Aurora-A kinase inhibition enhances the cytosine arabinoside-induced cell death in leukemia cells through apoptosis and mitotic catastrophe

Arsenic trioxide synergistically promotes the antileukaemic activity of venetoclax by downregulating Mcl-1 in acute myeloid leukaemia cells

BACKGROUND

The evasion of apoptosis through dysregulated Bcl-2 family members is a hallmark of leukaemia stem cells (LSCs) in acute myeloid leukaemia (AML). Therefore, targeting Bcl-2 with venetoclax has been suggested as an attractive strategy for inducing apoptosis in AML LSCs. However, the selective inhibition of Bcl-2 in AML often leads to upregulation of Mcl-1, another dominant anti-apoptotic Bcl-2 family protein conferring venetoclax resistance.

METHODS

We assessed the combined effect of venetoclax and arsenic trioxide (ATO) on leukaemic cell viability, apoptosis, combination index, and cell cycle in the human LSC-like KG1 and KG1a cells. The synergistic effect of venetoclax and ATO on apoptosis was also examined in primary CD34⁺ and CD34⁺CD38^- LSCs from the bone marrow (BM) of AML patients, and compared with those from healthy donors.

RESULTS

Venetoclax efficiently impaired cell viability and dose-dependently promoted apoptosis when combined with ATO; their synergism was aptly represented by the combination index. The combination of venetoclax and ATO impaired cell cycle progression by restricting cells within the sub-G1 phase and facilitating caspase-dependent apoptotic cell death associated with the loss of mitochondrial membrane potential, while sparing healthy BM haematopoietic stem cells. Mechanistically, ATO mitigated venetoclax-induced upregulation of Mcl-1 by the inhibition of AKT and ERK, along with activation of GSK-3β. This led to the Mcl-1 destabilisation, triggering Noxa and Bim to facilitate apoptosis and the consequent activation of the apoptosis executioner protein Bak. Moreover, the combination promoted phosphorylation of ATM, Chk2, p38, and H2AX, indicating an active DNA damage response.

CONCLUSIONS

Our findings demonstrate the synergistic, preferential antileukaemic effects of venetoclax and ATO on LSCs, providing a rationale for preclinical and clinical trials by combining these agents already being used in clinical practice to treat acute leukaemia.

RNA Interference-Mediated Aurora Kinase A Gene Silencing Inhibits Human Glioma Cells Proliferation and Tumor Growth in Mice

Objective: This study aims to explore the roles of Aurora Kinase A (Aurora A) in human glioma progression and relevant molecular mechanisms involved. Methods: RNA interference (RNAi) technology was performed to silence the Aurora A gene in human glioma cell line U251 and U87. Western blot and real-time PCR were used to determine the protein and mRNA expression levels of Aurora A. Flow cytometry was performed to analyze the cell cycle distribution and MTT was used to examine the cell viability. Annexin V/FITC double staining and Hoechst 33258 staining were carried out to examine cell apoptosis. Xenograft tumor model was established to examine the effect of Aurora A siRNA on tumor growth in vivo. Results: RNAi-mediated Aurora A gene silencing with specific short interfering RNA (siRNA) significantly decreased Aurora A protein and mRNA expression levels in human glioma cell line U251 and U87. Aurora A knockdown in glioma cells with siRNA strongly inhibited cell proliferation, along with the accumulation of cells in the G1, G2/M phase and decrease in S phase. Furthermore, the enhancement of cell apoptosis in vitro and the suppression of xenograft tumor growth in vivo were also observed after Aurora A silencing in U251 cell. In addition, Aurora A knockdown resulted in decreased expression of anti-apoptotic protein Bcl-2 and cell cycle protein Cyclin D1, while increased expression of pro-apoptotic factor caspase-3. Conclusion: Aurora A can be used as a candidate targeting gene and inhibition of Aurora A is a potentially promising therapy for glioblastoma.

