Significance of AZD1152 as a potential treatment against Aurora B overexpression in acute promyelocytic leukemia

Aurora B facilitates cholangiocarcinoma progression by stabilizing c-Myc

BACKGROUND

Cholangiocarcinoma (CCA), a malignancy that arises from biliary epithelial cells, has a dismal prognosis, and few targeted therapies are available. Aurora B, a key mitotic regulator, has been reported to be involved in the progression of various tumors, yet its role in CCA is still unclarified.

METHODS

Human CCA tissues and murine spontaneous CCA models were used to assess Aurora B expression in CCA. A loss-of-function model was constructed in CCA cells to determine the role of Aurora B in CCA progression. Subcutaneous and liver orthotopic xenograft models were used to assess the therapeutic potential of Aurora B inhibitors in CCA.

RESULTS

In murine spontaneous CCA models, Aurora B was significantly upregulated. Elevated Aurora B expression was also observed in 62.3% of human specimens in our validation cohort (143 CCA specimens), and high Aurora B expression was positively correlated with pathological parameters of tumors and poor survival. Knockdown of Aurora B by siRNA and heteroduplex oligonucleotide (HDO) or an Aurora B kinase inhibitor (AZD1152) significantly suppressed CCA progression via G2/M arrest induction. An interaction between Aurora B and c-Myc was found in CCA cells. Targeting Aurora B significantly reduced this interaction and accelerated the proteasomal degradation of c-Myc, suggesting that Aurora B promoted the malignant properties of CCA by stabilizing c-Myc. Furthermore, sequential application of AZD1152 or Aurora B HDO drastically improved the efficacy of gemcitabine in CCA.

CONCLUSIONS

Aurora B plays an essential role in CCA progression by modulating c-Myc stability and represents a new target for treatment and chemosensitization in CCA.

Aurora kinase inhibitors: a patent review (2014-2020)

Introduction: Aurora kinases are a family of serine/threonine kinases, and promote mitotic spindle assembly by regulating centrosome duplication and separation. Aurora kinases are overexpressed in a variety of tumor cell lines, thus, the use of Aurora kinase small-molecule inhibitors has become a potential treatment option for cancer.Areas covered: As a continuing review of Aurora kinase inhibitors and their patents published in 2009, 2011 and 2014. Herein, we updated the information for Aurora kinase inhibitors in clinical trials and the patents filed from 2014 to 2020. PubMed, Scopus, SciFinder, and www.clinicaltrials.gov databases were used for searching the clinical information and patents of Aurora kinase inhibitors.Expert opinion: Even though Aurora A or B selective as well as pan inhibitors show preclinical and clinical efficacy, so far, no Aurora kinase inhibitor has been approved for clinical use. Preliminary evidence suggested that highly selective Aurora kinase or multi-target inhibitors as a single agent as well as in combination therapy are still the current main development trend of Aurora kinase inhibitors.

Aurora kinase B inhibitor barasertib (AZD1152) inhibits glucose metabolism in gastric cancer cells

Barasertib is a highly selective Aurora kinase B (AURKB) inhibitor and has been widely applied in a variety of cancer cells to investigate the regulatory function of AURKB. However, the effect of barasertib on glucose metabolism in gastric cancer (GC) remains illustrated. Here, barasertib was identified to effectively reduce glucose uptake and lactate production in GC cells in a dose-dependent and time-dependent manner. The expression levels of GLUT1, LDHA and HK2 were decreased by barasertib treatment of GC cells. Furthermore, we found that barasertib induced the expression of ribosomal protein S7 (RPS7), as a tumor suppressor, to regulate glucose metabolism. Silencing of RPS7 rescued the effects of barasertib on glucose metabolism in GC cells. Overexpression of RPS7 suppressed the promoter activity of C-Myc, which has been identified as an important regulator of glucose metabolism in cancer cells. The clinical data showed that the expression level of AURKB in GC patients' sera and tissues were positively correlated with those of C-Myc, GLUT1 and LDHA, but negatively with that of RPS7. Therefore, these findings provide new evidence that barasertib regulates GC cell glucose metabolism by inducing the RPS7/C-Myc signal pathway, and have important implications for the development of therapeutic approaches using AURKB as a target protein to prevent tumor recurrence.

