Orally active microtubule-targeting agent, MPT0B271, for the treatment of human non-small cell lung cancer, alone and in combination with erlotinib

Discovery of novel amide derivatives against VEGFR-2/tubulin with potent antitumor and antiangiogenic activity

Dual-target agents have more advantages than drug combinations for cancer treatment. Here, we designed and synthesized a series of novel VEGFR-2/tubulin dual-target inhibitors through a molecular hybridization strategy, and the activities of all the synthesized compounds were tested against tubulin and VEGFR-2. Among which, compound 19 exhibited strong potency against tubulin and VEGFR-2, with IC50 values of 0.76 ± 0.11 μM and 15.33 ± 2.12 nM, respectively. Additionally, compound 19 not only had significant antiproliferative effects on a series of human cancer cell lines, especially MGC-803 cells (IC50 = 0.005 ± 0.001 μM) but also overcame drug resistance in Taxol-resistant MGC-803 cells, with an RI of 1.8. Further studies showed that compound 19 could induce tumor cell apoptosis by reducing the mitochondrial membrane potential, increasing the level of ROS, facilitating the induction of G2/M phase arrest, and inhibiting the migration and invasion of tumor cells in a dose-dependent manner. In addition, compound 19 also exhibits potent antiangiogenic effects by blocking the VEGFR-2/PI3K/AKT pathway and inhibiting the tubule formation, invasion, and migration of HUVECs. More importantly, compound 19 demonstrated favorable pharmacokinetic profiles, robust in vivo antitumor efficacy, and satisfactory safety profiles. Overall, compound 19 can be used as a lead compound for the development of tubulin/VEGFR-2 dual-target inhibitors.

Leaf Extract of Nerium oleander L. Inhibits Cell Proliferation, Migration and Arrest of Cell Cycle at G2/M Phase in HeLa Cervical Cancer Cell

BACKGROUND

Cervical cancer is one of the most common gynaecological malignant tumors reported in women. Although a number of early screening and treatment options are available, mortality due to cervical cancer remains high. Nerium oleander L. is a potential medicinal plant that possesses a wide spectrum of pharmacological and physiological activities including anticancer activities.

OBJECTIVE

This study aims to evaluate the antiproliferative activity, inhibition of cell migration and cell cycle arrest by the chloroform extract of leaves of Nerium Oleander L. in HeLa cervical cancer cells. The chloroform extract of Catharanthus roseus which contains anti-cancer compounds, Vinblastin and Vincristin, was used as a positive control for this study.

METHODS

The chloroform extracts of Nerium oleander L. and Catharanthus roseus were prepared using the standard protocol. The cytotoxic effects were studied by MTT assay. Cell migration was studied by in vitro scratch assay. Analysis of the cell cycle was carried out by Propidium iodide staining and Flow Cytometry. The expression level of various proteins was evaluated by immunocytochemistry.

RESULTS

In this study, we showed that the leaf extract of Nerium oleander inhibited the growth of HeLa cervical cancer cells in culture and inhibited cell migration. Besides, it arrested the cell cycle at the G2/M phase. The Epidermal Growth Factor Receptor (EGFR) expression and phosphorylated p-Rb (Ser 780) level were significantly downregulated by leaf extract of Nerium oleander.

CONCLUSION

The extract of Nerium oleander L. contains potential bioactive compounds that inhibit HeLa cell proliferation, cell migration and arrest cell cycle at the G₂/M phase.

NMK-BH2, a novel microtubule-depolymerising bis (indolyl)-hydrazide-hydrazone, induces apoptotic and autophagic cell death in cervical cancer cells by binding to tubulin at colchicine - site

BACKGROUND

Microtubules, the key components of the eukaryotic cytoskeleton and mitotic spindle, are one of the most sought-after targets for cancer chemotherapy, especially due to their indispensible role in mitosis. Cervical cancer is a prevalent malignancy among women of developing countries including India. In spite of the remarkable therapeutic advancement, the non-specificity of chemotherapeutic drugs adversely affect the patients' survival and well-being, thus, necessitating the quest for novel indole-based anti-microtubule agent against cervical cancer, with high degree of potency and selectivity.

METHODS

For in vitro studies, we used MTT assay, confocal microscopy, fluorescence microscopy, flow cytometry and Western blot analysis. Study in cell free system was accomplished by spectrophotometry, fluorescence spectroscopy and TEM and computational analysis was done by AutodockTools 1.5.6.

RESULTS

NMK-BH2 exhibited significant and selective anti-proliferative activity against cervical cancer HeLa cells (IC₅₀ = 1.5 μM) over normal cells. It perturbed the cytoskeletal and spindle microtubules of HeLa cells leading to mitotic block and cell death by apoptosis and autophagy. Furthermore, NMK-BH2 targeted the tubulin-microtubule system through fast and strong binding to the αβ-tubulin heterodimers at colchicine-site.

