Amplification and overexpression of Aurora kinase A (AURKA) in immortalized human ovarian epithelial (HOSE) cells

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Abstract
Immortalization is an early and essential step of human carcinogenesis. Amplification of chromosome 20q has been shown to be a common event in immortalized cells and cancers. We have previously reported that gain and amplification of chromosome 20q is a non‐random and common event in immortalized human ovarian surface epithelial (HOSE) cells. The chromosome 20q harbors genes including TGIF2 (20q11.2‐q12), AIB1 (20q12), PTPN1 (20q13.1), ZNF217 (20q13.2), and AURKA (20q13.2‐q13.3), which were previously reported to be amplified and overexpressed in ovarian cancers. Some of these genes may be involved in immortalization of HOSE cells and represent crucial premalignant changes in ovarian surface epithelium. Investigation of the involvement of these genes was examined in four pairs of pre‐crisis (preimmortalized) and post‐crisis (immortalized) HOSE cells. Overexpression of AURKA (Aurora kinase A), also known as BTAK and STK15, by both real time‐quantitative polymerase chain reaction (RT‐QPCR) and Western blotting was detected in all the four immortalized HOSE cells examined while overexpression of AIB1 and ZNF217 was observed in two of four immortalized HOSE cells examined. Overexpression of TGIF2 and PTPN1 was not significant in our immortalized HOSE cell systems. The degree of overexpression of AURKA was shown to be closely associated with the amplification of chromosome 20q in immortalized HOSE cells. Fluorescence in situ hybridization (FISH) with labeled P1 artificial clone (PAC) confirmed the amplification of the chromosomal region (20q13.2‐13.3) where AURKA resides. DNA amplification of AURKA was also confirmed using semi‐quantitative PCR. Our study showed that amplification and overexpression of AURKA is a common and significant event during immortalization of HOSE cells and may represent an important premalignant change in ovarian carcinogenesis.

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