The balance between mitotic death and mitotic slippage in acute leukemia: a new therapeutic window?

Mitosis is the process whereby an eukaryotic cell divides into two identical copies. Different multiprotein complexes are involved in the fine regulation of cell division, including the mitotic promoting factor and the anaphase promoting complex. Prolonged mitosis can result in cellular division, cell death, or mitotic slippage, the latter leading to a new interphase without cellular division. Mitotic slippage is one of the causes of genomic instability and has an important therapeutic and clinical impact. It has been widely studied in solid tumors but not in hematological malignancies, in particular, in acute leukemia. We review the literature data available on mitotic regulation, alterations in mitotic proteins occurring in acute leukemia, induction of prolonged mitosis and its consequences, focusing in particular on the balance between cell death and mitotic slippage and on its therapeutic potentials. We also present the most recent preclinical and clinical data on the efficacy of second-generation mitotic drugs (CDK1-Cyclin B1, APC/CCDC20, PLK, Aurora kinase inhibitors). Despite the poor clinical activity showed by these drugs as single agents, they offer a potential therapeutic window for synthetic lethal combinations aimed to selectively target leukemic cells at the right time, thus decreasing the risk of mitotic slippage events.

Polyploid giant cancer cells: Unrecognized actuators of tumorigenesis, metastasis, and resistance

Cancer led to the deaths of more than 9 million people worldwide in 2018, and most of these deaths were due to metastatic tumor burden. While in most cases, we still do not know why cancer is lethal, we know that a total tumor burden of 1 kg-equivalent to one trillion cells-is not compatible with life. While localized disease is curable through surgical removal or radiation, once cancer has spread, it is largely incurable. The inability to cure metastatic cancer lies, at least in part, to the fact that cancer is resistant to all known compounds and anticancer drugs. The source of this resistance remains undefined. In fact, the vast majority of metastatic cancers are resistant to all currently available anticancer therapies, including chemotherapy, hormone therapy, immunotherapy, and systemic radiation. Thus, despite decades-even centuries-of research, metastatic cancer remains lethal and incurable. We present historical and contemporary evidence that the key actuators of this process-of tumorigenesis, metastasis, and therapy resistance-are polyploid giant cancer cells.

Targeting mitosis exit: A brake for cancer cell proliferation

The transition from mitosis to interphase, referred to as mitotic exit, is a critical mitotic process which involves activation and inactivation of multiple mitotic kinases and counteracting protein phosphatases. Loss of mitotic exit checkpoints is a common feature of cancer cells, leading to mitotic dysregulation and confers cancer cells with oncogenic characteristics, such as aberrant proliferation and microtubule-targeting agent (MTA) resistance. Since MTA resistance results from cancer cells prematurely exiting mitosis (mitotic slippage), blocking mitotic exit is believed to be a promising anticancer strategy. Moreover, based on this theory, simultaneous inhibition of mitotic exit and additional cell cycle phases would likely achieve synergistic antitumor effects. In this review, we divide the molecular regulators of mitotic exit into four categories based on their different regulatory functions: 1) the anaphase-promoting complex/cyclosome (APC/C, a ubiquitin ligase), 2) cyclin B, 3) mitotic kinases and phosphatases, 4) kinesins and microtubule-binding proteins. We also review the regulators of mitotic exit and propose prospective anticancer strategies targeting mitotic exit, including their strengths and possible challenges to their use.

Reactive oxygen species generation and increase in mitochondrial copy number: new insight into the potential mechanism of cytotoxicity induced by aurora kinase inhibitor, AZD1152-HQPA

