Epigenetics, chromosome 3 and early detection of metastasis

Abstract

Abstract Purpose Uveal melanoma patients that present a tumor with monosomy 3 have a high propensity to develop metastases. Based on the two‐hit hypothesis, one might expect that the remaining copy of chromosome 3 contains a genetically‐modified gene and that loss of this gene is responsible for malignant progression. Identification of the gene and the genetic or epigenetic mechanisms that influence genes on chromosome 3 will enlighten the pathway(s) that determine uveal melanoma progression. In addition, studying epigenetics may result in useful molecular markers: whereas analysis of monosomy 3 is useful in primary tumors, it is useless in the detection of spreading tumor cells in the blood. We propose that a molecular marker in the form of a (tumor specific) genetic or epigenetic modification will be more helpful in this respect. Methods We have analyzed genes on chromosome 3 for epigenetic regulation that may suffice in non‐invasive testing for spreading tumor cells. Results We have identified RASSF1a methylation as a predictor of metastasis in uveal melanoma based on analysis of uveal melanoma tissues. In order to detect disseminating tumor cells in the bloodstream of uveal melanoma patients we have developed a very sensitive assay for methylation of RASSF1a. The detection limit of RASSF1a methylation exceeds 1/10,000 and in combination with isolation cell‐free DNA we are able to detect tumor DNA in the background of a vast excess of normal blood cells. With this assay we will test patient blood and validate the prognostic and diagnostic value of this marker. Conclusion With this assay we will test patient blood and validate the prognostic and diagnostic value of this marker.