Agnieszka Morgenroth

Fatty acid synthase overexpression: target for therapy and reversal of chemoresistance in ovarian cancer

BackgroundFatty acid synthase (FASN) is crucial to de novo long-chain fatty acid synthesis, needed to meet cancer cells’ increased demands for membrane, energy, and protein production.MethodsWe investigated FASN overexpression as a therapeutic and chemosensitization target in ovarian cancer tissue, cell lines, and primary cell cultures. FASN expression at mRNA and protein levels was determined by quantitative real-time polymerase chain reaction and immunoblotting and immunohistochemistry, respectively. FASN inhibition’s impact on cell viability, apoptosis, and fatty acid metabolism was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide assay, cell death detection enzyme-linked immunosorbent assay, immunoblotting, and 18 F-fluoromethylcholine uptake measurement, respectively.ResultsRelative to that in healthy fallopian tube tissue, tumor tissues had 1.8-fold average FASN protein overexpression; cell lines and primary cultures had 11-fold–100-fold mRNA and protein overexpression. In most samples, the FASN inhibitor cerulenin markedly decreased FASN expression and cell viability and induced apoptosis. Unlike concomitant administration, sequential cerulenin/cisplatin treatment reduced cisplatin’s half maximal inhibitory concentration profoundly (up to 54%) in a cisplatin-resistant cell line, suggesting platinum (re)sensitization. Cisplatin-resistant cells displayed lower 18 F-fluoro-methylcholine uptake than did cisplatin-sensitive cells, suggesting that metabolic imaging might help guide therapy.ConclusionsFASN inhibition induced apoptosis in chemosensitive and platinum-resistant ovarian cancer cells and may reverse cisplatin resistance.

123I-ITdU-mediated nanoirradiation of DNA efficiently induces cell kill in HL60 leukemia cells and in doxorubicin-, beta-, or gamma-radiation-resistant cell lines.

Resistance to radiotherapy or chemotherapy is a common cause of treatment failure in high-risk leukemias. We evaluated whether selective nanoirradiation of DNA with Auger electrons emitted by 5-123I-iodo-4′-thio-2′-deoxyuridine (123I-ITdU) can induce cell kill and break resistance to doxorubicin, β-, and γ-irradiation in leukemia cells. Methods: 4′-thio-2′-deoxyuridine was radiolabeled with 123/131I and purified by high-performance liquid chromatography. Cellular uptake, metabolic stability, DNA incorporation of 123I-ITdU, and the effect of the thymidylate synthase (TS) inhibitor 5-fluoro-2′-deoxyuridine (FdUrd) were determined in HL60 leukemia cells. DNA damage was assessed with the comet assay and quantified by the olive tail moment. Apoptosis induction and irradiation-induced apoptosis inhibition by benzoylcarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD.fmk) were analyzed in leukemia cells using flow cytometry analysis. Results: The radiochemical purity of ITdU was 95%. Specific activities were 900 GBq/μmol for 123I-ITdU and 200 GBq/μmol for 131I-ITdU. An in vitro cell metabolism study of 123I-ITdU with wild-type HL60 cells demonstrated an uptake of 1.5% of the initial activity/106 cells of 123I-ITdU. Ninety percent of absorbed activity from 123I-ITdU in HL60 cells was specifically incorporated into DNA. 123I-ITdU caused extensive DNA damage (olive tail moment > 12) and induced more than 90% apoptosis in wild-type HL60 cells. The broad-spectrum inhibitor of caspases zVAD-fmk reduced 123I-ITdU–induced apoptosis from more than 90% to less than 10%, demonstrating that caspases were central for 123I-ITdU–induced cell death. Inhibition of TS with FdUrd increased DNA uptake of 123I-ITdU 18-fold and the efficiency of cell kill about 20-fold. In addition, 123I-ITdU induced comparable apoptotic cell death (>90%) in sensitive parental leukemia cells and in leukemia cells resistant to β-irradiation, γ-irradiation, or doxorubicin at activities of 1.2, 4.1, 12.4, and 41.3 MBq/mL after 72 h. This finding indicates that 123I-ITdU breaks resistance to β-irradiation, γ-irradiation, and doxorubicin in leukemia cells. Conclusion: 123I-ITdU–mediated nanoirradiation of DNA efficiently induced apoptosis in sensitive and resistant leukemia cells against doxorubicin, β-irradiation, and γ-irradiation and may provide a novel treatment strategy for overcoming resistance to conventional radiotherapy or chemotherapy in leukemia. Cellular uptake and cell kill are highly amplified by inhibiting TS with FdUrd.

