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


METHODS
Bromodeoxyuridine (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.


RESULTS
We 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.


CONCLUSION
We 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.
['Kao|Yu-Ting|YT|', 'Wu|Chin-Han|CH|', 'Wu|Shan-Ying|SY|', 'Lan|Sheng-Hui|SH|', 'Liu|Hsiao-Sheng|HS|', 'Tseng|Ya-Shih|YS|']
D000818:Animals D001151:Arsenic D064096:Aurora Kinase A D015153:Blotting, Western D063646:Carcinogenesis D002295:Carcinoma, Transitional Cell D045744:Cell Line, Tumor D049109:Cell Proliferation D047369:Chromatin Immunoprecipitation D050687:E2F1 Transcription Factor D005434:Flow Cytometry D005455:Fluorescent Antibody Technique D006801:Humans D007150:Immunohistochemistry D051379:Mice D008807:Mice, Inbred BALB C D020133:Reverse Transcriptase Polymerase Chain Reaction D001749:Urinary Bladder Neoplasms
Arsenic Aurora-A Bladder Carcinogenesis