Kinesin spindle protein (KSP) inhibitors in combination with chemotherapeutic agents for cancer therapy

Identifying and characterising promising small molecule inhibitors of kinesin spindle protein using ligand-based virtual screening, molecular docking, molecular dynamics and MM‑GBSA calculations

The kinesin spindle protein (Eg5) is a mitotic protein that plays an essential role in the formation of the bipolar spindles during the mitotic phase. Eg5 protein controls the segregation of the chromosomes in mitosis which renders it a vital target for cancer treatment. In this study our approach to identifying novel scaffold for Eg5 inhibitors is based on targeting the novel allosteric pocket (α4/α6/L11). Extensive computational techniques were applied using ligand-based virtual screening and molecular docking by two approaches, MOE and AutoDock, to screen a library of commercial compounds. We identified compound 8-(3-(1H-imidazol-1-ylpropylamino)-3-methyl-7-((naphthalen-3-yl)methyl)-1H-purine-2, 6 (3H,7H)-dione (compound 5) as a novel scaffold for Eg5 inhibitors. This compound inhibited cancer cell Eg5 ATPase at 2.37 ± 0.15 µM. The molecular dynamics simulations revealed that the identified compound formed stable interactions in the allosteric pocket (α4/α6/L11) of the receptor, indicating its potential as a novel Eg5 inhibitor.

The Application of Kinesin Inhibitors in Medical Issues

Kinesins are a group of motor proteins in charge of several crucial functions in the cell. These proteins often bind to microtubules and perform their functions using the energy produced by ATP hydrolysis. One function of mitotic kinesin, a subclass of kinesin that is expressed during cell division at the mitotic phase, is to create the mitotic spindle. Uncontrolled cell growth is one trait of cancerous cells. Traditional anticancer medications still used in clinics include taxanes (paclitaxel) and vinca alkaloids (vincristine, vinblastine), which interfere with microtubule dynamics. However, because non-dividing cells like post-mitotic neurons contain microtubules, unwanted side effects like peripheral neuropathy are frequently found in patients taking these medications. More than ten members of the mitotic kinesin family play distinct or complementary roles during mitosis. The mitotic kinesin family's KSP, or Eg5, is regarded as its most dramatic target protein. The current work systematically reviews the use of kinesin inhibitors in the medical field. The challenges of KSP and the practical solutions are also examined, and the outcomes of the previous works are reported. The significant gaps and shortcomings of the related works are also highlighted, which can be an onset topic for future works.

Organometallic Ru, Os, Rh and Ir half-sandwich conjugates of ispinesib - impact of the organometallic group on the antimitotic activity

Antimitotic agents are among the most important drugs used in anticancer therapy. Kinesin spindle protein (KSP) was proposed as a promising target for new antimitotic drugs. Herein, we report the synthesis of Ru, Os, Rh, and Ir half-sandwich complexes with the KSP inhibitor ispinesib and its (S)-enantiomer. Conjugation of the organometallic moiety with ispinesib and its (S)-enantiomer resulted in a significantly increased cytotoxicity of up to 5.6-fold compared to the parent compounds, with IC50 values in the nanomolar range. The most active derivatives were the ispinesib Ru and Rh conjugates which were able to generate reactive oxygen species (ROS), which may at least partially explain their high cytotoxicity. At the same time, the Os and Ir derivatives acted as KSP inhibitors with no effects on ROS generation.

Kinesin spindle protein inhibitors in cancer: from high throughput screening to novel therapeutic strategies

Bringing to a halt the cell cycle in mitosis and interfering with its normal progression is one of the most successful anti-cancer strategies used nowadays. Classically, several kinds of anti-cancer drugs like taxanes and vinca alkaloids directly inhibit microtubules during cell division. These drugs exhibit serious side effects, most importantly, severe peripheral neuropathies. Alternatively, KSP inhibitors are grasping a lot of research attention as less toxic mitotic inhibitors. In this review, we track the medicinal chemistry developmental stages of KSP inhibitors. Moreover, we address the challenges that are faced during the development of KSP inhibitor therapy for cancer and future insights for the latest advances in research that are directed to find active KSP inhibitor drugs.

