Arsenic treatment increase Aurora-A overexpression through E2F1 activation in bladder cells

Abstract

BackgroundArsenic is a widely distributed metalloid compound that has biphasic effects on cultured cells. In large doses, arsenic can be toxic enough to trigger cell death. In smaller amounts, non-toxic doses may promote cell proliferation and induces carcinogenesis. Aberration of chromosome is frequently detected in epithelial cells and lymphocytes of individuals from arsenic contaminated areas. Overexpression of Aurora-A, a mitotic kinase, results in chromosomal instability and cell transformation. We have reported that low concentration (≦1 μM) of arsenic treatment increases Aurora-A expression in immortalized bladder urothelial E7 cells. However, how arsenic induces carcinogenesis through Aurora-A activation remaining unclear.MethodsBromodeoxyuridine (BrdU) staining, MTT assay, and flow cytometry assay were conducted to determine cell proliferation. Messenger RNA and protein expression levels of Aurora-A were detected by reverse transcriptional-PCR and Western blotting, respectively.Centrosome of cells was observed by immunofluorescent staining. The transcription factor of Aurora-A was investigated by promoter activity, chromosome immunoprecipitation (ChIP), and small interfering RNA (shRNA) assays. Mouse model was utilized to confirm the relationship between arsenic and Aurora-A.ResultsWe reveal that low dosage of arsenic treatment increased cell proliferation is associated with accumulated cell population at S phase. We also detected increased Aurora-A expression at mRNA and protein levels in immortalized bladder urothelial E7 cells exposed to low doses of arsenic. Arsenic-treated cells displayed increased multiple centrosome which is resulted from overexpressed Aurora-A. Furthermore, the transcription factor, E2F1, is responsible for Aurora-A overexpression after arsenic treatment. We further disclosed that Aurora-A expression and cell proliferation were increased in bladder and uterus tissues of the BALB/c mice after long-term arsenic (1 mg/L) exposure for 2 months.ConclusionWe reveal that low dose of arsenic induced cell proliferation is through Aurora-A overexpression, which is transcriptionally regulated by E2F1 both in vitro and in vivo. Our findings disclose a new possibility that arsenic at low concentration activates Aurora-A to induce carcinogenesis.

Molecular Mechanisms of Arsenic-Induced Disruption of DNA Repair

“…Arsenite-induced cell proliferation was shown to arise from elevated levels of epidermal growth factor receptor (EGFR) ligand, heparin-binding EGF, and its subsequent activation of EGFR phosphorylation that induces pERK and cyclin D1 expression in human cells . Arsenite-elicited ERK signaling is required for arsenic-induced transactivation of NF-κB, which might be mediated by arsenic-stimulated oxidative stress. − Additionally, low-dose arsenite treatment has been documented to activate ERK, as well as transcription factors E2F1 and Activating Protein 1 (AP-1), enhance the DNA binding activities of AP-1 and NF-κB, and elevate the expression of a number of positive cell growth-related genes including FOS , JUN , MYC , and EGR-1 . ,,− …”

“…The major cell growth and ROS-mediated pathways are regulated by protein tyrosine phosphorylation, which itself is controlled by tyrosine kinases and protein tyrosine phosphatases. Therefore, arsenite exposure is believed to inactivate protein tyrosine phosphatases by ROS/RNS-induced modifications of redox-sensitive cysteines at their active sites, thereby augmenting the total cellular tyrosine phosphorylation. ,− Combined, arsenite and arsenite-induced ROS/RNS can stimulate a phosphorylated state of EGFR, and activate ERK, transcription factor AP-1 complex, and its downstream target genes JUN , FOS , and MYC , thereby increasing cyclin D1 expression. , Together with arsenite-activated E2F transcription factors and their modulation of cyclin E levels, arsenite exposure elicits unchecked cell cycle progression and uncontrolled cell proliferation. ,− …”

A mathematical model of kinetochore-microtubule attachment regulated by Aurora A activity gradient describes chromosome oscillation and correction of erroneous attachments

“…Our results limit the range within which erroneous attachments are efficiently eliminated between approximately 80% and 180% (approximately −0.1 and 0.25 respectively, on a base 10 logarithmic scale) of the Aurora A expression level used to reproduce the oscillation observed in normal cells. Despite these values are merely a stipulation of what the real range could be, our model suggests that Aurora A inhibition as well as its upregulation, like the condition observed in cancer cells (Ertych et al, 2014;He et al, 2014;Nicholson et al, 2015;Kao et al, 2017), leads to deficient erroneous attachment correction, and consequently to chromosome missegregation and CIN. Although further considerations and new parameters will fade the gap between simulation and reality, our model provides a framework to understand the relevance of Aurora A expression level on the error correction mechanism and chromosome dynamics.…”

“…Then we defined a mathematical correlation to adjust our Aurora A interpretation parameter Aur A in order to reproduce the experimental observations of the Aurora A-inhibited cells. Finally, we assumed that cancer cells, even though they are usually overexpressing Aurora A (He et al, 2014;Kao et al, 2017;Umene et al, 2015), behaved analogously, as they showed a comparable Hec1 phosphorylation impairment.…”

“…4F). Finally, we tried to reproduce the situation of cancer cells, in which Aurora A is commonly upregulated (He et al, 2014;Kao et al, 2017;Umene et al, 2015). Our model showed an erratic directional instability, as well as an inter-KT stretching (approximately 1 μm; Fig.…”