Fei Meng Zheng

The Mitotic Kinase Aurora-A Induces Mammary Cell Migration and Breast Cancer Metastasis by Activating the Cofilin-F-actin Pathway

The mitotic kinase Aurora-A (Aur-A) is required to form the bipolar spindle and ensure accurate chromosome segregation before cell division. Aur-A dysregulation represents an oncogenic event that promotes tumor formation. Here, we report that Aur-A promotes breast cancer metastasis. Aur-A overexpression enhanced mammary cell migration by dephosphorylation and activation of cofilin, which facilitates actin reorganization and polymerization. Cofilin knockdown impaired Aur-A-driven cell migration and protrusion of the cell membrane. Conversely, overexpression of activated cofilin abrogated the effects of Aur-A knockdown on cell migration. Moreover, Aur-A overexpession increased the expression of the cofilin phosphatase Slingshot-1 (SSH1), contributing to cofilin activation and cell migration. We found that phosphatidylinositol 3-kinase (PI3K) inhibition blocked Aur-A-induced cofilin dephosphorylation, actin reorganization, and cell migration, suggesting crosstalk with PI3K signaling and a potential benefit of PI3K inhibition in tumors with deregulated Aur-A. Additionally, we found an association between Aur-A overexpression and cofilin activity in breast cancer tissues. Our findings indicate that activation of the cofilin-F-actin pathway contributes to tumor cell migration and metastasis enhanced by Aur-A, revealing a novel function for mitotic Aur-A kinase in tumor progression.

Curcumin reduces expression of Bcl-2, leading to apoptosis in daunorubicin-insensitive CD34+ acute myeloid leukemia cell lines and primary sorted CD34+ acute myeloid leukemia cells

BackgroundAcute myeloid leukemia (AML) is an immunophenotypically heterogenous malignant disease, in which CD34 positivity is associated with poor prognosis. CD34+ AML cells are 10-15-fold more resistant to daunorubicin (DNR) than CD34- AML cells. Curcumin is a major component of turmeric that has shown cytotoxic activity in multiple cancers; however, its anti-cancer activity has not been well studied in DNR-insensitive CD34+ AML cells. The aim of this study was to therefore to explore curcumin-induced cytotoxicity in DNR-insensitive CD34+ AML cell lines (KG1a, Kasumi-1), DNR-sensitive U937 AML cells, and primary CD34+ AML bone-marrow-derived cells.MethodsPrimary human CD34+ cells were isolated from peripheral blood mononuclear cells or bone marrow mononuclear cells using a CD34 MicroBead kit. The growth inhibitory effects of curcumin were evaluated by MTT and colony-formation assays. Cell cycle distribution was examined by propidium iodide (PI) assay. Apoptosis was analyzed by Wright-Giemsa, Hoechst 33342 and Annexin-V/PI staining assays. The change in mitochondrial membrane potential (MMP) was examined by JC-1 staining and flow cytometry. Expression of apoptosis-related proteins was determined by reverse transcription-polymerase chain reaction and Western blotting. Short interfering RNA (siRNA) against Bcl-2 was used in CD34+ KG1a and Kasumi-1 cells incubated with/without DNR.ResultsCurcumin inhibited proliferation and induced apoptosis and G1/S arrest in both DNR-insensitive KG1a, Kasumi-1 and DNR-sensitive U937 cells. Curcumin-induced apoptosis was associated with reduced expression of both Bcl-2 mRNA and protein, subsequent loss of MMP, and activation of caspase-3 followed by PARP degradation. Curcumin synergistically enhanced the cytotoxic effect of DNR in DNR-insensitive KG1a and Kasumi-1 cells, consistent with decreased Bcl-2 expression. Accordingly, siRNA against Bcl-2 increased the susceptibility of KG1a and Kasumi-1 cells to DNR-induced apoptosis. More importantly, curcumin suppressed Bcl-2 expression, selectively inhibited proliferation and synergistically enhanced the cytotoxicity of DNR in primary CD34+ AML cells, while showing limited lethality in normal CD34+ hematopoietic progenitors.ConclusionCurcumin down-regulates Bcl-2 and induces apoptosis in DNR-insensitive CD34+ AML cell lines and primary CD34+ AML cells.