Scientists have recognized the importance of selective KSP inhibitors in the early 2000s and so various KSP protein inhibitors have been investigated. Only ten of these have been clinically evaluated for cancer treatment. Ispinesib (SB-715992) and filanesib (Arry-520) were the most promising small molecules in clinical trials against the KSP protein. Many challenges are faced during the development of an active anti-KSP drug; most importantly are the unsatisfactory clinical trial results. Designing dual inhibitors, antibody–drug conjugates, combination therapy and gene therapy approach are among the main strategies that are being investigated nowadays to find new effective KSP inhibitors. The scientific research efforts are still devoted to find an effective and tolerable KSP inhibitor drug that can gain US FDA approval.

Exploiting immune-dependent effects of microtubule-targeting agents to improve efficacy and tolerability of cancer treatment

Microtubule-targeting agents (MTAs), like taxanes and vinca alkaloids, are tubulin-binding drugs that are very effective in the treatment of various types of cancers. In cell cultures, these drugs appear to affect assembly of the mitotic spindle and to delay progression through mitosis and this correlates with their ability to induce cell death. Their clinical efficacy is, however, limited by resistance and toxicity. For these reasons, other spindle-targeting drugs, affecting proteins such as certain kinesins like Eg5 and CENP-E, or kinases like Plk1, Aurora A and B, have been developed as an alternative to MTAs. However, these attempts have disappointed in the clinic since these drugs show poor anticancer activity and toxicity ahead of positive effects. In addition, whether efficacy of MTAs in cancer treatment is solely due to their ability to delay mitosis progression remains controversial. Here we discuss recent findings indicating that the taxane paclitaxel can promote a proinflammatory response by activation of innate immunity. We further describe how this can help adaptive antitumor immune response and suggest, on this basis and on the recent success of immune checkpoint inhibitors in cancer treatment, that a combination therapy based on low doses of taxanes and immune checkpoint inhibitors may be of high clinical advantage in terms of wide applicability, reduced toxicity, and increased antitumor response.

Design, Synthesis, and Biological Evaluation of Tetrahydro-β-carboline Derivatives as Selective Sub-Nanomolar Gelatinase Inhibitors

Targeting matrix metalloproteinases (MMPs) is a pursued strategy for treating several pathological conditions, such as multiple sclerosis and cancer. Herein, a series of novel tetrahydro-β-carboline derivatives with outstanding inhibitory activity toward MMPs are present. In particular, compounds 9 f, 9 g, 9 h and 9 i show sub-nanomolar IC₅₀ values. Interestingly, compounds 9 g and 9 i also provide remarkable selectivity toward gelatinases; IC₅₀ =0.15 nm for both toward MMP-2 and IC₅₀ =0.63 and 0.58 nm, respectively, toward MMP-9. Molecular docking simulations, performed by employing quantum mechanics based partial charges, shed light on the rationale behind binding involving specific interactions with key residues of S1' and S3' domains. Taken together, these studies indicate that tetrahydro-β-carboline represents a promising scaffold for the design of novel inhibitors able to target MMPs and selectively bias gelatinases, over the desirable range of the pharmacokinetics spectrum.

