Simultaneous Aurora-A/STK15 overexpression and centrosome amplification induce chromosomal instability in tumour cells with a MIN phenotype.
BACKGROUND
Genetic instability is a hallmark of tumours and preneoplastic lesions. The predominant form of genome instability in human cancer is chromosome instability (CIN). CIN is characterized by chromosomal aberrations, gains or losses of whole chromosomes (aneuploidy), and it is often associated with centrosome amplification. Centrosomes control cell division by forming a bipolar mitotic spindle and play an essential role in the maintenance of chromosomal stability.However, whether centrosome amplification could directly cause aneuploidy is not fully established. Also, alterations in genes required for mitotic progression could be involved in CIN.A major candidate is represented by Aurora-A/STK15 that associates with centrosomes and is overexpressed in several types of human tumour.


METHODS
Centrosome amplification were induced by hydroxyurea treatment and visualized by immunofluorescence microscopy. Aurora-A/STK15 ectopic expression was achieved by retroviral infection and puromycin selection in HCT116 tumour cells. Effects of Aurora-A/STK15 depletion on centrosome status and ploidy were determined by Aurora-A/STK15 transcriptional silencing by RNA interference. Changes in the expression levels of some mitotic genes were determined by Real time RT-PCR.


RESULTS
We investigated whether amplification of centrosomes and overexpression of Aurora-A/STK15 induce CIN using as a model system a colon carcinoma cell line (HCT116). We found that in HCT116 cells, chromosomally stable and near diploid cells harbouring a MIN phenotype, centrosome amplification induced by hydroxyurea treatment is neither maintained nor induces aneuploidy. On the contrary, ectopic overexpression of Aurora-A/STK15 induced supernumerary centrosomes and aneuploidy. Aurora-A/STK15 transcriptional silencing by RNA interference in cells ectopically overexpressing this kinase promptly decreased cell numbers with supernumerary centrosomes and aneuploidy.


CONCLUSIONS
Our results show that centrosome amplification alone is not sufficient to induce chromosomal instability in colon cancer cells with a MIN phenotype. Alternatively, centrosome amplification has to be associated with alterations in genes regulating mitosis progression such as Aurora-A/STK15 to trigger CIN.
Lentini
Laura
L
Department of Cellular and Developmental Biology A, Monroy, University of Palermo, viale delle Scienze, Palermo, Italy. laura.lentini@unipa.it
Amato
Angela
A
Schillaci
Tiziana
T
Di Leonardo
Aldo
A
D000782:Aneuploidy; D017209:Apoptosis; D064096:Aurora Kinase A; D064127:Aurora Kinases; D002450:Cell Communication; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D018385:Centrosome; D043171:Chromosomal Instability; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D053842:Microsatellite Instability; D008856:Microscopy, Fluorescence; D010641:Phenotype; D011003:Ploidies; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000235:genetics*; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D008941:Spindle Apparatus; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D034741:RNA, Small Interfering; C576917:AURKA protein, human; D064096:Aurora Kinase A; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases