor necrosis factor α (TNF-α)-converting enzyme (TACE) are prominent membrane-anchored metalloproteinases that regulate the turnover of extracellular matrix (ECM) components and bioactive molecules required for cancer proliferation. In this study, we describe a novel approach that would allow tissue inhibitor of metalloproteinase 1 (TIMP-1), the endogenous inhibitor of the matrix metalloproteinases (MMPs), to be translocated to the cell membrane for simultaneous MT1-MMP/TACE inhibition. We achieve this by fusing T1^TACE, a designer TIMP-1 with superb affinities for MT1-MMP and TACE, to the glycosyl-phosphatidyl inositol anchor of prions to create a membrane-tethered, broad-spectrum inhibitor, named T1^{Pr αTACE}, that colocalizes with MT1-MMP and TACE on the cell surface. Transduction of T1^{Pr αTACE} in human fibrosarcoma cells results not only in a substantial reduction in gelatinolytic and TNF-α/heparin binding epithelial growth factor shedding activities but also in a loss of tubulogenic capability in three-dimensional matrices. In renal carcinoma, T1^{Pr αTACE} triggers cellular senescence and disrupts MMP-mediated proteolysis of ECM components such as fibronectin and collagen I, leading to an impairment in cell motility and survival under both in vitro and in vivo conditions. Taken together, our findings may provide a new perspective in TIMP targeting that could be exploited to halt metastatic renal carcinoma progression.

MT1-MMP-dependent cell migration: proteolytic and non-proteolytic mechanisms

Membrane-type 1 matrix metalloproteinase (MT1-MMP) is a type I transmembrane proteinase that belongs to the matrix metalloproteinase (MMP) family. It is a potent modifier of cellular microenvironment and promotes cell migration and invasion of a wide variety of cell types both in physiological and pathological conditions. It promotes cell migration by degrading extracellular matrix on the cell surface and creates a migration path, by modifying cell adhesion property by shedding cell adhesion molecules to increase cell motility, and by altering cellular metabolism. Thus, MT1-MMP is a multifunctional cell motility enhancer. In this review, we will discuss the current understanding of the proteolytic and non-proteolytic mechanism of MT1-MMP-dependent cell migration.

Targeting a Designer TIMP-1 to the Cell Surface for Effective MT1-MMP Inhibition: A Potential Role for the Prion Protein in Renal Carcinoma Therapy

Renal carcinoma cells express Membrane Type 1-Matrix Metalloproteinase (MT1-MMP, MMP-14) to degrade extracellular matrix components and a range of bioactive molecules to allow metastasis and cell proliferation. The activity of MT1-MMP is modulated by the endogenous inhibitors, Tissue Inhibitor of Metalloproteinases (TIMPs). In this study, we describe a novel strategy that would enable a "designer" TIMP-1 tailored specifically for MT1-MMP inhibition (V4A/P6V/T98L; K_i^app 1.66 nM) to be targeted to the plasma membrane for more effective MT1-MMP inhibition. To achieve this, we fuse the designer TIMP-1 to the glycosyl-phosphatidyl inositol (GPI) anchor of the prion protein to create a membrane-tethered, high-affinity TIMP variant named "T1^{Pr αMT1}" that is predominantly located on the cell surface and co-localised with MT1-MMP. Confocal microscopy shows that T1^{Pr αMT1} is found throughout the cell surface in particular the membrane ruffles where MT1-MMP is most abundant. Expression of T1^{Pr αMT1} brings about a complete abrogation of the gelatinolytic activity of cellular MT1-MMP in HT1080 fibrosarcoma cells whilst in renal carcinoma cells CaKi-1, the GPI-TIMP causes a disruption in MMP-mediated proteolysis of ECM components such as fibronectin, collagen I and laminin that consequently triggers a downstream senescence response. Moreover, the transduced cells also suffer from an impairment in proliferation and survival in vitro as well as in NOD/SCID mouse xenograft. Taken together, our findings demonstrate that the GPI anchor of prion could be exploited as a targeting device in TIMP engineering for MT1-MMP inhibition with a potential in renal carcinoma therapy.

