Correction to: Fusion Imaging of X-ray and Transesophageal Echocardiography Improves the Procedure of Left Atrial Appendage Closure.

The article "Fusion Imaging of X-ray and Transesophageal Echocardiography Improves the Procedure of Left Atrial Appendage Closure."

Fusion Imaging of X-ray and Transesophageal Echocardiography Improves the Procedure of Left Atrial Appendage Closure.

BACKGROUND: Left atrial appendage closure (LAAC) is an alternative treatment strategy for patients with atrial fibrillation who are at risk for thromboembolic events and considered not suitable for oral anticoagulation (OAC). LAAC is mainly performed under the guidance of transesophageal echocardiography (TEE) and fluoroscopy. The study presented here should analyze whether fusion imaging (FI) of transesophageal echocardiography and X-ray performed during LAAC is feasible and can improve the results of the procedure. METHODS: The data presented here are from a retrospective single center study. Sample size was defined as 50 patients in which LAAC was performed without fusion imaging (control group) and 25 patients were the LAAC procedure was guided by fusion imaging (treatment group). Inclusion criteria were defined as age > 18 years and completion of an LAAC procedure defined as deployment of a WATCHMAN 2.5 LAA occluder. Study endpoints were procedure time, amount of used contrast medium, radiation dose, final position of the WATCHMAN in TEE (deviation from ideal positioning), and clinical endpoints, respectively. RESULTS: LAA closure was successfully performed in all patients. No case of device embolism was occurring, and none of the patients experienced a periprocedural stroke/TIA nor a systemic embolism, respectively. Mean procedure time was 15 min shorter in the group of patients where fusion imaging was applied (p < 0.001). Additionally, the use of fusion imaging was associated with a significant reduction of contrast medium (20.6 ml less than in control; p < 0.045). Regarding the final position of the WATCHMAN, no relevant differences were found between the groups. The use of fusion imaging significantly reduced procedure time and the amount of contrast medium in patients undergoing LAAC.

Impact of ultrasound contrast agent on the detection of thrombi during transoesophageal echocardiography.

Background: Atrial fibrillation (AF) carries the risk of thrombus formation in the left atrium and especially in the left atrial appendage (LAA). A transoesophageal echocardiography (TOE) is routinely performed in these patients to rule out thrombi before cardioversion or structural interventions like LAA closure or pulmonary vein isolation. However, in a certain number of cases, inconclusive results of the TOE may result. This study was performed to analyse whether the routine use of ultrasound contrast agent (UCA) has an influence on the frequency of thrombus detection. Methods: In patients with AF who were scheduled for a subsequent interventional procedure, a TOE was initially performed without contrast agent. Then, the TOE was repeated with the use of UCA. The percentage of diagnostic findings regarding the prevalence of thrombus in the LAA with and without UCA were compared (thrombus present (T+), no thrombus (T-) and inconclusive result (T+/-)). Results: 223 patients were prospectively included into the trial. The numbers of thrombus detection were as follows: without UCA: 17 T+ (7.6%), 154 T- (69.1%), 52 T+/- (23,3%); with UCA: 16 T+ (7.2%), 179 T- (80.3%), 28 T+/- (12.6%; χ2: p<0.01). In 29 examinations (13.0%), the use of UCA had an impact on the subsequent treatment strategy. Conclusions: The use of UCA during TOE in patients with AF has a significant impact on the subsequent patient management especially due to an improved rule out of LAA thrombi.

Tetraspanin 1 promotes invasiveness of cervical cancer cells.

Tetraspanins are a heterogeneous group of 4-transmembrane proteins that segregate into so-called tetraspanin-enriched microdomains (TEMs) along with other cell surface proteins such as integrins. TEMs of various types are reportedly involved in the regulation of cell growth, migration and invasion of several tumour cell types, both as suppressors or supporting structures. Tetraspanin 1 (Tspan1, NET-1), a member of the transmembrane 4 superfamily (TM4SF) of tetraspanins, is overexpressed in high-grade cervical intraepithelial neoplasia (CIN) and terminal carcinomas but its precise function in the context of carcinoma of the cervix uteri is not known. Here, we present a comprehensive investigation of the role of tetraspanin 1 in the cervical cancer cell lines SiHa and HeLa. We document that tetraspanin 1 increases the invasive potential of cervical cancer cells, whereas proliferation, growth in soft agar and adhesion are largely unaffected. In line with the latter findings, our data exclude the participation of testraspanin in integrin-mediated activation of focal adhesion kinase (FAK), paxillin and phosphoinositide-3-kinase (PI3K) and in EGFR-dependent signalling to the Ras/Erk pathway. In conclusion, our data argue against a role for tetraspanin 1 as a genuine mediator of cell surface receptor signalling but rather document a role for tetraspanin 1 in the control of cervical cancer cell motility and invasion.