Aurora-A down-regulates IkappaBα via Akt activation and interacts with insulin-like growth factor-1 induced phosphatidylinositol 3-kinase pathway for cancer cell survival

BackgroundThe mitotic Aurora-A kinase exerts crucial functions in maintaining mitotic fidelity. As a bona fide oncoprotein, Aurora-A aberrant overexpression leads to oncogenic transformation. Yet, the mechanisms by which Aurora-A enhances cancer cell survival remain to be elucidated.ResultsHere, we found that Aurora-A overexpression was closely correlated with clinic stage and lymph node metastasis in tongue carcinoma. Aurora-A inhibitory VX-680 suppressed proliferation, induced apoptosis and markedly reduced migration in cancer cells. We further showed that insulin-like growth factor-1, a PI3K physiological activator, reversed VX-680-decreased cell survival and motility. Conversely, wortmannin, a PI3K inhibitor, combined with VX-680 showed a synergistic effect on inducing apoptosis and suppressing migration. In addition, Aurora-A inhibition suppressed Akt activation, and VX-680-induced apoptosis was attenuated by Myr-Akt overexpression, revealing a cross-talk between Aurora-A and PI3K pathway interacting at Akt activation. Significantly, we showed that suppression of Aurora-A decreased phosphorylated Akt and was associated with increased IkappaBα expression. By contrast, Aurora-A overexpression upregulated Akt activity and downregulated IkappaBα, these changes were accompanied by nuclear translocation of nuclear factor-κB and increased expression of its target gene Bcl-xL. Lastly, Aurora-A overexpression induced IkappaBα reduction was abrogated by suppression of Akt either chemically or genetically.ConclusionTaken together, our data established that Aurora-A, via activating Akt, stimulated nuclear factor-κB signaling pathway to promote cancer cell survival, and promised a novel combined chemotherapy targeting both Aurora-A and PI3K in cancer treatment.

IKKα restoration via EZH2 suppression induces nasopharyngeal carcinoma differentiation

Lack of cellular differentiation is a key feature of nasopharyngeal carcinoma (NPC), but it also presents as a unique opportunity for intervention by differentiation therapy. Here using RNA-seq profiling analysis and functional assays, we demonstrate that reduced IKKα expression is responsible for the undifferentiated phenotype of NPC. Conversely, overexpression of IKKα induces differentiation and reduces tumorigenicity of NPC cells without activating NF-κB signalling. Importantly, we describe a mechanism whereby EZH2 directs IKKα transcriptional repression via H3K27 histone methylation on the IKKα promoter. The differentiation agent, retinoic acid, increases IKKα expression by suppressing EZH2-mediated H3K27 histone methylation, resulting in enhanced differentiation of NPC cells. In agreement, an inverse correlation between IKKα (low) and EZH2 (high) expression is associated with a lack of differentiation in NPC patient samples. Collectively, these findings demonstrate a role for IKKα in NPC differentiation and reveal an epigenetic mechanism for IKKα regulation, unveiling a new avenue for differentiation therapy.