The Precise Diagnosis of Cancer Invasion/Metastasis via 2D Laser Ablation Mass Mapping of Metalloproteinase in Primary Cancer Tissue

Cancer invasion and metastasis remain the major causes of over 90% of patient deaths. Molecular imaging methods such as computed tomography (CT)/magnetic resonance imaging (MRI) can precisely assess primary regional lymph node invasion and distant organ metastasis via body scanning; however, such diagnostic methods are often utilized too late for cancer therapy. To date, pathologic methods mainly provide information on differentiation/proliferation and potential drug therapy biomarkers of primary tumors rather than precisely reveal tumor regional invasion and distant metastasis in the body. We hypothesized that quantification of membrane type-1 matrix metalloproteinase (MT1-MMP) levels in primary tumor tissue will provide a precise assessment of tumor regional lymph node invasion and remote organ metastasis. In this work, we developed peptide-coated Au clusters with intrinsic red fluorescence and a specific mass signal. When these clusters labeled MT1-MMP in tumor tissue sections derived from the xenograft lung carcinoma model, human lung carcinoma and human renal carcinoma, we could directly observe MT1-MMP via optical fluorescence microscopy and quantitatively detect the MT1-MMP expression level via laser ablation inductively coupled plasma mass spectrometry 2D mapping (2D-LA-Mass Mapping). By observing and quantifying the MT1-MMP expression level in primary human lung carcinoma and human renal carcinoma tissue sections, we precisely assessed the risk of primary tumor invasion/metastasis. Importantly, the accuracy of this pathologic method was verified by CT/MRI molecular imaging of cancer patients and traditional hematoxylin and eosin (H&E) staining/immunohistochemistry (IHC)/immunofluorescence (IF) pathologic studies of primary tumor tissues.

Membrane-type matrix metalloproteinases: Their functions and regulations

Membrane-type matrix metalloproteinases (MT-MMPs) form a subgroup of the matrix metalloproteinase (MMP) family, and there are 6 MT-MMPs in humans. MT-MMPs are further sub-classified into type I transmembrane-type (MT1, -MT2-, MT3- and MT5-MMPs) and glycosylphosphatidylinositol (GPI)-anchored type (MT4- and MT6-MMPs). In either case MT-MMPs are tethered to the plasma membrane, and this cell surface expression provides those enzymes with unique functionalities affecting various cellular behaviours. Among the 6 MT-MMPs, MT1-MMP is the most investigated enzyme and many of its roles and regulations have been revealed to date, but the potential roles and regulatory mechanisms of other MT-MMPs are gradually getting clearer as well. Further investigations of MT-MMPs are likely to reveal novel pathophysiological mechanisms and potential therapeutic strategies for different diseases in the future.

VHL, the story of a tumour suppressor gene

Since the Von Hippel-Lindau (VHL) disease tumour suppressor gene VHL was identified in 1993 as the genetic basis for a rare disorder, it has proved to be of wide medical and scientific interest. VHL tumour suppressor protein (pVHL) plays a key part in cellular oxygen sensing by targeting hypoxia-inducible factors for ubiquitylation and proteasomal degradation. Early inactivation of VHL is commonly seen in clear-cell renal cell carcinoma (ccRCC), and insights gained from the functional analysis of pVHL have provided the foundation for the routine treatment of advanced-stage ccRCC with novel targeted therapies. However, recent sequencing studies have identified additional driver genes that are involved in the pathogenesis of ccRCC. As our understanding of the importance of VHL matures, it is timely to review progress from its initial description to current knowledge of VHL biology, as well as future prospects for novel medical treatments for VHL disease and ccRCC.

Differential proliferative index of cancer stem-like cells in primary and recurrent medulloblastoma in human

PURPOSE

Medulloblastoma is the most common malignant primitive neuroectodermal tumor found in children. It has a tendency to recur at a primary or distant site. The mechanism underlying the regulation of the recurrence of medulloblastoma remains largely unknown. Recently, several reports have described that cancer stem-like cells (CSCs) can be identified and isolated in medulloblastoma. The authors therefore attempted to demonstrate the correlation between the biological features of medulloblastoma's CSCs and its recurrence.

METHODS

The data used were obtained in five consecutive patients with medulloblastomas who subsequently experienced tumor recurrence from 2004 to 2007. The authors performed the immunohistochemical assays to analyze the expression of CSC markers, proliferation features, and proliferative status of CSCs in primary and recurrent medulloblastoma.