Radiolabeled Nanogels for Nuclear Molecular Imaging

An efficient and simple synthesis approach to form stable (68) Ga-labeled nanogels is reported and their fundamental properties investigated. Nanogels are obtained by self-assembly of amphiphilic statistical prepolymers derivatised with chelating groups for radiometals. The resulting nanogels exhibit a well-defined spherical shape with a diameter of 290 ± 50 nm. The radionuclide (68) Ga is chelated in high radiochemical yields in an aqueous medium at room temperature. The phagocytosis assay demonstrates a highly increased internalization of nanogels by activated macrophages. Access to these (68) Ga-nanogels will allow the investigation of general behavior and clearance pathways of nanogels in vivo by nuclear molecular imaging.

Preferential tumor targeting and selective tumor cell cytotoxicity of 5-[131/125I]iodo-4'-thio-2'-deoxyuridine.

Purpose: Auger electron emitting radiopharmaceuticals are attractive for targeted nanoirradiation therapy, provided that DNA of malignant cells is selectively addressed. Here, we examine 5-[123/125/131I]iodo-4′-thio-2′-deoxyuridine (ITdU) for targeting DNA in tumor cells in a HL60 xenograft severe combined immunodeficient mouse model. Experimental Design: Thymidine kinase and phosphorylase assays were done to determine phosphorylation and glycosidic bond cleavage of ITdU, respectively. The biodistribution and DNA incorporation of ITdU were determined in severe combined immunodeficient mice bearing HL60 xenografts receiving pretreatment with 5-fluoro-2′-deoxyuridine (FdUrd). Organ tissues were dissected 0.5, 4, and 24 h after radioinjection and uptake of [131I]ITdU (%ID/g tissue) was determined. Cellular distribution of [125I]ITdU was imaged by microautoradiography. Apoptosis and expression of the proliferation marker Ki-67 were determined by immunohistologic staining using corresponding paraffin tissue sections. Results: ITdU is phosphorylated by thymidine kinase 1 and stable toward thymidylate phosphatase-mediated glycosidic bond cleavage. Thymidylate synthase-mediated deiodination of [123/125/131I]ITdU was inhibited with FdUrd. Pretreatment with FdUrd increased preferentially tumor uptake of ITdU resulting in favorable tumor-to-normal tissue ratios and tumor selectivity. ITdU was exclusively localized within the nucleus and incorporated into DNA. In FdUrd-pretreated animals, we found in more than 90% of tumor cells apoptosis induction 24 h postinjection of ITdU, indicating a highly radiotoxic effect in tumor cells but not in cells of major proliferating tissues. Conclusion: ITdU preferentially targets DNA in proliferating tumor cells and leads to apoptosis provided that the thymidylate synthase is inhibited.

New Molecular Markers for Prostate Tumor Imaging: A Study on 2-Methylene Substituted Fatty Acids as New AMACR Inhibitors†

