Search

By assessment of the methylation status of 25 candidate tumor suppressor genes (TSGs) in 119 acute myeloid leukemia (AML) patients and 5 controls, we aimed to determine whether simultaneous methylation of multiple TSGs exerts prognostic impact. Methylation-specific multiplex ligation probe amplification (MS-MLPA) revealed methylation of at least one TSG in 59/119 patients, while no methylation was found in controls. Methylation of different TSGs within patients was substantially correlated (intra-class correlation; 0.38). ESR1 methylation (34/119) strongly predicted concurrent methylation of other genes, OR 7.33 (95%CI 4.13-12.99). A Cox regression model that included the three most frequently methylated TSGs ESR1, CDKN2B/p15 and IGSF4, showed ESR1 to have opposite effects on overall survival (OS) compared with the other two, HR 0.22 (95% CI 0.09-0.53) and HR 1.66 (95% CI 0.73-3.79), HR 1.61 (95%CI 0.66-3.93). By assessment of CDKN2B/p15 and IGSF4 methylation, patients with methylation at multiple loci can be identified. Accumulation of methylation aberrancies is much more pronounced in ESR1 methylated patients. When combined, the methylation status of ESR1, CDKN2B/p15 and IGSF4 enable identification of patient subgroups with large differences in OS (p <0.0001). This study shows that methylation profiling allows risk stratification in AML. In addition, ESR1 methylation may reflect a biological pathway that leads to hypermethylation of multiple genes, which is reflected by methylation of IGSF4 and/or CDKN2B/p15.

Copy number changes and CpG methylation of various genes are hallmarks of tumor development but are not yet widely used in diagnostic settings. The recently developed multiplex ligation-dependent probe amplification (MLPA) method has increased the possibilities for multiplex detection of gene copy number aberrations in a routine laboratory. Here we describe a novel robust method: the methylation-specific MLPA (MS-MLPA) that can detect changes in both CpG methylation as well as copy number of up to 40 chromosomal sequences in a simple reaction. In MS-MLPA, the ligation of MLPA probe oligonucleotides is combined with digestion of the genomic DNA-probe hybrid complexes with methylation-sensitive endonucleases. Digestion of the genomic DNA-probe complex, rather than double-stranded genomic DNA, allowed the use of DNA derived from the formalin treated paraffin-embedded tissue samples, enabling retrospective studies. To validate this novel method, we used MS-MLPA to detect aberrant methylation in DNA samples of patients with Prader-Willy syndrome, Angelman syndrome or acute myeloid leukemia.