| 1. |
- Lotfi, Kourosh, et al.
(författare)
-
Biochemical Pharmacology and Resistance to 2-Chloro-2′-arabino-fluoro-2′-deoxyadenosine, a Novel Analogue of Cladribine in Human Leukemic Cells
- 1999
-
Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 5:9, s. 2438-2444
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of the present study was to investigate the biochemical pharmacology of 2-chloro-2′-arabino-fluoro-2′-deoxyadenosine (CAFdA) — a fluorinated analogue of cladribine [2-chloro-2′-deoxyadenosine, Leustatin (CdA)] with improved acid and metabolic stability — in human leukemic cell lines and in mononuclear cells isolated from patients with chronic lymphocytic leukemia (CLL) and acute myelocytic leukemia (AML). We have also made and characterized two cell lines that are not sensitive to the growth inhibitory and cytotoxic effects of CAFdA. Incubation of cells isolated from the blood of CLL and AML patients with various concentrations of CdA or of CAFdA accumulated CdA and CAFdA nucleotides in a dose-dependent manner. A significantly higher rate of phosphorylation to monophosphates was observed for CAFdA than for CdA in cells from CLL patients (n = 14; P = 0.04). The differences in the phosphorylation were even more pronounced for the respective triphosphates in both CLL (n = 14; P = 0.001) and AML (n = 4; P = 0.04) cells. Retention of CAFdA 5′-triphosphate (CAFdATP) was also longer than that for CdA 5′-triphosphate (CdATP) in cells from leukemic patients. The relative efficacy of CAFdA as a substrate for purified recombinant deoxycytidine kinase (dCK), the key enzyme in the activation of nucleoside analogues, was very high and exceeded that of CdA as well as the natural substrate, deoxycytidine, by a factor of 2 and 8, respectively. The Km for CAFdA with dCK was also lower than that for CdA, as measured in crude extracts from the human acute lymphoblastic leukemia cell line CCRF-CEM and the promyelocytic leukemia cell line HL60. Acquired resistance to CAFdA in HL60 and in CCRF-CEM cell lines was directly correlated to the decreased activity of the nucleoside phosphorylating enzyme, dCK. Resistant cells also showed a considerable degree of cross-resistance to analogues that were activated by dCK. These observations demonstrated that dCK phosphorylates CAFdA more efficiently than CdA. Furthermore, CAFdATP is apparently more stable than CdATP and the mechanisms of resistance to CAFdA are similar to those leading to CdA resistance. These results encourage studies on the clinical effect of CAFdA in lymphoproliferative diseases.
|
|
| 2. |
|
|
| 3. |
- Sandström, Per, et al.
(författare)
-
Idiotypic-anti-idiotypic antibody interactions in experimental radioimmunotargeting.
- 1999
-
Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 5:10 Suppl, s. 3073s-3078s
-
Tidskriftsartikel (refereegranskat)abstract
- Idiotypic-anti-idiotypic antibody interactions can be used in vivo to regulate the serum levels of specific radiolabeled antibodies. Anti-idiotypic antibodies can also be used as clearing agents for radiolabeled antibodies in radioimmunolocalization and radioimmunotherapy. The present study describes the immunochemical interactions between the monoclonal idiotype (H7) and three generated monoclonal anti-idiotypic antibodies (alphaH7:1, alphaH7:35, and alphaH7:38). An unexpected variability in complex formation could be demonstrated in vitro, revealing three different stable complex patterns, i.e., low molecular weight 1:1 complexes, ladder formation with oligomeric, consecutively added constituents, and large linear polymeric complexes of high molecular weight. Within 24 h, the anti-idiotypes were able to cause a significant decrease in total body radioactivity, and the antibody generating a ladder formation (alphaH7:38) was found to be the most efficient at removing radiolabeled idiotypes from the circulation. It is concluded that monoclonal anti-idiotypic antibodies may be valuable tools in improving radioimmunolocalization and radioimmunotargeting.
|
|
