The phytochemical, corynoline, diminishes Aurora kinase B activity to induce mitotic defect and polyploidy.

Plants are a rich source for bioactive compounds. However, plant extracts can harbor a mixture of bioactive molecules that promote divergent phenotypes and potentially have confounding effects in bioassays. Even with further purification and identification, target deconvolution can be challenging. Corynoline and acetylcorynoline, are phytochemicals that were previously isolated through a screen for compounds able to induce mitotic arrest and polyploidy in oncogene expressing retinal pigment epithelial (RPE) cells. Here, we shed light on the mechanism by which these phytochemicals can attack human cancer cells. Mitotic arrest was coincident to the induction of centrosome amplification and declustering, causing multi-polar spindle formation. Corynoline was demonstrated to have true centrosome declustering activity in a model where A549 cells were chemically induced to have more than a regular complement of centrosomes. Corynoline could inhibit the centrosome clustering required for pseudo-bipolar spindle formation in these cells. The activity of AURKB, but not AURKA or polo-like kinase 4, was diminished by corynoline. It only partially inhibited AURKB, so it may be a partial antagonist or corynoline may work upstream on an unknown regulator of AURKB activity or localization. Nonetheless, corynoline and acetylcorynoline inhibited the viability of a variety of human cancer derived cell lines. These phytochemicals could serve as prototypes for a next-generation analog with improved potency, selectivity or in vivo bioavailability. Such an analog could be useful as a non-toxic component of combination therapies where inhibiting the chromosomal passenger protein complex is desired.

Targeting Aurora kinase B attenuates chemoresistance in glioblastoma via a synergistic manner with temozolomide.

BACKGROUND: Recent studies have demonstrated that aberrant expression or activation of kinases results in oncogenesis of a wide range of cancers including GBM. Inhibition of kinases expression induces a reduction of therapy resistance. In this study, we investigate the underlying mechanism by which glioblastoma (GBM) cells acquire resistance to Temozolomide (TMZ) through Aurora kinase B (AURKB) thus to identify novel therapeutic targets and prognostic biomarkers for GBM. METHODS: AURKB was identified as a key candidate kinase-encoding gene in chemoresistance regulation by using kinome-wide bioinformatic analysis. Afterwards, the potential biological functions of AURKB in oncogenesis and chemoresistance were investigated by lentivirus-dependent silencing of AURKB combined with qRT-PCR, western blot and in vivo intra-cranial xenograft mice models. Additionally, immunohistochemistry (IHC) assays were performed to explore the clinical significance of AURKB in glioma patients. Lastly, Chou-Talalay method was used to confirm the synergistic effect of TMZ combined with AURKB inhibitor. RESULTS: AURKB was among the most significantly up-regulated kinase-coding genes in TMZ resistant GBM cells according to database GSE68029, moreover, an increased expression of AURKB was closely associated with poor prognosis in glioma and GBM patients. AURKB knock-down resensitized U87 resistant cells to TMZ both in vitro and in vivo. Additionally, the combination of TMZ and Hesperadin, a specific AURKB inhibitor, significantly suppressed the proliferation of TMZ resistant GBM cells thus dramatically prolonged the survival of xenograft mice viaa synergistic effect with TMZ. CONCLUSION: Elevated AURKB expression was strongly correlated to TMZ resistant acquisition and poor prognosis, furthermore, targeting AURKB would be a potential therapeutic target for GBM patients.

Tozasertib Analogues as Inhibitors of Necroptotic Cell Death.

Receptor interacting protein kinase 1 (RIPK1) plays a crucial role in tumor necrosis factor (TNF)-induced necroptosis, suggesting that this pathway might be druggable. Most inhibitors of RIPK1 are classified as either type II or type III kinase inhibitors. This opened up some interesting perspectives for the discovery of novel inhibitors that target the active site of RIPK1. Tozasertib, a type I pan-aurora kinase (AurK) inhibitor, was found to show a very high affinity for RIPK1. Because tozasertib presents the typical structural elements of a type I kinase inhibitor, the development of structural analogues of tozasertib is a good starting point for identifying novel type I RIPK1 inhibitors. In this paper, we identified interesting inhibitors of mTNF-induced necroptosis with no significant effect on AurK A and B, resulting in no nuclear abnormalities as is the case for tozasertib. Compounds 71 and 72 outperformed tozasertib in an in vivo TNF-induced systemic inflammatory response syndrome (SIRS) mouse model.

Induction of p21CIP1 protein and cell cycle arrest after inhibition of Aurora B kinase is attributed to aneuploidy and reactive oxygen species.

Cell cycle progression requires a series of highly coordinated events that ultimately lead to faithful segregation of chromosomes. Aurora B is an essential mitotic kinase, which is involved in regulation of microtubule-kinetochore attachments and cytokinesis. Inhibition of Aurora B results in stabilization of p53 and induction of p53-target genes such as p21 to inhibit proliferation. We have previously demonstrated that induction of p21 by p53 after inhibition of Aurora B is dependent on the p38 MAPK, which promotes transcriptional elongation of p21 by RNA Pol II. In this study, we show that a subset of p53-target genes are induced in a p38-dependent manner upon inhibition of Aurora B. We also demonstrate that inhibition of Aurora B results in down-regulation of E2F-mediated transcription and that the cell cycle arrest after Aurora B inhibition depends on p53 and pRB tumor suppressor pathways. In addition, we report that activation of p21 after inhibition of Aurora B is correlated with increased chromosome missegregation and aneuploidy but not with binucleation or tetraploidy. We provide evidence that p21 is activated in aneuploid cells by reactive oxygen species (ROS) and p38 MAPK. Finally, we demonstrate that certain drugs that act on aneuploid cells synergize with inhibitors of Aurora B to inhibit colony formation and oncogenic transformation. These findings provide an important link between aneuploidy and the stress pathways activated by Aurora B inhibition and also support the use of Aurora B inhibitors in combination therapy for treatment of cancer.