ABSTRACT
BACKGROUND: The 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. RESULTS: Here, 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 IkappaBalpha expression. By contrast, Aurora-A overexpression upregulated Akt activity and downregulated IkappaBalpha, these changes were accompanied by nuclear translocation of nuclear factor-kappaB and increased expression of its target gene Bcl-xL. Lastly, Aurora-A overexpression induced IkappaBalpha reduction was abrogated by suppression of Akt either chemically or genetically. CONCLUSION: Taken together, our data established that Aurora-A, via activating Akt, stimulated nuclear factor-kappaB signaling pathway to promote cancer cell survival, and promised a novel combined chemotherapy targeting both Aurora-A and PI3K in cancer treatment.
Subject(s)
Down-Regulation/genetics , I-kappa B Proteins/metabolism , Insulin-Like Growth Factor I/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Protein Serine-Threonine Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Tongue Neoplasms/pathology , Apoptosis/drug effects , Aurora Kinases , Carcinoma, Squamous Cell/enzymology , Carcinoma, Squamous Cell/pathology , Cell Line, Tumor , Cell Movement/drug effects , Cell Nucleus/drug effects , Cell Nucleus/metabolism , Cell Proliferation/drug effects , Cell Survival/drug effects , Dose-Response Relationship, Drug , Down-Regulation/drug effects , Enzyme Activation/drug effects , Humans , Lymphatic Metastasis/pathology , NF-KappaB Inhibitor alpha , Neoplasm Staging , Phosphorylation/drug effects , Piperazines/pharmacology , Protein Binding/drug effects , Protein Serine-Threonine Kinases/antagonists & inhibitors , Protein Subunits/metabolism , Protein Transport/drug effects , Signal Transduction/drug effects , Tongue Neoplasms/enzymology , Transcription Factor RelA/metabolismABSTRACT
Mitotic Aurora kinases are essential for accurate chromosome segregation during cell division. Forced overexpression 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 G(2)/M-arrested cells with accumulation of 4N/8N DNA, similar to cells with genetically suppressed Aurora-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 GSK3alpha/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.
Subject(s)
Apoptosis/drug effects , Benzamides/pharmacology , Chromosome Segregation/drug effects , Protein Serine-Threonine Kinases/antagonists & inhibitors , Quinazolines/pharmacology , Aurora Kinase B , Aurora Kinases , Blotting, Western , Cell Line, Tumor , Cell Proliferation/drug effects , Collagen Type XI/metabolism , Flow Cytometry , Fluorescent Antibody Technique , Histones/metabolism , Humans , Immunoprecipitation , Phosphorylation/drug effects , RNA, Small Interfering/geneticsABSTRACT
Mitotic Aurora kinases are required for accurate chromosome segregation during cell division. Ectopic expression of Aurora-A (Aur-A) kinase results in centrosome amplification, aberrant spindles, and consequent aneuploidy. In the present study, we showed that Aurora kinase inhibitory small molecule VX-680 inhibited histone H3 phosphorylation at Ser10, a known in vivo substrate residue of Aurora kinase, in oral squamous cell carcinoma (OSCC) KB cells. In addition, monopolar spindle structures, typical abnormalities induced by inhibition of Aur-A, were generated in VX-680-treated cells. Inhibition of Aurora kinase led to reduced KB cell growth, as assessed by MTT assay. Western blot analysis revealed that VX-680 caused cleavage of two critical apoptotic associated proteins, PARP and caspase-3. In contrast, expression of cell survival factor Bcl-2 was reduced by VX-680 treatment in a dose-dependent manner. Subsequently, nuclear characteristic of DNA fragmentation, indicative of apoptotic cell death, was clearly observed in these OSCC cells with Aurora kinase inhibitory VX-680. Taken together, we showed that Aurora kinase inhibitory VX-680 led to apoptotic cell death in OSCC cells, suggesting a novel therapeutic target in oral cancer.