KSP inhibitor SB743921 inhibits growth and induces apoptosis of breast cancer cells by regulating p53, Bcl-2, and DTL

Kinesin spindle protein (KSP) is a microtubule-associated motor protein that is specifically expressed by mitosis cells. It is highly expressed in various types of tumors including hematomalignances and solid tumors. Chemical KSP inhibition has become a novel strategy in the development of anticancer drugs. SB743921 is a selective inhibitor for KSP, which is a mitotic protein essential for cell-cycle progression. Although SB743921 has shown antitumor activities for several types of cancers and entered into clinical trials, its therapeutic effects on breast cancer and mechanisms have not been explored. In this study, we tested the antitumor activity of SB743921 in breast cancer cell lines and partly elucidated its mechanisms. KSP and denticleless E3 ubiquitin–protein ligase homolog (DTL) are overexpressed in breast cancer cells compared with no-cancer tissues. Chemical inhibition of KSP by SB743921 not only reduces proliferation but also induces cell-cycle arrest and leads to apoptosis in breast cancer cells. Treatment of MCF-7 and MDA-MB-231 breast cancer cell lines with SB743921 results in decreased ability of colony formation in culture. SB743921 treatment also causes a KSP accumulation in protein level that is associated with cell arrest. Furthermore, we showed that SB743921 treatment significantly reduces the expression of bcl-2 and cell cycle-related protein DTL, and upregulates p53 and caspase-3 in breast cancer cells. Taken together, these data indicated that SB743921 can be expected to be a novel treatment agent for breast cancers.

Central spindle proteins and mitotic kinesins are direct transcriptional targets of MuvB, B-MYB and FOXM1 in breast cancer cell lines and are potential targets for therapy

The MuvB multiprotein complex, together with B-MYB and FOXM1 (MMB-FOXM1), plays an essential role in cell cycle progression by regulating the transcription of genes required for mitosis and cytokinesis. In many tumors, B-MYB and FOXM1 are overexpressed as part of the proliferation signature. However, the transcriptional targets that are important for oncogenesis have not been identified. Given that mitotic kinesins are highly expressed in cancer cells and that selected kinesins have been reported as target genes of MMB-FOXM1, we sought to determine which mitotic kinesins are directly regulated by MMB-FOXM1. We demonstrate that six mitotic kinesins and two microtubule-associated non-motor proteins (MAPs) CEP55 and PRC1 are direct transcriptional targets of MuvB, B-MYB and FOXM1 in breast cancer cells. Suppression of KIF23 and PRC1 strongly suppressed proliferation of MDA-MB-231 cells. The set of MMB-FOXM1 regulated kinesins genes and 4 additional kinesins which we referred to as the mitotic kinesin signature (MKS) is linked to poor outcome in breast cancer patients. Thus, mitotic kinesins could be used as prognostic biomarker and could be potential therapeutic targets for the treatment of breast cancer.

Downregulation of Kinesin spindle protein inhibits proliferation, induces apoptosis and increases chemosensitivity in hepatocellular carcinoma cells

Background: Kinesin spindle protein (KSP) plays a critical role in mitosis. Inhibition of KSP function leads to cell cycle arrest at mitosis and ultimately to cell death. The aim of this study was to suppress KSP expression by specific small-interfering RNA (siRNA) in Hep3B cells and evaluate its anti-tumor activity. Methods: Three siRNA targeting KSP (KSP-siRNA #1-3) and one mismatched-siRNA (Cont-siRNA) were transfected into cells. Subsequently, KSP mRNA and protein levels, cell proliferation, and apoptosis were examined in both Hep3B cells and THLE-3 cells. In addition, the chemosensitivity of KSP-siRNA-treated Hep3B cells with doxorubicin was also investigated using cell proliferation and clonogenic survival assays. Results: The expression of endogenous KSP at both mRNA and protein levels in Hep3B cells was higher than in THLE-3 cells. In Hep3B cells, KSP-siRNA #2 showed a further downregulation of KSP as compared to KSP-siRNA #1 or KSP-siRNA #3. It also exhibited greater suppression of cell proliferation and induction of apoptosis than KSP-siRNA #1 or KSP-siRNA #3; this could be explained by the significant downregulation of cyclin D1, Bcl-2, and survivin. In contrast, KSP-siRNAs had no or lower effects on KSP expression, cell proliferation and apoptosis in THLE-3 cells. We also noticed that KSP-siRNA transfection could increase chemosensitivity to doxorubicin in Hep3B cells, even at low doses compared to control. Conclusion: Reducing the expression level of KSP, combined with drug treatment, yields promising results for eradicating hepatocellular carcinoma (HCC) cells in vitro. This study opens a new direction for liver cancer treatment.