CONCLUSION

This study identifies and characterises NMK-BH2 as a novel anti-microtubule agent and provides insights into its key anti-cancer mechanism through two different cell death pathways: apoptosis and autophagy, which are mutually independent.

GENERAL SIGNIFICANCE

It navigates the potential of the novel bis (indolyl)-hydrazide-hydrazone, NMK-BH2, to serve as lead for development of new generation microtubule-disrupting chemotherapeutic with improved efficacy and remarkable selectivity towards better cure of cervical cancer.

Antitubulin sulfonamides: The successful combination of an established drug class and a multifaceted target

Tubulin, the microtubules and their dynamic behavior are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal drug targets. Sulfonamides are exemplary drugs with applications in the clinic, in veterinary and in the agrochemical industry. This review summarizes the actual state and recent progress of both fields looking from the double point of view of the target and its drugs, with special focus onto the structural aspects. The article starts with a brief description of tubulin structure and its dynamic assembly and disassembly into microtubules and other polymers. Posttranslational modifications and the many cellular means of regulating and modulating tubulin's biology are briefly presented in the tubulin code. Next, the structurally characterized drug binding sites, their occupying drugs and the effects they induce are described, emphasizing on the structural requirements for high potency, selectivity, and low toxicity. The second part starts with a summary of the favorable and highly tunable combination of physical-chemical and biological properties that render sulfonamides a prototypical example of privileged scaffolds with representatives in many therapeutic areas. A complete description of tubulin-binding sulfonamides is provided, covering the different species and drug sites. Some of the antimitotic sulfonamides have met with very successful applications and others less so, thus illustrating the advances, limitations, and future perspectives of the field. All of them combine in a mechanism of action and a clinical outcome that conform efficient drugs.

Enhancement of apoptotic activities on brain cancer cells via the combination of γ-tocotrienol and jerantinine A

BACKGROUND

γ-Tocotrienol, a vitamin E isomer possesses pronounced in vitro anticancer activities. However, the in vivo potency has been limited by hardly achievable therapeutic levels owing to inefficient high-dose oral delivery which leads to subsequent metabolic degradation. Jerantinine A, an Aspidosperma alkaloid, originally isolated from Tabernaemontana corymbosa, has proved to possess interesting anticancer activities. However, jerantinine A also induces toxicity to non-cancerous cells.

PURPOSE

We adopted a combinatorial approach with the joint application of γ-tocotrienol and jerantinine A at lower concentrations in order to minimize toxicity towards non-cancerous cells while improving the potency on brain cancer cells.

METHODS

The antiproliferative potency of individual γ-tocotrienol and jerantinine A as well as combined in low-concentration was firstly evaluated on U87MG cancer and MRC5 normal cells. Morphological changes, DNA damage patterns, cell cycle arrests and the effects of individual and combined low-concentration compounds on microtubules were then investigated. Finally, the potential roles of caspase enzymes and apoptosis-related proteins in mediating the apoptotic mechanisms were investigated using apoptosis antibody array, ELISA and Western blotting analysis.

RESULTS

Combinatorial study between γ-tocotrienol at a concentration range (0-24µg/ml) and fixed IC₂₀ concentration of jerantinine A (0.16µg/ml) induced a potent antiproliferative effect on U87MG cells and led to a reduction on the new half maximal inhibitory concentration of γ-tocotrienol (i.e._tIC₅₀=1.29µg/ml) as compared to that of individual γ-tocotrienol (i.e. IC₅₀=3.17µg/ml). A reduction on undesirable toxicity to MRC5 normal cells was also observed. G0/G1 cell cycle arrest was evident on U87MG cells receiving IC₅₀ of individual γ-tocotrienol and combined low-concentration compounds (1.29µg/ml γ-tocotrienol + 0.16µg/ml jerantinine A), whereas, a profound G2/M arrest was evident on cells treated with IC₅₀ of individual jerantinine A. Additionally, individual jerantinine A and combined compounds (except individual γ-tocotrienol) caused a disruption of microtubule networks triggering Fas- and p53-induced apoptosis mediated via the death receptor and mitochondrial pathways.

CONCLUSIONS

These findings demonstrated that the combined use of lower concentrations of γ-tocotrienol and jerantinine A induced potent cytotoxic effects on U87MG cancer cells resulting in a reduction on the required individual concentrations and thereby minimizing toxicity of jerantinine A towards non-cancerous MRC5 cells as well as probably overcoming the high-dose limiting application of γ-tocotrienol. The multi-targeted mechanisms of action of the combination approach have shown a therapeutic potential against brain cancer in vitro and therefore, further in vivo investigations using a suitable animal model should be the way forward.