RESULTS

Of the five patients, two had recurrence at the primary site and three had a distant recurrence. CSC markers such as CD133(Prominin-1), DCX, PSA-NCAM, TUC-4, and nestin were expressed regardless of primary or recurrent medulloblastoma. All the five tumor specimens had a high proliferation index (PI). The PI was even higher in the group of patients after recurrence at a distant site (p<0.05), while the PI remained almost the same after primary recurrence. The Ki67/nestin-, Ki67/DCX-, and Ki67/TUC-4-positive cells were significantly increased in recurrent medulloblastoma at both the primary and distant sites, whereas CSCs in primary medulloblastoma showed much lower proliferative features (p<0.05).

CONCLUSIONS

Our data suggest that tumorigenesis of medulloblastomas and their recurrence might be related to CSCs. More proliferating CSCs in medulloblastomas denote worse prognosis.

State of the science: an update on renal cell carcinoma

Renal cell carcinomas (RCC) are emerging as a complex set of diseases that are having a major socioeconomic impact and showing a continued rise in incidence throughout the world. As the field of urologic oncology faces these trends, several major genomic and mechanistic discoveries are altering our core understanding of this multitude of cancers, including several new rare subtypes of renal cancers. In this review, these new findings are examined and placed in the context of the well-established association of clear cell RCC (ccRCC) with mutations in the von Hippel-Lindau (VHL) gene and resultant aberrant hypoxia inducible factor (HIF) signaling. The impact of novel ccRCC-associated genetic lesions on chromatin remodeling and epigenetic regulation is explored. The effects of VHL mutation on primary ciliary function, extracellular matrix homeostasis, and tumor metabolism are discussed. Studies of VHL proteostasis, with the goal of harnessing the proteostatic machinery to refunctionalize mutant VHL, are reviewed. Translational efforts using molecular tools to elucidate discriminating features of ccRCC tumors and develop improved prognostic and predictive algorithms are presented, and new therapeutics arising from the earliest molecular discoveries in ccRCC are summarized. By creating an integrated review of the key genomic and molecular biological disease characteristics of ccRCC and placing these data in the context of the evolving therapeutic landscape, we intend to facilitate interaction among basic, translational, and clinical researchers involved in the treatment of this devastating disease, and accelerate progress toward its ultimate eradication.

Interleukin-1β mediates metalloproteinase-dependent renal cell carcinoma tumor cell invasion through the activation of CCAAT enhancer binding protein β

Effective treatment of metastatic renal cell carcinoma (RCC) remains a major medical concern, as these tumors are refractory to standard therapies and prognosis is poor. Although molecularly targeted therapies have shown some promise in the treatment of this disease, advanced RCC tumors often develop resistance to these drugs. Dissecting the molecular mechanisms underlying the progression to advanced disease is necessary to design alternative and improved treatment strategies. Tumor-associated macrophages (TAMs) found in aggressive RCC tumors produce a variety of inflammatory cytokines, including interleukin-1β (IL-1β). Moreover, the presence of TAMs and high serum levels of IL-1β in RCC patients correlate with advanced disease. We hypothesized that IL-1β in the tumor microenvironment promotes the development of aggressive RCC tumors by directing affecting tumor epithelial cells. To address this, we investigated the role of IL-1β in mediating RCC tumor cell invasion as a measure of tumor progression. We report that IL-1β induced tumor cell invasion of RCC cells through a process that was dependent on the activity of matrix metalloproteinases (MMPs) and was independent of migration rate. Specifically, IL-1β induced the expression of MMP-1, MMP-3, MMP-10, and MT1-MMP in a mechanism dependent on IL-1β activation of the transcription factor CCAAT enhancer binding protein β (CEBPβ). Consistent with its role in MMP gene expression, CEBPβ knockdown significantly reduced invasion, but not migration, of RCC tumor cells. These results identify the IL-1β /CEBPβ/MMP pathway as a putative target in the design of anti-metastatic therapies for the treatment of advanced RCC.

c-Myb regulates matrix metalloproteinases 1/9, and cathepsin D: implications for matrix-dependent breast cancer cell invasion and metastasis

Background

The c-Myb transcription factor is essential for the maintenance of stem-progenitor cells in bone marrow, colon epithelia, and neurogenic niches. c-Myb malfunction contributes to several types of malignancies including breast cancer. However, the function of c-Myb in the metastatic spread of breast tumors remains unexplored. In this study, we report a novel role of c-Myb in the control of specific proteases that regulate the matrix-dependent invasion of breast cancer cells.

