Publications by authors named "Astrid Heller"

5 Publications

  • Page 1 of 1

Thymidine Metabolism as a Confounding Factor for 3'-Deoxy-3'-F-Fluorothymidine Uptake After Therapy in a Colorectal Cancer Model.

J Nucl Med 2018 07 23;59(7):1063-1069. Epub 2018 Feb 23.

European Institute for Molecular Imaging, Westfälische Wilhelms-Universität Münster, Münster, Germany

Noninvasive monitoring of tumor therapy response helps in developing personalized treatment strategies. Here, we performed sequential PET and diffusion-weighted MRI to evaluate changes induced by a FOLFOX-like combination chemotherapy in colorectal cancer xenografts, to identify the cellular and molecular determinants of these imaging biomarkers. Tumor-bearing CD1 nude mice, engrafted with FOLFOX-sensitive Colo205 colorectal cancer xenografts, were treated with FOLFOX (5-fluorouracil, leucovorin, and oxaliplatin) weekly. On days 1, 2, 6, 9, and 13 of therapy, tumors were assessed by in vivo imaging and ex vivo analyses. In addition, HCT116 xenografts, which did not respond to the FOLFOX treatment, were imaged on day 1 of therapy. In Colo205 xenografts, FOLFOX induced a profound increase in uptake of the proliferation PET tracer 3'-deoxy-3'-F-fluorothymidine (F-FLT) accompanied by increases in markers for proliferation (Ki-67, thymidine kinase 1) and for activated DNA damage response (γH2AX), whereas the effect on cell death was minimal. Because tracer uptake was unaltered in the HCT116 model, these changes appear to be specific for tumor response. We demonstrated that F-FLT PET can noninvasively monitor cancer treatment-induced molecular alterations, including thymidine metabolism and DNA damage response. The cellular or imaging changes may not, however, be directly related to therapy response as assessed by volumetric measurements.
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http://dx.doi.org/10.2967/jnumed.117.206250DOI Listing
July 2018

Development of bispecific molecules for the in situ detection of protein-protein interactions and protein phosphorylation.

Chem Biol 2014 Mar 13;21(3):357-68. Epub 2014 Feb 13.

Roche Professional Diagnostics, Roche Diagnostics GmbH, 82377 Penzberg, Germany. Electronic address:

Investigation of protein-protein interactions (PPIs) and protein phosphorylation in clinical tissue samples can offer valuable information about the activation status and function of proteins involved in disease progression. However, existing antibody-based methods for phosphorylation detection have been found to lack specificity, and methods developed for examining PPIs in vitro cannot be easily adapted for tissues samples. In this study, we eliminated some of these limitations by developing a specific immunohistochemical staining method that uses "dual binders" (DBs), which are bispecific detection agents consisting of two Fab fragment molecules joined by a flexible linker, to detect PPIs and protein phosphorylation. We engineered DBs by selecting Fab fragments with fast off-rate kinetics, which allowed us to demonstrate that stable target binding was achieved only upon simultaneous, cooperative binding to both epitopes. We show that DBs specifically detect the activated HER2/HER3 complex in formalin-fixed, paraffin-embedded cancer cells and exhibit superior detection specificity for phospho-HER3 compared to the corresponding monoclonal antibody. Overall, the performance of DBs makes them attractive tools for future development for clinical applications.
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http://dx.doi.org/10.1016/j.chembiol.2013.12.018DOI Listing
March 2014

A phase II pharmacodynamic study of erlotinib in patients with advanced non-small cell lung cancer previously treated with platinum-based chemotherapy.

Clin Cancer Res 2008 Jun;14(12):3867-74

Medical Oncology Service and Pathology Service, Vall d'Hebron University Hospital, Barcelona, Spain.

Purpose: To examine potential markers of clinical benefit and the effects of erlotinib on the epidermal growth factor receptor (EGFR) signaling pathway in advanced non-small cell lung cancer patients refractory to platinum-based chemotherapy.

Experimental Design: Patients were given erlotinib (150 mg/d). Tumor biopsies were done immediately before treatment and in a subgroup of patients after 6 weeks' treatment.