Design, synthesis, biological evaluation of 6-(2-amino-1H-benzo[d]imidazole-6-yl)quinazolin-4(3H)-one derivatives as novel anticancer agents with Aurora kinase inhibition

Aurora A kinase, a member of the Aurora kinase family, is frequently overexpressed in various human cancers. In addition, Overexpression of Aurora A kinase is associated with drug resistance and poor prognosis in many cancers including breast cancer. Therefore, Aurora A kinase has been considered as an attractive anticancer target for the treatment of human cancers. Herein, A series of 6-(2-amino-1H-benzo[d]imidazole-6-yl)quinazolin-4(3H)-one derivatives were designed, synthesized, and evaluated as Aurora A kinase inhibitors. The cell-based cytotoxicity assays showed that compound 16h was the most potent cytotoxic agent against all tested cancer cells and had a lower IC₅₀ value than ENMD-2076 against MDA-MB-231 cells. Meanwhile, Aurora A kinase assay and Western blot analysis showed that 16h inhibited Aurora A kinase with an IC₅₀ value of 21.94 nM and suppressed the phosphorylation of Histone H3 on Ser10 and Aurora A kinase on Thr288, which were consistent with the activation of Aurora A kinase. Accordingly, 16h caused aberrant mitotic phenotypes and obvious G2/M phase arrest in MDA-MB-231 cells and induced caspase-dependent apoptosis in MDA-MB-231 cells. These results demonstrated that 16h is a potential candidate for the development of anticancer agents targeting Aurora A kinase.

CoA synthase regulates mitotic fidelity via CBP-mediated acetylation

The temporal activation of kinases and timely ubiquitin-mediated degradation is central to faithful mitosis. Here we present evidence that acetylation controlled by Coenzyme A synthase (COASY) and acetyltransferase CBP constitutes a novel mechanism that ensures faithful mitosis. We found that COASY knockdown triggers prolonged mitosis and multinucleation. Acetylome analysis reveals that COASY inactivation leads to hyper-acetylation of proteins associated with mitosis, including CBP and an Aurora A kinase activator, TPX2. During early mitosis, a transient CBP-mediated TPX2 acetylation is associated with TPX2 accumulation and Aurora A activation. The recruitment of COASY inhibits CBP-mediated TPX2 acetylation, promoting TPX2 degradation for mitotic exit. Consistently, we detected a stage-specific COASY-CBP-TPX2 association during mitosis. Remarkably, pharmacological and genetic inactivation of CBP effectively rescued the mitotic defects caused by COASY knockdown. Together, our findings uncover a novel mitotic regulation wherein COASY and CBP coordinate an acetylation network to enforce productive mitosis.

Inhibition of Aurora Kinase A Induces Necroptosis in Pancreatic Carcinoma

BACKGROUND & AIMS

Induction of nonapoptotic cell death could be an approach to eliminate apoptosis-resistant tumors. We investigated necroptosis-based therapies in mouse models of pancreatic ductal adenocarcinoma cancer (PDAC).

METHODS

We screened 273 commercially available kinase inhibitors for cytotoxicity against a human PDAC cell line (PANC1). We evaluated the ability of the aurora kinase inhibitor CCT137690 to stimulate necroptosis in PDAC cell lines (PANC1, PANC2.03, CFPAC1, MiaPaCa2, BxPc3, and PANC02) and the HEK293 cell line, measuring loss of plasma membrane integrity, gain in cell volume, swollen organelles, and cytoplasmic vacuoles. We tested the effects of CCT137690 in colon formation assays, and the effects of the necroptosis (necrostatin-1 and necrosulfonamide), apoptosis, autophagy, and ferroptosis inhibitors. We derived cells from tumors that developed in Pdx1-Cre;K-Ras^G12D/+;p53^R172H/+ (KPC) mice. Genes encoding proteins in cell death pathways were knocked out, knocked down, or expressed from transgenes in PDAC cell lines. Athymic nude or B6 mice were given subcutaneous injections of PDAC cells or tail-vein injections of KPC tumor cells. Mice were given CCT137690 (80 mg/kg) or vehicle and tumor growth was monitored; tumor tissues were collected and analyzed by immunohistochemistry. We compared gene expression levels between human pancreatic cancer tissues (n = 130) with patient survival times using the online R2 genomics analysis and visualization platform.

