| 1. |
- Baranowska-Kortylewicz, Janina, et al.
(author)
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Effect of platelet-derived growth factor receptor-beta inhibition with STI571 on radioimmunotherapy
- 2005
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In: Cancer Research. - 0008-5472 .- 1538-7445. ; 65:17, s. 7824-7831
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Journal article (peer-reviewed)abstract
- Whereas radioimmunotherapy of hematologic malignancies has evolved into a viable treatment option, the responses of solid tumors to radioimmunotherapy are discouraging. The likely cause of this problem is the interstitial hypertension inherent to all solid tumors. Remarkable improvements in tumor responses to radioimmunotherapy were discovered after the inclusion of STI571 in the therapy regimen. A combination of the tumor stroma-reactive STI571, a potent platelet-derived growth factor receptor-beta (PDGFr-beta) antagonist, and the tumor-seeking radiolabeled antibody B72.3 yielded long-lasting growth arrest of the human colorectal adenocarcinoma LS174T grown as s.c. xenografts in athymic mice. The interaction of STI571 with the stromal PDGFr-beta reduced tumor interstitial fluid pressure (P(IF)) by >50% and in so doing improved the uptake of B72.3. The attenuation of P(IF) also had a positive effect on the homogeneity of antibody distribution. These effects were dose-dependent and under optimized dosing conditions allowed for a 2.45 times increase in the tumor uptake of B72.3 as determined in the biodistribution studies. Single-photon emission computed tomography imaging studies substantiated these results and indicated that the homogeneity of the radioisotope distribution was also much improved when compared with the control mice. The increased uptake of radioimmunotherapy into the tumor resulted in >400% increase in the tumor absorbed radiation doses in STI571 + radioimmunotherapy-treated mice compared with PBS + radioimmunotherapy-treated mice. The improved antibody uptake in response to the attenuation of tumor P(IF) was identified as the primary reason for the growth arrest of the STI571 + radioimmunotherapy-treated tumors. Two related causes were also identified: (a) the improved homogeneity of monoclonal antibody distribution in tumor and (b) the increased tumor radiosensitivity resulting from the improved tumor oxygenation.
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| 2. |
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| 3. |
- Frings, Oliver, et al.
(author)
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Prognostic Significance in Breast Cancer of a Gene Signature Capturing Stromal PDGF Signaling
- 2013
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In: American Journal of Pathology. - : Elsevier BV. - 0002-9440 .- 1525-2191. ; 182:6, s. 2037-2047
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Journal article (peer-reviewed)abstract
- In this study, we describe a novel gene expression signature of platelet-derived growth factor (PDGF) activated fibroblasts, which is able to identify breast cancers with a PDGF-stimulated fibroblast stroma and displays an independent and strong prognostic significance. Global gene expression was compared between PDGF-stimulated human fibroblasts and cultured resting fibroblasts. The most differentially expressed genes were reduced to a gene expression signature of 113 genes. The biological significance and prognostic capacity of this signature were investigated using four independent clinical breast cancer data sets. Concomitant high expression of PDGF beta receptor and its cognate Ligands is associated with a high PDGF signature score. This supports the notion that the signature detects tumors with PDGF-activated stroma. Subsequent analyses indicated significant associations between high PDGF signature score and clinical characteristics, including human epidermal growth factor receptor 2 positivity, estrogen receptor negativity, high tumor grade, and large tumor size. A high PDGF signature score is associated with shorter survival in univariate analysis. Furthermore, the high PDGF signature score acts as a significant marker of poor prognosis in multivariate survival analyses, including classic prognostic markers, Ki-67 status, a proliferation gene signature, or other recently described stroma-derived gene expression signatures.
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| 4. |
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| 5. |
- Jarvius, Malin, et al.