Anti-leukemia effects of the novel synthetic 1-benzylindole derivative 21-900 in vitro and in vivo

Cancers are the major cause of death worldwide. Chemotherapy using cytotoxic drugs and targeted therapy is required when surgery is difficult, ineffective, or impossible. We previously synthesized the novel synthetic 1-benzylindole derivative 21-900 and found that it inhibits histone deacetylase (HDAC) activities and tubulin assembly. Here we tested its effects on the human leukaemia cell lines HL-60 and MOLT-4 in vitro and in vivo. We found that its potent cytotoxic effects were mediated through cell cycle arrest at the G2/M phase, which increased the population of sub-G1 cells, leading to apoptosis. Further, tubulin was depolymerized by 21-900 in a manner similar to that of vincristine, leading to disruption of microtubule dynamics and increased levels of the mitotic marker MPM-2. Further, 21-900 increased the expression of cleavage form of poly (ADP-ribose) polymerase (PARP), caspase 3, 7 (cleavage form), and pro-apoptotic protein BAK and decreased the expression of pro-survival BCL-2-family proteins BCL-2, MCL-1, and BID pro-form, leading to the induction of apoptosis. The growth of tumours in nude mice formed by xenografts of HL-60 and MOLT-4 cells was significantly inhibited by 21-900 without causing the mice to lose body weight. These findings indicate that 21-900 may serve as a potent anti-leukaemia drug.

Rh(III)-Catalyzed C-H Functionalization of Indolines with Readily Accessible Amidating Reagent: Synthesis and Anticancer Evaluation

The rhodium(III)-catalyzed direct C-H functionalization of various indolines with 1,4,2-dioxazol-5-ones as new amidating agents is described. This transformation provides efficient preparation of C7-amidated indolines known to display potent anticancer activity. The synthetic compounds were evaluated for in vitro anticancer activity against human prostate adenocarcinoma cells (LNCaP), human endometrial adenocarcinoma cells (Ishikawa), and human ovarian carcinoma cells (SKOV3). Compound 4f was found to be highly cytotoxic, with activity competitive with that of anticancer agent doxorubicin.

A Novel Nitrobenzoate Microtubule Inhibitor that Overcomes Multidrug Resistance Exhibits Antitumor Activity

Multidrug resistance is a major limitation for microtubule-binding agents in cancer treatment. Here we report a novel microtubule inhibitor (2-morpholin-4-yl-5-nitro-benzoic acid 4-methylsulfanyl-benzyl ester, IMB5046), its cytotoxicity against multidrug-resistant cell lines and its antitumor efficacy in animal models. IMB5046 disrupted microtubule structures in cells and inhibited purified tubulin polymerization in vitro. It bound to the colchicine pocket of tubulin. IMB5046 displayed potent cytotoxicity against multiple tumor cell lines with an IC50 range of 0.037-0.426 μM. Notably, several multidrug-resistant cell lines which were resistant to colchicine, vincristine and paclitaxel remained sensitive to IMB5046. IMB5046 was not a P-glycoprotein substrate. IMB5046 blocked cell cycle at G2/M phase and induced cell apoptosis. Microarray assay indicated that the differentially expressed genes after IMB5046 treatment were highly related to immune system, cell death and cancer. In a mouse xenograft model IMB5046 inhibited the growth of human lung tumor xenograft by 83% at a well-tolerated dose. It is concluded that IMB5046 is a tubulin polymerization inhibitor with novel chemical structure and can overcome multidrug resistance. It is a promising lead compound for cancer chemotherapy, especially for treatment of multidrug-resistant tumors.

Activity of cyclin B1 in HL-60 cells treated with etoposide

Cyclin B1 triggers G2/M phase transition phosphorylating with its catalytical partner - Cdc2 many of the molecular targets essential for cell cycle progression. Human leukemia cell line HL-60 were treated with increasing doses of etoposide (ETP) (0.5; 0.75; 1μM) to investigate how the drug affects cell morphology, viability, cell cycle distribution and expression of cyclin B1. To achieve this aim we applied light and transmission electron microscopy to observe morphological and ultra structural changes, image-based cytometry for apoptosis evaluation and cell cycle analysis, and then we conducted immunohistochemical and immunofluorescence staining to visualize cyclin localization and expression. Quantitive data about cyclin B1 expression were obtained from flow cytometry. Etoposide caused decrease in cell viability, induced apoptosis and G2/M arrest accompanied by enhanced expression of cyclin B1. Changes in expression and localization of cyclin B1 may constitute a part of the mechanism responsible for resistance of HL-60 cells to etoposide. Our results may reflect involvement of cyclin B1 in opposite processes - apoptosis induction and maintenance of cell viability in leukemia cells. We hypothesized possible roles and pathways by which cyclin B1 takes part in drug treatment response and chemosensitivity.