Results

Ectopically expressed c-Myb enhanced migration and ability of human MDA-MB-231 and mouse 4T1 mammary cancer cells to invade Matrigel but not the collagen I matrix in vitro. c-Myb strongly increased the expression/activity of cathepsin D and matrix metalloproteinase (MMP) 9 and significantly downregulated MMP1. The gene coding for cathepsin D was suggested as the c-Myb-responsive gene and downstream effector of the migration-promoting function of c-Myb. Finally, we demonstrated that c-Myb delayed the growth of mammary tumors in BALB/c mice and affected the metastatic potential of breast cancer cells in an organ-specific manner.

Conclusions

This study identified c-Myb as a matrix-dependent regulator of invasive behavior of breast cancer cells.

Graded activation of the MEK1/MT1-MMP axis determines renal epithelial cell tumor phenotype

Activation of Raf/Ras/mitogen-activated protein kinase (MEK)/mitogen-activated protein kinase signaling and elevated expression of membrane type-1 matrix metalloproteinase (MT1-MMP) are associated with von Hippel-Lindau gene alterations in renal cell carcinoma. We postulated that the degree of MEK activation was related to graded expression of MT1-MMP and the resultant phenotype of renal epithelial tumors. Madin Darby canine kidney epithelial cells transfected with a MEK1 expression plasmid yielded populations with morphologic phenotypes ranging from epithelial, mixed epithelial/mesenchymal to mesenchymal. Clones were analyzed for MEK1 activity, MT1-MMP expression and extent of epithelial-mesenchymal transition. Phenotypes of the MDCK-MEK1 clones were evaluated in vivo with nu/nu mice. Tissue microarray of renal cell cancers was quantitatively assessed for expression of phosphorylated MEK1 and MT1-MMP proteins and correlations drawn to Fuhrman nuclear grade. Graded increases in the MEK signaling module were associated with graded induction of epithelial-mesenchymal transition of the MDCK cells and induction of MT1-MMP transcription and synthesis. Inhibition of MEK1 and MT1-MMP activity reversed the epithelial-mesenchymal transition. Tumors generated by epithelial, mixed epithelial/mesenchymal and mesenchymal MDCK clones demonstrated a gradient of phenotypes extending from well-differentiated, fully encapsulated non-invasive tumors to tumors with an anaplastic morphology, high Fuhrman nuclear score, neoangiogenesis and invasion. Tumor microarray demonstrated a statistically significant association between the extent of phosphorylated MEK1, MT1-MMP expression and nuclear grade. We conclude that graded increases in the MEK1 signaling module are correlated with M1-MMP expression, renal epithelial cell tumor phenotype, invasive activity and nuclear grade. Phosphorylated MEK1 and MT1-MMP may represent novel, and mechanistic, biomarkers for the assessment of renal cell carcinoma.

Reduced expression of fumarate hydratase in clear cell renal cancer mediates HIF-2α accumulation and promotes migration and invasion

Germline mutations of FH, the gene that encodes for the tricarboxylic acid TCA (TCA) cycle enzyme fumarate hydratase, are associated with an inherited form of cancer referred to as Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC). Individuals with HLRCC are predisposed to the development of highly malignant and lethal renal cell carcinoma (RCC). The mechanisms of tumorigenesis proposed have largely focused on the biochemical consequences of loss of FH enzymatic activity. While loss of the tumor suppressor gene von Hippel Lindau (VHL) is thought to be an initiating event for the majority of RCCs, a role for FH in sporadic renal cancer has not been explored. Here we report that FH mRNA and protein expression are reduced in clear cell renal cancer, the most common histologic variant of kidney cancer. Moreover, we demonstrate that reduced FH leads to the accumulation of hypoxia inducible factor- 2α (HIF-2α), a transcription factor known to promote renal carcinogenesis. Finally, we demonstrate that overexpression of FH in renal cancer cells inhibits cellular migration and invasion. These data provide novel insights into the tumor suppressor functions of FH in sporadic kidney cancer.