Kinesin spindle protein inhibitor SB743921 induces mitotic arrest and apoptosis and overcomes imatinib resistance of chronic myeloid leukemia cells

Inhibition of the cell mitotic pathway may provide a novel means for therapeutic intervention in chronic myeloid leukemia (CML). Kinesin spindle protein (KSP), a microtubule-associated motor protein which is essential for cell cycle progression, is overexpressed in bcr-abl+ CML cells. Retrovirus mediated bcr-abl transduction increases KSP expression in cord blood CD34 + cells. SB743921 is a selective KSP inhibitor which is being investigated in ongoing clinical trials for treatment of myeloma, leukemia and solid tumors. Treatment of CML cells with SB743921 resulted in reduced proliferation and colony forming cell (CFC) formation ability. SB743921 also actively blocked cell cycle progression, leading to apoptosis in both primary CML cells and cell lines. KSP inhibition sensitized CML cells to imatinib-induced apoptosis. Importantly, SB743921 inhibited the proliferation of various CML cells including T315I mutation-harboring cells. Furthermore, we demonstrated that SB743921 treatment suppressed ERK and AKT activity in CML cells. These data indicate that SB743921 may become a novel treatment agent for patients with CML.

Chloroquine potentiates the anti-cancer effect of lidamycin on non-small cell lung cancer cells in vitro

AIM

To assess the synergistic actions of lidamycin (LDM) and chloroquine (CQ), a lysosomal enzyme inhibitor, in human non-small cell lung cancer (NSCLC) cells, and to elucidate the potential mechanisms.

METHODS

Human NSCLC cell lines A549 and H460 were treated with CQ and/or LDM. Cell proliferation was analyzed using MTT assay, and apoptosis was quantified using flow cytometry. Western blotting was used to detect the protein levels of caspase 3, PARP, Bcl-2, Bax, p53, LC3-I and LC3-II. A H460 cell xenograft model in BALB/c nude mice was used to evaluate the anticancer efficacy of CQ and LDM in vivo.

RESULTS

Both LDM and CQ concentration-dependently suppressed the proliferation of A549 and H460 cells in vitro (the IC50 values of LDM were 1.70 ± 0.75 and 0.043 ± 0.026 nmol/L, respectively, while the IC50 values of CQ were 71.3 ± 6.1 and 55.6 ± 12.5 μmol/L, respectively). CQ sensitized both NSCLC cell lines to LDM, and the majority of the coefficients of drug interaction (CDIs) for combination-doses were less than 1. The ratio of apoptosis of H460 cells induced by a combined treatment of CQ and LDM (77.0% ± 5.2%) was significantly higher than those caused by CQ (23.1% ± 4.2%) or by LDM (65.1% ± 4.1%) alone. Furthermore, the combined treatment markedly increased the cleaved PARP and cleaved caspase 3 in H460 cells, which were partly reversed by pretreatment with the caspase inhibitor zVAD.fmk. zVAD.fmk also partially reversed the inhibitory effect of the combination treatment on the proliferation of H460 cells. The combination therapy group had a notable increase in expression of Bax and a very slight decrease in expression of Bcl-2 and p53 protein. LDM alone scarcely affected the level of LC3-II in H460 cells, but slightly reduced CQ-induced LC3-II expression. 3-MA, an autophagy inhibitor also sensitized H460 cells to LDM. In nude mice bearing H460 cell xenograft, administration of LDM (25 μg/kg, iv) and CQ (60 mg/kg, ip) suppressed tumor growth by 57.14% and 73.02%, respectively.

CONCLUSION

The synergistic anticancer effect of LDM and CQ in vitro results from activation of a caspase-dependent and p53-independent apoptosis pathway as well as inhibition of cytoprotective autophagy.