Synergistic cytotoxic effects of combined δ-tocotrienol and jerantinine B on human brain and colon cancers

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Tabernaemontana has widespread distribution throughout tropical and subtropical parts of the world, i.e. Africa, Asia and America which has long been used for treatments of different disease conditions including tumours, wounds, syphilis, stomach ache and headache. Some Tabernaemontana species are used for treatment of piles, spleen and abdominal tumours in India. In particular, the leaf of Tabernaemontana corymbosa is used for treatment of tumours in Bangladesh. Parts of the plant or whole plants are used as decoctions, steam bath, powder and ointments.

AIM OF STUDY

The present study was undertaken to study the mechanism of apoptosis induction in human glioblastoma (U87MG) and colorectal adenocarcinoma (HT-29) cancer cells by a novel indole alkaloid, jerantinine B isolated from T. corymbosa, δ-tocotrienol and the combined low-dose treatments of δ-tocotrienol with IC20 dose of jerantinine B.

MATERIALS AND METHODS

Cell viability, isobologram and combinational index (CI) analyses were used to determine the pharmacological interaction between combined treatments based on the IC50 values obtained. Fluorescence and histochemical staining techniques as well as comet assay were used for evaluating the morphological changes and DNA damage pattern, respectively. The effects of treatments on microtubules, caspase activity and cell death were determined using immunofluorescence technique, caspase colorimetric and neutral red uptake assays, respectively.

RESULTS

Jerantinine B, δ-tocotrienol and combined low-dose treatments induced a dose-dependent growth inhibition against U87MG and HT-29 cells selectively with less toxicity acted towards the normal MRC5 cells. Synergistic growth inhibition observed with CI values of 0.85 and 0.77 for U87MG and HT-29 cells, resulting in up to 2-fold and 3.8-fold dose reduction of δ-tocotrienol and jerantinine B, respectively. U87MG and HT-29 cells exhibited morphological features of apoptosis and double stranded DNA breaks. Individual and combined treatments induced caspase 8 and 3 activities and cell death independent of caspase activation on U87MG and HT-29 cells. An increased caspase 9 activity was also evident on U87MG and HT-29 treated with combined treatments and HT-29 cells treated with jerantinine B. Jerantinine B and combined low-dose treatments with δ-tocotrienol undoubtedly disrupted the microtubule networks.

CONCLUSION

The present study demonstrated the mechanism for cytotoxic potency of δ-tocotrienol and jerantinine B against U87MG and HT-29 cells. Furthermore, combined low-dose treatments induced concurrent synergistic inhibition of cancer cell growth with concomitant dose reduction thus minimizing toxicity to normal cells and improving potency of δ-tocotrienol and jerantinine B.

Obatoclax as a perpetrator in drug-drug interactions and its efficacy in multidrug resistance cell lines

OBJECTIVES

Obatoclax is a pan-Bcl-2 inhibitor with promising efficacy, especially when combined with other antineoplastic agents. Pharmacokinetic drug-drug interactions can occur systemically and at the level of the tumour cell. Thus, this study scrutinised the interaction potential of obatoclax in vitro.

METHODS

Obatoclax was screened for P-gp inhibition by calcein assay, for breast cancer resistance protein (BCRP) inhibition by pheophorbide A assay and for inhibition of cytochrome P450 isoenzymes (CYPs) by commercial kits. Induction of mRNA of drug-metabolising enzymes and drug transporters was quantified in LS180 cells via real-time polymerase chain reaction and involvement of nuclear receptors was assessed by reporter gene assays. Proliferation assays were used to assess whether obatoclax retains its efficacy in cell lines overexpressing BCRP, P-glycoprotein (P-gp) or multidrug resistance-associated protein 2 (MRP2).

KEY FINDINGS

Obatoclax induced the mRNA expression of several genes (e.g. CYP1A1, CYP1A2 and ABCG2 (five to seven-fold) through activation of the aryl hydrocarbon receptor in the nanomolar range. Obatoclax inhibits P-gp, BCRP and some CYPs at concentrations exceeding plasma levels. P-gp, MPR2 or BCRP overexpression did not influence the efficacy of obatoclax.

CONCLUSIONS

Obatoclax retains its efficacy in cells overexpressing P-gp, MRP2 or BCRP and might act as a perpetrator drug in interactions with drugs, for example being substrates of CYP1A2 or BCRP.