Reversine, a novel Aurora kinases inhibitor, inhibits colony formation of human acute myeloid leukemia cells

Recent advancements in mechanistic research, therapeutic potential, and structure-activity relationships of aurora kinase inhibitors in cancer therapies

Aurora kinases (AURKs)-a family of serine/threonine protein kinases consisting of AURK-A, AURK-B, and AURK-C, are critical regulators of chromosomal segregation, centrosome maturation, and cytokinesis during the cell cycle. Each kinase is activated via phosphorylation at unique threonine residues: Thr288 (AURK-A), Thr232 (AURK-B), and Thr195 (AURK-C). Activation of AURK-A and AURK-B through phosphorylation triggers a series of downstream signaling pathways, including RalA, NF-κB, p53, PLK1, BRCA1/BRCA2, H2AX, and Kif2C, as well as multiple transmembrane kinase receptors. Dysregulation of these pathways has been implicated in cancer development and progression, positioning AURKs as pivotal targets for anticancer drug research. Inhibition of AURKs has demonstrated significant efficacy in tumor growth suppression and induction of cancer cell death, thereby focusing recent research on the development of potent AURK inhibitors. This review provides an in-depth exploration of AURK inhibitors, discussing their biological activities, structure-activity relationships, selectivity profiles, and mechanisms of action. Notably, compounds 6, 27, and 16 exhibit potent AURK-A inhibition with IC50 values of 1.7 nM, 11.83 nM, and 15 nM, respectively. Similarly, compounds 28, 16, and 7 demonstrate strong AURK-B inhibitory activity, with IC50 values of 10.5 nM, 12 nM, and 14.09 nM, respectively. This comprehensive overview aims to support medicinal chemists in developing more potent, selective, and safe AURK inhibitors as potential anticancer therapeutics.

Complex aneuploidy triggers autophagy and p53-mediated apoptosis and impairs the second lineage segregation in human preimplantation embryos

About 70% of human cleavage stage embryos show chromosomal mosaicism, falling to 20% in blastocysts. Chromosomally mosaic human blastocysts can implant and lead to healthy new-borns with normal karyotypes. Studies in mouse embryos and human gastruloids showed that aneuploid cells are eliminated from the epiblast by p53-mediated apoptosis while being tolerated in the trophectoderm. These observations suggest a selective loss of aneuploid cells from human embryos, but the underlying mechanisms are not yet fully understood. Here, we investigated the cellular consequences of aneuploidy in a total of 125 human blastocysts. RNA-sequencing of trophectoderm cells showed activated p53 pathway and apoptosis proportionate to the level of chromosomal imbalance. Immunostaining corroborated that aneuploidy triggers proteotoxic stress, autophagy, p53-signaling, and apoptosis independent from DNA damage. Total cell numbers were lower in aneuploid embryos, due to a decline both in trophectoderm and in epiblast/primitive endoderm cell numbers. While lower cell numbers in trophectoderm may be attributed to apoptosis, aneuploidy impaired the second lineage segregation, particularly primitive endoderm formation. This might be reinforced by retention of NANOG. Our findings might explain why fully aneuploid embryos fail to further develop and we hypothesize that the same mechanisms lead to the removal of aneuploid cells from mosaic embryos.

Targeting APC/C Ubiquitin E3-Ligase Activation with Pyrimidinethylcarbamate Apcin Analogues for the Treatment of Breast Cancer

Activation of the ubiquitin ligase APC/C by the protein Cdc20 is an essential requirement for proper cell division in higher organisms, including humans. APC/C is the ultimate effector of the Spindle Assembly Checkpoint (SAC), the signalling system that monitors the proper attachment of chromosomes to microtubules during cell division. Defects in this process result in genome instability and cancer. Interfering with APC/C substrate ubiquitylation in cancer cells delays mitotic exit, which induces cell death. Therefore, impairing APC/C function represents an opportunity for the treatment of cancer and malignancies associated with SAC dysregulation. In this study, we report a new class of pyrimidinethylcarbamate apcin analogues that interfere with APC/C activity in 2D and 3D breast cancer cells. The new pyrimidinethylcarbamate apcin analogues exhibited higher cytotoxicity than apcin in all breast cancer cell subtypes investigated, with much lower cytotoxicity observed in fibroblasts and RPE-1 cells. Further molecular rationalisation of apcin and its derivatives was conducted using molecular docking studies. These structural modifications selected from the in silico studies provide a rational basis for the development of more potent chemotypes to treat highly aggressive breast cancer and possibly other aggressive tumour types of diverse tissue origins.

Development of 2-Aminoadenine-Based Proteolysis-Targeting Chimeras (PROTACs) as Novel Potent Degraders of Monopolar Spindle 1 and Aurora Kinases

Monopolar spindle 1 (Mps1, also known as TTK) and Aurora kinase (AURK) A and B are critical regulators of mitosis and have been linked to the progression of various cancers. Here, we report the design, synthesis, and biological evaluation of a series of PROTACs (proteolysis-targeting chimeras) targeting TTK and AURKs. We synthesized various degrader molecules based on four different 2-aminoadenine-based ligands, recruiting either cereblon or VHL as the E3-ligase. Our research showed that the nature of the linker and modification of the ligand significantly influence the target specificity and degradation efficacy. Notably, compound 19, among the most potent degraders, demonstrated robust proteasome-mediated degradation of TTK with D max of 66.5% and DC50 value (6 h) of 17.7 nM as compared to its structurally akin inhibitor control, 23. The cytotoxicity of most of the synthesized chimeras against acute myeloid leukemia cell line MV4-11 was lower than that of the corresponding parent inhibitors. However, we could also identify degraders such as 15 and 26 that induce potent AURKA degradation and display comparable antiproliferative activities to their parent compound SF1. Compound 15 degrades AURKA with low DC50 value of 2.05 nM, which is 77-fold and 21-fold more selective toward AURKB and TTK and has an EC50 value of 39 nM against cancer MV4-11 cells. Overall, the observations we made with the degrader molecules we developed can further aid in the design and development of optimized TTK or AURK degraders for cancer therapy.

Design and synthesis of (E)-3-benzylideneindolin-2-one derivatives as potential allosteric inhibitors of Aurora A kinase

The mitotic kinase Aurora A, a pivotal regulator of the cell cycle, is overexpressed in various cancers and has emerged as one of the most promising targets for anticancer drug discovery. However, the lack of specificity and potential toxicity have impeded clinical trials involving orthosteric inhibitors. In this study, allosteric sites of Aurora A were predicted using the AlloReverse web server. Based on the non-ATP competitive inhibitor Tripolin A and molecular docking information targeting the desired allosteric site 3 of Aurora A, a series of (E)-3-benzylideneindolin-2-one derivatives were designed and synthesized. Compared to Tripolin A, our compounds AK09, AK34 and AK35 have stronger inhibitory effects and can be further investigated as potential allosteric inhibitors. Moreover, the compound AK34 with the strongest inhibitory activity (IC50 = 1.68 μM) has a high affinity for Aurora A (K D = 216 nM). According to the analysis of the structure-activity relationship of the compounds and the results of their molecular docking models, these compounds tend to act on the allosteric site 3 of Aurora A.

HIF1A contributes to the survival of aneuploid and mosaic pre-implantation embryos

Human fertility is suboptimal, partly due to error-prone divisions in early cleavage-stages that result in aneuploidy. Most human pre-implantation are mosaics of euploid and aneuploid cells, however, mosaic embryos with a low proportion of aneuploid cells have a similar likelihood of developing to term as fully euploid embryos. How embryos manage aneuploidy during development is poorly understood. This knowledge is crucial for improving fertility treatments and reducing developmental defects. To explore these mechanisms, we established a new mouse model of chromosome mosaicism to study the fate of aneuploid cells during pre-implantation development. We previously used the Mps1 inhibitor reversine to generate aneuploidy in embryos. Here, we found that treatment with the more specific Mps1 inhibitor AZ3146 induced chromosome segregation defects in pre-implantation embryos, similar to reversine. However, AZ3146-treated embryos showed a higher developmental potential than reversine-treated embryos. Unlike reversine-treated embryos, AZ3146-treated embryos exhibited transient upregulation of Hypoxia Inducible-Factor-1A (HIF1A) and lacked p53 upregulation. Pre-implantation embryos develop in a hypoxic environment in vivo, and hypoxia exposure in vitro reduced DNA damage in response to Mps1 inhibition and increased the proportion of euploid cells in the mosaic epiblast. Inhibiting HIF1A in mosaic embryos also decreased the proportion of aneuploid cells in mosaic embryos. Our work illuminates potential strategies to improve the developmental potential of mosaic embryos.