Hypoxia activates constitutive luciferase reporter constructs

Hypoxia has been identified as a contributing factor in the pathophysiology of several diseases and oxygen regulation is important during stem cell development, particularly in early embryogenesis. One aspect that has emerged is the role of hypoxia-inducible factors, or HIFs in regulating the effect of hypoxia. Studies in our laboratory sought to examine the hypoxic regulation of HIF activity in placental trophoblast cells, through the use of dual-reporter luciferase assays. Our study demonstrates that hypoxic conditions cause a significant increase in the level of constitutive luciferase reporter activity. We also show that this induction is not a cell type or species-specific phenomenon and provides an alternative method for normalizing transfection efficiency in luciferase assays under hypoxic conditions. Our results suggest that in studies dealing with hypoxic conditions, caution should be used when interpreting measurements of transcriptional activity by traditional dual-reporter assays.

From vessel sprouting to normalization: role of the prolyl hydroxylase domain protein/hypoxia-inducible factor oxygen-sensing machinery

The accepted model of vessel branching distinguishes several endothelial cell fates. At the forefront of a vessel sprout, "tip cells" guide the sprouting vessel toward an angiogenic stimulus. Behind the tip, "stalk cells" proliferate to elongate the vessel branch and create a lumen. In mature vessels, endothelial cells acquire a streamlined shape to optimally conduct blood flow. For this purpose, endothelial cells switch to the "phalanx" cell fate, which is characterized by quiescent and nonproliferating cells aligned in a tight cobblestonelike layer. Vessel maturation also requires the recruitment of mural cells (ie, smooth muscle cells and pericytes). These cell fates are often altered in pathological conditions, most prominently during the formation of tumor vasculature. Given the essential role of hypoxia as the driving force for initiating angiogenesis, it is not surprising that the hypoxia-sensing machinery controls key steps in physiological and pathological angiogenesis.

The NADPH oxidase subunit p22phox inhibits the function of the tumor suppressor protein tuberin

Mutations in the von Hippel-Lindau (VHL) gene give rise to renal cell carcinoma. Reactive oxygen species, generated by Nox oxidases, are involved in tumorigenesis. We have previously demonstrated that in VHL-deficient cells, p22(phox)-dependent Nox1 and Nox4 oxidases maintain hypoxia inducible factor-2alpha (HIF-2alpha) protein expression through an Akt-dependent translational pathway. Phosphorylation of tuberin, by Akt, results in its inactivation. Here we show that diphenyleneiodonium chloride, an inhibitor of Nox oxidases, and small-interfering RNA-mediated down-regulation of p22(phox) inhibit Akt-dependent phosphorylation of tuberin and stabilizes tuberin protein levels in VHL-deficient renal carcinoma cells. p22(phox)-mediated inactivation of tuberin is associated with an increase in ribosomal protein S6 kinase 1 and eukaryotic initiation factor 4E-binding protein-1 (4E-BP1) phosphorylation as well as HIF-2alpha stabilization. Importantly, we find that marked up-regulation of p22(phox) in human renal cell carcinoma correlates with increased tuberin phosphorylation, decreased tuberin protein levels, and increased phosphorylation of 4E-BP1. Our data provide the first evidence that p22(phox)-based Nox oxidases maintain HIF-2alpha protein expression through inactivation of tuberin and downstream activation of ribosomal protein S6 kinase 1/4E-BP1 pathway.

PTEN suppression of YY1 induces HIF-2 activity in von-Hippel-Lindau-null renal-cell carcinoma