Knockdown of eIF4E suppresses cell growth and migration, enhances chemosensitivity and correlates with increase in Bax/Bcl-2 ratio in triple-negative breast cancer cells

Elevated activity of the eukaryotic translation initiation factor 4E (eIF4E) plays crucial roles in tumorigenesis and disease progression by disproportionately increasing translation of mRNAs coding proteins that play significant roles in all aspects of malignancy, providing that eIF4E as an attractive target for therapeutic intervention. In this study, we showed that inhibition of eIF4E by small interfering RNAs (siRNA) resulted in cell cycle arrest and suppression of colony formation in MDA-MB-231 triple-negative (TN) breast cancer cells. Migration transwell assay revealed that repression of eIF4E effectively inhibited motility of MDA-MB-231 cancer cells. Importantly, we showed that silencing of eIF4E sensitized MDA-MB-231 cells to chemotherapeutic drugs of cisplatin, adriamycin, paclitaxel and docetaxel as assessed by MTT assay. Moreover, Western blot assay showed that eIF4E siRNA increased Bax/Bcl-2 ratio in MDA-MB-231 cells. Taken together, we showed that knockdown of eIF4E suppressed cell growth and migration, enhanced chemosensitivity, suggesting a potential therapeutic target in TN breast carcinoma.

Inhibition of mTOR Pathway Sensitizes Acute Myeloid Leukemia Cells to Aurora Inhibitors by Suppression of Glycolytic Metabolism

Aurora kinases are overexpressed in large numbers of tumors and considered as potential therapeutic targets. In this study, we found that the Aurora kinases inhibitors MK-0457 (MK) and ZM447439 (ZM) induced polyploidization in acute myeloid leukemia (AML) cell lines. The level of glycolytic metabolism was significantly increased in the polyploidy cells, which were sensitive to glycolysis inhibitor 2-deoxy-D-glucose (2DG), suggesting that polyploidy cells might be eliminated by metabolism deprivation. Indeed, inhibition of mTOR pathway by mTOR inhibitors (rapamycin and PP242) or 2DG promoted not only apoptosis but also autophagy in the polyploidy cells induced by Aurora inhibitors. Mechanically, PP242 or2DGdecreased the level of glucose uptake and lactate production in polyploidy cells as well as the expression of p62/SQSTM1. Moreover, knockdown of p62/SQSTM1 sensitized cells to the Aurora inhibitor whereas overexpression of p62/SQSTM1 reduced drug efficacy. Thus, our results revealed that inhibition of mTOR pathway decreased the glycolytic metabolism of the polyploidy cells, and increased the efficacy of Aurora kinases inhibitors, providing a novel approach of combination treatment in AML. Mol Cancer Res; 11(11); 1326–36. ©2013 AACR.

A Novel Small Molecule Aurora Kinase Inhibitor Attenuates Breast Tumor–Initiating Cells and Overcomes Drug Resistance

Chemoresistance is a major cause of cancer treatment failure. Tumor-initiating cells (TIC) have attracted a considerable amount of attention due to their role in chemoresistance and tumor recurrence. Here, we evaluated the small molecule Aurora kinase inhibitor AKI603 as a novel agent against TICs in breast cancer. AKI603 significantly inhibited Aurora-A (AurA) kinase and induced cell-cycle arrest. In addition, the intragastric administration of AKI603 reduced xenograft tumor growth. Interestingly, we found that breast cancer cells that were resistant to epirubicin expressed a high level of activated AurA and also have a high CD24Low/CD44High TIC population. The inhibition of AurA kinase by AKI603 abolished the epirubicin-induced enrichment of TICs. Moreover, AKI603 suppressed the capacity of cells to form mammosphere and also suppressed the expression of self-renewal genes (β-catenin, c-Myc, Sox2, and Oct4). Thus, our work suggests the potential clinical use of the small molecule Aurora kinase inhibitor AKI603 to overcome drug resistance induced by conventional chemotherapeutics in breast cancer. Mol Cancer Ther; 13(8); 1991–2003. ©2014 AACR.