Hypoxia induced CA9 inhibitory targeting by two different sulfonamide derivatives including acetazolamide in human glioblastoma.

HIF-1α regulated genes are mainly responsible for tumour resistance to radiation- and chemo-therapy. Among these genes, carbonic anhydrase isoform IX (CA9) is highly over expressed in many types of cancer especially in high grade brain cancer like Glioblastoma (GBM). Inhibition of the enzymatic activity by application of specific chemical CA9 inhibitor sulphonamides (CAI) like Acetazolamide (Aza.), the new sulfonamide derivative carbonic anhydrase inhibitor (SU.D2) or indirect inhibitors like the HIF-1α inhibitor Chetomin or molecular inhibitors like CA9-siRNA are leading to an inhibition of the functional role of CA9 during tumorigenesis. Human GBM cells were treated with in vitro hypoxia (1, 6, or 24 h at 0.1%, O2). Aza. application was at a range between 250 and 8000 nM and the HIF-1α inhibitor Chetomin at a concentration range of 150-500 nM. Cell culture plates were incubated for 24 h under hypoxia (0.1% O2). Further, CA9-siRNA constructs were transiently transfected into GBM cells exposed to extreme hypoxic aeration conditions. CA9 protein expression level was detectable in a cell-type specific manner under normoxic conditions. Whereas U87-MG exhibited a strong aerobic expression, U251 and U373 displayed moderate and GaMG very weak normoxic CA9 protein bands. Aza. as well as SU.D2 displayed inhibitory characteristics to hypoxia induced CA9 expression in the four GBM cell lines for 24 h of hypoxia (0.1% O2) at concentrations between 3500 and 8000 nM, on both the protein and mRNA level. Parallel experiments using CA9-siRNA confirmed these results. Application of 150-500 nM of the glycolysis inhibitor Chetomin under similar oxygenation conditions led to a sharply reduced expression of both CA IX protein and CA9 mRNA levels, indicating a clear glucose availability involvement for the hypoxic HIF-1α and CA9 expression in GBM cells. Hypoxia significantly influences the behaviour of human tumour cells by activation of genes involved in the adaptation to hypoxic stress. The main objective in malignant GBM therapy is either to eradicate the tumour or to convert it into a controlled, quiescent chronic disease. Aza., SU.D2, Chetomin or CA9-siRNA possesses functional CA9 inhibitory characteristics when applied against human cancers with hypoxic regions like GBM. They may be used as alternative or in conjunction with other direct inhibitors possessing similar functionality, thereby rendering them as potential optimal tools for the development of an optimized therapy in human brain cancer treatment.

Inhibition of N-Myc down regulated gene 1 in in vitro cultured human glioblastoma cells.

AIM: To study short dsRNA oligonucleotides (siRNA) as a potent tool for artificially modulating gene expression of N-Myc down regulated gene 1 (NDRG1) gene induced under different physiological conditions (Normoxia and hypoxia) modulating NDRG1 transcription, mRNA stability and translation. METHODS: A cell line established from a patient with glioblastoma multiforme. Plasmid DNA for transfections was prepared with the Endofree Plasmid Maxi kit. From plates containing 5 × 10(7) cells, nuclear extracts were prepared according to previous protocols. The pSUPER-NDRG1 vectors were designed, two sequences were selected from the human NDRG1 cDNA (5'-GCATTATTGGCATGGGAAC-3' and 5'-ATGCAGAGTAACGTGGAAG-3'. reverse transcription polymerase chain reaction was performed using primers designed using published information on ß-actin and hypoxia-inducible factor (HIF)-1α mRNA sequences in GenBank. NDRG1 mRNA and protein level expression results under different conditions of hypoxia or reoxygenation were compared to aerobic control conditions using the Mann-Whitney U test. Reoxygenation values were also compared to the NDRG1 levels after 24 h of hypoxia (P < 0.05 was considered significant). RESULTS: siRNA- and iodoacetate (IAA)-mediated downregulation of NDRG1 mRNA and protein expression in vitro in human glioblastoma cell lines showed a nearly complete inhibition of NDRG1 expression when compared to the results obtained due to the inhibitory role of glycolysis inhibitor IAA. Hypoxia responsive elements bound by nuclear HIF-1 in human glioblastoma cells in vitro under different oxygenation conditions and the clearly enhanced binding of nuclear extracts from glioblastoma cell samples exposed to extreme hypoxic conditions confirmed the HIF-1 Western blotting results. CONCLUSION: NDRG1 represents an additional diagnostic marker for brain tumor detection, due to the role of hypoxia in regulating this gene, and it can represent a potential target for tumor treatment in human glioblastoma. The siRNA method can represent an elegant alternative to modulate the expression of the hypoxia induced NDRG1 gene and can help to monitor the development of the cancer disease treatment outcome through monitoring the expression of this gene in the patients undergoing the different therapeutic treatment alternatives available nowadays.