RESULTS

CCT137690 induced necrosis-like death in PDAC cell lines and reduced colony formation; these effects required RIPK1, RIPK3, and MLKL, as well as inhibition of aurora kinase A (AURKA). AURKA interacted directly with RIPK1 and RIPK3 to reduce necrosome activation. AURKA-mediated phosphorylation of glycogen synthase kinase 3 beta (GSK3β) at serine 9 inhibited activation of the RIPK3 and MLKL necrosome. Mutations in AURKA (D274A) or GSK3β (S9A), or pharmacologic inhibitors of RIPK1 signaling via RIPK3 and MLKL, reduced the cytotoxic activity of CCT137690 in PDAC cells. Oral administration of CCT137690 induced necroptosis and immunogenic cell death in subcutaneous and orthotopic tumors in mice, and reduced tumor growth and tumor cell phosphorylation of AURKA and GSK3β. CCT137690 increased survival times of mice with orthotopic KPC PDACs and reduced tumor growth, stroma, and metastasis. Increased expression of AURKA and GSK3β mRNAs associated with shorter survival times of patients with pancreatic cancer.

CONCLUSIONS

We identified the aurora kinase inhibitor CCT137690 as an agent that induces necrosis-like death in PDAC cells, via RIPK1, RIPK3, and MLKL. CCT137690 slowed growth of orthotopic tumors from PDAC cells in mice, and expression of AURKA and GSK3β associate with patient survival times. AURKA might be targeted for treatment of pancreatic cancer.

Induction of cytosine arabinoside-resistant human myeloid leukemia cell death through autophagy regulation by hydroxychloroquine

We investigated the effects of the autophagy inhibitor hydroxychloroquine (HCQ) on cell death of cytosine arabinoside (Ara-C)-resistant human acute myeloid leukemia (AML) cells. Ara-C-sensitive (U937, AML-2) and Ara-C-resistant (U937/AR, AML-2/AR) human AML cell lines were used to evaluate HCQ-regulated cytotoxicity, autophagy, and apoptosis as well as effects on cell death-related signaling pathways. We found that HCQ-induced dose- and time-dependent cell death in Ara-C-resistant cells compared to Ara-C-sensitive cell lines. The extent of cell death and features of HCQ-induced autophagic markers including increase in microtubule-associated protein light chain 3 (LC3) I conversion to LC3-II, beclin-1, ATG5, as well as green fluorescent protein-LC3 positive puncta and autophagosome were remarkably greater in U937/AR cells. Also, p62/SQSTM1 was increased in response to HCQ. p62/SQSTM1 protein interacts with both LC3-II and ubiquitin protein and is degraded in autophagosomes. Therefore, a reduction of p62/SQSTM1 indicates increased autophagic degradation, whereas an increase of p62/SQSTM1 by HCQ indicates inhibited autophagic degradation. Knock down of p62/SQSTM1 using siRNA were prevented the HCQ-induced LC3-II protein level as well as significantly reduced the HCQ-induced cell death in U937/AR cells. Also, apoptotic cell death and caspase activation in U937/AR cells were increased by HCQ, provided evidence that HCQ-induced autophagy blockade. Taken together, our data show that HCQ-induced apoptotic cell death in Ara-C-resistant AML cells through autophagy regulation.

Aurora A kinase expression is increased in leukemia stem cells, and a selective Aurora A kinase inhibitor enhances Ara-C-induced apoptosis in acute myeloid leukemia stem cells

BACKGROUND

The overexpression of Aurora A kinase (AurA) has been reported in various malignancies, including acute myeloid leukemia (AML). However, the expression of AurA and the effects of AurA inhibition in cancer stem cells are not yet fully understood. We investigated the expression and inhibition of AurA in AML stem cells (CD34(+)/CD38(-)).

