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Comparison of the ability of anti-proliferative KU-72, KU-80 and KU-70, jasplakinolide (JAS) and the known microtubule destabilizing anticancer drug vincristine (VCR) to alter the kinetics of glycerol-induced tubulin polymerization in vitro. The conditions of the assays were identical to those of Figure 5B. The polymerization reactions were incubated in the presence or absence (control) of 10 μM VCR, 48, 120 or 300 μM KU-72, 300 μM KU-80, 120 μM KU-70, and 5 μM JAS. Results are expressed as the percentage of the rate of glycerol-induced tubulin polymerization based on the linear increase in turbidity between 80 and 520 s in vehicle-treated control assays (Δ A340 nm =0.190±0.012; 100±6.6%). Data are means±SD (n=2). a Not different from control; b p<0.05, significantly less than control.
Source publication
Synthetic 6,7-annulated-4-substituted indole compounds, which elicit interesting antitumor effects in murine L1210 leukemia cells, were tested for their ability to inhibit human HL-60 tumor cell proliferation, disrupt mitosis and cytokinesis, and interfere with tubulin and actin polymerization in vitro.
Various markers of metabolic activity, mitoti...
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Context 1
... 300 μM, KU- 72 mimics the inhibitory effect of VCR and reduces the rate and extent of glycerol-induced tubulin polymerization by 72.2% and 70.5%, respectively, suggesting that this annulated indole, which increased the mitotic cell index like VCR ( Figure 3A), might also be a MT de-stabilizing drug that prevents MT assembly ( Figure 5B). Glycerol-induced tubulin polymerization between 80 and 520 s is inhibited by 93.7% in the presence of 10 μM of the known tubulin binder VCR but remains unaltered in the presence of 5 μM of the known actin binder JAS ( Figure 6). In contrast, the three annulated indoles, which increased the mitotic index of HL-60 tumor cells, are also capable of inhibiting the polymerization of tubulin in the cell-free turbidity assay. ...
Context 2
... contrast, the three annulated indoles, which increased the mitotic index of HL-60 tumor cells, are also capable of inhibiting the polymerization of tubulin in the cell-free turbidity assay. Indeed, 120 μM KU-70 and 300 μM KU-80 reduced the rate of glycerol-induced tubulin polymerization by 57.9% and 59.0%, respectively, whereas 48, 120 and 300 μM KU-72 clearly induced concentration-dependent inhibitory effects that reduced tubulin polymerization by 23.0, 46.3 and 70.5%, respectively ( Figure 6). Stimulation of actin polymerization. ...
Citations
... GM-4-53 and GM-3-121 were further evaluated for effects on replicative DNA synthesis using radio-labeled incorporation of TdR (Figure 3), findings which showed significant losses that would otherwise be required for cell division. Likewise, these changes correlated with static cytoskeletal changes fostering giant multinucleated cells in a similar fashion often reported for paclitaxel (20,21) (Figure 4A). These changes occurred tantamount to altered polymerized tubulin ( Figure 4B) which is otherwise required to disassemble and reform into spindle platforms for chromosome assembly during cell division. ...
Triple-negative breast cancer (TNBC) occurs at greater frequency amongst African-Americans, being characterized by the absence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal receptor 2 (HER2). TNBC is often invasive and typically treated with cytostatic agents such as taxanes in combination with anthracyclines or platinum-based drugs. In this study, we synthesized a number of tetrahydroisoquinoline moieties by Namination of substituted isoquinolines by O-mesytelene sulfonylhydroxylamine followed by ylide formation and reduction, which yielded the desired, substituted tetrahydroisoquinolines (THIQs) in moderate to good yield. Using a differential scatter plot to identify potential selective ERmodulating drugs in ER-positive control cells (MCF-7) driven by estradiol vs. TNBC (MDA-MB-231) cells, the in vitro data showed an absence of effects on the ER (compared to 4-hydroxytamoxifen and raloxifene). In contrast, two lead compounds halted proliferation (cytostatic) in MDA-MB-231 TNBC cells at a potency level below 2.5 M concomitant with mitotic arrest, attenuated replicative DNA synthesis, halted microtubule nucleation/stunted tubulin polymerization, abnormal expansive cytoskeletal tubulin and actin morphologies with multinucleation of cells. The most effective cytostatic compounds GM-4-53 and GM-3-121 blocked replicative processes at the G2 growth phase. These findings suggest that specific THIQs work independently of the ER, by holding static the microtubule network thereby preventing mitosis. Future work is required to establish the safety and efficacy of these drugs and their potential adjunct therapeutic gain in the presence of taxanes in TNBC.
A practical, multi-gram 10-step synthesis of racemic herbindole A, B, and C from a common intermediate is described. The key step features a remarkably regioselective C-7 metal-halogen exchange and elimination from a Bartoli-generated N-t-butyldimethylsilyl-4,6,7-tribromo-5-methylindole scaffold to afford the 6,7-indole aryne. Cycloaddition with cyclopentadiene, oxidative cleavage, and Fujimoto reduction gave a common intermediate from which all three herbindoles were readily derived. A final Pd(0)-catalyzed Negishi and Stille cross-coupling reaction at the C-4 bromide afforded each of the herbindoles on a multigram scale.