Hypoxia and cytokines regulate carbonic anhydrase 9 expression in hepatocellular carcinoma cells in vitro.

AIM: To study the expression of carbonic anhydrase (CA) 9 in human hepatocellular carcinoma (HCC) cells. METHODS: We studied CA9 protein, CA9 mRNA and hypoxia-inducible factor-1 alpha (HIF-1α) protein levels in Hep3B cells exposed in different parallel approaches. In one of these approaches, HCC cells were exposed to extreme in vitro hypoxia (24 h 0.1% O(2)) without or with interleukin (IL)-1, IL-6, tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-ß) stimulation for the same hypoxic exposure time or exposed to normoxic oxygenation conditions without or with cytokine stimulation. RESULTS: The tumour cell line analysed showed a strong hypoxic CA9 mRNA expression pattern in response to prolonged severe hypoxia with cell-line specific patterns and a marked induction of CA9 protein in response to severe hypoxia. These results were paralleled by the results for HIF-1α protein under identical oxygenation conditions with a similar expression tendency to that displayed during the CA9 protein expression experimental series. Continuous stimulation with the cytokines, IL-1, IL-6, TNF-α and TGF-ß, under normoxic conditions significantly increased the carbonic anhydrase 9 expression level at both the protein and mRNA level, almost doubling the CA9 mRNA and CA9 and HIF-1α protein expression levels found under hypoxia. The findings from these experiments indicated that hypoxia is a positive regulator of CA9 expression in HCC, and the four signal transduction pathways, IL-1, IL-6, TNF-α and TGF-ß, positively influence CA9 expression under both normoxic and hypoxic conditions. CONCLUSION: These findings may potentially be considered in the design of anti- cancer therapeutic approaches involving hypoxia-induced or cytokine stimulatory effects on expression. In addition, they provide evidence of the stimulatory role of the examined cytokine families resulting in an increase in CA9 expression under different oxygenation conditions in human cancer, especially HCC, and on the role of the CA9 gene as a positive disease regulator in human cancer.

A complete compilation of matrix metalloproteinase expression in human malignant gliomas.

Glioblastomas are characterized by an aggressive local growth pattern, a marked degree of invasiveness and poor prognosis. Tumor invasiveness is facilitated by the increased activity of proteolytic enzymes which are involved in destruction of the extracellular matrix of the surrounding healthy brain tissue. Elevated levels of matrix metalloproteinases (MMPs) were found in glioblastoma (GBM) cell-lines, as well as in GBM biopsies as compared with low-grade astrocytoma (LGA) and normal brain samples, indicating a role in malignant progression. A careful review of the available literature revealed that both the expression and role of several of the 23 human MMP proteins is controversely discussed and for some there are no data available at all. We therefore screened a panel of 15 LGA and 15 GBM biopsy samples for those MMPs for which there is either no, very limited or even contradictory data available. Hence, this is the first complete compilation of the expression pattern of all 23 human MMPs in astrocytic tumors. This study will support a better understanding of the specific expression patterns and interaction of proteolytic enzymes in malignant human glioma and may provide additional starting points for targeted patient therapy.

Human decidua and invasive trophoblasts are rich sources of nearly all human matrix metalloproteinases.

