HOXA5 and neoplasm: For example, HOXA5 (which is considered to have a tumour-suppressor rather than pro-oncogenic role) undergoes increasing promoter methylation with age and a corresponding loss of expression at both the RNA and protein level [32], and in a study of muscle cells from young (27 ± 4.4 years) and old (83 ± 4 years) healthy volunteers, significantly increased methylation of regulatory regions was shown for multiple HOX genes [33].