Biomedical subjects

Gerhard Fritz

Publications and source records attributed to Gerhard Fritz.

At least 19 recordsLinked to original sources

PubMed2006

Determination of pair correlation functions of dense colloidal systems by means of indirect Fourier transformation.

The interparticle pair correlation gr function is determined by the small angle scattering data of interacting, monodisperse, globular colloidal particles. The new approach to this problem requires that the form factor and the particle number density must be known. Instrumental broadening effects and experimental imperfections are included in a way that makes it unnecessary to deconvolute the scattering function from beam profiles. The applicability of the approach is demonstrated by the simulated data of a charged colloidal dispersion and by way of the neutron scattering data of nonionic micellar solutions. In both cases, gr functions are obtained that are in good agreement with the known behavior of the systems.

Journal Article↗

PubMed2006

Lovastatin protects human endothelial cells from killing by ionizing radiation without impairing induction and repair of DNA double-strand breaks.

PURPOSE: 3-hydroxy-3-methylglutaryl CoA reductase inhibitors (statins) are frequently used lipid-lowering drugs. Moreover, they are reported to exert pleiotropic effects on cellular stress responses, proliferation, and apoptosis. Whether statins affect the sensitivity of primary human cells to ionizing radiation (IR) is still unknown. The present study aims at answering this question. EXPERIMENTAL DESIGN: The effect of lovastatin on IR-provoked cytotoxicity was analyzed in primary human umbilical vein endothelial cells (HUVEC). To this end, cell viability, proliferation, and apoptosis as well as DNA damage-related stress responses were investigated. RESULTS: The data show that lovastatin protects HUVEC from IR-induced cell death. Lovastatin did not confer radioresistance to human fibroblasts. The radioprotective, antiapoptotic effect of lovastatin was observed at low, physiologically relevant dose level (1 micromol/L). Lovastatin affected various IR-induced stress responses in HUVEC: It attenuated the increase in p53/p21 protein level and impaired the activation of nuclear factor-kappaB, Chk-1, and Akt kinase but did not inhibit extracellular signal-regulated kinase activation. Exposure of HUVEC to IR did not change the level of Bax and Bcl-2 and did not cause activation of caspase-3, indicating that radioprotection by lovastatin does not depend on the modulation of the mitochondrial death pathway. Also, IR-induced DNA double-strand break formation and repair were not influenced by lovastatin. CONCLUSIONS: The data show that lovastatin has multiple inhibitory effects on IR-stimulated DNA damage-dependent stress responses in HUVEC. Because lovastatin causes radioresistance, it might be useful in the clinic for attenuating side effects of radiation therapy that are related to endothelial cell damage.

Apoptosis↗

PubMed2006

Azathioprine suppresses ezrin-radixin-moesin-dependent T cell-APC conjugation through inhibition of Vav guanosine exchange activity on Rac proteins.

We have shown recently that the azathioprine metabolite 6-Thio-GTP causes immunosuppression by blockade of GTPase activation in T lymphocytes. In the present study, we describe a new molecular mechanism by which 6-Thio-GTP blocks GTPase activation. Although 6-Thio-GTP could bind to various small GTPases, it specifically blocked activation of Rac1 and Rac2 but not of closely related Rho family members such as Cdc42 and RhoA in primary T cells upon stimulation with alphaCD28 or fibronectin. Binding of 6-Thio-GTP to Rac1 did not suppress Rac effector coupling directly but blocked Vav1 exchange activity upon 6-Thio-GTP hydrolysis, suggesting that 6-Thio-GTP loading leads to accumulation of 6-Thio-GDP-loaded, inactive Rac proteins over time by inhibiting Vav activity. In the absence of apoptosis, blockade of Vav-mediated Rac1 activation led to a blockade of ezrin-radixin-moesin dephosphorylation in primary T cells and suppression of T cell-APC conjugation. Azathioprine-generated 6-Thio-GTP thus prevents the development of an effective immune response via blockade of Vav activity on Rac proteins. These findings provide novel insights into the immunosuppressive effects of azathioprine and suggest that antagonists of the Vav-Rac signaling pathway may be useful for suppression of T cell-dependent pathogenic immune responses.

