The antiproliferative properties of tamoxifen and phenothiazines may be mediated by a unique histamine receptor (?H3) distinct from the calmodulin-binding site

Abstract

N,N-diethyl-2-[(4-phenylmethyl)-phenoxyl]-ethanamine HCl (DPPE), a novel histamine antagonist (?H3), which selectively binds with high affinity to the antiestrogen-binding site (AEBS/?H3), inhibits the activity of calmodulin-dependent myosin light chain kinase (MLCK) only at concentrations >1 mM, as opposed to tamoxifen (TAM), which has an IC50=4 μM in the same assay. This suggests that the antiestrogen-binding site is distinct from the site on calmodulin which binds TAM and phenothiazines. However, at an in vitro concentration of 1×10-6 M, the antiproliferative effects of DPPE and several phenothiazines, which also compete for binding to AEBS/?H3, are about equal; this suggests that affinity for AEBS/?H3 rather than that for the calmodulin-binding site may correlate with clinically relevant antigrowth effects of these compounds.

DOI: 10.1007/BF00253057

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@article{Brandes1986TheAP, title={The antiproliferative properties of tamoxifen and phenothiazines may be mediated by a unique histamine receptor (?H3) distinct from the calmodulin-binding site}, author={Lorne J. Brandes and R. Patricia Bogdanovic and Max D. Cawker and Ratna Bose}, journal={Cancer Chemotherapy and Pharmacology}, year={1986}, volume={18}, pages={21-23} }