The antineoplastic agent estramustine and the derivative estramustine-phosphate inhibit secretion of interleukin-3 in leukemic cells. Possible roles of MAPs.
The antineoplastic drug estramustine is an adduct of estradiol and nor-nitrogen mustard. It has been shown that this drug interferes with microtubule assembly, an effect mediated by estramustine interaction with microtubule-associated proteins (MAPs). In the present report we demonstrate that estramustine and the phosphorylated derivative of the drug, estramustine-phosphate, inhibit the secretion of interleukin-3 by WEHI-3B cells. These studies also show that the estramustine derivative specifically interacts with a MAPs component found in these cells, which exhibited characteristics ressembling those of tau protein isoforms. Western blots using a unique monoclonal antibody MTB6.22 that recognizes microtubule-binding domains on MAPs, indicated that this WEHI protein factor contained the antigenic determinant that are functionally significant for microtubule assembly. ELISA assays using this antibody, also showed a decrease in the levels of the immunoreactive protein in WEHI cells after treatment with EMP. Interestingly, it has been recently described that the action of estramustine-phosphate is mediated by a direct interaction with MAP-binding sites on the microtubule surface, which are recognized by the site-specific monoclonal antibody. These findings together with immuno-precipitation experiments using anti-interleukin-3 antibodies and the inhibitory effect of the estramustine derivative on WEHI secretion process suggest that this anti-mitotic agent may block IL-3 secretion by a mechanism involving its interaction with a 'tau-like' MAPs component present in these cells.
Martínez
J
J
Instituto de Nutrición y Tecnología de Alimentos (INTA), Universidad de Chile, Santiago.
Santibáñez
J F
JF
Vial
C
C
Maccioni
R B
RB
D000818:Animals; D002846:Chromatography, Affinity; D004261:DNA Replication / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D004961:Estramustine / Q000378:metabolism / Q000494:pharmacology*; D007377:Interleukin-3 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000302:isolation & purification / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D013936:Thymidine / Q000378:metabolism; D014316:Tritium; D014407:Tumor Cells, Cultured
D007377:Interleukin-3; D008869:Microtubule-Associated Proteins; D013462:Sulfur Radioisotopes; D014316:Tritium; D004961:Estramustine; D008715:Methionine; D013936:Thymidine