Adult↗

PubMed2006

Rho GTPases: promising cellular targets for novel anticancer drugs.

Ras-homologous (Rho) GTPases play a pivotal role in the regulation of numerous cellular functions associated with malignant transformation and metastasis. Rho GTPases are localized at membranes and become activated upon stimulation of cell surface receptors. In their GTP-bound (=active) state, Rho proteins bind to effector proteins, thereby triggering specific cellular responses. Members of the Rho family of small GTPases are key regulators of actin reorganization, cell motility, cell-cell and cell-extracellular matrix (ECM) adhesion as well as of cell cycle progression, gene expression and apoptosis. Each of these functions is of importance for the development and progression of cancer. Furthermore, Rho guanine exchange factors (GEFs) are often oncogenic and the expression level of Rho GTPases frequently increases with malignancy. Rho proteins also affect cellular susceptibility to DNA damaging agents, including antineoplastic drugs and ionizing radiation (IR). Thus, modulation of Rho driven mechanisms may influence the therapeutic efficiency and/or the side effects of conventional antineoplastic therapy. Because of their pleiotropic functions, Rho proteins appear to be promising targets for the development of novel anticancer drugs. Experimental approaches to inhibit Rho (and Ras) have focused on the attenuation of their C-terminal isoprenylation. This is because C-terminal lipid modification is required for correct intracellular localization and function of Rho/Ras. Inhibitors of farnesyltransferase (FTI), geranylgeranyltransferase (GGTI) as well as of HMG-CoA-reductase (i. e. statins) have been investigated with respect to their usefulness in tumor therapy. The studies showed that these compounds affect tumor progression and furthermore have impact on the frequency of cell death induced by tumor therapeutics. A possible drawback of inhibitors of isoprenylation is their poor selectivity for individual Rho GTPases. Therefore, specific inhibitors of individual Rho functions (notably RhoA-, RhoB-, Rac1- or Cdc42-related functions) are predicted to be of great therapeutic benefit. Indeed, compounds developed as specific inhibitors of the RhoA-effector molecule Rho-kinase (ROK) have been demonstrated to exert anti-metastatic activity in vivo.

Animals↗

PubMed2005

Late activation of stress kinases (SAPK/JNK) by genotoxins requires the DNA repair proteins DNA-PKcs and CSB.

Although genotoxic agents are powerful inducers of stress kinases (SAPK/JNK), the contribution of DNA damage itself to this response is unknown. Therefore, SAPK/JNK activation of cells harboring specific defects in DNA damage-recognition mechanisms was studied. Dual phosphorylation of SAPK/JNK by the genotoxin methyl methanesulfonate (MMS) occurred in two waves. The early response (< or = 2 h after exposure) was similar in cells knockout for ATM, PARP, p53, and CSB or defective in DNA-PK(cs) compared with wild-type cells. The late response however (> or = 4 h), was drastically reduced in DNA-PK(cs) and Cockayne's syndrome B (CSB)-deficient cells. Similar results were obtained with human cells lacking DNA-PK(cs) and CSB. Activation of SAPK/JNK by MMS was not affected upon inhibition of base excision repair (BER), indicating base damage itself does not signal to SAPK/JNK. Because SAPK/JNK activation was attenuated in nongrowing cells, DNA replication-dependent processing of lesions, involving DNA-PK(cs) and CSB, appears to be required. DNA-PK(cs) coprecipitates with SEK1/MKK4 and SAPK/JNK, supporting a role of DNA-PK(cs) in SAPK/JNK activation. In this process, Rho GTPases are involved since inhibition of Rho impairs MMS-induced signaling to SAPK/JNK. The data show that sensing of DNA damage by DNA-PK(cs) and CSB causes a delayed SEK1/MKK4-mediated dual phosphorylation of SAPK/JNK.