Despite recent advances in cancer therapies, metastatic renal cell carcinoma (RCC) remains difficult to treat. Most RCCs result from inactivation of the von Hippel Lindau (VHL) tumor suppressor, leading to stable expression of Hypoxia-Inducible Factor-alpha (HIF-1alpha, -2alpha, -3alpha) and the induction of downstream target genes, including those responsible for angiogenesis and metastasis. While VHL is inactivated in the majority of RCC cases, expression of the PTEN tumor suppressor is reduced in about 30% of cases. PTEN functions to antagonize PI3K/Akt/mTOR signaling, thereby controlling cell growth and survival. Activation of PI3K/Akt/mTOR leads to increased HIF-1alpha expression in certain cancer cells, supporting the rationale of using mTOR inhibitors as anti-cancer agents. Notably, HIF-2alpha, rather than HIF-1alpha, has been shown to play a critical role in renal tumorigenesis. To investigate whether HIF-2alpha is similarly regulated by the PI3K pathway in VHL(-/-)RCC cells, we manipulated PI3K signaling using PTEN overexpression and siRNA knockdown studies and pharmacologic inhibition of PI3K or Akt. Our data support a novel role for wild-type PTEN in promoting HIF-2alpha activity in VHL null RCC cells. This mechanism is unique to the cellular environment in which HIF-2alpha expression is deregulated, resulting from the loss of VHL function. Our data show that PTEN induces HIF-2alpha transcriptional activity by inhibiting expression of Yin Yang 1 (YY1), which acts as a novel corepressor of HIF-2alpha. Further, PTEN suppression of YY1 is mediated through antagonism of PI3K signaling. We conclude that wild-type PTEN relieves the repressive nature of YY1 at certain HIF-2alpha target promoters and that this mechanism may promote early renal tumorigenesis resulting from VHL inactivation by increasing HIF-2alpha activity.

CXCR4 and matrix metalloproteinase-1 are elevated in breast carcinoma-associated fibroblasts and in normal mammary fibroblasts exposed to factors secreted by breast cancer cells

The complex molecular communications that occur between neoplastic and stromal cells within the tumor microenvironment play an integral role in breast cancer pathogenesis. Carcinoma-associated fibroblasts (CAF) produce tumor-enhancing factors and have been strongly implicated in breast cancer development. Similar to the way in which tumors have been compared with "wounds that never heal," CAFs have been equated to activated fibroblasts, which are present in inflammatory environments, in which they aid in wound healing through tissue remodeling and repair. Matrix metalloproteinase-1 (MMP-1) and G protein-coupled receptor, CXCR4, are elevated in these activated fibroblasts, in which they facilitate angiogenesis and matrix degradation, processes that are also vital to breast cancer metastasis. In this study, we investigated MMP-1 and CXCR4 expression in normal human mammary fibroblasts (HMF) exposed to soluble breast cancer factors. Historically, elevated CXCR4 expression is associated with breast cancer cells. However, we show that soluble factors secreted by SUM102 breast cancer cells stimulated the expression of MMP-1 and CXCR4 in HMFs. As a result, these stromal cells acquired an invasive and migratory phenotype. To confirm the clinical relevancy of our findings, we analyzed CAFs obtained from primary breast cancers. These cells also displayed elevated MMP-1 and CXCR4 levels compared with counterpart fibroblasts, and were more invasive and migratory. Together, our data suggest that soluble breast cancer factors initiate the transdifferentiation of normal HMFs to tumor-promoting CAFs, and that through the induction of MMP-1 and CXCR4 levels, these cells exhibit an invasive and migratory phenotype.

Assessment of local proteolytic milieu as a factor in tumor invasiveness and metastasis formation: in vitro collagen degradation and invasion assays

Matrix invasion by a tumor cell requires the degradation of components in the extracellular matrix (ECM) as one of the initial steps in the metastatic process. Tumors cells achieve ECM invasion primarily through the overexpression of matrix metalloproteinases (MMPs), a family of enzymes that function to degrade ECM proteins. In this chapter, an in vitro collagen degradation assay and a modified collagen invasion assay system are described. The collagen degradation assay is a simple method to measure the ability of tumor cells to degrade type I collagen, the main constituent of the stromal compartment, in a 3-D matrix environment. The modified collagen invasion assay system enables researchers to study the effects of transient overexpression and/or targeted knockdown (as with siRNAs) of a given gene on collagen invasion of tumor cells in a real-time format.