The development of prostate carcinoma is associated with alterations in fatty acid metabolism. α-Methylacyl-CoA racemase (AMACR) is a peroxisomal and mitochondrial enzyme that catalyses interconversion between the (S)/(R)-isomers of a range of α-methylacyl-CoA thioesters. AMACR is involved in the β-oxidation of the dietary branched-chain fatty acids and bile acid intermediates. It is highly expressed in prostate (more than 95 %), colon (92 %), and breast cancers (44 %) but not in the respective normal or hyperplastic tissues. Thus, targeting of AMACR could be a new strategy for molecular imaging and therapy of prostate and some other cancers. Unlabeled 2-methylenacyl-CoA thioesters (12 a-c) were designed as AMACR binding ligands. The thioesters were tested for their ability to inhibit the AMACR-mediated epimerization of (25R)-THC-CoA and were found to be strong AMACR inhibitors. Radioiodinated (E)-(131) I-13-iodo-2-methylentridec-12-enoic acid ((131) I-7 c) demonstrated preferential retention in AMACR-positive prostate tumor cells (LNCaP, LNCaP C4-2wt and DU145) compared with both AMACR-knockout LNCaP C4-2 AMACR-siRNA and benign BPH1 prostate cell lines. A significant protein-bound radioactive fraction with main bands at 47 (sum of molecular weights of AMACR plus 12 c), 70, and 75 kDa was detected in LNCaP C4-2 wt cells. In contrast, only negligible amounts of protein-bound radioactivity were found in LNCaP C4-2 AMACR-siRNA cells.

Targeted endoradiotherapy using nucleotides

Increased cellular proliferation is an integral part of the cancer phenotype. Hence, the sustained and continued demand on supply of DNA building blocks during the DNA replication presents a potential target for therapeutic intervention. For this propose, the α and Auger electron emitting nucleotides analogs are attractive for targeted endoradiotherapy, given that DNA of malignant cells is selectively addressed. This review summarizes development and preclinical and clinical studies of endoradiotherapeutic acting nucleoside analogs with a special focus on thymidine analogs.

Synthesis and Biologic Study of IV-14, a New Ribonucleoside Radiotracer for Tumor Visualization

Uridine-cytidine kinase (UCK) 2, an enzyme normally expressed in human placenta and testis and highly overexpressed in many neoplasias of blood and solid tissues, catalyzes monophosphorylation of pyrimidine ribonucleosides with efficiency 15- to 20-fold higher than that of ubiquitously expressed isozyme UCK1. In this paper, we report the synthesis of 3′-(E)-(2-iodovinyl)uridine (IV-14) and its preclinical evaluation as a new radiotracer derived from a UCK2-selective antitumor agent, 3′-(ethynyl)uridine. Methods: Radioiodinated IV-14 was prepared from the respective stannyl precursor. 131I-IV-14 was studied in cellular uptake assays and tested for stability in serum as well as for stability to thymidine phosphorylase, liver-, and mucosa-specific murine uridine phosphorylases. UCK1 and UCK2 expression levels in different tumor cell lines were determined by Western blot. Cellular distribution of 131I-IV-14 was determined in HL60 cells. Biodistribution studies and γ-camera scintigraphy were performed on an HL60-xenografted severe combined immunodeficiency (SCID) mouse model. Results: 131I-IV-14 demonstrated excellent stability in serum. It was stable to human thymidine phosphorylase and to liver- and mucosa-specific murine uridine phosphorylases. Cellular uptake after 24 h of incubation with 131I-IV-14 was 4.27 ± 0.21, 3.66 ± 0.13, 2.69 ± 0.07, 2.24 ± 0.18, and 3.26 ± 0.18 percentage injected dose per 5 × 105 Mia-PaCa-2, CX-1, HL60, Capan-1, and Panc-1 cells, respectively. Uptake and retention of IV-14 were regulated by 2 factors: UCK2 expression level and intracellular transport mediated partially via human equilibrating nucleoside transporter 1. A biodistribution study of 131I-IV-14 in an HL60-xenografted SCID mouse model showed that at 4 h after injection the greatest amount of retained radioactivity was in tumor. The tissue-to-tumor ratio 4 h after injection was 1.0 ± 0.24 for tumor, 0.40 ± 0.18 for spleen, 0.25 ± 0.12 for colon, 0.14 ± 0.07 for small intestine, and less than 0.1 for other sites. Scintigraphy with 123I-IV-14 4 h after injection showed the tumor well. In addition, high accumulation of radioiodide in the stomach content was observed and was presumably due to metabolic degradation of IV-14. Conclusion: IV-14 is a UCK2-specific marker, allowing for in vivo addressing of tumors with high RNA synthesis independent of proliferation rate.