Alkylation↗

PubMed2005

Small-angle X-ray scattering, light scattering, and NMR study of PEO-PPO-PEO triblock copolymer/cationic surfactant complexes in aqueous solution.

The formation of triblock copolymer/surfactant complexes upon mixing a nonionic Pluronic polymer (PEO-PPO-PEO) with a cationic surfactant, hexadecyltrimethylammonium chloride (CTAC), has been studied in dilute aqueous solutions using small-angle X-ray scattering, static and dynamic light scattering, and self-diffusion NMR. The studied copolymer (denoted P123, EO(20)PO(68)EO(20)) forms micelles with a radius of 10 nm and a molecular weight of 7.5 x 10(5), composed of a hydrophobic PPO-rich core of radius 4 nm and a water swollen PEO corona. The P123/CTAC system has been investigated between 1 and 5 wt % P123 and with varying surfactant concentration up to approximately 170 mM CTAC (or a molar ratio n(CTAC)/n(P123) = 19.3). When CTAC is mixed with micellar P123 solutions, two different types of complexes are observed at various CTAC concentrations. At low molar ratios (>/=0.5) a "P123 micelle-CTAC" complex is obtained as the CTAC monomers associate noncooperatively with the P123 micelle, forming a spherical complex. Here, an increased interaction between the complexes with increasing CTAC concentration is observed. The interaction has been investigated by determining the structure factor obtained by using the generalized indirect Fourier transformation (GIFT) method. The interaction between the P123 micelle-CTAC complexes was modeled using the Percus-Yevick closure. For the low molar ratios a small decrease in the apparent molecular weight of the complex was obtained, whereas the major effect was the increase in electrostatic repulsion between the complexes. Between molar ratios 1.9 and 9 two coexisting complexes were found, one P123 micelle-CTAC complex and one "CTAC-P123" complex. The latter one consists of one or a few P123 unimers and a few CTAC monomers. As the CTAC concentration increases above a molar ratio of 9, the P123 micelles are broken up and only the CTAC-P123 complex that is slightly smaller than a CTAC micelle exists. The interaction between the P123/CTAC complexes was modeled with the hypernetted-chain closure using a Yukawa type potential in the GIFT analysis, due to the stronger electrostatic repulsion.

Journal Article↗

PubMed2005

TraA and its N-terminal relaxase domain of the Gram-positive plasmid pIP501 show specific oriT binding and behave as dimers in solution.

TraA is the DNA relaxase encoded by the broad-host-range Grampositive plasmid pIP501. It is the second relaxase to be characterized from plasmids originating from Gram-positive organisms. Full-length TraA (654 amino acids) and the N-terminal domain (246 amino acids), termed TraAN246, were expressed as 6xHis-tagged fusions and purified. Small-angle X-ray scattering and chemical cross-linking proved that TraAN246 and TraA form dimers in solution. Both proteins revealed oriTpIP501 (origin of transfer of pIP501) cleavage activity on supercoiled plasmid DNA in vitro. oriT binding was demonstrated by electrophoretic mobility shift assays. Radiolabelled oligonucleotides covering different parts of oriTpIP501 were subjected to binding with TraA and TraAN246. The KD of the protein-DNA complex encompassing the inverted repeat, the nick site and an additional 7 bases was found to be 55 nM for TraA and 26 nM for TraAN246. The unfolding of both protein constructs was monitored by measuring the change in the CD signal at 220 nm upon temperature change. The unfolding transition of both proteins occurred at approx. 42 degrees C. CD spectra measured at 20 degrees C showed 30% a-helix and 13% b-sheet for TraA, and 27% alpha-helix and 18% beta-sheet content for the truncated protein. Upon DNA binding, an enhanced secondary structure content and increased thermal stability were observed for the TraAN246 protein, suggesting an induced-fit mechanism for the formation of the specific relaxase-oriT complex.

Base Sequence↗

PubMed2005

Premature senescence is a primary fail-safe mechanism of ERBB2-driven tumorigenesis in breast carcinoma cells.

