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Biomedical subjects

R Osieka

Publications and source records attributed to R Osieka.

98 records · Page 6Linked to original sources
PubMedDate not supplied

5-Azacytidine modulates the response of sensitive and multidrug-resistant K562 leukemic cells to cytostatic drugs.

In an endeavor to improve responsiveness of tumor cells to drug combination treatments, we analyzed the effect of 5-azacytidine (5AC) as a model compound for a new class of drugs, DNA-demethylating agents. We used parental K562/WT chronic myelogenous leukemia cells and a multidrug-resistant subline thereof, K562/ADM. Multidrug-resistant cells were more resistant to daunorubicin, but more sensitive to cisplatin than parental K562 cells as measured by growth inhibition and apoptosis assays. Resistance to daunorubicin can be explained by amplification of the MDR1 drug transporter gene. Cisplatin induced more DNA damage in specific genes and in the entire genome of K562/ADM cells compared to K562/WT cells using PCR stop assays and atomic absorption spectroscopy. Pretreatment with 5AC modulated the response of K562/ADM cells toward MDR-type drugs (daunorubicin, vincristine, etoposide) and reduced function and expression of MDR1 as analyzed by flow cytometry and RT-PCR. Analysis of CpG island methylation in the promotor region of the MDR1 gene by bisulfite sequencing and a methylation-sensitive HpaII-digestion/PCR approach revealed that methylation of the MDR1 promotor of K562/ADM cells was greater than in K562/WT cells. 5AC treatment completely abolished MDR1 promotor methylation. The unexpected observation that DNA demethylation by 5AC rather decreases than increases MDR1 expression in K5612/ADM cells points to still unexplored sequences in the MDR1 promotor whose transcriptional activity may be affected by the methylation status. 5AC pretreatment also modulated K562/WT and K562/ADM cells to non-MDR-type drugs such as cisplatin and increased cisplatin-induced DNA damage.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Experimental and clinical efficacy of 2', 2'-difluorodeoxycytidine (gemcitabine) against renal cell carcinoma.

Preclinical and clinical studies have been performed to evaluate the efficacy of gemcitabine (2',2'-difluorodeoxycytidine; dFdC) in human renal cell carcinoma. Experimental data corroborated dFdC as an effective drug against cell lines from renal cell carcinomas (ACHN, A-498, SN12C) at concentrations much below clinically achievable doses. ACHN-bearing nude mice showed an overall response rate of 27% to dFdC (3 mice with complete response, 1 with partial response, 3 with stable and 8 with progressive disease). Objective response from 37 evaluable patients was 8.1% (1 patient with complete response and 2 patients with partial response). Gemcitabine was well tolerated thus, although gemcitabine at the dosage and schedule chosen had only small activity, the observed toxicity may permit further dose escalation or a more frequent administration of the drug.

Adolescent↗
PubMedDate not supplied

Leptin contributes to the protection of human leukemic cells from cisplatinum cytoxicity.

Leptin (ob gene) and its cognate receptor (obr) are relevant for fat metabolism. Obr shares homology with the IL-6 signal transducer gp130 and is expressed in hematopoietic cells. Since cytokines and growth factors regulate both hematopoiesis and response to chemotherapy, we tested the hypothesis of whether leptin protects leukemic cells from cytotoxicity of cisplatinum. Antisense phosphorothioate oligodeoxynucleotides (ODNs) and antisense peptide nucleic acids (PNAs) complementary to the obr gene were first tested for their growth inhibitory activity in obr expressing leukemic cells. Liposome-mediated transfection of ODNs (1-2 microM) or PNAs (0.01-1 microM) inhibited growth up to 50%. Combination treatments of cisplatinum and 0.01 microM PNA reduced growth more than cisplatinum alone. Vice versa, recombinant human leptin (rhL) diminished cisplatinum-induced growth inhibition. Finally, we investigated whether rhL affects cisplatinum-induced DNA damage and repair in the housekeeping gene beta-actin by means of real time TaqMan polymerase chain reaction. RhL reduced DNA damage and increased DNA repair. The effects are, however, modest and leptin is probably not the only player in the armory of growth factors which affect drug resistance.

Antineoplastic Agents↗
PubMedDate not supplied

Damage of the kinesin heavy chain gene contributes to the antagonism of cisplatin and paclitaxel.

Paclitaxel (TAX) and cisplatin (DDP) rank among the most promising anti-neoplastic agents for the treatment of epithelial cancer. Pre-clinical and clinical data show that the cytotoxicity resulting from the combined use of TAX and DDP is governed by the order (TAX prior DDP) > (DDP prior TAX). Since this also occurs with DNA damaging agents other than DDP, damage of a sensitivity gene may be of importance. Recently, a role of kinesin heavy chain (KHC) was uncovered for the cytotoxicity of many natural drug derivatives by use of genetic suppressor elements (Gudkov et al. (1994) Proc. Natl. Acad. Sci. USA, 91, 3744-3748). We first confirmed the dependency on the order of addition for TAX and DDP in human leukemic K562 cells taking apoptotic fraction and cell growth as endpoints. We then inhibited KHC gene expression by antisense oligodeoxy-nucleotides or KHC protein function by monoclonal antibody SUK4. Both approaches led to a reduced cytotoxicity of TAX indicating that KHC may confer sensitivity to TAX. Using a PCR-stop assay, we found that DDP indeed caused dose related DNA damage in the KHC gene. There was more DNA damage in the KHC gene than in four other genes (AFP, G6PD, MDR1, TCR-delta). Increasing doses of DDP down-regulated KHC mRNA expression more than of G6PD. There may therefore be a role of KHC for the use of TAX and DDP in combination.

Antineoplastic Agents↗
PubMedDate not supplied

Induction of apoptosis, depletion of glutathione, and DNA damage by extracorporeal photochemotherapy and psoralen with exposure to UV light in vitro.

Extra corporeal photochemotherapy (ECPT) is a novel treatment for disorders caused by aberrant T lymphocytes. The effects of ECPT were investigated in mononuclear cells (MNC) of six patients suffering from either Sezary syndrome, mycosis fungoides, systemic sclerosis, pemphigus vulgaris or Hodgkin's disease. ECPT caused moderate to severe induction of apoptosis and depletion of glutathione in the MNC of two out of these six patients. The MNC were then treated with 8-methoxypsoralen (8-MOP) and UV light in vitro and analyzed for apoptosis and glutathione levels. 8-MOP and UV light induced a profile of cellular alterations that is similar to ECPT. In addition, we measured DNA damage by means of a PCR-based methodology. As exemplified by the T-cell receptor-delta and glucose-6-phosphate dehydrogenase genes, DNA damage correlated with induction of apoptosis and depletion of glutathione. It is, therefore, reasonable to propose that UV-induced glutathione depletion contributes to DNA lesions which ultimately account for the onset of apoptosis.

Adult↗