The identification of novel genes involved in the initiation and development of thyroid neoplasia

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Thyroid cancer is the most frequently diagnosed endocrine malignancy, comprising 1% of all human malignancy. However, its actual occurrence indicated by autopsy studies may be as high as 10%. To date, a number of genes, both oncogenes (genes that are inappropriately switched on and take part in the process of tumour development) and tumour suppressor genes (genes that are switched off and lose their protective role against tumour development), have been implicated in the development of thyroid cancer. However mutations, mistakes in the genetic code, of these genes account for only a small percentage of thyroid tumours and none of these genes have been shown to be useful as clear prognostic markers for tumour progression or aggressiveness. The merging of the 2 fields of cytogenetics (the study of chromosomes) and molecular genetics (the study of genes at the DNA and RNA level) has strengthened our ability to understand the process of tumour development. We are proposing use of a technique called Comparative Genomic Hybridisation to aid in the identification of new genes associated with tumour development in both benign and malignant thyroid disease. This technique has already been used to aid in the location of genes with a role in ovarian and brain cancer and in some familial syndromes characterised by breast and gastrointestinal malignancies. This method involves the detection of regions of chromosomal amplifications or deletions in tumour DNA that is fluorescently labelled (green), mixed with normal human DNA also fluorescently labelled (red). If the tumour contains regions of amplification (likely housing an oncogene), analyses show increased green fluorescence and if deletions are present (likely housing a tumour suppressor gene), analyses show increased red fluorescence. Chromosomal regions identified by this method will be further analysed to identify the precise genes they contain and establish a role for these genes in the development of thyroid tumours.