The receptor tyrosine kinase ERBB2 plays a central role in the development of breast cancer and other epithelial malignancies. Elevated ERBB2 activity is believed to transform cells by transmitting mitogenic and antiapoptotic signals. Here we show that tightly regulated overexpression of oncogenic ERBB2 in human breast carcinoma cells does not stimulate proliferation but provokes premature senescence, accompanied by up-regulation of the cyclin-dependent kinase inhibitor P21(WAF1/CIP1). A similar effect was caused by retrovirus-mediated overexpression of oncogenic ERBB2 in low-passage murine embryonic fibroblasts. In contrast to previous observations based on constitutively overexpressing cell lines, P21 induced by tetracycline-regulated ERBB2 localizes to the nucleus in arrested cells. P21 up-regulation seems to be independent of the P53 tumor suppressor protein, and senescence-associated phenotypic alterations are reversed by specific inhibition of P38 mitogen-activated protein kinases. Functional inactivation of P21 by antisense oligonucleotides is sufficient to prevent cell cycle arrest as well as the senescent phenotype, thereby identifying the P21 protein as the key mediator of hypermitogenic cell cycle arrest and premature senescence in breast carcinoma cells. Our results may thus indicate that premature senescence represents an inherent anticarcinogenic program during ERBB2-driven mammary tumorigenesis. We propose a multistep model for the process of malignant transformation by ERBB2 wherein secondary lesions either target P21 or downstream effectors of senescence to bypass this primary fail-safe mechanism.

Breast Neoplasms↗

PubMed2005

HMG-CoA reductase inhibitors (statins) as anticancer drugs (review).

Apart from their lipid lowering activity, HMG-CoA reductase inhibitors (statins) impair numerous cellular functions associated with metastasis, e.g. gene expression, angiogenesis, cell adhesion, cell motility and invasiveness. Furthermore, statins have impact on apoptotic cell death and modulate cellular susceptibility to cell killing by anticancer drugs and ionizing radiation. Part of the effects provoked by statins are due to the inhibition of the prenylation of low molecular weight GTPases, in particular Ras and Rho, which play key roles in signaling evoked by stimulation of cell surface receptors. C-terminal lipid modification of Ras/Rho GTPases is essential for their correct intracellular localization and function. By depletion of the cellular pool of isoprene precursor molecules, statins reduce the level of membrane-bound active Ras/Rho proteins, thereby impairing corresponding functions. Since broad clinical experience already exists for statins, their incorporation into established tumor-therapeutic regimens would be realizable in a rather short period of time. Here, data available at present arguing for the usefulness of statins in anticancer therapy are summarized and discussed.

Cell Adhesion↗

PubMed2005

Lovastatin stimulates p75 TNF receptor (TNFR2) expression in primary human endothelial cells.

HMG-CoA reductase inhibitors (statins) exert pleiotropic physiological effects. Among others they attenuate cellular responses to genotoxic and inflammatory stress. We investigated the effect of lovastatin on the expression level of TNF receptors (TNFR) in primary human endothelial cells (HUVEC). ELISA, FACS and immunocytochemical analyses show that lovastatin selectively increases the cell surface expression of TNFR2 without affecting the expression level of TNFR1. This effect of lovastatin is independent from inhibition of cell-cycle progression since cells both in G1- and G2-phase showed elevated levels of TNFR2 after lovastatin treatment. To analyze the physiological relevance of lovastatin-mediated upregulation of TNFR2, we investigated the expression of the cell adhesion molecule E-selectin, which is inducible by TNFalpha. While lovastatin on its own did not change the number of HUVEC expressing E-selectin protein, it promoted the TNFalpha-stimulated increase in the percentage of E-selectin expressing endothelial cells in a dose-dependent manner. This indicates that lovastatin sensitizes HUVEC towards TNFalpha-induced signaling by upregulation of TNFR2 expression. Based on the data, we suggest that statins have impact on endothelial responses to inflammatory stress by modulation of the expression of cytokine receptors.

Cell Cycle↗

PubMed2004

Long-term activation of SAPK/JNK, p38 kinase and fas-L expression by cisplatin is attenuated in human carcinoma cells that acquired drug resistance.

