Somatic mutations of the lysyl oxidase gene on chromosome 5q23.1 in colorectal tumors

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Abstract
Lysyl oxidase (LOX), a copper‐dependent amine oxidase, has been implicated in tumor suppression and cell growth regulation. The chromosomal locus of LOX, 5q23, is affected by loss of heterozygosity (LOH) in colon cancer, suggesting that the LOX gene could be affected by LOH and consequently, loss or reduction of LOX function contribute to the tumorigenic process. Identification of microsatellite markers within the LOX locus has allowed us to map the LOX gene within the 5q23.1 region. Analysis of this locus and flanking loci in matched tumor and blood DNA samples from a panel of colorectal cancer patients, demonstrated that 38% (16/42) of informative samples were affected by LOH or allelic imbalance. Furthermore, 75% (6/8) of these tumor samples were shown to have significantly reduced LOX mRNA levels. Similar reduction in LOX levels were detected in a panel of matched normal colon and colon tumor samples. Tumor samples demonstrating LOH by RFLP, were subject to mutational analysis, including RT‐PCR, exonic deletion detection by PCR, cDNA and genomic DNA sequencing, and were found to have a spectrum of alterations and mutations affecting the LOX gene. These results confirm that loss or reduction of LOX function during tumor development is a direct consequence of somatic mutations and is associated with colon tumor pathogenesis.