Trophoblast cell (CTB) invasion into the maternal endometrium plays a crucial role during human embryo implantation and placentation. As for all invasive cell types, the ability of CTB to infiltrate the uterine wall is facilitated by the activity of matrix metalloproteinases (MMPs), which is regulated by tissue inhibitors of MMPs (TIMPs). There is evidence for the expression of several MMPs and TIMPs in decidua. However, published data are limited. Therefore, to set a foundation for future research, we screened a panel of healthy human deciduas obtained during first, second and third trimester of pregnancy in addition to isolated decidual cell populations for the expression of all known human MMPs and TIMPs by RT-PCR, western blot and immunohistochemistry. In the decidual samples, we detected almost all MMPs and all four TIMPs at mRNA level. While the expression of proMMP-3 and active MMP-13 and -23 was down-regulated in the course of pregnancy, the pro forms of MMP-8, -19 and -23, active MMP-9, -10, -12, -15, -16, -26 and -28, and pro- and active MMP-14 increased towards the end of gestation. All MMPs and TIMPs were expressed in uterine natural killer cells, decidual fibroblasts and/or trophoblasts, with the exception of MMP-20 and -25. In summary, a remarkably broad spectrum of MMPs was expressed at the human feto-maternal interface, reflecting the highly invasive and remodelling effect on placenta formation. It can be speculated that expression of MMPs correlates with the invasive potential of CTBs together with a crucial role in activation of labour at term.

The cohesin-interacting protein, precocious dissociation of sisters 5A/sister chromatid cohesion protein 112, is up-regulated in human astrocytic tumors.

Glioblastoma multiforme (GBM) is the most prevalent, highly malignant, invasive and difficult-to-treat primary brain tumor in adults. At the genetic level, it is characterized by a high degree of chromosomal instability and aneuploidy. It has been shown that defects in the mitotic spindle checkpoint could lead to the development of aneuploidy as well as tumorigenesis. Additional proteins regulating sister chromatid cohesion could also be involved in maintaining the fidelity of chromosome segregation. One such protein is the precocious dissociation of sisters 5A (Pds5A), also known as sister chromatid cohesion protein 112. It is a nuclear protein, expressed from the S right through to the mitotic phase. It is highly conserved from yeast to man and plays a role in the establishment, maintenance and dissolution of sister chromatid cohesion. The mutation of Pds5A orthologs in lower organisms results in chromosome missegregation, aneuploidy and DNA repair defects. It is considered that such defects can cause either cell death or contribute to the development of cancer cells. Indeed, altered expression levels of Pds5A have been observed in tumors of the breast, kidney, oesophagus, stomach, liver and colon. Malignant gliomas, however, have not been analysed so far. Herein, we report on the cloning of Rattus norvegicus Pds5A and on the analysis of its expression pattern in rat tissue. We also show that Pds5A is significantly overexpressed at both the mRNA and protein level and that this overexpression correlates positively with the WHO grade of human gliomas. However, functional assays show that the siRNA-mediated knockdown of Pds5A affects sister chromatid cohesion but does not influence mitotic checkpoint function or the proliferation and survival of GBM cells. Although the mechanism by which Pds5A functions in GBM cells remains unclear, its overexpression in high grade gliomas implies that it could play a pivotal role during the development and progression of astrocytic tumors.

Comparative expression pattern of Matrix-Metalloproteinases in human glioblastoma cell-lines and primary cultures.

BACKGROUND: Glioblastomas (GBM), the most frequent malignant brain tumors in adults, are characterized by an aggressive local growth pattern and highly invasive tumor cells. This invasion is facilitated by expression of matrix metalloproteinases (MMPs), a family of zinc-dependent endopeptidases. They mediate the degradation of protein components of the extracellular matrix. Twenty-three family members are known. Elevated levels of several of them have been reported in GBM. GBM cell-lines are used for in vitro studies of cell migration and invasion. Therefore, it is essential to know their MMP expression patterns. Only limited data for some of the cell-lines are published, yet. To fill the gaps in our knowledge would help to choose suitable model systems for analysis of regulation and function of MMPs during GBM tumorigenesis, cell migration and invasion. FINDINGS: We analysed MMP-1, -8, -9, -10, -11, -13, -17, -19, -20, -21, -23, -24, -26, -27, and MMP-28 expression in seven GBM cell-lines (SNB-19, GaMG, U251, U87, U373, U343, U138) and in four primary cell cultures by semiquantitative RT-PCR, followed changes in the MMP expression pattern with increasing passages of cell culture and examined the influence of TNF-α and TGF-ß1 stimulation on the expression of selected MMPs in U251 and U373 cells.MMP-13, -17, -19 and -24 were expressed by all analyzed cell-lines, whereas MMP-20 and MMP-21 were not expressed by any of them. The other MMPs showed variable expression, which was dependent on passage number. Primary cells displayed a similar MMP-expression pattern as the cell-lines. In U251 and U373 cells expression of MMP-9 and MMP-19 was stimulated by TNF-α. MMP-1 mRNA expression was significantly increased in U373 cells, but not in U251 cells by this cytokine. Whereas TGF-ß1 had no impact on MMP expression in U251 cells, it significantly induced MMP-11 and MMP-24 expression in U373 cells. CONCLUSIONS: Literature-data and our own results suggest that the expression pattern of MMPs is highly variable, dependent on the cell-line and the cell-culture conditions used and that also regulation of MMP expression by cytokines is cell-line dependent. This is of high impact for the transfer of cell-culture experiments to clinical implementation.

