Identification of novel matrix metalloproteinases and the effect of polymorphisms in colorectal cancer
The matrix metalloproteinases (MMPs) are a family of proteases responsible for degradation of the extracellular matrix. Due to this activity they are involved in a variety of cellular processes, particularly cell growth and motility during development as well as pathological conditions such as tumour progression and arthritis. Characterisation of the activity of these proteases is of considerable importance to the understanding of the disease states. The identification of novel MMPs was attempted by two techniques. Firstly antibodies were designed and produced with wide-ranging binding ability towards the MMP family. A conserved epitope was identified in the MMP family and the antibodies raised showed considerable cross-reactivity. These antibodies were then used to screen expression libraries. However, it was not possible to achieve MMP selection from libraries. The other method was the searching of DNA databases for partial sequences similar to those of MMPs. An expressed sequence tag (EST) was discovered with similarity to the membrane-associated MMPs. This gene was then analysed for expression in cell lines, chromosomal location and the attempted isolation of the full length sequence by use of antibodies and PCR techniques. A polymorphism was recently discovered in the promoter region of MMP-1 and proposed to be involved in the expression levels of this enzyme. MMP-1 expression levels are directly implicated in the progression of colorectal cancer. An assay was developed to detect the polymorphism in colorectal cancer patients and identify any correlation of the polymorphism with the occurrence or progression of cancer. Comparisons showed that possession of the polymorphism correlated with an increased chance of tumour progression to Dukes grade C at the time of diagnosis. The significance of this finding appeared to be enhanced in female patients.