Synergy between tamoxifen and cisplatin in human melanoma cells is dependent on the presence of antiestrogen-binding sites.
We have demonstrated previously that cisplatin (DDP) and tamoxifen (TAM) act synergistically to kill human melanoma T-289 cells, and that the observed synergy is lost in the 3-fold TAM-resistant subline, 289/TAM6. We have identified the intracellular antiestrogen-binding sites (AEBSs), defined by their ability to bind antiestrogens while having no affinity for estrogen, as a possible mediator of this synergy. We report here that [3H]TAM binds to AEBSs, as defined by the ability of N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine-HCl, an AEBS-specific ligand, to compete with [3H]TAM binding. Furthermore, we have characterized the number of binding sites and their affinity for [3H]TAM by Scatchard analysis in whole-cell lysates, microsomal fractions, and nuclear fractions of both cell lines by competing [3H]TAM binding with increasing concentrations of unlabeled TAM. These data demonstrate that the loss of a high-affinity AEBS from the nuclear fraction of the 289/TAM6 cell line correlates with the loss of synergy between DDP and TAM in these cells. This implicates AEBSs as a critical component of the mechanism that mediates the synergistic interaction of DDP and TAM in human melanoma cells.
Jones
J A
JA
Department of Medicine, Medical University of South Carolina, Charleston 29403, USA.
Albright
K D
KD
Christen
R D
RD
Howell
S B
SB
McClay
E F
EF
D001667:Binding, Competitive; D002945:Cisplatin / Q000378:metabolism*; D006632:Histamine / Q000378:metabolism; D006633:Histamine Antagonists / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000378:metabolism*; D010647:Phenyl Ethers / Q000378:metabolism; D011955:Receptors, Drug / Q000378:metabolism*; D013629:Tamoxifen / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D006633:Histamine Antagonists; D010647:Phenyl Ethers; D011955:Receptors, Drug; D013629:Tamoxifen; D006632:Histamine; C043062:tesmilifene; D002945:Cisplatin