(author)
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In situ detection of phosphorylated platelet-derived growth factor receptor beta using a generalized proximity ligation method
- 2007
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In: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 6:9, s. 1500-1509
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Journal article (peer-reviewed)abstract
- Improved methods are needed for in situ characterization of post-translational modifications in cell lines and tissues. For example, it is desirable to monitor the phosphorylation status of individual receptor tyrosine kinases in samples from human tumors treated with inhibitors to evaluate therapeutic responses. Unfortunately the leading methods for observing the dynamics of tissue post-translational modifications in situ, immunohistochemistry and immunofluorescence, exhibit limited sensitivity and selectivity. Proximity ligation assay is a novel method that offers improved selectivity through the requirement of dual recognition and increased sensitivity by including DNA amplification as a component of detection of the target molecule. Here we therefore established a generalized in situ proximity ligation assay to investigate phosphorylation of platelet-derived growth factor receptor β (PDGFRβ) in cells stimulated with platelet-derived growth factor BB. Antibodies specific for immunoglobulins from different species, modified by attachment of DNA strands, were used as secondary proximity probes together with a pair of primary antibodies from the corresponding species. Dual recognition of receptors and phosphorylated sites by the primary antibodies in combination with the secondary proximity probes was used to generate circular DNA strands; this was followed by signal amplification by replicating the DNA circles via rolling circle amplification. We detected tyrosine phosphorylated PDGFRβ in human embryonic kidney cells stably overexpressing human influenza hemagglutinin-tagged human PDGFRβ in porcine aortic endothelial cells transfected with the β-receptor, but not in cells transfected with the α-receptor, and also in immortalized human foreskin fibroblasts, BJ hTert, endogenously expressing the PDGFRβ. We furthermore visualized tyrosine phosphorylated PDGFRβ in tissue sections from fresh frozen human scar tissue undergoing wound healing. The method should be of great value to study signal transduction, screen for effects of pharmacological agents, and enhance the diagnostic potential in histopathology.
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| 6. |
- Kappert, Kai, et al.
(author)
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Dynamic changes in the expression of DEP-1 and other PDGF receptor-antagonizing PTPs during onset and termination of neointima formation
- 2007
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In: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 21:2, s. 523-534
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Journal article (peer-reviewed)abstract
- Growth factor-dependent tissue remodeling, such as restenosis, is believed to be predominantly regulated by changes in expression of receptor-tyrosine-kinases (RTKs) and their ligands. As endogenous antagonists of RTKs, protein-tyrosine-phosphatases (PTPs) are additional candidate regulators of these processes. Using laser-capture-microdissection and quantitative RT-polymerase chain reaction (qRT-PCR), we investigated the layer-specific expression of the four platelet-derived growth factor (PDGF) isoforms, the PDGF-alpha and beta receptors, and five PTPs implied in control of PDGF-receptor signaling 8 and 14 days after balloon injury of the rat carotid. Results were correlated with analyses of PDGF-beta receptor phosphorylation and vascular smooth muscle cell (VSMC) proliferation in vivo. The expression levels of all components, as well as receptor activation and VSMC proliferation, showed specific changes, which varied between media and neointima. Interestingly, PTP expression--particularly, DEP-1 levels--appeared to be the dominating factor determining receptor-phosphorylation and VSMC proliferation. In support of these findings, cultured DEP-1(-/-) cells displayed increased PDGF-dependent cell signaling. Hyperactivation of PDGF-induced signaling was also observed after siRNA-down-regulation of DEP-1 in VSMCs. The results indicate a previously unrecognized role of PDGF-receptor-targeting PTPs in controlling neointima formation. In more general terms, the observations indicate transcriptional regulation of PTPs as an important mechanism for controlling onset and termination of RTK-dependent tissue remodeling.
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| 7. |
- Kappert, Kai, et al.