METHODS

Expression of AurA was investigated in cell lines (NB4 and KG1) that express high levels of CD34 and low levels of CD38. Primary AML cells were harvested from 8 patients. The expression of AurA and cell death induced by inhibition of AurA were analyzed in CD34(+)/CD38(-) cells.

RESULTS

AurA was shown to be overexpressed in both primary AML cells and leukemia stem cells (LSCs) compared to normal hematopoietic stem cells. Inhibition of AurA plus cytarabine treatment in LSCs resulted in increased cytotoxicity compared to cytarabine treatment alone. Additional stimulation with granulocyte-colony stimulating factor (G-CSF) increased the cell death caused by AurA inhibition plus cytarabine treatment.

CONCLUSION

To our knowledge, this is the first report describing increased expression of AurA in LSCs. Our results suggest that selective AurA inhibition may be used to reduce LSCs, and this reduction may be enhanced by stimulation with G-CSF. Further exploration of relationship between nuclear factor kappa-B and AurA inhibition and the potential of AurA inhibition for use in leukemia treatment is needed.

Targeting of polo-like kinases and their cross talk with Aurora kinases--possible therapeutic strategies in human acute myeloid leukemia?

INTRODUCTION

Five human polo-like kinases (PLKs) have been identified, and PLK1 - 4 seem to interact with Aurora kinases and act as cell cycle regulators in both normal and malignant human cells.

AREAS COVERED

The present review describes i) experimental evidence for a role for PLKs and Aurora kinases in human leukemogenesis and ii) the results from clinical studies of PLK and Aurora kinase inhibitors in the treatment of human acute myeloid leukemia (AML). The review was based on searches in the PubMed and the ClinicalTrials.gov databases. These inhibitors have antiproliferative and proapoptotic effects in AML cells. Hematological and gastrointestinal toxicities are frequently dose limiting, and this may limit the use of these agents in combination with conventional AML therapy. Aurora kinase inhibitors seem to be most effective for patients with high expression of the target kinases, and the same may be true for PLK inhibitors.

EXPERT OPINION

PLK inhibition is a promising strategy for the treatment of AML. Future clinical studies have to clarify i) whether this strategy is most effective for certain subsets of patients; ii) whether multikinase inhibitors targeting several cell cycle regulators should be preferred; and iii) how this therapeutic strategy eventually should be combined with conventional antileukemic chemotherapy.

TIG3 tumor suppressor-dependent organelle redistribution and apoptosis in skin cancer cells

TIG3 is a tumor suppressor protein that limits keratinocyte survival during normal differentiation. It is also important in cancer, as TIG3 level is reduced in tumors and in skin cancer cell lines, suggesting that loss of expression may be required for cancer cell survival. An important goal is identifying how TIG3 limits cell survival. In the present study we show that TIG3 expression in epidermal squamous cell carcinoma SCC-13 cells reduces cell proliferation and promotes morphological and biochemical apoptosis. To identify the mechanism that drives these changes, we demonstrate that TIG3 localizes near the centrosome and that pericentrosomal accumulation of TIG3 alters microtubule and microfilament organization and organelle distribution. Organelle accumulation at the centrosome is a hallmark of apoptosis and we demonstrate that TIG3 promotes pericentrosomal organelle accumulation. These changes are associated with reduced cyclin D1, cyclin E and cyclin A, and increased p21 level. In addition, Bax level is increased and Bcl-XL level is reduced, and cleavage of procaspase 3, procaspase 9 and PARP is enhanced. We propose that pericentrosomal localization of TIG3 is a key event that results in microtubule and microfilament redistribution and pericentrosomal organelle clustering and that leads to cancer cell apoptosis.