Reversine inhibits proliferation and induces apoptosis of human osteosarcoma cells through targeting MEK1

Reversine, or 2-(4-morpholinoanilino)-6-cyclohexylaminopurine, is a 2,6-disubstituted purine derivative. This small molecule shows anti-tumor potential by playing a central role in the inhibition of several kinases related to cell cycle regulation and cytokinesis. In this study, systematic review demonstrated the feasibility and pharmacological mechanism of anti-tumor effect of reversine. Firstly, we grafted MNNG/HOS, U-2 OS, MG-63 osteosarcoma cell aggregates onto chicken embryonic chorioallantoic membrane (CAM) to examine the tumor volume of these grafts after reversine treatment. Following culture, reversine inhibited the growth of osteosarcoma cell aggregates on CAM significantly. In vitro experiment, reversine suppressed osteosarcoma cell viability, colony formation, proliferation, and induced apoptosis and cell cycle arrest at G0-G1 phase. Scratch wound assay demonstrated that reversine restrained cell migration. Reversine increased the protein expression of E-cadherin. The mRNA expression of Rac1, RhoA, CDC42, PTK2, PXN, N-cadherin, Vimentin in MNNG/HOS, U-2 OS and MG-63 cells were suppressed and PTEN increased after reversine treatment. Network pharmacology prediction, molecular docking and systematic review revealed MEK1 can be used as an effective target for reversine to inhibit osteosarcoma. Western blot results show the regulation of MEK1 and ERK1/2 by reversine was not consistent in different osteosarcoma cell lines, but we found that reversine significantly inhibited the protein expression of MEK1 in MNNG/HOS, U-2 OS and MG-63. All these suggested that reversine can exert its anti-tumor effect by targeting the expression of MEK1.

A comprehensive review on role of Aurora kinase inhibitors (AKIs) in cancer therapeutics

Aurora kinases (AURKs) are a family of serine /threonine protein kinases that have a crucial role in cell cycle process mainly in the event of chromosomal segregation, centrosome maturation and cytokinesis. The family consists of three members including Aurora kinase A (AURK-A), Aurora kinase B (AURK-B) and Aurora kinase C (AURK-C). All AURKs contain a conserved kinase domain for their activity but differ in their cellular localization and functions. AURK-A and AURK-B are expressed mainly in somatic cells while the expression of AURK-C is limited to germ cells. AURK-A promotes G2 to M transition of cell cycle by controlling centrosome maturation and mitotic spindle assembly. AURK-B and AURK-C form the chromosome passenger complex (CPC) that ensures proper chromosomal alignments and segregation. Aberrant expression of AURK-A and AURK-B has been detected in several solid tumours and malignancies. Hence, they have become an attractive therapeutic target against cancer. The first part of this review focuses on AURKs structure, functions, subcellular localization, and their role in tumorigenesis. The review also highlights the functional and clinical impact of selective as well as pan kinase inhibitors. Currently, >60 compounds that target AURKs are in preclinical and clinical studies. The drawbacks of existing inhibitors like selectivity, drug resistance and toxicity have also been addressed. Since, majority of inhibitors are Aurora kinase inhibitor (AKI) type-1 that bind to the active (DFGin and Cin) conformation of the kinase, this information may be utilized to design highly selective kinase inhibitors that can be combined with other therapeutic agents for better clinical outcomes.

In Vitro Characterization of Reversine-Treated Gingival Fibroblasts and Their Safety Evaluation after In Vivo Transplantation

Reversine is a purine derivative that has been investigated with regard to its biological effects, such as its anticancer properties and, mostly, its ability to induce the dedifferentiation of adult cells, increasing their plasticity. The obtained dedifferentiated cells have a high potential for use in regenerative procedures, such as regenerative dentistry (RD). Instead of replacing the lost or damaged oral tissues with synthetic materials, RD uses stem cells combined with matrices and an appropriate microenvironment to achieve tissue regeneration. However, the currently available stem cell sources present limitations, thus restricting the potential of RD. Based on this problem, new sources of stem cells are fundamental. This work aims to characterize mouse gingival fibroblasts (GFs) after dedifferentiation with reversine. Different administration protocols were tested, and the cells obtained were evaluated regarding their cell metabolism, protein and DNA contents, cell cycle changes, morphology, cell death, genotoxicity, and acquisition of stem cell characteristics. Additionally, their teratoma potential was evaluated after in vivo transplantation. Reversine caused toxicity at higher concentrations, with decreased cell metabolic activity and protein content. The cells obtained displayed polyploidy, a cycle arrest in the G2/M phase, and showed an enlarged size. Additionally, apoptosis and genotoxicity were found at higher reversine concentrations. A subpopulation of the GFs possessed stem properties, as supported by the increased expression of CD90, CD105, and TERT, the existence of a CD106+ population, and their trilineage differentiation capacity. The dedifferentiated cells did not induce teratoma formation. The extensive characterization performed shows that significant functional, morphological, and genetic changes occur during the dedifferentiation process. The dedifferentiated cells have some stem-like characteristics, which are of interest for RD.

Treatment of CHO cells with Taxol and reversine improves micronucleation and microcell-mediated chromosome transfer efficiency

Microcell-mediated chromosome transfer is an attractive technique for transferring chromosomes from donor cells to recipient cells and has enabled the generation of cell lines and humanized animal models that contain megabase-sized gene(s). However, improvements in chromosomal transfer efficiency are still needed to accelerate the production of these cells and animals. The chromosomal transfer protocol consists of micronucleation, microcell formation, and fusion of donor cells with recipient cells. We found that the combination of Taxol (paclitaxel) and reversine rather than the conventional reagent colcemid resulted in highly efficient micronucleation and substantially improved chromosomal transfer efficiency from Chinese hamster ovary donor cells to HT1080 and NIH3T3 recipient cells by up to 18.3- and 4.9-fold, respectively. Furthermore, chromosome transfer efficiency to human induced pluripotent stem cells, which rarely occurred with colcemid, was also clearly improved after Taxol and reversine treatment. These results might be related to Taxol increasing the number of spindle poles, leading to multinucleation and delaying mitosis, and reversine inducing mitotic slippage and decreasing the duration of mitosis. Here, we demonstrated that an alternative optimized protocol improved chromosome transfer efficiency into various cell lines. These data advance chromosomal engineering technology and the use of human artificial chromosomes in genetic and regenerative medical research.

Progress on the Pharmacological Targeting of Janus Pseudokinases

The Janus kinases (JAKs) are key components of the JAK-STAT signaling pathway and are involved in myriad physiological processes. Though they are the molecular targets of many FDA-approved drugs, these drugs manifest adverse effects due in part to their inhibition of the requisite JAK kinase activity. However, the JAKs uniquely possess an integrated pseudokinase domain (JH2) that regulates the adjacent kinase domain (JH1). The therapeutic targeting of JH2 domains has been less thoroughly explored and may present an avenue to modulate the JAKs without the adverse effects associated with targeting the adjacent JH1 domain. The potential of this strategy was recently demonstrated with the FDA approval of the TYK2 JH2 ligand deucravacitinib for treating plaque psoriasis. In this light, the structure and targetability of the JAK pseudokinases are discussed, in conjunction with the state of development of ligands that bind to these domains.

