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ABSTRACT: Cytarabine (ara-C) and gemcitabine (dFdC) are commonly used anticancer drugs, which depend on the equilibrative (ENT) and concentrative-nucleoside-transporters to enter the cell. To bypass transport-related drug resistance, lipophilic derivatives elacytarabine (CP-4055), ara-C-5'elaidic-acid-ester, and CP-4126, (CO 1.01) gemcitabine-5'elaidic-acid-ester, were investigated for the entry into the cell, distribution, metabolism and retention. The leukemic CEM-cell-line and its deoxycytidine-kinase deficient variant (CEM/dCK-) were exposed for 30 and 60 min to the radiolabeled drugs; followed by culture in drug-free medium in order to determine drug retention in the cell. The cellular fractions were analyzed with thin-layer-chromatography and HPLC. Elacytarabine and CP-4126 were converted to the parent compounds both inside and outside the cell (35-45%). The ENT-inhibitor dipyridamole did not affect their uptake or retention. Inside the cell Elacytarabine and CP-4126 predominantly localized in the membrane and cytosolic fraction, leading to a long retention after removal of the medium. In contrast, in cells exposed to the parent drugs ara-C and dFdC, intracellular drug concentration increased during exposure but decreased to undetectable levels after drug removal. In the dCK- cell line, no metabolism was observed. The concentrations of ara-CTP and dFdCTP reached a peak at the end of the incubation with the drugs, and decreased after drug removal; peak levels of dFdCTP were 35 times higher than ara-CTP and was retained better. In contrast, after exposure to elacytarabine or CP-4126, ara-CTP and dFdCTP levels continued to increase not only during exposure but also during 120 min after removal of the elacytarabine and CP-4126. Levels of ara-CTP and dFdCTP were higher than after exposure to the parent drugs. In conclusion, the lipophilic derivatives elacytarabine and CP-4126 showed a nucleoside-transporter independent uptake, with long retention of the active nucleotides. These lipophilic nucleoside analogues are new chemical entities suitable for novel clinical applications.
Investigational New Drugs 10/2011; 30(5):1908-16. · 3.36 Impact Factor
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R Jonas A Nilsson,
Leonora Balaj,
Esther Hulleman,
Sjoerd van Rijn,
D Michiel Pegtel,
Maudy Walraven,
Anders Widmark,
Winald R Gerritsen, Henk M Verheul,
W Peter Vandertop,
David P Noske,
Johan Skog,
Thomas Würdinger
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ABSTRACT: Diagnostic platforms providing biomarkers that are highly predictive for diagnosing, monitoring, and stratifying cancer patients are key instruments in the development of personalized medicine. We demonstrate that tumor cells transfer (mutant) RNA into blood platelets in vitro and in vivo, and show that blood platelets isolated from glioma and prostate cancer patients contain the cancer-associated RNA biomarkers EGFRvIII and PCA3, respectively. In addition, gene-expression profiling revealed a distinct RNA signature in platelets from glioma patients compared with normal control subjects. Because platelets are easily accessible and isolated, they may form an attractive platform for the companion diagnostics of cancer.
Blood 08/2011; 118(13):3680-3. · 9.90 Impact Factor
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Elisa Giovannetti,
Niccola Funel,
Godefridus J Peters,
Marco Del Chiaro,
Leyla A Erozenci,
Enrico Vasile,
Leticia G Leon,
Luca E Pollina,
Annemieke Groen,
Alfredo Falcone,
Romano Danesi,
Daniela Campani, Henk M Verheul,
Ugo Boggi
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ABSTRACT: MicroRNA-21 (miR-21) was reported to be overexpressed and contributes to invasion and gemcitabine resistance in pancreatic ductal adenocarcinoma (PDAC). The aim of this study was to evaluate whether miR-21 expression was associated with the overall survival (OS) of PDAC patients treated with gemcitabine and to provide mechanistic insights for new therapeutic targets. miR-21 expression was evaluated in cells (including 7 PDAC cell lines, 7 primary cultures, fibroblasts, and a normal pancreatic ductal cell line) and tissues (neoplastic specimens from 81 PDAC patients and normal ductal samples) isolated by laser microdissection. The role of miR-21 on the pharmacologic effects of gemcitabine was studied with a specific miR-21 precursor (pre-miR-21). Patients with high miR-21 expression had a significantly shorter OS both in the metastatic and in the adjuvant setting. Multivariate analysis confirmed the prognostic significance of miR-21. miR-21 expression in primary cultures correlated with expression in their respective tissues and with gemcitabine resistance. Pre-miR-21 transfection significantly decreased antiproliferative effects and apoptosis induction by gemcitabine, whereas matrix metalloproteinase (MMP)-2/MMP-9 and vascular endothelial growth factor expression were upregulated. Addition of inhibitors of phosphoinositide 3-kinase and mammalian target of rapamycin resulted in decrease of phospho-Akt and prevented pre-miR-21-induced resistance to the proapoptotic effects of gemcitabine. miR-21 expression correlated with outcome in PDAC patients treated with gemcitabine. Modulation of apoptosis, Akt phosphorylation, and expression of genes involved in invasive behavior may contribute to the role of miR-21 in gemcitabine chemoresistance and to the rational development of new targeted combinations.
