DNA copy number changes at 8q11-24 in metastasized colorectal cancer

C-Myc, a well-known oncogene located on 8q24.12-q24.23, is often amplified and over-expressed in both primary and metastasizing colorectal cancer. In addition, PRL-3 (also known as PTP4A3), a tyrosine phosphatase located on 8q24.3, is amplified in colorectal cancer metastasis. Beside PRL-3 and c-myc, other oncogenes located on the 8q23-24 region might be involved in this process. Therefore, the present study aims to correlate DNA copy number status of a series of genes at 8q23-24 in colorectal cancer at high resolution in correlation to metastatic disease. Thirty-two cases of colorectal cancer, 10 stage B1, 10 B2 and 12 D (Astler-Coller) with their corresponding liver metastasis and one colorectal cell line (colo205, previously analyzed by array-CGH), were included in this study. A chromosome 8 specific MLPA probe mixture was used to analyze the presence of DNA copy number changes. The probe mixture contained 29 probes covering 25 genes on chromosome 8, as well as 6 control probes on other chromosomes. MLPA results obtained of the colo205 colorectal cell line were comparable with previous array-CGH results, thus validating the MLPA probe mixture. Astler-Coller B1 and B2 colorectal cancers differed significantly in DNA copy number of the genes, MOS (p=0.04), MYC (p=0.007), DDEF1 (p=0.004), PTK2 (p=0.02) and PTP4A3 (p=0.04). When comparing these with Astler-Coller D primary tumors, significant differences were seen for several genes as well (MYC (p