Aurora B Inhibitors as Cancer Therapeutics

The Aurora kinases (A, B, and C) are a family of three isoform serine/threonine kinases that regulate mitosis and meiosis. The Chromosomal Passenger Complex (CPC), which contains Aurora B as an enzymatic component, plays a critical role in cell division. Aurora B in the CPC ensures faithful chromosome segregation and promotes the correct biorientation of chromosomes on the mitotic spindle. Aurora B overexpression has been observed in several human cancers and has been associated with a poor prognosis for cancer patients. Targeting Aurora B with inhibitors is a promising therapeutic strategy for cancer treatment. In the past decade, Aurora B inhibitors have been extensively pursued in both academia and industry. This paper presents a comprehensive review of the preclinical and clinical candidates of Aurora B inhibitors as potential anticancer drugs. The recent advances in the field of Aurora B inhibitor development will be highlighted, and the binding interactions between Aurora B and inhibitors based on crystal structures will be presented and discussed to provide insights for the future design of more selective Aurora B inhibitors.

A screening of inhibitors targeting the receptor kinase FERONIA reveals small molecules that enhance plant root immunity

Receptor-like kinases (RLKs) constitute the largest receptor family involved in the regulation of plant immunity and growth, but small-molecule inhibitors that target RLKs to improve agronomic traits remain unexplored. The RLK member FERONIA (FER) negatively regulates plant resistance to certain soil-borne diseases that are difficult to control and cause huge losses in crop yields and economy. Here, we identified 33 highly effective FER kinase inhibitors from 1494 small molecules by monitoring FER autophosphorylation in vitro. Four representative inhibitors (reversine, cenisertib, staurosporine and lavendustin A) inhibited the kinase activity of FER and its homologues in several crops by targeting the conserved ATP pocket in the kinase structure. FER contributes to the physiological impact of representative inhibitors in plants. The treatment of roots with reversine, staurosporine and lavendustin A enhanced innate immunity in plant roots and thus alleviated soil-borne diseases in tobacco, tomato and rice without growth penalties. Consistently, RNA sequencing assays showed that lavendustin A and reversine exert profound impacts on immunity-related gene expression. Our results will set a new milestone in the development of the plant RLK kinase regulation theory and provide a novel strategy for the prevention and control of plant soil-borne diseases without growth penalties.

Discovery of potential Aurora-A kinase inhibitors by 3D QSAR pharmacophore modeling, virtual screening, docking, and MD simulation studies

The Aurora-kinase family comprises of cell cycle-regulated serine/threonine kinases playing a vital role during mitosis. Aurora-A kinase is involved in multiple mitotic events in cell cycle and is a major regulator of centrosome function during mitosis. Aurora-A is overexpressed in breast, lung, colon, ovarian, glial, and pancreatic cancer. Hence, Aurora-A kinase is a promising target in cancer therapy. In our current study, a four-point 3D QSAR pharmacophore model has been generated using substituted pyrimidine class of Aurora-A kinase inhibitors. It had a fixed cost value 88.7429. The model mapped well to the external test set comprising of clinically active molecules, with a correlation coefficient r = 0.99. From the mapping, it was found that the hydrophobic features (HY) of a molecule play an important role for Aurora-A kinase inhibitory activity, whereas the ring aromatic feature provides geometric constraint for spatial alignment of different functional group. The hypothesis, with one hydrogen bond acceptor, two ring aromatic features, and one hydrophobic feature, was selected to screen miniMaybridge database. The screened ligands were filtered on the basis of activity, shape, and drug likeliness. This led to the identification of five top hits. These identified potential leads were further subjected to docking with the ATP-binding site of Aurora-A kinase. The molecular dynamic simulation studies of top lead molecules having diverse scaffolds endorsed that the identified molecules had distinctive ability to inhibit Aurora-A kinase. Thus, this study may facilitate the medicinal chemists to design promising ligands with various scaffolds to inhibit Aurora-A kinase. Communicated by Ramaswamy H. Sarma.

Computational Biology Dynamics of Mps1 Kinase Molecular Interactions with Isoflavones Reveals a Chemical Scaffold with Potential to Develop New Therapeutics for the Treatment of Cancer

The protein kinase Mps1 (monopolar spindle 1) is an important regulator of the Spindle Assembly Checkpoint (SAC), the evolutionary conserved checkpoint system of higher organisms that monitors the proper bipolar attachment of all chromosomes to the mitotic spindle during cell division. Defects in the catalytic activity and the transcription regulation of Mps1 are associated with genome instability, aneuploidy, and cancer. Moreover, multiple Mps1 missense and frameshift mutations have been reported in a wide range of types of cancer of different tissue origin. Due to these features, Mps1 arises as one promising drug target for cancer therapy. In this contribution, we developed a computational biology approach to study the dynamics of human Mps1 kinase interaction with isoflavones, a class of natural flavonoids, and compared their predicted mode of binding with that observed in the crystal structure of Mps1 in complex with reversine, a small-sized inhibitor of Mps1 and Aurora B kinases. We concluded that isoflavones define a chemical scaffold that can be used to develop new Mps1 inhibitors for the treatment of cancer associated with Mps1 amplification and aberrant chromosome segregation. In a broader context, the present report illustrates how modern chemoinformatics approaches can accelerate drug development in oncology.

Co-treatment with miR-21-5p inhibitor and Aurora kinase inhibitor reversine suppresses breast cancer progression by targeting sprouty RTK signaling antagonist 2

Numerous studies have reported the regulatory effects of miR-21-5p and reversine in human breast cancer (HBC). However, the mechanism of reversine and miR-21-5p has not been fully investigated in HBC. The aim of the current study was to assess the mechanism of action of reversine, with or without miR-21-5p, in HBC progression. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot results confirmed the upregulation of miR-21-5p and downregulation of sprouty RTK signaling antagonist 2 (SPRY2) in HBC. Bioinformatics analysis and luciferase assay identified the correlation between miR-21-5p and SPRY2. Cell function experiment results indicated a decrease in migration, proliferation, and invasion of HBC cells treated with miR-21-5p inhibitor and reversine; however, an increase in apoptosis was observed in these cells. Apoptotic ability was more enhanced and migration, proliferation, and invasion were more impaired in HBC cells treated with both miR-21-5p inhibitor and reversine than in those treated individually with either inhibitors. SPRY2, downstream of miR-21-5p, participated in HBC progression with reversine. Overall, our study proved that combining the miR-21-5p inhibitor with reversine produced a synergistic effect by regulating SPRY2, thereby limiting HBC progression. This knowledge might offer insights into the clinical therapy of HBC.

Exploration of the structural requirements of Aurora Kinase B inhibitors by a combined QSAR, modelling and molecular simulation approach

Aurora kinase B plays an important role in the cell cycle to orchestrate the mitotic process. The amplification and overexpression of this kinase have been implicated in several human malignancies. Therefore, Aurora kinase B is a potential drug target for anticancer therapies. Here, we combine atom-based 3D-QSAR analysis and pharmacophore model generation to identify the principal structural features of acylureidoindolin derivatives that could potentially be responsible for the inhibition of Aurora kinase B. The selected CoMFA and CoMSIA model showed significant results with cross-validation values (q²) of 0.68, 0.641 and linear regression values (r²) of 0.971, 0.933 respectively. These values support the statistical reliability of our model. A pharmacophore model was also generated, incorporating features of reported crystal complex structures of Aurora kinase B. The pharmacophore model was used to screen commercial databases to retrieve potential lead candidates. The resulting hits were analyzed at each stage for diversity based on the pharmacophore model, followed by molecular docking and filtering based on their interaction with active site residues and 3D-QSAR predictions. Subsequently, MD simulations and binding free energy calculations were performed to test the predictions and to characterize interactions at the molecular level. The results suggested that the identified compounds retained the interactions with binding residues. Binding energy decomposition identified residues Glu155, Trp156 and Ala157 of site B and Leu83 and Leu207 of site C as major contributors to binding affinity, complementary to 3D-QSAR results. To best of our knowledge, this is the first comparison of WaterSwap field and 3D-QSAR maps. Overall, this integrated strategy provides a basis for the development of new and potential AK-B inhibitors and is applicable to other protein targets.