(author)
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Highly Active Antiretroviral Therapy Attenuates Re-Endothelialization and Alters Neointima Formation in the Rat Carotid Artery After Balloon Injury
- 2006
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In: Journal of Acquired Immune Deficiency Syndromes. - : Ovid Technologies (Wolters Kluwer Health). - 1525-4135 .- 1944-7884. ; 43:4, s. 383-392
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Journal article (peer-reviewed)abstract
- Highly active antiretroviral therapy (HAART) has led to a sustained decline of HIV-associated morbidity and mortality. HAART exhibits significant side effects, however, such as hyperlipidemia and hyperglycemia, which possibly contribute to accelerated atherosclerosis in HAART-treated patients. In addition, direct effects of HAART on vascular cells have been described, which may promote atherosclerotic lesion formation. The effects of HAART on balloon-induced neointima formation have not been studied previously. The rat carotid artery balloon model was used to evaluate the effects of HAART (lopinavir, ritonavir, lamivudine, and zidovudine) on neointima formation and endothelial recovery. Furthermore, the effects of concomitant administration of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor rosuvastatin were investigated. HAART-treated animals displayed an increase in lesion size (neointima/media ratio: 1.14 +/- 0.32 vs. 1.31 +/- 0.20 in control vs. HAART; P < 0.05) and an impaired regenerative capacity of the endothelium, as indicated by reduction in endothelial regrowth from an adjacent undilated vessel segment 14 days after injury (re-endothelialization area: 8.29 +/- 1.45 mm vs. 5.09 +/- 0.53 mm in control vs. HAART; P < 0.05). When rosuvastatin was given in addition to HAART, these effects were not observed. In conclusion, HAART inhibited endothelial cell-mediated healing and promoted neointima formation after angioplasty in rats. These deleterious effects were attenuated by cotreatment with rosuvastatin, however. Our studies suggest that currently used drug regimens against HIV infection may lead to an increased risk for restenosis after percutaneous vascular interventions. Moreover, the findings indicate that the additional treatment with statins might counteract these adverse effects by HAART.
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| 8. |
- Koos, Björn, et al.
(author)
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Platelet-derived growth factor receptor expression and activation in choroid plexus tumors
- 2009
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In: American Journal of Pathology. - : Elsevier BV. - 0002-9440 .- 1525-2191. ; 175:4, s. 1631-1637
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Journal article (peer-reviewed)abstract
- Choroid plexus tumors are intraventricular neoplasms predominantly affecting young children. In contrast to choroid plexus papillomas, choroid plexus carcinomas progress frequently, necessitating the development of adjuvant treatment concepts. Platelet derived growth factor (PDGF) signaling has been shown to support growth in a variety of tumors. The finding of PDGF receptor expression in choroid plexus tumors prompted us to elucidate PDGF receptor activation state using a novel method, in situ proximity ligation assay, on formalin-fixed, paraffin-embedded, archival samples of 19 choroid plexus tumors. As assessed by in situ proximity ligation assay, the proportion of phosphorylated PDGF receptor alpha was low in choroid plexus papillomas and choroid plexus carcinomas, whereas phosphorylated PDGF receptor beta was found to be significantly higher in choroid plexus carcinomas. In the immortalized choroid plexus epithelial cell line Z310 expressing PDGF receptor beta, PDGF-BB exhibited a time- and dose-dependent proliferative response, which was significantly attenuated by imatinib (gleevec). In conclusion, our findings suggest that PDGF receptor beta is functionally involved in the biology of choroid plexus tumors and may represent a molecular target for therapy. In addition, this study demonstrates the feasibility and usefulness of in situ proximity ligation assay for monitoring receptor tyrosine kinase activation in formalin-fixed, paraffin-embedded, archival tissues.
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| 9. |
- Palmberg, Ebba, et al.
(author)
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Metronomic scheduling of imatinib abrogates clonogenicity of neuroblastoma cells and enhances their susceptibility to selected chemotherapeutic drugs in vitro and in vivo
- 2009
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In: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 124:5, s. 1227-1234
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Journal article (peer-reviewed)abstract
- Imatinib is currently in early clinical trials as targeted therapy for relapsed neuroblastomas and other childhood solid tumors expressing platelet-derived growth factor receptors (PDGFR) or c-Kit. Short-term treatment with imatinib in clinically achievable concentrations is ineffective in neuroblastoma in vitro. However, clinically, imatinib is administered daily over long time periods. The effects of combining imatinib with chemotherapy in neuroblastoma are unknown. Here, a panel of neuroblastoma cell lines (n = 5) were studied, representing tumors with different biological (MYCN-amplification +/-) and clinical (drug resistance) features. Using a protracted low-dose treatment schedule (1-3 weeks; 0.5-5microM) imatinib dose-dependently inhibited proliferation and clonogenic survival for all tested cell lines with IC50 <2.5microM. In contrast, short-term treatment (<96 hrs) was ineffective. Low-dose imatinib was synergistic in combination with doxorubicin and caused increased G2/M- and S-phase arrest and apoptosis as evidenced by enhanced caspase-3 activation and sub-G1 DNA accumulation. A significant but less pronounced effect was observed when imatinib was combined with etoposide or vincristine, as opposed to cisplatin, melphalan, or irinotecan. All cell lines expressed PDGFRbeta, whereas no protein expression of PDGFRalpha was detected in MYCN amplified cell lines. PDGF-BB caused PDGFRbeta phosphorylation and partially rescued neuroblastoma cells from doxorubicin-induced apoptosis, in an imatinib-sensitive manner. In vivo, treatment with imatinib in combination with doxorubicin induced a significant growth inhibition of established neuroblastoma xenografts. These findings suggest clinical testing of imatinib in combination with selected chemotherapeutic drugs, in particular doxorubicin, in children with high-risk neuroblastoma.