Expression pattern of matrix metalloproteinases in human gynecological cancer cell lines.

BACKGROUND: Matrix metalloproteinases (MMPs) are involved in the degradation of protein components of the extracellular matrix and thus play an important role in tumor invasion and metastasis. Their expression is related to the progression of gynecological cancers (e.g. endometrial, cervical or ovarian carcinoma). In this study we investigated the expression pattern of the 23 MMPs, currently known in humans, in different gynecological cancer cell lines. METHODS: In total, cell lines from three endometrium carcinomas (Ishikawa, HEC-1-A, AN3 CA), three cervical carcinomas (HeLa, Caski, SiHa), three chorioncarcinomas (JEG, JAR, BeWo), two ovarian cancers (BG-1, OAW-42) and one teratocarcinoma (PA-1) were examined. The expression of MMPs was analyzed by RT-PCR, Western blot and gelatin zymography. RESULTS: We demonstrated that the cell lines examined can constitutively express a wide variety of MMPs on mRNA and protein level. While MMP-2, -11, -14 and -24 were widely expressed, no expression was seen for MMP-12, -16, -20, -25, -26, -27 in any of the cell lines. A broad range of 16 MMPs could be found in the PA1 cells and thus this cell line could be used as a positive control for general MMP experiments. While the three cervical cancer cell lines expressed 10-14 different MMPs, the median expression in endometrial and choriocarcinoma cells was 7 different enzymes. The two investigated ovarian cancer cell lines showed a distinctive difference in the number of expressed MMPs (2 vs. 10). CONCLUSIONS: Ishikawa, Caski, OAW-42 and BeWo cell lines could be the best choice for all future experiments on MMP regulation and their role in endometrial, cervical, ovarian or choriocarcinoma development, whereas the teratocarcinoma cell line PA1 could be used as a positive control for general MMP experiments.

Modulation of carbonic anhydrase 9 (CA9) in human brain cancer.

Hypoxia is a crucial factor in tumour aggressiveness and its treatment resistance, particularly in human brain cancer. Tumour resistance against radiation- and chemo- therapy is facilitated by oxygenation reduction at tumour areas. HIF-1α regulated genes are mostly responsible for this type of resistance. Among these genes, carbonic anhydrase isoform 9 (CA9) is highly overexpressed in many types of cancer especially in high grade brain cancer like GBM. CA IX contributes to tumour environment acidification by catalyzing the carbon dioxide hydration to bicarbonate and protons, leading to the acquisition of metastasic phenotypes and chemoresistance to weakly basic anticancer drugs and therefore to inadequate application of radio-therapeutic or chemotherapeutic anti-cancer treatment strategies. Inhibition of this enzymatic activity by application of specific chemical CA9 inhibitors (sulphonamide derivative compounds) or indirect inhibitors like HIF-1α inhibitors (chetomin) or molecular inhibitors like CA9-siRNA leads to reversion of these processes, leading to the CA9 functional role inhibition during tumourigenesis. Hypoxia significantly influences the tumour microenvironment behaviour via activation of genes involved in the adaptation to the hypoxic stress. It also represents an important cancer prognosis indicator and is associated with aggressive growth, malignant progression, metastasis and poor treatment response. The main objective in malignant GBM therapy is either to eradicate the tumour or to convert it into a controlled, quiescent chronic disease. Sulfonamide derivative compounds with CA9 inhibitory characteristics represent one of the optimal treatment options beside other CA9 inhibitory agents or chemical inhibitory compounds against its main regulating transcription factor which is the hypoxia induced HIF-1α when applied against human cancers with hypoxic regions like GBM, bearing potential for an effective role in human brain tumour therapeutic strategies. Glycolytic inhibitors, when added in controlled doses under hypoxia, lead to a reduced accumulation of HIF-1α and can function as indirect hypoxia regulated genes inhibitors like CA9. These may be used as alternative or in conjunction with other direct inhibitors like the sulphonamide derivate compounds, chetomin or specific siRNAs, or other different chemical compounds possessing similar functionality making them as optimal tools for optimized therapy development in cancer treatment, especially against human brain cancer. Further experimental analysis towards the tumour stage specific inhibitory CA9 characteristics determination are necessary to find the optimal therapeutic solutions among the different available modalities; whether they are direct or indirect chemical, molecular or natural inhibitors to be able to set up successful treatment approaches against the different human tumour diseases.