Aza-Reversine Promotes Reprogramming of Lung (MRC-5) and Differentiation of Mesenchymal Cells into Osteoblasts

Reversine or 2-(4-morpholinoanilino)-N6-cyclohexyladenine was originally identified as a small organic molecule that induces dedifferentiation of lineage-committed mouse myoblasts, C2C12, and redirects them into lipocytes or osteoblasts under lineage-specific conditions (LISCs). Further, it was proven that this small molecule can induce cell cycle arrest and apoptosis and thus selectively lead cancer cells to cell death. Further studies demonstrated that reversine, and more specifically the C2 position of the purine ring, can tolerate a wide range of substitutions without activity loss. In this study, a piperazine analog of reversine, also known as aza-reversine, and a biotinylated derivative of aza-reversine were synthesized, and their potential medical applications were investigated by transforming the endoderm originates fetal lung cells (MRC-5) into the mesoderm originated osteoblasts and by differentiating mesenchymal cells into osteoblasts. Moreover, the reprogramming capacity of aza-reversine and biotinylated aza-reversine was investigated against MRC-5 cells and mesenchymal cells after the immobilization on PMMA/HEMA polymeric surfaces. The results showed that both aza-reversine and the biofunctionalized, biotinylated analog induced the reprogramming of MRC-5 cells to a more primitive, pluripotent state and can further transform them into osteoblasts under osteogenic culture conditions. These molecules also induced the differentiation of dental and adipose mesenchymal cells to osteoblasts. Thus, the possibility to load a small molecule with useful “information” for delivering that into specific cell targets opens new therapeutic personalized applications.

Targeting glioma cells by antineoplastic activity of reversine

Gliomas are the most common type of primary central nervous system tumors and despite great advances in understanding the molecular basis of the disease very few new therapies have been developed. Reversine, a synthetic purine analog, is a multikinase inhibitor that targets aurora kinase A (AURKA) and aurora kinase B (AURKB). In gliomas, a high expression of AURKA or AURKB is associated with a malignant phenotype and a poor prognosis. The present study investigated reversine-related cellular and molecular antiglioma effects in HOG, T98G and U251MG cell lines. Gene and protein expression were assessed by reverse transcription-quantitative PCR and western blotting, respectively. For functional assays, human glioma cell lines (HOG, T98G and U251MG) were exposed to increasing concentrations of reversine (0.4–50 µM) and subjected to various cellular and molecular assays. Reversine reduced the viability and clonogenicity in a dose- and/or time-dependent manner in all glioma cells, with HOG (high AURKB-expression) and T98G (high AURKA-expression) cells being more sensitive compared with U251MG cells (low AURKA- and AURKB-expression). Notably, HOG cells presented higher levels of polyploidy, while T98G presented multiple mitotic spindles, which is consistent with the main regulatory functions of AURKB and AURKA, respectively. In molecular assays, reversine reduced AURKA and/or AURKB expression/activity and increased DNA damage and apoptosis markers, but autophagy-related proteins were not modulated. In conclusion, reversine potently induced mitotic catastrophe and apoptosis in glioma cells and higher basal levels of aurora kinases and genes responsive to DNA damage and may predict improved antiglioma responses to the drug. Reversine may be a potential novel drug in the antineoplastic arsenal against gliomas.

Reversine, a selective MPS1 inhibitor, induced autophagic cell death via diminished glucose uptake and ATP production in cholangiocarcinoma cells

Reversine is a selective inhibitor of mitotic kinase monopolar spindle 1 (MPS1) and has been reported as an anticancer agent in various cancers. The effects of reversine on bile duct cancer, cholangiocarcinoma (CCA), a lethal cancer in Northeastern Thailand, were investigated. This study reports that reversine inhibited cell proliferation of CCA cell lines in dose- and time-dependent manners but had less inhibitory effect on an immortalized cholangiocyte cell line. Reversine also triggered apoptotic cell death by decreasing anti-apoptotic proteins, Bcl-XL and Mcl-1, increasing Bax pro-apoptotic protein and activating caspase-3 activity. Moreover, reversine induced autophagic cell death by increasing LC3-II and Beclin 1 while decreasing p62. Reversine activated autophagy via the AKT signaling pathway. Additionally, this study demonstrated for the first time that reversine could diminish the expression of Hypoxia-Inducible Factor 1- alpha (HIF-1α) and glucose transporter 1 (GLUT1), resulting in a reduction of glucose uptake and energy production in CCA cell lines. These findings suggest that reversine could be a good candidate as an alternative or supplementary drug for CCA treatment.

Targeting AURKA in Cancer: molecular mechanisms and opportunities for Cancer therapy

Aurora kinase A (AURKA) belongs to the family of serine/threonine kinases, whose activation is necessary for cell division processes via regulation of mitosis. AURKA shows significantly higher expression in cancer tissues than in normal control tissues for multiple tumor types according to the TCGA database. Activation of AURKA has been demonstrated to play an important role in a wide range of cancers, and numerous AURKA substrates have been identified. AURKA-mediated phosphorylation can regulate the functions of AURKA substrates, some of which are mitosis regulators, tumor suppressors or oncogenes. In addition, enrichment of AURKA-interacting proteins with KEGG pathway and GO analysis have demonstrated that these proteins are involved in classic oncogenic pathways. All of this evidence favors the idea of AURKA as a target for cancer therapy, and some small molecules targeting AURKA have been discovered. These AURKA inhibitors (AKIs) have been tested in preclinical studies, and some of them have been subjected to clinical trials as monotherapies or in combination with classic chemotherapy or other targeted therapies.

Tumor-specific lytic path “hyperploid progression mediated death”: Resolving side effects through targeting retinoblastoma or p53 mutant

A major advance was made to reduce the side effects of cancer therapy via the elucidation of the tumor-specific lytic path “hyperploid progression-mediated death” targeting retinoblastoma (Rb) or p53-mutants defective in G1 DNA damage checkpoint. The genetic basis of human cancers was uncovered through the cloning of the tumor suppressor Rb gene. It encodes a nuclear DNA-binding protein whose self-interaction is regulated by cyclin-dependent kinases. A 3D-structure of Rb dimer is shown, confirming its multimeric status. Rb assumes a central role in cell cycle regulation and the “Rb pathway” is universally inactivated in human cancers. Hyperploidy refers to a state in which cells contain one or more extra chromosomes. Hyperploid progression occurs due to continued cell-cycling without cytokinesis in G1 checkpoint-defective cancer cells. The evidence for the triggering of hyperploid progression-mediated death in RB-mutant human retinoblastoma cells is shown. Hence, the very genetic mutation that predisposes to cancer can be exploited to induce lethality. The discovery helped to establish the principle of targeted cytotoxic cancer therapy at the mechanistic level. By triggering the lytic path, targeted therapy with tumor specificity at the genetic level can be developed. It sets the stage for systematically eliminating side effects for cytotoxic cancer therapy.

Reversine exerts cytotoxic effects through multiple cell death mechanisms in acute lymphoblastic leukemia

PURPOSE

Acute lymphoblastic leukemia (ALL) is an aggressive hematological cancer with limited therapeutic options for adult patients. Aurora kinases have drawn attention as potential targets in hematological neoplasms due to their high expression and biological functions. Aurora kinase A (AURKA) and AURKB are essential for a successful mitosis, acting in spindle mitotic organization and cytokinesis. Reversine is a synthetic purine analog that acts as a multi-kinase inhibitor with anti-neoplastic activity by targeting AURKA and AURKB.

METHODS

ALL patient gene expression data were retrieved from the Amazonia!

DATABASE

For functional assays, Jurkat (T-ALL) and Namalwa (B-ALL) cells were exposed to increasing concentrations of reversine and submitted to various cellular and molecular assays.