Tumor cells chronically exposed to cisplatin (cDDP) acquire cDDP resistance that impacts tumor therapy. To elucidate the mechanism of acquired cDDP resistance (ACR), we compared HeLa cells that gained ACR upon chronic cDDP treatment with the parental strain. We show that ACR is due to a lower level of induced apoptosis. Further, upon cDDP treatment, the levels of Fas, Bax and Bid remained unchanged, whereas Bcl-2 and p-Bad were reduced at late times (120 hr) after treatment. At early times, Fas ligand (fas-L) expression was significantly enhanced in sensitive compared to resistant cells and remained upregulated up to the onset of apoptosis. Thus, activation of the Fas system is critical, which is in line with the finding that in sensitive cells, caspase-8 along with caspase-9 and -3 were activated by cDDP. cDDP provoked the activation of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and p38 kinase dose-dependently, with significantly lower levels in ACR cells than in the sensitive parental line. cDDP induces c-Jun and AP-1 activity, as measured by a reporter gene assay, which was again attenuated in ACR cells. Time course analysis revealed that SAPK/JNK and p38 kinase activity was sustained upregulated (> 72 hr postexposure), which occurred at much higher level in sensitive than in ACR cells. Inhibition of either JNK or p38 kinase (by JNK inhibitor II and SB 203580, respectively) attenuated cDDP-induced apoptosis, supporting the role of JNK and p38 kinase in the cDDP response. Since several independently derived cDDP-resistant cell lines displayed attenuated MAPK signaling, sustained SAPK/JNK and p38 kinase activation may be a general mechanism of cDDP-induced cell death. ACR cells displayed a reduced level of DNA damage, indicating long-term stimulation of SAPK/JNK and p38 kinase is triggered by nonrepaired cDDP-induced DNA lesions.

Antineoplastic Agents↗

PubMed2004

Structural evolution in cationic micelles upon incorporation of a polar organic dopant.

Micelles of cetyltrimethylammonium bromide (CTAB), when doped with increasing levels of 4-ethylphenol, show microstructural transitions from spherical micelles to elongated wormlike micelles, disks, and subsequently to globular and then to tubular vesicles. Wormlike micelles are observed at a dopant-to-CTAB molar ratio of 1:3. At higher dopant ratios (1:1), globular vesicles are observed which transition to tubular vesicles when the dopant becomes the predominant species at a ratio of 3:1. These transitions are reflected in small-angle neutron scattering analysis and, interestingly, can be directly observed through cryo-transmission electron microscopy. The para-substituted phenol is interfacially active and modulates interfacial curvature of the micelles. The observations of microstructure modifications have relevance to the synthesis of mesoporous materials using CTAB as the template.

Journal Article↗

PubMed2004

Clostridium difficile toxin A induces expression of the stress-induced early gene product RhoB.

Clostridium difficile toxin A monoglucosylates the Rho family GTPases Rho, Rac, and Cdc42. Glucosylation leads to the functional inactivation of Rho GTPases and causes disruption of the actin cytoskeleton. A cDNA microarray revealed the immediate early gene rhoB as the gene that was predominantly up-regulated in colonic CaCo-2 cells after treatment with toxin A. This toxin A effect was also detectable in epithelial cells such as HT29 and Madin-Darby canine kidney cells, as well as NIH 3T3 fibroblasts. The expression of RhoB was time-dependent and correlated with the morphological changes of cells. The up-regulation of RhoB was approximately 15-fold and was based on the de novo synthesis of the GTPase because cycloheximide completely inhibited the toxin A effect. After 8 h, a steady state was reached, with no further increase in RhoB. The p38 MAPK inhibitor SB202190 reduced the expression of RhoB, indicating a participation of the p38 MAPK in this stress response. Surprisingly, newly formed RhoB protein was only partially glucosylated by toxin A, sparing a pool of potentially active RhoB, as checked by sequential C3bot-catalyzed ADP-ribosylation. A pull-down assay in fact revealed a significant amount of active RhoB in toxin A-treated cells that was not present in control cells. We demonstrate for the first time that toxin A has not only the property to inactivate the GTPases RhoA, Rac1, and Cdc42 by glucosylation, but it also has the property to generate active RhoB that likely contributes to the overall picture of toxin treatment.