Expression of matrix metalloproteinases (MMPs) in primary human breast cancer and breast cancer cell lines: New findings and review of the literature.

BACKGROUND: Matrix metalloproteinases (MMPs) are a family of structural and functional related endopeptidases. They play a crucial role in tumor invasion and building of metastatic formations because of their ability to degrade extracellular matrix proteins. Under physiological conditions their activity is precisely regulated in order to prevent tissue disruption. This physiological balance seems to be disrupted in cancer making tumor cells capable of invading the tissue. In breast cancer different expression levels of several MMPs have been found. METHODS: To fill the gap in our knowledge about MMP expression in breast cancer, we analyzed the expression of all known human MMPs in a panel of twenty-five tissue samples (five normal breast tissues, ten grade 2 (G2) and ten grade 3 (G3) breast cancer tissues). As we found different expression levels for several MMPs in normal breast and breast cancer tissue as well as depending on tumor grade, we additionally analyzed the expression of MMPs in four breast cancer cell lines (MCF-7, MDA-MB-468, BT 20, ZR 75/1) commonly used in research. The results could thus be used as model for further studies on human breast cancer. Expression analysis was performed on mRNA and protein level using semiquantitative RT-PCR, Western blot, immunohistochemistry and immunocytochemistry. RESULTS: In summary, we identified several MMPs (MMP-1, -2, -8, -9, -10, -11, -12, -13, -15, -19, -23, -24, -27 and -28) with a stronger expression in breast cancer tissue compared to normal breast tissue. Of those, expression of MMP-8, -10, -12 and -27 is related to tumor grade since it is higher in analyzed G3 compared to G2 tissue samples. In contrast, MMP-7 and MMP-27 mRNA showed a weaker expression in tumor samples compared to healthy tissue. In addition, we demonstrated that the four breast cancer cell lines examined, are constitutively expressing a wide variety of MMPs. Of those, MDA-MB-468 showed the strongest mRNA and protein expression for most of the MMPs analyzed. CONCLUSION: MMP-1, -2, -8, -9, -10, -11, -12, -13, -15, -19, -23, -24, -27 and -28 might thus be associated with breast cancer development and tumor progression. Therefore, these MMPs are proper candidates for further functional analysis of their role in breast cancer.

Absence of GAPDH regulation in tumor-cells of different origin under hypoxic conditions in - vitro.

BACKGROUND: Gene expression studies related to cancer diagnosis and treatment are important. In order to conduct such experiment accurately, absolutely reliable housekeeping genes are essential to normalize cancer related gene expression. The most important characteristics of such genes are their presence in all cells and their expression levels remain relatively constant under different experimental conditions. However, no single gene of this group of genes manifests always stable expression levels under all experimental conditions. Incorrect choice of housekeeping genes leads to interpretation errors of experimental results including evaluation and quantification of pathological gene expression. Here, we examined (a) the degree of GAPDH expression regulation in Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines as well as in human lung adenocarcinoma epithelial cell line (A-549) in addition to both HT-29, and HCT-116 colon cancer cell lines, under hypoxic conditions in vitro in comparison to other housekeeping genes like beta-actin, serving as experimental loading controls, (b) the potential use of GAPDH as a target for tumor therapeutic approaches was comparatively examined in vitro on both protein and mRNA level, by western blot and semi quantitative RT-PCR, respectively. FINDINGS: No hypoxia-induced regulatory effect on GAPDH expression was observed in the cell lines studied in vitro that were; Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines, Human lung adenocarcinoma epithelial cell line (A-549), both colon cancer cell lines HT-29, and HCT-116. CONCLUSION: As it is the case for human hepatocellular carcinoma, mouse hepatoma, human colon cancer, and human lung adenocarcinoma, GAPDH represents an optimal choice of a housekeeping gene and/(or) loading control to determine the expression of hypoxia induced genes in tumors of different origin. The results confirm our previous findings in human glioblastoma that this gene is not an attractive target for tumor therapeutic approaches because of the lack of GAPDH regulation under hypoxia.