RESULTS

We found that AURKB expression was higher in ALL patient samples compared to normal lymphocytes (p < 0.0001). The ALL cell lines tested displayed aberrant AURKA and AURKB expression. In Jurkat and Namalwa cells, reversine reduced cell viability in a dose- and time-dependent manner (p < 0.05). Reversine also significantly reduced the viability of primary ALL cells. Reversine induced apoptosis and autophagy, and reduced cell proliferation in both cell lines (p < 0.05). Mitotic catastrophe markers, including cell cycle arrest at G₂/M, increased cell size and DNA damage, were observed upon reversine exposure. Short- and long-term treatment with reversine inhibited autonomous clonogenicity (p < 0.05). At the molecular level, reversine reduced AURKB activity, induced SQSTM1/p62 consumption, and increased LC3BII and γ-H2AX levels. In Namalwa cells, reversine modulated 25 out of 84 autophagy-related genes, including BCL2, BAD, ULK1, ATG10, IRGM and MAP1LC3B, which indicates that reversine acts by initiating and sustaining autophagy signals in ALL cells.

CONCLUSIONS

From our data we conclude that reversine reduces the viability of ALL cells by triggering multiple cell death mechanisms, including apoptosis, mitotic catastrophe, and autophagy. Our findings highlight reversine as a potential anticancer agent for ALL.

Reversine: A Synthetic Purine with a Dual Activity as a Cell Dedifferentiating Agent and a Selective Anticancer Drug

The development of new therapeutic applications for adult and embryonic stem cells has dominated regenerative medicine and tissue engineering for several decades. However, since 2006, induced Pluripotent Stem Cells (iPSCs) have taken center stage in the field, as they promised to overcome several limitations of the other stem cell types. Nonetheless, other promising approaches for adult cell reprogramming have been attempted over the years, even before the generation of iPSCs. In particular, two years before the discovery of iPSCs, the possibility of synthesizing libraries of large organic compounds, as well as the development of high-throughput screenings to quickly test their biological activity, enabled the identification of a 2,6-disubstituted purine, named reversine, which was shown to be able to reprogram adult cells to a progenitor-like state. Since its discovery, the effect of reversine has been confirmed on different cell types, and several studies on its mechanism of action have revealed its central role in inhibitory activity on several kinases implicated in cell cycle regulation and cytokinesis. These key features, together with its chemical nature, suggested a possible use of the molecule as an anti-cancer drug. Remarkably, reversine exhibited potent cytotoxic activity against several tumor cell lines in vitro and a significant effect in decreasing tumor progression and metastatization in vivo. Thus, 15 years since its discovery, this review aims at critically summarizing the current knowledge to clarify the dual role of reversine as a dedifferentiating agent and anti-cancer drug.

Autophagy inhibition by reversine and its suppressive effects on human hepatocellular carcinoma cells

INTRODUCTION

Therapy for human hepatocellular carcinoma (HCC) remains a great challenge for physicians and patients worldwide. The anti-tumor effects of reversine have attracted much more concerns.

MATERIALS AND METHODS

This study evaluated the growth regulatory effects of reversine on HCC cells lines. Meanwhile, the underlying mechanism including autophagy modulation was also identified.

RESULTS

reversine markedly inhibited the proliferation of both HCC cells and induced cell apoptosis and multinuclear in a dose-dependent manner. In addition, the decreased ratio of LC3II/LC3I as well as elevated p62 expression were observed under reversine treatment, indicating the autophagy inhibition by reversine in HepG2 cell line. Moreover, modulation of autophagy with rapamycin and chloroquine significantly attenuated and enhanced the cytostatic effects of reversine, respectively.

CONCLUSIONS

reversine could reduce the cell viability of HCC cells via inducing cell apoptosis and polyploidy. In addition, cell autophagy was involved and might play a protective role in HCC cells, the joint use of autophagy inhibitor enhanced reversine-mediating antitumor effects. Our data offered novel ideas for comprehensive therapeutic regimes on human hepatocellular carcinoma.

Reversine inhibits MMP-3, IL-6 and IL-8 expression through suppression of ROS and JNK/AP-1 activation in interleukin-1β-stimulated human gingival fibroblasts

OBJECTIVE

Periodontitis is an inflammatory disease of the supporting tissue around teeth commonly caused by gram-negative bacterial infections. Interleukin (IL)-1β, a cytokine involved in host immune and inflammatory responses, is known to induce the activation of various intracellular signaling pathways. One of these signaling mechanisms involves the regulation of gene expression by activation of transcription factors (AP-1 and NF-κB). These transcription factors are controlled by mitogen-activated protein kinases (MAPKs), which increase cytokine and matrix metalloproteinase (MMP) expression. We examined the preventive effects of reversine, a 2,6-disubstituted purine derivative, on cytokine and MMP-3 expression in human gingival fibroblasts (HGFs) stimulated with IL-lβ.

STUDY DESIGN

Western blot analyses were performed to verify the activities of MAPK, p65, p50, and c-Jun and the expression of MMPs in IL-1β-stimulated HGFs. Cytokine and MMP-3 expression in IL-1β-stimulated HGFs was measured by real-time quantitative polymerase chain reaction.

RESULTS

Reversine decreased the IL-1β-induced expression of proinflammatory cytokines (IL-6 and IL-8) and MMP-3 in HGFs. Furthermore, the mechanism underlying the effects of reversine involved the suppression of IL-1β-stimulated MAPK activation and AP-1 activation.

CONCLUSION

Reversine inhibits IL-1β-induced MMP and cytokine expression via inhibition of MAPK/AP-1 activation and ROS generation. Therefore, we suggest that reversine may be an effective therapeutic candidate for preventing periodontitis.

Reversine exhibits antineoplastic activity in JAK2V617F-positive myeloproliferative neoplasms

JAK2/STAT signaling participates in the Ph-negative myeloproliferative neoplasms (MPN) pathophysiology and has been targeted by ruxolitinib, a JAK1/2 inhibitor. In the present study, the impact of ruxolitinib treatment on cytoskeleton-related genes expression was explored. In SET2 cells, AURKA and AURKB expression/activity were downregulated in a dose- and time-dependent manner by ruxolitinib. Reversine, a multikinase inhibitor selective for aurora kinases, reduced cell viability in a dose- and/or time-dependent manner in JAK2^V617F cells. Reversine significantly increased apoptosis and mitotic catastrophe, and reduced cell proliferation and clonogenic capacity in SET2 and HEL cells. In the molecular scenario, reversine induced DNA damage and apoptosis markers, as well as, reduced AURKA and AURKB expression/activity. In SET2 cells, reversine modulated the expression of 32 out of 84 apoptosis-related genes investigated, including downregulation of antiapoptotic (BCL2, BCL2L1, and BIRC5) and upregulation of proapoptotic (BIK, BINP3, and BNIP3L) genes. Synergism experiments indicated that low dose of reversine had a potentiating effect under ruxolitinib treatment at low doses in SET2 cells. In summary, our exploratory study establishes new targets, related to the regulation of the cellular cytoskeleton, for potential pharmacological intervention in MPN. These findings indicate that AURKA and AURKB participate in the JAK2/STAT signaling pathway and contribute to the MPN phenotype.

Relation of AURKB over-expression to low survival rate in BCRA and reversine-modulated aurora B kinase in breast cancer cell lines

Background

New therapeutic drug for breast cancer (BRCA), especially triple negative BRCA (TNBC), is urgently needed. Even though 2-(4-morpholinoanilino)-6-cyclohexylaminopurine (reversine) is an aurora kinase inhibitor, it also inhibits some cancer cells and human BRCA cells. However, the potential roles of reversine as a novel therapeutic agent for the treatment of BRCA remains unknown and must be further investigation. Thus, the relationship of reversine to aurora kinase in BCRA has not been reported. The relationship between AURKB and survival rate in BRCA has never been reported. Herein, we tested the roles of reversine on different BRCA cell line subtypes. We also investigated the relationship between AURKB and survival rate in BRCA as well as reversine to Aurora kinase expression in BCRA cell lines, including TNBC subtype, 4T1, MDA-MB-231, and luminal subtype MCF-7.

Methods

Cell viability and apoptosis were detected using Cell Counting Kit-8 and flow cytometry analysis, respectively. Apoptotic and tumor-related proteins were tested using Western blot analysis. Important microRNAs that regulate BRCA were analyzed using RT-PCR. UALCAN public databases were used to analyze the targeted gene profiles, and the PROGgeneV2 database was used to study the prognostic implications of genes.