Cancer Research 06/2010; 70(11):4528-38. · 7.86 Impact Factor
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Hans J Hammers, Henk M Verheul,
Brenda Salumbides,
Rajni Sharma,
Michelle Rudek,
Janneke Jaspers,
Preeti Shah,
Leigh Ellis,
Li Shen,
Silvia Paesante,
Karl Dykema,
Kyle Furge,
Bin T Teh,
George Netto,
Roberto Pili
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ABSTRACT: Tyrosine kinase inhibitors (TKI) targeting angiogenesis via inhibition of the vascular endothelial growth factor pathway have changed the medical management of metastatic renal cell carcinoma. Although treatment with TKIs has shown clinical benefit, these drugs will eventually fail patients. The potential mechanisms of resistance to TKIs are poorly understood. To address this question, we obtained an excisional biopsy of a skin metastasis from a patient with clear cell renal carcinoma who initially had a response to sunitinib and eventually progressed with therapy. Tumor pieces were grafted s.c. in athymic nude mice. Established xenografts were treated with sunitinib. Tumor size, microvascular density, and pericyte coverage were determined. Plasma as well as tissue levels for sunitinib were assessed. A tumor-derived cell line was established and assessed in vitro for potential direct antitumor effects of sunitinib. To our surprise, xenografts from the patient who progressed on sunitinib regained sensitivity to the drug. At a dose of 40 mg/kg, sunitinib caused regression of the subcutaneous tumors. Histology showed a marked reduction in microvascular density and pericyte dysfunction. More interestingly, histologic examination of the original skin metastasis revealed evidence of epithelial to mesenchymal transition, whereas the xenografts showed reversion to the clear cell phenotype. In vitro studies showed no inhibitory effect on tumor cell growth at pharmacologically relevant concentrations. In conclusion, the histologic examination in this xenograft study suggests that reversible epithelial to mesenchymal transition may be associated with acquired tumor resistance to TKIs in patients with clear cell renal carcinoma.
Molecular Cancer Therapeutics 06/2010; 9(6):1525-35. · 5.23 Impact Factor
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ABSTRACT: Bacterial proteins provide promising tools for novel anticancer therapies. Staphylococcal superantigen-like 5 (SSL5) was recently described to bind P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes and to inhibit neutrophil rolling on a P-selectin surface. As leukocytes and tumor cells share many characteristics in migration and dissemination, we explored the potential of SSL5 as an antagonist of malignant cell behavior. Previously, it was demonstrated that rolling of human HL-60 leukemia cells on activated endothelial cells was mediated by P-selectin. In this study, we show that SSL5 targets HL-60 cells. Binding of SSL5 was rapid and without observed toxicity. Competition of SSL5 with the binding of three anti-PSGL-1 antibodies and P-selectin to HL-60 cells identified PSGL-1 as the ligand on HL-60 cells. Presence of sialyl Lewis x epitopes on PSGL-1 was crucial for its interaction with SSL5. Importantly, SSL5 not only inhibited the interaction of HL-60 cells with activated endothelial cells but also with platelets, which both play an important role in growth and metastasis of cancers. These data support the concept that SSL5 could be a lead in the search for novel strategies against hematological malignancies.
Cellular oncology: the official journal of the International Society for Cellular Oncology 01/2010; 32(1-2):1-10. · 4.17 Impact Factor
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ABSTRACT: Many drugs that are currently used for the treatment of cancer have limitations, such as induction of resistance and/or poor biological half-life, which reduce their clinical efficacy. To overcome these limitations several strategies have been explored. Chemical modification by the attachment of lipophilic moieties to (deoxy)nucleoside analogs should enhance the plasma half live, change the biodistribution and improve cellular uptake of the drug. Attachment of a lipophilic moiety to a phosphorylated (deoxy)nucleoside analog will improve the activity of the drugs by circumventing the rate-limiting activation step of (deoxy)nucleoside analogs. Duplex and multiplex drugs consist of distinct active drugs with different mechanisms of action, which are linked to each other with either a lipid or a phosphodiester. Enzymatic cleavage of such a prodrug inside the cell releases the drug or the phosphorylated form of the drug. Antitumor activity of cytotoxic drugs can also be enhanced by the use of nanoparticles as carriers. Nanoparticles have the advantage of high stability, high carrier capacity, incorporation of hydrophobic and hydrophilic compounds and variable routes of administration. Encapsulating drugs in liposomes protects the drug against enzymatic breakdown in the plasma and makes it possible to get lipophilic compounds to the tumor site. Nanoparticles and liposomes can be used to target drugs either actively or passively to the tumor. In this review we discuss the considerable progress that has been made in increasing the efficacy of classic (deoxy)nucleoside and fluoropyrimidine compounds by chemical modifications and alternative delivery systems. We expect that combining different strategies could further increase the efficacy of these compounds.
Current Medicinal Chemistry 11/2009; 16(35):4632-43. · 4.86 Impact Factor