Breaking the Invulnerability of Cancer Stem Cells: Two-Step Strategy to Kill the Stem-like Cell Subpopulation of Multiple Myeloma

In multiple myeloma, the presence of highly resistant cancer stem cells (CSC) that are responsible for tumor metastasis and relapse has been proven. Evidently, for achieving complete response, new therapeutic paradigms that effectively eradicate both, CSCs and bulk cancer populations, need to be developed. For achieving that goal, an innovative two-step treatment combining targeting of thymidine de novo synthesis pathway and a nanoirradiation by the Auger electron emitting thymidine analogue 123/125I-5-iodo-4′-thio-2′-deoxyuridine (123/125I-ITdU) could be a promising approach. The pretreatment with thymidylate synthase inhibitor 5-fluoro-2′-deoxyuridine (FdUrd, 1 μmol/L for 1 hour) efficiently induced proliferation and terminal differentiation of isolated myeloma stem-like cells. Moreover, FdUrd stimulation led to a decreased activity of a functional CSC marker, aldehyde dehydrogenase (ALDH). The metabolic conditioning by FdUrd emerged to be essential for enhanced incorporation of 125I-ITdU (incubation with 50 kBq/2 × 104 cells for 4 days) and, consequently, for the induction of irreparable DNA damage. 125I-ITdU showed a pronounced antimyeloma effect on isolated tumor stem-like cells. More than 85% of the treated cells were apoptotic, despite activation of DNA repair mechanisms. Most important, exposure of metabolically conditioned cells to 125I-ITdU resulted in a complete inhibition of clonogenic recovery. This is the first report showing that pretreatment with FdUrd sensitizes the stem-like cell compartment in multiple myeloma to apoptosis induced by 125I-ITdU–mediated nanoirradiation of DNA. Mol Cancer Ther; 13(1); 144–53. ©2013 AACR.

Multistage Passive and Active Delivery of Radiolabeled Nanogels for Superior Tumor Penetration Efficiency

Development of nanosized drug delivery systems in cancer therapy is directed toward improving tumor selectivity and minimizing damages of healthy tissue. We introduce a delivery system with synergistic optimization and combination of passive and active targeting strategies. The approach is based on radiopeptide labeled redox sensitive hydrophilic nanogels, which exploit passive targeting by the enhanced permeability and retention effect while avoiding elimination by the mononuclear phagocyte system and fast hepatic and renal clearance. The targeting peptide promotes endocytotic uptake of the nanogels by cancer cells. Specific to this delivery system, tumor-specific degradation by the antioxidant glutathione enhances penetration and retention within the tumor tissue. Using in vivo molecular imaging we demonstrate the superiority of combined passive and active targeting with down-sizable nanogels over exclusive passive targeting. Furthermore, the homogeneous tumor distribution of functionalized nanogels compared to the clinically used mere radiopeptide supports the potentially high impact of our targeting concept.

Nondestructive monitoring of tissue-engineered constructs

Abstract Tissue engineering as a multidisciplinary field enables the development of living substitutes to replace, maintain, or restore diseased tissue and organs. Since the term was introduced in medicine in 1987, tissue engineering strategies have experienced significant progress. However, up to now, only a few substitutes were able to overcome the gap from bench to bedside and have been successfully approved for clinical use. Substantial donor variability makes it difficult to predict the quality of tissue-engineered constructs. It is essential to collect sufficient data to ensure that poor or immature constructs are not implanted into patients. The fulfillment of certain quality requirements, such as mechanical and structural properties, is crucial for a successful implantation. There is a clear need for new nondestructive and real-time online monitoring and evaluation methods for tissue-engineered constructs, which are applicable on the biomaterial, tissue, cellular, and subcellular levels. This paper reviews current established nondestructive techniques for implant monitoring including biochemical methods and noninvasive imaging.