Results

Reversine inhibits cell proliferation and induces cell apoptosis by modulating caspase-3 and bax/bcl-2 among the three cell lines. Data from the UALCAN public database show that BRCA tissues expressed high gene levels of AURKB, TIMP1, MMP9, and TGFB1 compared with the normal tissue. Among the over-expressed genes in BRCA, AURKB ranks 9th in TNBC, 49th in luminal subtype, and 48th in HER2 subtype. High AURKB level in BRCA is highly related to the low survival rate in patients displayed in 18 databases searched via PROGgeneV2. The protein levels of aurora B kinase (Aurora B), which is encoded by AURKB gene, are highly suppressed by reversine in the three cell lines. The tumor-related proteins TGF-β1, TIMP1, and MMP9 are partially suppressed by reversine but with different sensitivity in the three cell lines. The reversine-affected microRNAs, such as miR129-5p, miR-199a-3p, and miR-3960, in MDA-MB-231 cell line might be the research targets in TNBC regulation.

Conclusions

In BRCA, the level of AURKB are over-expressed and is related to low survival rate. Reversine contributes to anti-growth effect in BRCA cell lines, especially for TNBC, by modulating the aurora B. However, the invasiveness, metastasis, and anti-tumor effects of reversine in vivo and in vitro must be further investigated.

Novel Thienopyrimidine Derivative, RP-010, Induces β-Catenin Fragmentation and Is Efficacious against Prostate Cancer Cells

Thienopyrimidines containing a thiophene ring fused to pyrimidine are reported to have a wide-spectrum of anticancer efficacy in vitro. Here, we report for the first time that thieno[3,2-d]pyrimidine-based compounds, also known as the RP series, have efficacy in prostate cancer cells. The compound RP-010 was efficacious against both PC-3 and DU145 prostate cancer (PC) cells (IC₅₀ < 1 µM). The cytotoxicity of RP-010 was significantly lower in non-PC, CHO, and CRL-1459 cell lines. RP-010 (0.5, 1, 2, and 4 µM) arrested prostate cancer cells in G2 phase of the cell cycle, and induced mitotic catastrophe and apoptosis in both PC cell lines. Mechanistic studies suggested that RP-010 (1 and 2 µM) affected the wingless-type MMTV (Wnt)/β-catenin signaling pathway, in association with β-catenin fragmentation, while also downregulating important proteins in the pathway, including LRP-6, DVL3, and c-Myc. Interestingly, RP-010 (1 and 2 µM) induced nuclear translocation of the negative feedback proteins, Naked 1 and Naked 2, in the Wnt pathway. In addition, RP-010 (0.5, 1, 2 and 4 µM) significantly decreased the migration of PC cells in vitro. Finally, RP-010 did not produce significant toxic effects in zebrafish at concentrations of up to 6 µM. In conclusion, RP-010 may be an efficacious and relatively nontoxic anticancer compound for prostate cancer. Future mechanistic and in vivo efficacy studies are needed to optimize the hit compound RP-010 for lead optimization and clinical use.

Combinatorial Use of Chitosan Nanoparticles, Reversine, and Ionising Radiation on Breast Cancer Cells Associated with Mitosis Deregulation

Breast cancer is the most commonly occurring cancer in women worldwide and the second most common cancer overall. The development of new therapies to treat this devastating malignancy is needed urgently. Nanoparticles are one class of nanomaterial with multiple applications in medicine, ranging from their use as drug delivery systems and the promotion of changes in cell morphology to the control of gene transcription. Nanoparticles made of the natural polymer chitosan are easy to produce, have a very low immunogenic profile, and diffuse easily into cells. One hallmark feature of cancer, including breast tumours, is the genome instability caused by defects in the spindle-assembly checkpoint (SAC), the molecular signalling mechanism that ensures the timely and high-fidelity transmission of the genetic material to an offspring. In recent years, the use of nanoparticles to treat cancer cells has gained momentum. This is in part because nanoparticles made of different materials can sensitise cancer cells to chemotherapy and radiotherapy. These advances prompted us to study the potential sensitising effect of chitosan-based nanoparticles on breast cancer cells treated with reversine, which is a small molecule inhibitor of Mps1 and Aurora B that induces premature exit from mitosis, aneuploidy, and cell death, before and after exposure of the cancer cells to X-ray irradiation. Our measurements of metabolic activity as an indicator of cell viability, DNA damage by alkaline comet assay, and immunofluorescence using anti-P-H3 as a mitotic biomarker indicate that chitosan nanoparticles elicit cellular responses that affect mitosis and cell viability and can sensitise breast cancer cells to X-ray radiation (2Gy). We also show that such a sensitisation effect is not caused by direct damage to the DNA by the nanoparticles. Taken together, our data indicates that chitosan nanoparticles have potential application for the treatment of breast cancer as adjunct to radiotherapy.

Reversine induces caspase-dependent apoptosis of human osteosarcoma cells through extrinsic and intrinsic apoptotic signaling pathways

BACKGROUND

The 2-(4-morpholinoanilino)-6-cyclohexylaminopurine (reversine) acts as a chemopreventive agent and induces apoptotic cell death in various cancer cells. However, the anticancer effects of reversine on osteosarcoma cells are not clearly established.

OBJECTIVE

The purpose of this study was to investigate the effect of reversine on cell proliferation and induction of apoptosis in human osteosarcoma cells.

METHODS

Cell viability assay, histological analysis, DAPI staining, caspase activation analysis, flow cytometric analysis and immunoblotting were carried out in MG-63 osteosarcoma cells.

RESULTS

Reversine inhibited the growth of cells in a dose-dependent manner and induced nuclear condensation and fragmentation. Reversine-treated cells showed caspase-3/7 activation and increased apoptosis versus control cells. FasL, a death ligand associated with extrinsic apoptotic signaling pathways, was significantly up-regulated by reversine treatment. Moreover, the caspase-8, a part of the extrinsic apoptotic pathway, was activated by reversine treatments. Expressions of anti-apoptotic factors such as Bcl-2 and Bcl-xL, components of the mitochondria dependent intrinsic apoptosis pathway, significantly decreased following reversine treatment. The expressions of pro-apoptotic factors such as BAX, BAD and caspase-9 increased by reversine treatments. In addition, reversine activated caspase-3 and Poly (ADP-ribose) polymerase (PARP) to induce cell death. The Z-VAD-fmk significantly inhibited cell death through the suppression of caspase-3 expression in MG-63 cells treated with reversine.

CONCLUSION

These results suggest that the reversine may inhibit cell proliferation and induce apoptotic cell death in MG-63 osteosarcoma cells through both the mitochondria-mediated intrinsic pathway and the death receptor-mediated extrinsic pathway, and may have potential properties for the discovery of anti-cancer agents.

Reversine induces cell cycle arrest and apoptosis via upregulation of the Fas and DR5 signaling pathways in human colorectal cancer cells

Reversine, a 2,6‑diamino‑substituted purine analogue, has been reported to be effective in tumor suppression via induction of cell growth arrest and apoptosis of cancer cells. However, it remains unclear whether reversine exerts anticancer effects on human colorectal cancer cells. In the present study, in vitro experiments were conducted to investigate the anticancer properties of reversine in human colorectal cancer cells. The effect of reversine on human colorectal cancer cell lines, SW480 and HCT‑116, was examined using a WST‑1 cell viability assay, fluorescence microscopy, flow cytometry, DNA fragmentation, small interfering RNA (siRNA) and western blotting. Reversine treatment demonstrated cytotoxic activity in human colorectal cancer cells. It also induced apoptosis by activating poly(ADP‑ribose) polymerase, caspase‑3, ‑7 and ‑8, and increasing the levels of the pro‑apoptotic protein second mitochondria‑derived activator of caspase/direct inhibitor of apoptosis‑binding protein with low pI. The pan‑caspase inhibitor Z‑VAD‑FMK attenuated these reversine‑induced apoptotic effects on human colorectal cancer cells. Additionally, reversine treatment induced cell cycle arrest in the subG1 and G2/M phases via increase in levels of p21, p27 and p57, and decrease in cyclin D1 levels. The expression of Fas and death receptor 5 (DR5) signaling proteins in SW480 and HCT116 cells was upregulated by reversine treatment. Reversine‑induced apoptosis and cell cycle arrest were suppressed by inhibition of Fas and DR5 expression via siRNA. In conclusion, Reversine treatment suppressed tumor progression by the inhibition of cell proliferation, induction of cell cycle arrest and induction of apoptosis via upregulation of the Fas and DR5 signaling pathways in human colorectal cancer cells. The present study indicated that reversine may be used as a novel anticancer agent in human colorectal cancer.

