Molekulare Mechanismen der Toxizität und Kanzerogenität des Mykotoxins Ochratoxin A

• Applicant: Professorin Dr. Angela Mally
• Subject Area: Pharmacology
• Term: from 2005 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 15478177

The mycotoxin and food contaminant ochratoxin A (OTA) is one of the most potent renal carcinogens studied to date. The molecular events leading to renal tumor formation by OTA are still poorly understood, but increasing evidence suggests that OTA is not a mutagenic, DNA-reactive carcinogen. Recent work in our laboratory provide important new evidence in support of a mechanism of OTA carciogenicity involving disruption of mitosis through interference with key regulators of chromosome separation and progression through mitosis, resulting in blocked or asymmetric cell division, accompanied by an increased risk of aneuploidy acquisition and subsequent tumor formation. In OTA treated cell cultures, condensed and abnormally separated metaphase chromosomes were frequently observed, suggesting that premature separation of sister chromatids in the presence of OTA may provide the initial trigger for aberrant cell division and cell death at mitosis. It is now known that cohesion between sister chromatids is controlled by several mitotic kinases, e.g. Cdk1, Aurora, or Polo-like-kinases (Plk), and aberrant expression of these key regulators of mitosis has been associated with malignant transformation. Gene expression analyses in kidneys of OTA treated rats support a role of Cdk1, Aurora B and Plk1 in OTA mediated Molecular Mechanism of Ochratoxin A Toxicity and Carcinogenicity 3 carcinogenicity, and preliminary results in vitro also suggest that OTA may indeed alter the activity of mitotic kinases known to be involved in chromosome condensation and segregation. However, for a comprehensive understanding of the mechanism of OTA toxicity, the temporal sequence of events and primary cellular targets of OTA remain to be elucidated. Within this project, we aim to determine the time- and concentration-dependent effects of OTA on the acitivty of Cdk1/Cyclin B1, Plk1 and aurora B through determination of the phosphorylation status of their cellular targets (e.g. histon H1, histon H3 and cohesin) both in renal epithelial cells in vitro and in kidneys of OTA treated rats in vivo using a combination of modern cell & molecular biology techniques, such as immunoblotting, immunofluorescence/confocal microscopy and FACS analysis. It is expected that results from this study will not only help to elucidate the mechanism of OTA carcinogenicity as a basis for improved risk assessment, but will also further our understanding of the carcinogenic action of non-mutagenic, non-DNA reactive chemicals.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Wolfgang Dekant