Loss of Imprinting as an Epigenetic Marker in Bladder Cancer

摘要: Currently, it is well recognized that epigenetic changes and genetic alterations are involved in the initiation and progression of human cancer. Epigenetics refers to the study of changes in gene expression caused by mechanisms other than classical mutations in the DNA sequence; these changes are potentially reversible but are generally stably maintained during cell division. The most common biological processes resulting from epigenetic mechanisms include X-chromosome inactivation, cellular differentiation, maintenance of cell identity and genomic imprinting.Genomic imprinting is an epigenetic process of gene regulation in which the parental origin of an allele determines whether the allele will be expressed or repressed [1]. The imprinting is maintained by epigenetic modifications such as DNA methylation and repressive histone marks that are transmitted to the gametes from the parental germ lines to ensure the expression of a gene in a parent-specific manner. In somatic cells, the imprinted patternisinherited during mitotic division leading to the specific-monoallelic expression of the opposite allele on the homologous chromosome [2]. However, in adult tissues, the patterns of imprinting of a gene may be complex, in which the specific-monoallelic expression is restricted to a limited number of cell types while biallelic transcripts produced from different promoters can be observed in other cells or tissues [3]. Furthermore, the majority of the genes regulated by imprinting are clustered with a long non-coding RNA; the expression of the genes in these clusters is controlled in cis by an imprinting control region (ICR) containing a differentially …