Breaking Bad: Uncoupling of Modularity in Centriole Biogenesis and the Generation of Excess Centrioles in Cancer

Centrosomes are tiny yet complex cytoplasmic structures that perform a variety of roles related to their ability to act as microtubule-organizing centers. Like the genome, centrosomes are single copy structures that undergo a precise semi-conservative replication once each cell cycle. Precise replication of the centrosome is essential for genome integrity, because the duplicated centrosomes will serve as the poles of a bipolar mitotic spindle, and any number of centrosomes other than two will lead to an aberrant spindle that mis-segregates chromosomes. Indeed, excess centrosomes are observed in a variety of human tumors where they generate abnormal spindles in situ that are thought to participate in tumorigenesis by driving genomic instability. At the heart of the centrosome is a pair of centrioles, and at the heart of centrosome duplication is the replication of this centriole pair. Centriole replication proceeds through a complex macromolecular assembly process. However, while centrosomes may contain as many as 500 proteins, only a handful of proteins have been shown to be essential for centriole replication. Our observations suggest that centriole replication is a modular, bottom-up process that we envision akin to building a house; the proper site of assembly is identified, a foundation is assembled at that site, and subsequent modules are added on top of the foundation. Here, we discuss the data underlying our view of modularity in the centriole assembly process, and suggest that non-essential centriole assembly factors take on greater importance in cancer cells due to their function in coordination between centriole modules, using the Monopolar spindles 1 protein kinase and its substrate Centrin 2 to illustrate our model.

Aurora kinase B regulates axonal outgrowth and regeneration in the spinal motor neurons of developing zebrafish

Aurora kinase B (AurkB) is a serine/threonine protein kinase with a well-characterised role in orchestrating cell division and cytokinesis, and is prominently expressed in healthy proliferating and cancerous cells. However, the role of AurkB in differentiated and non-dividing cells has not been extensively explored. Previously, we have described a significant upregulation of AurkB expression in cultured cortical neurons following an experimental axonal transection. This is somewhat surprising, as AurkB expression is generally associated only with dividing cells Frangini et al. (Mol Cell 51:647-661, 2013); Hegarat et al. (J Cell Biol 195:1103-1113, 2011); Lu et al. (J Biol Chem 283:31785-31790, 2008); Trakala et al. (Cell Cycle 12:1030-1041, 2014). Herein, we present the first description of a role for AurkB in terminally differentiated neurons. AurkB was prominently expressed within post-mitotic neurons of the zebrafish brain and spinal cord. The expression of AurkB varied during the development of the zebrafish spinal motor neurons. Utilising pharmacological and genetic manipulation to impair AurkB activity resulted in truncation and aberrant motor axon morphology, while overexpression of AurkB resulted in extended axonal outgrowth. Further pharmacological inhibition of AurkB activity in regenerating axons delayed their recovery following UV laser-mediated injury. Collectively, these results suggest a hitherto unreported role of AurkB in regulating neuronal development and axonal outgrowth.

How Selective Are Pharmacological Inhibitors of Cell-Cycle-Regulating Cyclin-Dependent Kinases?

Cyclin-dependent kinases (CDKs) are an important and emerging class of drug targets for which many small-molecule inhibitors have been developed. However, there is often insufficient data available on the selectivity of CDK inhibitors (CDKi) to attribute the effects on the presumed target CDK to these inhibitors. Here, we highlight discrepancies between the kinase selectivity of CDKi and the phenotype exhibited; we evaluated 31 CDKi (claimed to target CDK1-4) for activity toward CDKs 1, 2, 4, 5, 7, 9 and for effects on the cell cycle. Our results suggest that most CDKi should be reclassified as pan-selective and should not be used as a tool. In addition, some compounds did not even inhibit CDKs as their primary cellular targets; for example, NU6140 showed potent inhibition of Aurora kinases. We also established an online database of commercially available CDKi for critical evaluation of their utility as molecular probes. Our results should help researchers select the most relevant chemical tools for their specific applications.

Reversine promotes browning of white adipocytes by suppressing miR-133a

Brown adipocytes are characterized by a high number of uncoupling protein 1 (UCP1)-positive mitochondrial content and increased thermogenic capacity. As UCP1-enriched cells can consume lipids by generating heat, browning of white adipocytes is now highlighted as a promising approach for the prevention of obesity and obesity-associated metabolic diseases. Upon cold exposure or β-adrenergic stimuli, downregulation of microRNA-133 (miR-133) elevates the expression levels of PR domain containing 16 (Prdm16), which has been shown to be a brown adipose determination factor, in brown adipose tissue and subcutaneous white adipose tissues (WAT). Here, we show that treatment of reversine to white adipocytes induces browning via suppression of miR-133a. Reversine treatment promoted the expression of brown adipocyte marker genes, such as Prdm16 and UCP1, increasing the mitochondrial content, while decreasing the levels of miR-133a and white adipocyte marker genes. Ectopic expression of miR-133a mimic reversed the browning effects of the reversine treatment. Moreover, intraperitoneal administration of reversine in mice upregulated thermogenesis and resulted in resistance to high-fat diet-mediated weight gain as well as browning of subcutaneous and epididymal WAT. Taken together, we found a novel way to promote browning of white adipocytes through downregulation of miR-133a followed by activation of Prdm16, with a synthetic chemical, reversine.

Synthesis of 2,6-Diamino-Substituted Purine Derivatives and Evaluation of Cell Cycle Arrest in Breast and Colorectal Cancer Cells

Reversine is a potent antitumor 2,6-diamino-substituted purine acting as an Aurora kinases inhibitor and interfering with cancer cell cycle progression. In this study we describe three reversine-related molecules, designed by docking calculation, that present structural modifications in the diamino units at positions 2 and 6. We investigated the conformations of the most stable prototropic tautomers of one of these molecules, the N6-cyclohexyl-N6-methyl-N2-phenyl-7H-purine-2,6-diamine (3), by Density Functional Theory (DFT) calculation in the gas phase, water and chloroform, the last solvent considered to give insights into the detection of broad signals in NMR analysis. In all cases the HN(9) tautomer resulted more stable than the HN(7) form, but the most stable conformations changed in different solvents. Molecules 1–3 were evaluated on MCF-7 breast and HCT116 colorectal cancer cell lines showing that, while being less cytotoxic than reversine, they still caused cell cycle arrest in G2/M phase and polyploidy. Unlike reversine, which produced a pronounced cell cycle arrest in G2/M phase in all the cell lines used, similar concentrations of 1–3 were effective only in cells where p53 was deleted or down-regulated. Therefore, our findings support a potential selective role of these structurally simplified, reversine-related molecules in p53-defective cancer cells.

Reversine inhibits Colon Carcinoma Cell Migration by Targeting JNK1

Colorectal cancer is one of the most commonly diagnosed cancers and the third most common cause of cancer-related death. Metastasis is the leading reason for the resultant mortality of these patients. Accordingly, development and characterization of novel anti-cancer drugs limiting colorectal tumor cell dissemination and metastasis are needed. In this study, we found that the small molecule Reversine reduces the migration potential of human colon carcinoma cells in vitro. A coupled kinase assay with bio-informatics approach identified the c-Jun N-terminal kinase (JNK) cascade as the main pathway inhibited by Reversine. Knockdown experiments and pharmacological inhibition identified JNK1 but not JNK2, as a downstream effector target in cancer cell migration. Xenograft experiments confirm the effect of JNK inhibition in the metastatic potential of colon cancer cells. These results highlight the impact of individual JNK isoforms in cancer cell metastasis and propose Reversine as a novel anti-cancer molecule for treatment of colon cancer patients.