Oxygen-dependent regulation of NDRG1 in human glioblastoma cells in vitro and in vivo.

NDRG1 is a member of the N-myc downregulated gene (NDRG) family. Its induction occurs via diverse physiological and pathological conditions (hypoxia, cellular differentiation, heavy metal, N-myc, neoplasia) which modulate NDRG1 transcription, mRNA stability and translation. Hypoxia, among other factors, induces NDRG1 expression and plays an important role in its regulation of expression. To date, the complete detailed function of this protein in humans remains unknown. Hypoxia represents a common feature of solid tumors. In our study, differences in NDRG1 expression between different WHO grades of astrocytic tumors were comparatively examined in vivo in human low-grade astrocytoma (WHO grade 2) and glioblastoma (WHO grade 4) at both the protein and mRNA level by Western blot analysis and semi-quantitative RT-PCR, respectively. Furthermore, the same proteins were determined in vitro in U373, U251 and GaMG human glioblastoma cells using the same methods. HIF-1alpha protein and mRNA regulation under hypoxia was also determined in vitro in U251, U373 and GaMG cells. This regulation was shown at the same levels in vivo in human low-grade astrocytoma (WHO grade 2) and glioblastoma which showed a higher NDRG1 overexpression level in glioblastoma than in low-grade astrocytoma. siRNA- and iodoacetate (IAA)-mediated downregulation of NDRG1 mRNA and protein expression in vitro in human glioblastoma cell lines showed a nearly complete inhibition of NDRG1 expression when compared to the results obtained due to the inhibitory role of glycolysis inhibitor IAA. Hypoxia responsive elements (HREs) bound by nuclear HIF-1alpha in human glioblastoma cells in vitro under different oxygenation conditions and the clearly enhanced binding of nuclear extracts from glioblastoma cell samples exposed to extreme hypoxic conditions confirmed the HIF-1 Western blotting results. Due to its clear regulatory behavior under hypoxic condition in human tumor cells, NDRG1 represents an additional diagnostic marker for brain tumor detection, due to the role of hypoxia in regulating this gene, and it can represent a potential target for tumor treatment in human glioblastoma.

RAF expression in human astrocytic tumors.

RAF proteins are well known oncoproteins. The B-RAF has been shown to be activated by mutations in a multitude of human cancers. Alterations of C-RAF expression are discussed to play a role in lung cancer. Only for A-RAF no link to tumorigenesis has been published so far. Malignant gliomas are the most prevalent primary brain tumors of adults. They are highly invasive and very difficult to treat, despite of surgery, gamma-irradiation and chemotherapy. Although a role of the mitogenic Ras-RAF-MEK-ERK signalling cascade in brain tumor development is well established, there are only few reports available addressing alterations in RAF sequence or protein expression and function in human gliomas. We analysed the mutational status of A-RAF and B-RAF in human glioblastomas (GBM) by sequencing. Then we checked for RAF gene amplification by dot blot hybridization and examined RAF mRNA and protein expression patterns in human astrocytic gliomas of WHO grade II (LGA) and IV (GBM) by semiquantitative RT-PCR and Western blotting, respectively. The results were correlated with patients prognosis. Finally, we performed functional assays to address a putative function of A-RAF in glioma cell proliferation and migration. We showed that RAF mutations are a rare event in glioblastoma multiforme. A-raf gene amplification was more often detected and overexpression of all three RAF proteins on mRNA and protein level was regularly found in human malignant gliomas. Whereas A-RAF and C-RAF expression was negatively correlated with the patients prognosis, B-RAF expression had a positive effect. Since neither A-RAF, nor C-RAF expression had any influence on proliferation and migration of GBM cells, putative functions of C-RAF in angiogenesis and of A-RAF in regulation of metabolism are discussed. Our data indicate that RAF proteins might be valuable targets for small molecule therapies. However, initially specific functions of RAF during tumorigenesis have to be elucidated.