Role of the VHL (von Hippel-Lindau) gene in renal cancer: a multifunctional tumour suppressor

The VHL (von Hippel-Lindau) tumour-suppressor gene is inactivated in VHL disease and in sporadic cases of CCRCC [clear-cell RCC (renal cell carcinoma)]. pVHL (VHL protein) functions as part of an E3 ubiquitin ligase complex that targets proteins for proteasomal degradation. The best-characterized substrate is HIF-alpha (hypoxia-inducible factor-alpha). Loss of pVHL and subsequent up-regulation of HIF target genes has been attributed to the highly vascular nature of these neoplasms. However, pVHL does not just function as the executioner of HIF-alpha. Additional functions of pVHL that may be important in preventing CCRCC tumorigenesis have been identified, including primary cilium maintenance, assembly of the extracellular matrix and roles in the stabilization of p53 and Jade-1 (gene for apoptosis and differentiation in epithelia). Current evidence indicates that pVHL probably requires additional co-operating signalling pathways for CCRCC initiation and tumorigenesis.

Matrix metalloproteinase-1 promotes breast cancer angiogenesis and osteolysis in a novel in vivo model

Matrix metalloproteinase-1 (MMP-1) is critical for mediating breast cancer metastasis to bone. We investigated the role of MMP-1 in breast cancer invasion of soft tissues and bone using human MDA MB-231 breast cancer cells stably transfected with shRNAs against MMP-1 and a novel murine model of bone invasion. MMP-1 produced by breast cancer cells with control shRNA facilitated invasion of tumors into soft tissue in vivo, which correlated with enhanced blood vessel formation at the invasive edge, compared to tumors with silenced MMP-1 expression. Tumors expressing MMP-1 were also associated with osteolysis in vivo, whereas tumors with inhibited MMP-1 levels were not. Additionally, tumor-secreted MMP-1 activated bone-resorbing osteoclasts in vitro. Together, these data suggest a mechanism for MMP-1 in the activation of osteoclasts in vivo. We conclude that breast cancer-derived MMP-1 mediates invasion through soft tissues and bone via mechanisms involving matrix degradation, angiogenesis, and osteoclast activation.

Multitasking by pVHL in tumour suppression

Functional inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene product, pVHL, leads to cancer in humans. It is widely accepted that pVHL functions to destabilise hypoxia inducible factor alpha (HIFalpha) subunits, key effectors of the hypoxia signalling pathway. However, growing evidence indicates that tumour suppression by pVHL also involves the control of a wide variety of HIFalpha-independent processes including microtubule dynamics, primary cilium maintenance, cell proliferation, neuronal apoptosis, extracellular matrix deposition and responses to DNA damage. Moreover, it is becoming apparent that tumour initiation requires not only VHL mutation but also the alteration of additional cooperating cancer pathways. These studies are beginning to provide insights into the signalling networks involving pVHL that normally control diverse cellular processes and how disruption of these networks leads to tumour formation.

Induction of matrix metalloproteinase-2 and matrix metalloproteinase-9 expression in gastric cancer cells by tumor necrosis factor-α

AIM: To investigate the inductive effect of tumor necrosis factor-α (TNF-α) on the expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in gastric cancer cells.

METHODS: Gastric cancer cells were stimulated by exogenous TNF-α and the cells without stimulation served as controls. The contents of MMP-2 and MMP-9 in the supernatant fluid of gastric cancer cells were measured by enzyme-linked immunosorbnent assay (ELISA). The expression of MMP-2 and MMP-9 mRNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). Western blot was used to detect the expression of MMP-2 and MMP-9 protein in gastric cancer cells.

RESULTS: Following stimulation with 1, 10 and 100 mg/L TNF-α, the contents of MMP-2 (8.24 ± 1.36, 23.65 ± 3.45, 14.83 ± 2.54 ng/L) and MMP-9 (12.47 ± 2.66, 34.12 ± 6.78, 23.31 ± 4.45 ng/L) in the supernatant fluid of gastric cancer cells were increased significantly as compared with those in the control group (MMP-2: 1.56 ± 0.23 ng/L; 5.25 ± 0.89 ng/L; all P < 0.01). After 16 h of stimulation with TNF-α, the contents of MMP-2 and MMP-9 in the supernatant fluid reached the peak values, which were 23.65 ± 3.45 and 34.12 ± 6.78 ng/L, respectively. MMP-2 and MMP-9 expression were up-regulated both at mRNA and protein level.

CONCLUSION: TNF-α can up-regulate the expression of MMP-2 and MMP-9 in gastric cancer cells.