Reversine induces autophagic cell death through the AMP-activated protein kinase pathway in urothelial carcinoma cells

Urothelial carcinoma is one of the most common malignancies of the urinary tract. Effective treatment of advanced urothelial carcinoma remains a clinical challenge with poor outcomes in these patients. Previous reports have shown that the expression of aurora kinase is associated with clinical stage and prognosis; hence, aurora kinases are potential targets in urothelial carcinoma therapy. Reversine, an aurora kinase inhibitor, was analyzed for its cytotoxicity in this study. Cell proliferation, flow cytometry, western blotting, and immunofluorescent assay were used to determine the effect of reversine on urothelial carcinoma cells. The results showed that reversine significantly inhibits the growth of urothelial carcinoma cell lines. Reversine induced cell cycle arrest at the G2/M phase, leading to autophagic cell death by activating the AMP-activated protein kinase pathway. Reversine induced significant cell death in urothelial carcinoma cells. Our results suggest that reversine may be a suitably small molecule for treating urothelial carcinoma in the future.

Small molecule tools in mitosis research

Mitosis belongs to the most appealing cellular processes. Yet, the highly dynamic and complex nature of mitosis represents a major challenge when it comes to the functional dissection of mitotic proteins. Due to their fast and often reversible mode of action, small molecules have proven themselves as invaluable tools to dissect mitotic processes. In this chapter, we provide a broad overview of available compounds affecting mitosis. We discuss the different application fields of small molecules and important aspects that have to be considered when using them. Finally, we provide two detailed protocols for the application of small molecules to study mitosis in tissue culture cells.

Stable aneuploid tumors cells are more sensitive to TTK inhibition than chromosomally unstable cell lines

Inhibition of the spindle assembly checkpoint kinase TTK causes chromosome mis-segregation and tumor cell death. However, high levels of TTK correlate with chromosomal instability (CIN), which can lead to aneuploidy. We show that treatment of tumor cells with the selective small molecule TTK inhibitor NTRC 0066-0 overrides the mitotic checkpoint, irrespective of cell line sensitivity. In stable aneuploid cells NTRC 0066-0 induced acute CIN, whereas in cells with high levels of pre-existing CIN there was only a small additional fraction of cells mis-segregating their chromosomes. In proliferation assays stable aneuploid cells were more sensitive than cell lines with pre-existing CIN. Tetraploids are thought to be an intermediate between diploid and unstable aneuploid cells. TTK inhibitors had the same potency on post-tetraploid and parental diploid cells, which is remarkable because the post-tetraploids are more resistant to mitotic drugs. Finally, we confirm that the reference compound reversine is a TTK inhibitor and like NTRC 0066-0, inhibits the proliferation of patient-derived colorectal cancer organoids. In contrast, treatment with TTK inhibitor did not reduce the viability of non-proliferating T cell acute lymphoblastic leukemia cells samples. Consequently, TTK inhibitor therapy is expected to spare non-dividing cells, and may be used to target stable aneuploid tumors.

Reversine, a substituted purine, exerts an inhibitive effect on human renal carcinoma cells via induction of cell apoptosis and polyploidy

Background

Human renal cell carcinoma (RCC) is the most common type of kidney cancer that arises from the renal epithelium. Up to 33.3% of RCC patients treated with local tumor resections will subsequently develop recurrence or metastases. Thus, optimized therapeutic regimes are urgently needed to improve the prognosis of RCC. Reversine was recently reported to exert critical roles in cancer therapy.

Materials and methods

This study evaluated the anti-tumor effects of reversine on cell viability, colony formation, apoptosis, and cell cycle in 786-O and ACHN cell lines.

Results

It was demonstrated that reversine significantly inhibited the proliferation of both cell lines in time- and dose-dependent manners. Polyploidy formation was observed under high-concentration reversine treatment. In addition, reversine induced cell death via caspase-dependent apoptotic pathways, which could be partially inhibited by Z-VAD-FMK, a pan-caspase inhibitor.

Conclusion

Reversine could effectively suppress the proliferation of human RCC cells, and may serve as a novel therapeutic regimen for RCC in clinical practice.

Reversine inhibits MMP-1 and MMP-3 expressions by suppressing of ROS/MAPK/AP-1 activation in UV-stimulated human keratinocytes and dermal fibroblasts

UVB has been shown to stimulate the generation of reactive oxygen species (ROS), which subsequently results in the activation of various intracellular signalling pathways and transcription factors (AP-1, NF-κB). These transcription factors are regulated by MAPKs, which increase cytokine and MMP expression. We examined the preventive effects of reversine on MMP-1 and MMP-3 expressions in NHEKs and NHDFs exposed to UVB irradiation. Also, we confirmed that reversine decreased pro-inflammatory cytokine expression in NHEKs. The mechanism underlying the MMP inhibitory effects of reversine occurred via the suppression of UVB-induced ROS generation and MAPK/AP-1 activation. Therefore, reversine is an effective therapeutic candidate for preventing skin photoageing.

Effect of small molecules on cell reprogramming

The essential idea of regenerative medicine is to fix or replace tissues or organs with alive and patient-specific implants. Pluripotent stem cells are able to indefinitely self-renew and differentiate into all cell types of the body which makes them a potent substantial player in regenerative medicine. The easily accessible source of induced pluripotent stem cells may allow obtaining and cultivating tissues in vitro. Reprogramming refers to regression of mature cells to its initial pluripotent state. One of the approaches affecting pluripotency is the usage of low molecular mass compounds that can modulate enzymes and receptors leading to the formation of pluripotent stem cells (iPSCs). It would be great to assess the general character of such compounds and reveal their new derivatives or modifications to increase the cell reprogramming efficiency. Many improvements in the methods of pluripotency induction have been made by various groups in order to limit the immunogenicity and tumorigenesis, increase the efficiency and accelerate the kinetics. Understanding the epigenetic changes during the cellular reprogramming process will extend the comprehension of stem cell biology and lead to potential therapeutic approaches. There are compounds which have been already proven to be or for now only putative inducers of the pluripotent state that may substitute for the classic reprogramming factors (Oct3/4, Sox2, Klf4, c-Myc) in order to improve the time and efficiency of pluripotency induction. The effect of small molecules on gene expression is dosage-dependent and their application concentration needs to be strictly determined. In this review we analysed the role of small molecules in modulations leading to pluripotency induction, thereby contributing to our understanding of stem cell biology and uncovering the major mechanisms involved in that process.

Novel pyrrolopyrimidines as Mps1/TTK kinase inhibitors for breast cancer

New targeted therapy approaches for certain subtypes of breast cancer, such as triple-negative breast cancers and other aggressive phenotypes, are desired. High levels of the mitotic checkpoint kinase Mps1/TTK have correlated with high histologic grade in breast cancer, suggesting a potential new therapeutic target for aggressive breast cancers (BC). Novel small molecules targeting Mps1 were designed by computer assisted docking analyses, and several candidate compounds were synthesized. These compounds were evaluated in anti-proliferative assays of a panel of 15 breast cancer cell lines and further examined for their ability to inhibit a variety of Mps1-dependent biological functions. The results indicate that the lead compounds have strong anti-proliferative potential through Mps1/TTK inhibition in both basal and luminal BC cell lines, exhibiting IC₅₀ values ranging from 0.05 to 1.0μM. In addition, the lead compounds 1 and 13 inhibit Mps1 kinase enzymatic activity with IC₅₀ values from 0.356μM to 0.809μM, and inhibited Mps1-associated cellular functions such as centrosome duplication and the spindle checkpoint in triple negative breast cancer cells. The most promising analog, compound 13, significantly decreased tumor growth in nude mice containing Cal-51 triple negative breast cancer cell xenografts. Using drug discovery technologies, computational modeling, medicinal chemistry, cell culture and in vivo assays, novel small molecule Mps1/TTK inhibitors have been identified as potential targeted therapies for breast cancers.