Interference of a novel indolylmaleimide with microtubules induces mitotic arrest and apoptosis in human progenitor and cancer cells

Indole derivatives as tubulin polymerization inhibitors for the development of promising anticancer agents

The α- and β-tubulins are the major polypeptide components of microtubules (MTs), which are attractive targets for anticancer drug development. Indole derivatives display a variety of biological activities including antitumor activity. In recent years, a great number of indole derivatives as tubulin polymerization inhibitors have sprung up, which encourages medicinal chemists to pursue promising inhibitors with improved antitumor activities, excellent physicochemical, pharmacokinetic and pharmacodynamic properties. In this review, the recent progress from 2010 to present in the development of indole derivatives as tubulin polymerization inhibitors was summarized and reviewed, which would provide useful clues and inspirations for further design of outstanding tubulin polymerization inhibitors.

A Simple LC-MS/MS Method for the Quantification of PDA-66 in Human Plasma

The treatment of cancer is one of the most important pharmacotherapeutic challenges. To this end, chemotherapy has for some time been complemented by targeted therapies against specific structures. PDA-66, a structural analogue of the inhibitor of serine–threonine kinase glycogen synthase kinase 3β SB216763, has shown preclinical antitumour effects in various cell lines, with the key pathways of its anticancer activity being cell cycle modulation, DNA replication and p53 signalling. For the monitoring of anticancer drug treatment in the context of therapeutic drug monitoring, the determination of plasma concentrations is essential, for which an LC-MS/MS method is particularly suitable. In the present study, a sensitive LC-MS/MS method for the quantification of the potential anticancer drug PDA-66 in human plasma with a lower limit of quantification of 2.5 nM is presented. The method was successfully validated and tested for the determination of PDA-66 in mouse plasma and sera.

PDA Indolylmaleimides Induce Anti-Tumor Effects in Prostate Carcinoma Cell Lines Through Mitotic Death

Castrate resistant prostate cancer in men shares several characteristics with canine prostate cancer (PCa). Due to current insufficient therapies, evaluating novel therapeutic agents for late-stage PCa is of considerable interest for both species. PDA indolylmaleimides showed anticancer effects in several neoplastic cell lines. Herein, a comparative characterization of PDA-66 and PDA-377 mediated effects was performed in human and canine PCa cell lines, which is also the first detailed characterization of these agents on cells derived from solid tumors in general. While PDA-377 showed only weak growth inhibition on human PCa cell lines, PDA-66 inhibited proliferation and induced apoptosis in human and canine cell lines with concentrations in the low micromolar range. Morphological characterization and whole transcriptome sequencing revealed that PDA-66 induces mitotic death through its microtubule-depolymerizing ability. PDA-66 appears to be a worthwhile anti-mitotic agent for further evaluation. The similarities in cellular and molecular response observed in the cell lines of both origins form a solid basis for the use of canine PCa in vivo models to gain valuable interchangeable data to the advantage of both species.

Characterization of the novel indolylmaleimides' PDA-66 and PDA-377 effect on canine lymphoma cells

Protein kinase inhibitors are widely used in chemotherapeutic cancer regimens. Maleimide derivatives such as SB-216763 act as GSK-3 inhibitor targeting cell proliferation, cell death and cell cycle progression.

Herein, the two arylindolylmaleimide derivatives PDA-66 and PDA-377 were evaluated as potential chemotherapeutic agents on canine B-cell lymphoma cell lines. Canine lymphoma represents a naturally occurring model closely resembling the human high-grade non-Hodgkin's lymphoma (NHL). PDA-66 showed more pronounced effects on both cell lines. Application of 2.5μM PDA-66 resulted in a significant induction of apoptosis (approx. 11 %), decrease of the metabolic activity (approx. 95 %), anti-proliferative effect (approx. 85 %) and cell death within 48h. Agent induced mode of action was characterized by whole transcriptome sequencing, 12 h and 24 h post-agent exposure. Key PDA-66-modulated pathways identified were cell cycle, DNA replication and p53 signaling. Expression analyses indicated that the drug acting mechanism is mediated through DNA replication and cycle arrest involving the spindle assembly checkpoint.