Aurora-B kinase overexpression plays important roles in the malignant progression of prostate cancer (PCa). AZD1152-HQPA, as an inhibitor of Aurora-B, has recently emerged as a promising agent for cancer treatment. In this study, we aimed to investigate the effects of AZD1152-HQPA on reactive oxygen species (ROS) generation and mitochondrial function in PCa. We used AZD1152-HQPA (Barasertib), a highly potent and selective inhibitor of Aurora-B kinase. The effects of AZD1152-HQPA on cell viability, DNA content, cell morphology, and ROS production were studied in the androgen-independent PC-3 PCa cell line. Moreover, the mitochondrial copy number and the expression of genes involved in cell survival and cancer stem cell maintenance were investigated. We found that AZD1152-HQPA treatment induced defective cell survival, polyploidy, micronuclei formation, cell enlargement, and cell death by significant overexpression of p73, p21 and downregulation of cell cycle-regulatory genes in a drug concentration-dependent manner. Moreover, AZD1152 treatment led to an excessive ROS generation and an increase in the mitochondrial copy number not only in PC-3 but also in several other malignant cells. AZD1152 treatment also led to downregulation of genes involved in the maintenance of cancer stem cells. Our results showed a functional relationship between the aurora kinase inhibition, an increase in mitochondrial copy number, and ROS generation in therapeutic modalities of cancer. This study suggests that the excessive ROS generation may be a novel mechanism of cytotoxicity induced by the aurora kinase inhibitor, AZD1152-HQPA.

Lovastatin induced Kruppel like factor 2 (KLF2), Kruppel like factor 6 (KLF6) and Ras homolog family member B (RHOB) genes and preferentially led to viability reduction of Cisplatin-resistant cells

It was reported that statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase that are used to prevent hypercholesterolemia, have antitumor activity in several cancers. In this study, we investigated the cell viability of statins in Cisplatin-resistant HCP4 and PCDP5 cells compared with their parent Hela and PC3 cells, respectively, and found that HCP4 and PCDP5 cells were 37-fold and 18-fold more resistant to Cisplatin but 13-fold and 7-fold more sensitive to Lovastatin by cell proliferation assay. Lovastatin induced the apoptosis of HCP4 cells more rapidly and to greater extent than in Hela cells as assessed by flow cytometry and western blotting analyses. The MVA pathway was not involved in this acquired Cisplatin resistance. To elucidate the mechanism underlying the reduced viability to Lovastatin, we performed cDNA microarray analysis and identified 65 and 54 genes that were induced more than 2-fold by Lovastatin in HCP4 and PCDP5 cells, respectively. Of these, only three genes, KLF2, KLF6, and RHOB, were commonly induced between HCP4 and PCDP5 cells. These mRNAs were strongly induced by Lovastatin with transcriptional regulation in HCP4 cells. Consistent with transcription, the protein expression of RHOB also was induced by Lovastatin. The induction of these genes was associated with cell cycle arrest and apoptosis. Combination treatment with Cisplatin and Lovastatin resulted in an agonistic effect in Hela and PC3 cells and an antagonistic effect in HCP4 and PCDP5 cells. These results suggest that statins might have the potential to overcome Cisplatin resistance as single-agent therapy.

Janus face-like effects of Aurora B inhibition: antitumoral mode of action versus induction of aneuploid progeny

The mitotic Aurora B kinase is overexpressed in tumors and various inhibitors for Aurora B are currently under clinical assessments. However, when considering Aurora B kinase inhibitors as anticancer drugs, their mode of action and the role of p53 status as a possible predictive factor for response still needs to be investigated. In this study, we analyzed the effects of selective Aurora B inhibition using AZD1152-HQPA/Barasertib (AZD1152) on HCT116 cells, U87-MG, corresponding isogenic p53-deficient cells and a primary glioblastoma cell line. AZD1152 treatment caused polyploidy and non-apoptotic cell death in all cell lines irrespective of p53 status and was accompanied by poly-merotelic kinetochore-microtubule attachments and DNA damage. In p53 wild-type cells a DNA damage response induced an inefficient pseudo-G1 cell cycle arrest, which was not able to halt ongoing endoreplication of cells. Of note, release of tumor cells from AZD1152 resulted in recovery of aneuploid progenies bearing numerical and structural chromosomal aberrations. Yet, AZD1152 treatment enhanced death receptor TRAIL-R2 levels in all tumor cell lines investigated. A concomitant increase of the activating natural killer (NK) cell ligand MIC A/B in p53-deficient cells and an induction of FAS/CD95 in cells containing p53 rendered AZD1152-treated cells more susceptible for NK-cell-mediated lysis. Our study mechanistically explains a p53-independent mode of action of a chemical Aurora B inhibitor and suggests a potential triggering of antitumoral immune responses, following polyploidization of tumor cells, which might constrain recovery of aneuploid tumor cells.