The aims of our study were to assess the release of cytotoxic nucleoside analogs 5-fluorouracil and 2-chloro-2'-deoxyadenosine from different lactide-glycolide or lactide-caprolactone biodegradable copolymers and the effects of sterilization on this release. The polymers were sterilized either with ethylene oxide at 37°C, or with gamma radiation (15 kGy, 20 kGy, or 25 kGy). The kinetics of nucleoside release from the copolymers were measured over 50 days. Four copolymers exhibited relatively constant release of nucleosides in micromolar concentrations during the entire observation period. Sterilization with either ethylene oxide or gamma radiation only slightly influenced nucleoside release. Further development of these copolymers as an intracerebral nucleoside delivery system for local treatment of brain tumors is indicated.
The aim of the study was to determine the relation between the cytotoxic and cytostatic effects of tezacitabine and cladribine on a HL-60 cell line and the time of exposure of cells to these drugs. Cell viability and induction of apoptosis were assessed using flow cytometry methods. Apoptosis was confirmed by direct microscopic observation. Growth inhibition was examined by cell counting. After 24 h incubation tezacitabine was equally or less toxic compared to cladribine. However, toxicity of tezacitabine strongly rose after 48 h incubation leading to massive cell death at doses much lower than those of cladribine. Assessment of the effect of increased exposure time on the clinical efficacy of tezacitabine is indicated.
Phenylacetic and retinoic acids are carboxyacidic cell differentiating agents displaying anticancer activities. We report on a new class of compounds including the 5'-esters of 2'-deoxyadenosine (dA) or 2-chloro-2'-deoxyadenosine (cladribine, 2CdA) and the aforementioned acids. The rationale behind the synthesis of these esters was that if they are hydrolyzed inside the lymphoid cells, either dA will be removed from the intracellular environment by deamination, or 2CdA will be phosphorylated and accumulated. In either case targetted delivery of the differentiating agent to the lymphoid cells may be envisaged. The said compounds were synthesized by the Mitsunobu procedure employing triphenylphosphine and azadicarboxylic acid esters, and their stability was tested against various esterases. Esters of dA and 2CdA with phenylacetic acids were found to be resistant to enzymatic hydrolysis, whereas those with retinoic acids were efficiently hydrolyzed by commercially available hepatic esterase as well as by esterases present in the blood plasma and in diluted human lymphocyte lysate. Susceptibility to enzymatic hydrolysis was found to be a prerequisite of cytotoxic and/or differentiating activity of these esters in leukemic cell lines.
The aim of this review is the presentation of molecular mechanisms of action of cytostatic drugs used in the therapy of neurological disorders, mostly of multiple sclerosis (MS). From many years cytostatics like mitoxantrone, cyclophosphamide, cladribine and methotrexate were used in the MS clinical trials. So far only mitoxantrone has been approved by FDA for the treatment of progressive MS. The other cytostatics are still studied in clinical trials, the main problem with their approval for human therapy are their numerous side effects. So far those drugs are mostly used in oncology and haematology where the usage of this type of drugs is better justified. Now there are many studies leading to better understanding of mechanisms of action of cytostatics at the cellular and subcellular level. Mitoxantrone induces apoptosis and reduce the population of inflammatory egzocells capable to initiate demyelination in the central nervous system (CNS). At the molecular level mitoxantrone damages genome of inflammatory cells by inhibition of activity of topoisomerase II (TOP II) or direct interaction with DNA structure. Cyclophosphamide is a cytostatic acting mainly on dividing cells, in which it alkylates DNA and interferes with replication and cell apoptosis. Methotrexate inhibits activity of dehydrofolate reductase what leads to disturbance of replication and blocks phase S of the cell cycle in leukocytes. Cladribine is an antagonist of transcription. The detailed analysis of these mechanisms may lead to diminishing of the level of their side effects and to increase of their therapeutic potential, also in neurological therapy.
PL
Celem niniejszej pracy jest przedstawienie molekularnych mechanizmów działania cytostatyków stosowanych w próbach terapii niektórych chorób neurologicznych, głównie stwardnienia rozsianego (SM). Od wielu lat w terapii tego schorzenia próbuje się wykorzystywać takie cytostatyki, jak mitoksantron, cyklofosfamid, metotreksat i kladrybina. W chwili obecnej jedynym lekiem z tej grupy zatwierdzonym przez FDA do leczenia postępującego SM jest mitoksantron. Pozostałe cytostatyki wciąż poddawane są badaniom, a główny problem we wprowadzeniu ich do terapii neurologicznej stanowią liczne efekty uboczne. Leki te wykorzystywane są głównie w onkologii i hematologii, gdzie stosowanie tego typu leków jest bardziej uzasadnione. W chwili obecnej prowadzone są liczne badania zmierzające do lepszego poznania mechanizmów działania cytostatyków na poziomach komórkowym i subkomórkowym. Przyjmuje się, że mitoksantron indukuje apoptozę, co zmniejsza pulę komórek zapalnych zdolnych do wywoływania demielinizacji w obrębie ośrodkowego układu nerwowego (OUN). Na poziomie molekularnym mechanizm jego działania polega na uszkodzeniu genomu tych komórek poprzez hamowanie aktywności topoizomerazy II (TOPII) lub bezpośrednie wbudowywanie się w strukturę ich DNA. Cyklofosfamid jest cytostatykiem działającym w głównej mierze na komórki dzielące się, w których alkiluje on DNA, co indukuje zaburzenia replikacji oraz apoptozę tych komórek. Działanie lecznicze metotreksatu wynika ze zdolności do hamowania aktywności reduktazy dehydrofolianowej. W ten sposób zaburzony zostaje metabolizm zasad azotowych prowadzący do zaburzeń replikacji i bloku fazy S cyklu komórkowego leukocytów. Kladrybina działa jako antagonista procesu transkrypcji. Dokładne poznanie mechanizmów działania prezentowanych leków może doprowadzić do zmniejszenia nasilenia ich efektów ubocznych oraz do zwiększenia ich potencjału leczniczego, również w terapii neurologicznej.
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