Results: Of 73 evaluable patients, 7 (10%) had partial response and 28 (38%) had stable disease. In 53 patients with baseline tumor samples, no relationship was observed between pretreatment levels of EGFR, phosphorylated (p)-EGFR, p-AKT, p-mitogen-activated protein kinase (MAPK), or p27 and clinical benefit (i.e., response, or stable disease >/=12 weeks). Tumors from 15 of 57 patients had high EGFR gene copy number, assessed using fluorescence in situ hybridization (FISH positive), 10 of whom had clinical benefit, compared with 5 of 42 FISH-negative patients. FISH-positive patients had longer median progression-free [137 versus 43 days, P = 0.002; hazard ratio (HR), 0.37] and overall (226 versus 106 days, P = 0.267; HR, 0.70) survival than FISH-negative patients. In paired biopsy samples from 14 patients, p-EGFR (P = 0.002), p-MAPK (P = 0.001), and Ki-67 (P = 0.025) levels were significantly reduced after 6 weeks' treatment. Apoptosis was significantly increased in patients with clinical benefit (P = 0.029), and may be a marker of clinical benefit.

Conclusion: In this study, EGFR FISH-positive status was associated with improved outcome after erlotinib therapy. Erlotinib led to reduced levels of p-EGFR, p-MAPK, and Ki-67, and stimulated apoptosis in tumor samples from patients with clinical benefit.
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http://dx.doi.org/10.1158/1078-0432.CCR-07-5186DOI Listing
June 2008

Peptide-beta2-microglobulin-MHC fusion molecules bind antigen-specific T cells and can be used for multivalent MHC-Ig complexes.

J Immunol Methods 2002 Dec;271(1-2):125-35

Abteilung Gastroenterologie, Hepatologie und Endokrinologie, Medizinische Hochschule Hannover, FZ-Oststadt, Raum 310, Pasteurallee 5, Germany.

Recombinant soluble MHC molecules are widely used for visualization, activation and inhibition of antigen-specific immune responses. Using a genetic approach, we have generated two novel peptide-beta2-microglobulin-MHC constructs. We have linked the MHC molecule with the peptide of interest, without limiting the recognition by the cognate TCR. This molecule can also be joined with the IgG heavy chain resulting in a dimeric MHC-Ig fusion protein. These molecules bind antigen-specific T cells with high specificity and sensitivity, therefore, providing a valuable tool for detection as well as enrichment of antigen-specific T cells.
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http://dx.doi.org/10.1016/s0022-1759(02)00346-0DOI Listing
December 2002

Characterization of chimeric enzymes between caprine arthritis--encephalitis virus, maedi--visna virus and human immunodeficiency virus type 1 integrases expressed in Escherichia coli.

J Gen Virol 2001 Jan;82(Pt 1):139-148

Federal Research Centre for Virus Diseases of Animals, Institute for Immunology, Paul-Ehrlich-Strasse 28, D-72076 Tübingen, Germany1.

In order to investigate the functions of the three putative lentiviral integrase (IN) protein domains on viral DNA specificity and target site selection, enzymatically active chimeric enzymes were constructed using the three wild-type IN proteins of caprine arthritis-encephalitis virus (CAEV), maedi-visna virus (MVV) and human immunodeficiency virus type 1 (HIV-1). The chimeric enzymes were expressed in Escherichia coli, purified by affinity chromatography and analysed in vitro for IN-specific endonuclease and integration activities on various DNA substrates. Of the 21 purified chimeric IN proteins constructed, 20 showed distinct site-specific cleavage activity with at least one substrate and six were able to catalyse an efficient integration reaction. Analysis of the chimeric IN proteins revealed that the central domain together with the C terminus determines the activity and substrate specificity of the enzyme. The N terminus appears to have no considerable influence. Furthermore, an efficient integration activity of CAEV wild-type IN was successfully demonstrated after detailed characterization of the reaction conditions that support optimal enzyme activities of CAEV IN. Also, under the same in vitro assay conditions, MVV and HIV-1 IN proteins exhibited endonuclease and integration activities, an indispensable prerequisite of domain-swapping experiments. Thus, the following report presents a detailed characterization of the activities of CAEV IN in vitro as well as the analysis of functional chimeric lentiviral IN proteins.
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http://dx.doi.org/10.1099/0022-1317-82-1-139DOI Listing
January 2001