Bacterial Toxins↗

PubMed2004

Structural evolution of a two-component organogel.

Dry reverse micelles of AOT in isooctane spontaneously undergo a microstructural transition to an organogel upon the addition of a phenolic dopant, p-chlorophenol. This microstructural evolution has been studied through a combination of light scattering, small-angle neutron scattering (SANS), NMR, and rheology. Several equilibrium stages between the system of dry reverse micelles of AOT and a 1:1 AOT/p-chlorophenol (molar ratio) gel in isooctane have been examined. To achieve this, p-chlorophenol is added progressively to the dilute solutions of AOT in isooctane, and this concentration series is then analyzed. The dry micelles of AOT in isooctane do not undergo any detectable structural change up to a certain p-chlorophenol concentration. Upon a very small increment in the concentration of p-chlorophenol beyond this "threshold" concentration, large strandlike aggregates are observed which then evolve to the three-dimensional gel network.

Chlorophenols↗

PubMed2004

Dependence of lipoprotein-lipase-catalyzed triacylglycerol hydrolysis on droplet size of synthetic monodisperse emulsions measured with static light scattering.

Well-defined triolein emulsions of low polydispersity were prepared by shearing a crude emulsion in a modified Couette cell, resulting in radii in the range of 300 to 900 nm. These emulsions were used as synthetic substrates for lipoprotein lipase, a key enzyme for the hydrolysis of serum triacylglycerols. The change in radius with time was studied with on-line static light scattering at 37 degrees C. An optimum radius of about 750 nm was found for this reaction.

Journal Article↗

PubMed2004

Inhibition of Rho modulates cytokine-induced prostaglandin E2 formation in renal mesangial cells.

Stimulation of rat mesangial cells for 24 h with interleukin-1beta (IL- 1beta) plus forskolin (Fk) leads to a marked increase in prostaglandin E2 (PGE2) synthesis. This effect is further enhanced by the small G-protein Rho inhibitor toxin A. A similar increase in PGE2 formation is obtained with Y27632, a Rho-dependent kinase inhibitor, and with lovastatin, a hydroxymethylglutaryl-coenzyme A inhibitor which depletes cells from geranylgeranyl moieties and thus blocks Rho activation. In parallel to the increased PGE2 synthesis, a potentiation of IL-1beta-induced secretory group IIA phospholipases A2 (sPLA2-IIA) protein expression also occurs by Rho inhibition. However, only toxin A triggers an increased sPLA2-IIA activity consistent with the elevated levels of protein expression, whereas Y27632 and lovastatin rather reduced IL-1beta-induced sPLA2-IIA activity. In vitro activity studies reveal that Y27632 and lovastatin can directly block sPLA2-IIA enzyme activity in a concentration-dependent manner. Interestingly, in the absence of IL-1beta/Fk stimulation and the lack of sPLA2-IIA protein expression, all Rho inhibitors exert a small but significant increase in PGE2 formation suggesting that additional PLA2s or downstream enzymes like cyclooxygenases or prostaglandin synthases may be activated by Rho inhibitors. Western blot analyses of toxin A-, Y27632- and lovastatin-stimulated cells reveal that the cytosolic group IV PLA2 (cPLA2) and the cytosolic PGE2 synthase (cPGES), but not the sPLA2-IIA, cyclooxygenase-2 or the microsomal PGE2 synthase (mPGES), are upregulated compared to unstimulated cells. Furthermore, the Rho inhibitors induced arachidonic acid release from intact cells which is blocked by the cPLA2 inhibitor methyl arachidonyl fluorophosphonate (MAFP). In summary, these data show that inhibition of the small G-protein Rho, either by toxin A, lovastatin, or Y27632, exert a dual effect on mesangial cells: (i) in the absence of an inflammatory stimulus it activates the constitutive cPLA2 and cPGE2 synthase and generates low amount of PGE2. (ii) In the presence of inflammatory cytokines it potentiates sPLA2-IIA expression and subsequent PGE2 formation. In addition, we identified lovastatin and Y27632 as direct inhibitors of sPLA2-IIA in a cell-free system.

