Cell-based and biochemical structure-activity analyses of analogs of the microtubule stabilizer dictyostatin.
Compounds that bind to microtubules (MTs) and alter their dynamics are highly sought as a result of the clinical success of paclitaxel and docetaxel. The naturally occurring compound (-)-dictyostatin binds to MTs, causes cell cycle arrest in G(2)/M at nanomolar concentrations, and retains antiproliferative activity in paclitaxel-resistant cell lines, making dictyostatin an attractive candidate for development as an antineoplastic agent. In this study, we examined a series of dictyostatin analogs to probe biological and biochemical structure-activity relationships. We used a high-content multiparameter fluorescence-based cellular assay for MT morphology, chromatin condensation, mitotic arrest, and cellular toxicity to identify regions of dictyostatin that were essential for biological activity. Four analogs (6-epi-dictyostatin, 7-epi-dictyostatin, 16-normethyldictyostatin, and 15Z,16-normethyldictyostatin) retained low nanomolar activity in the cell-based assay and were chosen for analyses with isolated tubulin. All four compounds were potent inducers of MT assembly. Equilibrium binding constant (K(i)) determinations using [(14)C]epothilone B, which has a 3-fold higher affinity for the taxoid binding site than paclitaxel, indicated that 6-epi-dictyostatin and 7-epi-dictyostatin displaced [(14)C]epothilone B with K(i) values of 480 and 930 nM, respectively. 16-Normethyldictyostatin and 15Z,16-normethyldictyostatin had reduced affinity (K(i) values of 4.55 and 4.47 muM, respectively), consistent with previous reports showing that C16-normethyldictyostatin loses potency in paclitaxel-resistant cell lines that have a Phe270-to-Val mutation in the taxoid binding site of beta-tubulin. Finally, we developed a set of quantitative structure-activity relationship equations correlating structures with antiproliferative activity. The equations accurately predicted biological activity and will help in the design of future analogs.
Raccor
Brianne S
BS
Departments of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Vogt
Andreas
A
Sikorski
Rachel P
RP
Madiraju
Charitha
C
Balachandran
Raghavan
R
Montgomery
Kia
K
Shin
Youseung
Y
Fukui
Yoshikazu
Y
Jung
Won-Hyuk
WH
Curran
Dennis P
DP
Day
Billy W
BW
D000473:Alkanes / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity; D000818:Animals; D001562:Benzimidazoles / Q000378:metabolism; D001665:Binding Sites; D001923:Brain Chemistry; D002219:Carbamates / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity; D002277:Carcinoma / Q000188:drug therapy / Q000473:pathology; D002417:Cattle; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D034261:Epothilones / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000633:toxicity; D005260:Female; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes / Q000378:metabolism; D016195:G2 Phase / Q000187:drug effects; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007783:Lactones / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity; D018942:Macrolides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D008870:Microtubules / Q000187:drug effects*; D015394:Molecular Structure; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000473:pathology; D017239:Paclitaxel / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D011753:Pyrones / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity; D021281:Quantitative Structure-Activity Relationship; D011869:Radioligand Assay; D014404:Tubulin / Q000096:biosynthesis; D050257:Tubulin Modulators / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity
D000473:Alkanes; D001562:Benzimidazoles; D002219:Carbamates; D034261:Epothilones; D005456:Fluorescent Dyes; D006657:Histones; D007783:Lactones; D018942:Macrolides; D011753:Pyrones; D014404:Tubulin; D050257:Tubulin Modulators; C470814:dictyostatin; C071229:discodermolide; D016650:Fluorescein-5-isothiocyanate; D017239:Paclitaxel; C017807:bisbenzimide ethoxide trihydrochloride; C093788:epothilone B