Human aurora kinases are three highly conserved serine/threonine kinases with regulatory function in chromosome alignment, chromosome segregation, and cytokinesis during cell cycle progression and their overexpression associates with malignant transformation and proliferation of cancer cells. Aurora genes are located at loci that are commonly altered in cancers. Aurora-A has oncogenic activity while Aurora-B does not. Aurora-C is only detected in mammals with involvement in meiosis. Oncogenic activity of Aurora-C is still in dispute. We evaluated the expression of three Aurora kinases by real-time RT-PCR in well-known breast and prostate cancer cell lines. Cell cycle was studied with flow cytometry. In both more invasive cell lines' p53-null cells, PC-3 and MDA-MB-231, an increase in mRNA expression of three Aurora kinases, especially Aurora-C, was observed. Genomic DNA was examined for gene amplification and aneuploidy as a mechanism of overexpression. At DNA level, only Aurora-C showed gene amplification in breast cancer cell lines (p < 0.005). Here we provide evidence for the first time of Aurora-C overexpression and gene amplification.