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| 10. |
- Paulsson, Janna
(author)
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Analyses of Akt and PDGF receptor expression and activation in human tumors
- 2009
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Doctoral thesis (other academic/artistic)abstract
- These studies aimed at developing methodology for detection of proteins involved in cancer and the evaluation of their prognostic significance in human tumors. Signal transduction profiling of tumors are becoming increasingly interesting based on the accumulating evidence of its prognostic and drug response-predicative value. Realization of the full potential of this information requires novel assay formats. We have explored the possibility to adapt the micro-fluidic Gyros platform for determination of Akt phosphorylation and the in situ PLA to investigate phosphorylation of PDGFR. The Gyros analyses clearly demonstrated that the drug-induced reduction in phosphorylation of Akt could be detected in the Gyrolab bioaffy device. A correlation between high pAkt/Akt expression and high Gleason score was seen when prostate tumors were analyzed. These preliminary findings encourage to further evaluation of the Gyrolab bioaffy device as a novel platform for analyses of tumor signal transduction. By in situ PLA we detected phosphorylated PDGFRbeta in cells stably over-expressing the human PDGFRbeta but not in cells transfected with the PDGF alpha-receptor and in immortalized human fibroblasts endogenously expressing the PDGFRbeta. We also demonstrated detection of tyrosine phosphorylated PDGFRbeta in tissue sections from fresh-frozen human scar tissue undergoing wound healing. PDGFR signaling has been shown in brain malignancies like glioma and medulloblastoma. We determined PDGF receptor expression in human choroid plexus tumors by immunohistochemistry and found that the majority expressed PDGFR. PDGFRbeta was more frequently expressed. Gene amplification was also more frequent for the PDGFRB. Next we also looked at grade I choroid plexus papillomas and grade II atypical choroid plexus papillomas and the activation status of both PDGF alpha and beta receptors by in situ PLA in formalin fixed paraffin embedded tumor tissue. Both the alpha- and beta-receptor was less expressed in the carcinomas compared to the two papillomas. In contrast the activated beta-receptor was found more frequently in the carcinomas whereas the activated alpha-receptor did not differ between the tumor types. In glioblastoma samples from patients of a randomized trial that compared hydroxyurea monotherapy with combination of hydroxyurea and imatinib, PDGFRalpha was expressed in 32% of the tumors. It was associated with male sex, young age at presentation, and loss of PTEN expression. PDGFRalpha expression status was independently associated with short survival in the entire series and associated with poor survival in the subset of patients treated with hydroxyurea monotherapy but not among those treated with the combination. PDGF receptor expression is common in the tumor stroma of common solid tumors. We found that PDGF alpha- and beta-receptors were independently expressed, at variable frequencies, in the tumor stroma of all tested tumor types. In breast cancer, high stromal PDGFRbeta expression was significantly associated with high histopathological grade, ER negativity and high HER2 expression. High stromal PDGFRbeta expression was correlated with significantly shorter recurrence-free and breast cancer specific survival. The prognostic significance of stromal PDGF beta-receptor expression was particularly prominent in tumors from pre-menopausal women. These findings highlight the prognostic significance of stromal markers, and should be considered in ongoing clinical development of PDGF receptor inhibitors. In summary, we have developed generic methods for analyses of tumor relevant proteins; Gyrolab bioaffy and in situ PLA. Furthermore, analyses of human tumors have revealed clinically relevant previously unrecognized associations between PDGFR and survival in GBM and breast cancer.
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