Animals↗

PubMed2004

Ionizing radiation-induced E-selectin gene expression and tumor cell adhesion is inhibited by lovastatin and all-trans retinoic acid.

E-selectin mediated tumor cell adhesion plays an important role in metastasis. Here we show that ionizing radiation (IR) induces E-selectin gene and protein expression in human endothelial cells at therapeutically relevant dose level. E-selectin expression is accompanied by an increase in the adhesion of human colon carcinoma cells to primary human umbilical vein endothelial cells (HUVEC). The HMG-CoA reductase inhibitor lovastatin impairs IR-stimulated E-selectin expression as analyzed at the level of the protein, mRNA and promoter. Inactivation of Rho GTPases either by use of Clostridium difficile toxin A or by co-expression of dominant-negative Rho blocked IR-induced E-selectin gene induction, indicating Rho GTPases to be essential. Radiation-induced expression of E-selectin was also blocked by all-trans retinoic acid (at-RA), whereas 9-cis retinoic acid was ineffective. Abrogation of IR-stimulated E-selectin expression by lovastatin and at-RA reduced tumor cell adhesion in a dose-dependent manner. Combined treatment with lovastatin and at-RA exerted additive inhibitory effects on radiation-induced E-selectin expression and tumor cell adhesion. Therefore, application of statins and at-RA might have clinical impact in protecting against E-selectin-promoted metastasis, which might arise as an unwanted side effect from radiation treatment.

Blotting, Western↗

PubMed2004

Nuclear expression of apurinic/apyrimidinic endonuclease increases with progression of ovarian carcinomas.

OBJECTIVE: Apurinic/apyrimidinic endonuclease (APE alias Ref-1) is a key enzyme in the base excision repair pathway. Besides its function in DNA repair, APE serves to maintain several transcription factors in an active reduced state such as c-Fos, c-Jun, NF-kappaB, p53 and HIF-1alpha, all of which have been shown to play a role in tumorigenesis. Because of the importance of APE in maintaining genomic stability and gene regulation, we examined whether APE expression is associated with survival and histopathological parameters of patients with ovarian cancer. METHODS: Tissue sections of primary epithelial ovarian carcinomas from 141 patients were immunostained using a monoclonal antibody directed against APE. RESULTS: Nuclear expression of APE was clearly associated with progression of ovarian carcinomas. Patients with Federation of Gynecology and Obstetrics (FIGO) stages III and IV showed a higher nuclear APE expression level than patients with FIGO stages I and II (P < 0.0001). Similarly, nuclear APE expression was associated with histological grading (grade 1 vs. 2 vs. 3; P = 0.025). In contrast, cytoplasmic and stromal APE expression were not associated with progression. The fraction of APE-positive nuclei (P = 0.0185), the intensity of nuclear staining (P = 0.0496) and a combination of both (P = 0.0070) were associated with survival of ovarian cancer patients, as evidenced by a univariable proportional hazards model. CONCLUSIONS: Multivariable analysis, adjusted to FIGO stage, histological grade and type as well as residual tumor after surgery showed that APE is not independent from "classical" prognostic factors of ovarian cancer. An unexpected observation was the inverse correlation between nuclear and cytoplasmic expression of APE. Tumors with strong cytoplasmic APE reactivity showed a higher fraction of APE-negative nuclei than tumors with weak or negative cytoplasmic APE expression (P = 0.045). This suggests that nuclear translocation of APE is impaired during ovarian carcinogenesis. In conclusion, we have shown that nuclear APE expression increases during tumor progression. This suggests that increased base excision repair capacity and/or APE-mediated activation of transcription factors may contribute to more aggressive proliferation of ovarian carcinomas.

Biomarkers, Tumor↗