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Carcinogenesis Advance Access published online on February 23, 2009
Carcinogenesis, doi:10.1093/carcin/bgp049
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© The Author 2009. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Modulation of key regulators of mitosis linked to chromosomal instability is an early event in ochratoxin A carcinogenicity

Melanie Adler, Katja Müller, Eva Rached, Wolfgang Dekant and Angela Mally

Department of Toxicology, University of Würzburg, Würzburg, Germany

Corresponding author: Dr. Angela Mally, Department of Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany, Tel.: +49-931-20148894, Fax: +49-931-20148865, e-mail: mally{at}toxi.uni-wuerzburg.de

Ochratoxin A (OTA) is a potent renal carcinogen, but little is known regarding the mechanism of OTA carcinogenicity. Early histopathological alterations induced by OTA in rat kidney include single cell death, stimulation of cell proliferation and prominent karyomegaly indicative of blocked nuclear division during mitosis. Based on these observations, it has been suggested that disruption of mitosis by OTA may be the principal cause of cell death and subsequent trigger for cell proliferation to compensate for cell loss. To gain further insight into the molecular mechanism of OTA toxicity, we used targeted qRT-PCR arrays to investigate the expression of genes involved in cell cycle control and mitosis in kidneys of male F344 rats treated with 0, 21, 70 and 210 µg/kg bw OTA for up to 90 days. Treatment with OTA resulted in overexpression of key regulators of mitosis, including the mitotic protein kinases Polo-like kinase 1, Aurora B and cyclin-dependent-kinase 1 (Cdk1Cdc2), several cyclins and cyclin-dependent-kinase inhibitors, topoisomerase II and survivin. Immunohistochemical analysis confirmed up-regulation of Cdk1, p21WAF1/CIP1, topoisomerase II and survivin in S3 proximal tubule cells, from which OTA induced tumors in rats arise, and demonstrated increased phosphorylation of histone H3, a target of Aurora B. Importantly, many of the genes found to be deregulated in response to OTA have been linked to chromosomal instability and malignant transformation, supporting the hypothesis that aberrant mitosis, resulting in blocked or asymmetric cell division, accompanied by an increased risk of aneuploidy acquisition, may play a critical role in OTA carcinogenicity.

Key Words: Ochratoxin A • carcinogenesis • mitosis • chromosomal instability • gene expression

Received November 14, 2008; revised February 9, 2009; accepted February 14, 2009.


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