In conclusion, both PDA derivatives displayed strong anti-proliferation activity in canine B-cell lymphoma cells. The cell and molecular PDA-induced effect characterization and the molecular characterization of the agent acting mechanism provides the basis for further evaluation of a potential drug for canine lymphoma serving as model for human NHL.

5-(Furan-2-yl)-4-(3,4,5-trimethoxyphenyl)-3H-1,2-dithiol-3-one oxime (6f), a new synthetic compound, causes human fibrosarcoma HT-1080 cell apoptosis by disrupting tubulin polymerisation and inducing G2/M arrest

In the current study, we synthesized a series of new compounds targeting tubulin and tested their anti-proliferative activities. Among these new synthetic com-pounds, 5-(furan-2-yl)-4-(3,4,5-trimethoxyphenyl)-3H-1,2-dithiol-3-one oxime (6f) exhibited significant anti-proliferative activity against different human cancer cell lines including human gastric adenocarcinoma SGC-7901, human non-small cell lung cancer A549, and human fibrosarcoma HT-1080. As a result, 6f was selected to further test the sensitivity to different cancer cell lines including human cervical cancer cell line HeLa, human breast cancer cell line MCF-7, non-small cell lung cancer cell line A549, human liver carcinoma cell line HepG-2, human oral squamous cell carcinoma cell lines KB, SGC-7901 and HT-1080. Among these cell lines, HT-1080 and HeLa are the most sensitive. Therefore, HT-1080 was selected to further explore the properties of anti-proliferative activity and the underlying mechanisms. Our data proved that 6f exhibited strong anti-proliferative effects against HT-1080 cells in a time- and dose-dependent manner. We showed that the growth inhibitory effect of 6f in HT-1080 cells was related with microtubule depolymerisation. Molecular docking studies revealed that 6f interacted and bound efficiently with the colchicine-binding site of tubulin. In addition, 6f treatment induced G2/M cell cycle arrest dose-dependently and subsequently induced cell apoptosis. Western blot study indicated that upregulation of cyclin B1 and p-cdc2 was related with G2/M arrest. 6f-induced cell apoptosis was associated with both mitochondrial and death receptor pathway. In conclusion, our data showed that 6f, among the newly synthetic compounds, exhibited highest anti-proliferative activity by disrupting the microtubule polymerisation, causing G2/M arrest and subsequently inducing cell apoptosis in HT-1080 cells. Hence, 6f is a promising microtubule depolymerising agent for the treatment of various cancers especially human fibrosarcoma.

Zerumbone, a ginger sesquiterpene, induces apoptosis and autophagy in human hormone-refractory prostate cancers through tubulin binding and crosstalk between endoplasmic reticulum stress and mitochondrial insult

Zerumbone, a natural monocyclic sesquiterpene, is the main component of the tropical plant Zingiber zerumbet Smith. Zerumbone induced antiproliferative and apoptotic effects against PC-3 and DU-145, two human hormone-refractory prostate cancer (HRPC) cell lines. Zerumbone inhibited microtubule assembly and induced an increase of MPM-2 expression (specific recognition of mitotic proteins). It also caused an increase of phosphorylation of Bcl-2 and Bcl-xL, two key events in tubulin-binding effect, indicating tubulin-binding capability and mitotic arrest to zerumbone action. Furthermore, zerumbone induced several cellular effects distinct from tubulin-binding properties. First, zerumbone significantly increased, while paclitaxel (as a tubulin-binding control) decreased, Mcl-1 protein expression. Second, paclitaxel but not zerumbone induced Cdk1 activity. Third, zerumbone other than paclitaxel induced Cdc25C downregulation. The data suggest that, in addition to targeting tubulin/microtubule, zerumbone may act on other targets for signaling transduction. Zerumbone induced mitochondrial damage and endoplasmic reticulum (ER) stress as evidenced by the loss of mitochondrial membrane potential and upregulation of GRP-78 and CHOP/GADD153 expression. Zerumbone induced an increase of intracellular Ca(2+) levels, a crosstalk marker between ER stress and mitochondrial insult, associated with the formation of active calpain I fragment. It induced apoptosis through a caspase-dependent way and caused autophagy as evidenced by dramatic LC3-II formation. In summary, the data suggest that zerumbone is a multiple targeting compound that inhibits tubulin assembly and induces a crosstalk between ER stress and mitochondrial insult, leading to apoptosis and autophagy in HRPCs.

MCL-1 degradation mediated by JNK activation via MEKK1/TAK1-MKK4 contributes to anticancer activity of new tubulin inhibitor MT189

Colchicine site-targeted tubulin inhibitors are a promising type of anticancer drugs. MT189 is a new derivative of MT119, a previously reported colchicine site-binding antitubulin agent. In this study, MT189 was demonstrated to retain the property of MT119 in disrupting microtubulin via binding to the colchicine site, causing mitotic arrest and inducing apoptosis, and to display 8.7-fold enhanced proliferative inhibition in a panel of cancer cells. MT189 was shown to elicit in vivo anticancer effects on MDA-MB-231 xenografts in nude mice, and the tumor growth was suppressed by 35.9% over 14 days. MT189 led to degradation of MCL-1, a member of the antiapoptotic BCL-2 protein family. Its overexpression reduced but its silenced expression increased the apoptotic induction followed by the treatment with MT189. Moreover, the treatment with MT189 caused activation of the MEKK1/TAK1-MKK4-JNK signaling pathway. The activated JNK resulted in phosphorylation of MCL-1, which facilitated its ubiquitination-mediated degradation. Our results show that MT189 inhibits microtubulin polymerization by binding to the colchicine site. Relief of apoptotic suppression by MCL-1 degradation together with mitotic arrest contributes to the anticancer activity of MT189.

The novel arylindolylmaleimide PDA-66 displays pronounced antiproliferative effects in acute lymphoblastic leukemia cells

Background

Prognosis of adult patients suffering from acute lymphoblastic leukemia (ALL) is still unsatisfactory. Targeted therapy via inhibition of deregulated signaling pathways appears to be a promising therapeutic option for the treatment of ALL. Herein, we evaluated the influence of a novel arylindolylmaleimide (PDA-66), a potential GSK3β inhibitor, on several ALL cell lines.

Methods

ALL cell lines (SEM, RS4;11, Jurkat and MOLT4) were exposed to different concentrations of PDA-66. Subsequently, proliferation, metabolic activity, apoptosis and necrosis, cell cycle distribution and protein expression of Wnt and PI3K/Akt signaling pathways were analyzed at different time points.

Results

PDA-66 inhibited the proliferation of ALL cells significantly by reduction of metabolic activity. The 72 h IC50 values ranged between 0.41 to 1.28 μM PDA-66. Additionally, caspase activated induction of apoptosis could be detected in the analyzed cell lines. PDA-66 influenced the cell cycle distribution of ALL cell lines differently. While RS4;11 and MOLT4 cells were found to be arrested in G2 phase, SEM cells showed an increased cell cycle in G0/1 phase.

Conclusion

PDA-66 displays significant antileukemic activity in ALL cells and classifies as candidate for further evaluation as a potential drug in targeted therapy of ALL.

Intrinsic apoptotic pathway and G2/M cell cycle arrest involved in tubeimoside I-induced EC109 cell death

OBJECTIVE

Squamous esophageal carcinoma is highly prevalent in developing countries, especially in China. Tu Bei Mu (TBM), a traditional folk medicine, has been used to treat esophageal squamous cell carcinoma (ESCC) for a long term. tubeimoside I (TBMS1) is the main component of TBM, exhibiting great anticancer potential. In this study, we investigated the mechanism of TBMS1 cytotoxic effect on EC109 cells.

METHODS

Comparative nuclear proteomic approach was applied in the current study and we identified several altered protein spots. Further biochemical studies were carried out to detect the mitochondrial membrane potential, cell cycle and corresponding proteins' expression and location.

RESULTS

Subcellular proteomic study in the nucleus from EC109 cells revealed that altered proteins were associated with mitochondrial function and cell proliferation. Further biochemical studies showed that TBMS1-induced molecular events were related to mitochondria-induced intrinsic apoptosis and P21-cyclin B1/cdc2 complex-related G2/M cell cycle arrest.

CONCLUSIONS

Considering the conventional application of TBM in esophageal cancer, TBMS1 therefore may have a great potential as a chemotherapeutic drug candidate for ESCC.