ZM 447439 inhibition of aurora kinase induces Hep2 cancer cell apoptosis in three-dimensional culture

Mitotic Aurora kinases are essential for accurate chromosome segregation during cell division. Forced over-expression of Aurora kinase results in centrosome amplification and multipolar spindles, causing aneuploidy, a hallmark of cancer. ZM447439 (ZM), an Aurora selective ATP-competitive inhibitor, interferes with the spindle integrity checkpoint and chromosome segregation. Here, we showed that inhibition of Aurora kinase by ZM reduced histone H3 phosphorylation at Ser10 in Hep2 carcinoma cells. Multipolar spindles were induced in these ZM-treated G2/M-arrested cells with accumulation of 4N/8N DNA, similar to cells with genetically suppressed Aur-B. Cells subsequently underwent apoptosis, as assessed by cleavage of critical apoptotic associated protein PARP. Hep2 cells formed a tumor-like cell mass in 3-dimensional matrix culture; inhibition of Aurora kinase by ZM either destructed the preformed cell mass or prevented its formation, by inducing apoptotic cell death as stained for cleaved caspase-3. Lastly, ZM inhibition of Aurora kinase was potently in association with decrease of Akt phosphorylation at Ser473 and its substrates GSK3α/beta; phosphorylation at Ser21 and Ser9. Together, we demonstrated that Aurora kinase served as a potential molecular target of ZM for more selective therapeutic cancer treatment.

Targeting GLI1 Suppresses Cell Growth and Enhances Chemosensitivity in CD34+ Enriched Acute Myeloid Leukemia Progenitor Cells

Background/Aims: Resistance of leukemia stem cells (LSCs) to chemotherapy in patients with acute myeloid leukemia (AML) causes relapse of disease. Hedgehog (Hh) signaling plays a critical role in the maintenance and differentiation of cancer stem cells. Yet its role in AML remains controversial. The purpose of the present study is to investigate the role of GLI1, the transcriptional activator of Hh signaling, in AML progenitor cells and to explore the anti-AML effects of GLI small-molecule inhibitor GANT61. Methods: The expression of GLI1 mRNA and protein were examined in AML progenitor cells and normal cells. The proliferation, colony formation, apoptosis and differentiation of AML progenitor cells were also analyzed in the presence of GANT61. Results: Kasumi-1 and KG1a cells, containing more CD34+ cells, expressed higher level of GLI1 compared to U937 and NB4 cells with fewer CD34+ cells. Consistently, a positive correlation between the protein levels of GLI1 and CD34 was validated in the bone marrow mononuclear cells (BMMC) of AML patients tested. GANT61 inhibited the proliferation and colony formation in AML cell lines. Importantly, GANT61 induced apoptosis in CD34+ enriched Kasumi-1 and KG1a cells, whereas it induced differentiation in U937 and NB4 cells. Furthermore, GANT61 enhanced the cytotoxicity of cytarabine (Ara-c) in primary CD34+ AML cells, indicating that inhibition of GLI1 could be a promising strategy to enhance chemosensitivity. Conclusions: The present findings suggested that Hh signaling was activated in AML progenitor cells. GLI1 acted as a potential target for AML therapy.

A novel compound against oncogenic Aurora kinase A overcomes imatinib resistance in chronic myeloid leukemia cells

Drug resistance still represents a major obstacle to successful chronic myeloid leukemia (CML) treatment and novel compounds or strategies to override this challenging problem are urgently required. Here, we evaluated a novel compound AKI603 against oncogenic Aurora kinase A (Aur-A) in imatinib-resistant CML cells. We found that Aur-A was highly activated in imatinib-resistant KBM5-T315I cells. AKI603 significantly inhibited the phosphorylation of Aur-A kinase at Thr288, while had little inhibitory effect on BCR-ABL kinase in both KBM5 and KBM5-T315I cells. AKI603 inhibited cell viability, and induced cell cycle arrest with polyploidy accumulation in KBM5 and KBM5-T315I cells. Moreover, inhibition of Aur-A kinase by AKI603 suppressed colony formation capacity without promoting obvious apoptosis. Importantly, AKI603 promoted cell differentiation in both CML cell types. Thus, our study suggested the potential clinical use of small molecule Aurora kinase inhibitor AKI603 to overcome imatinib resistance in CML treatment.