Egr-1 is not upregulated in response to hypoxic and oxygenation conditions in human glioblastoma in vitro.

The early growth response factor 1 (Egr-1) gene (also known as krox24, NGFI-A, TIS8 or zif268) belongs to a family of immediate early response genes. This family of proteins contains a conserved zinc finger DNA-binding domain and can bind to a GC-rich sequence in the promoter region of target genes. Egr-1 expression is rapidly and transiently activated in many different cell types during development. In adult tissues, a variety of signals, including serum, growth factors, cytokines and hormones, stimulate Egr-1 expression. In several studies, it was demonstrated that the transcription factor Egr-1 is regulated by hypoxia, and it is hypothesized that Egr-1 is responsible for the hypoxia-induced regulation of the N-Myc downregulated gene 1 (NDRG1) in human tumor cells. In the present study, Egr-1 regulation was examined in the human glioblastoma cell lines U373, U251, GaMG and U87-MG under extreme hypoxic aeration conditions (0.1% O2) for 1, 6 and 24 h, 24-h extreme hypoxia with reoxygenation for 24 and 48 h, respectively, as well as oxygenated conditions (21% O2 and 5% CO2) in vitro. Protein and mRNA levels were detected in the lysates by Western blotting and RT-PCR, respectively. Egr-1 expression under hypoxic conditions was compared with the well-known and characterized hypoxia-induced gene regulator hypoxia-inducible factor-1α (HIF-1α) in parallel experimental sets. Cells incubated for 24 h with 100 µM desferroxamine served as a positive control for hypoxia, and ß-tubulin and ß-actin were used as loading controls. The experimental data indicate that Egr-1 was not upregulated under extreme hypoxic conditions (0.1% O2) or by reoxygenation after hypoxia in different glioblastoma cells in vitro. In conclusion, the regulation of Egr-1 in reaction to hypoxic development, at both the protein and mRNA levels, is not a general phenomenon. In contrast to previously published data, no Egr-1 regulatory events were observed in glioblastoma under hypoxic conditions in vitro. We suggest that Egr-1 regulation in human tumors in reaction to hypoxia could be a cell-specific post-translational event. Therefore, at least in glioblastoma, HIF-1α can be considered a major regulator of NDRG1 under hypoxic conditions. Further extensive analysis of tumor cells from different origins under similar physiological conditions is necessary to increase our knowledge of the conditions and functional role of Egr-1 in the regulation of hypoxia-induced gene expression.

Expression analysis of the autosomal recessive primary microcephaly genes MCPH1 (microcephalin) and MCPH5 (ASPM, abnormal spindle-like, microcephaly associated) in human malignant gliomas.

Patients with autosomal recessive primary microcephaly have a small but architecturally normal brain containing a reduced number of neurons. Microcephalin and ASPM are two of the genes causing this disease. Both are centrosomal proteins involved in cell cycle regulation. Whereas microcephalin is a component of the DNA damage response and a repressor of telomerase function, ASPM is required for the proper formation of a central mitotic spindle and ensures symmetric, proliferative divisions of neuro-epithelial cells. Both proteins are also involved in the regulation of tumor growth. Microcephalin expression is reduced in breast cancer cell lines and human tumors of the ovary and prostate. Reduction in microcephalin mRNA expression correlates with increased chromosomal instability. ASPM mRNA is overexpressed in transformed human cell lines and tumors, and its increased expression is positively associated with proliferation of glioblastoma cells. Glioblastomas are the most prevalent malignant brain tumors in adults, characterized by increased invasiveness, an aggressive local growth pattern and short survival periods of patients. In this study, we analysed the expression of microcephalin mRNA and ASPM mRNA and protein in a panel of 15 glioblastomas and 15 astrocytoma WHO grade II by semi-quantitative RT-PCR, Western blotting and immunohistochemistry. Whereas microcephalin expression did not seem to be altered during glioma development, there was a clear increase in ASPM mRNA and protein expression that corresponded with the WHO grade of the tumor. Our findings are significant as the expression of ASPM may be used as a marker for glioma malignancy and represents a potential therapeutic target.