Abstract
In acute myeloid leukemia (AML) promoter methylation has been observed for the estrogen receptor (ESR1) as well as for a number of Tumor Suppressor Genes (TSGs). These individual aberrancies were suggested to be part of a general methylation defect in subsets of AML patients, rather than random events. The objective of this study was to assess whether aberrant promoter methylation of multiple genes, as observed in AML samples, are associated and whether such associations render impact on clinical outcome. By Methylation-Specific Multiplex Ligation Probe Amplification (MS-MLPA) the methylation status of 26 TSGs was determined in bone marrow samples of 119 primary AML patients and 5 control individuals. No promoter methylation was detected in any of the controls, while at least one TSG was methylated in 59/119 patients. Methylation was observed in 12 out of 26 assessed sites, most frequently for ER, CDKN2B/p15, and IGSF4 (28–36% of all patients). A substantial intra-class correlation of 0.38 existed between methylation of different TGSs. ESR1 methylation (34/119) strongly predicted concurrent methylation of TSGs, OR 7.33 (95%CI 4.13–12.99). A regression model that included both the ESR1 methylation status and the number of methylated TSGs (methylation index), showed both parameters to be independent oppositely directed predictors for overall survival (OS), HR 0.06 (95%CI 0.01–0.33; p=.001) and HR 1.92 (95%CI 1.19–3.10; p=.007), respectively. In line with this observation, a higher methylation index was found to yield a significant negative effect on patient OS in both the ESR1 methylated (ESR1+) and ESR1 unmethylated (ESR1−) subgroups.
Combining ESR1 methylation status with the absence or presence of promoter methylation of other TSGs (TSG+ or TSG−); yielded 4 patient subgroups with large differences in OS in univariate analysis (p=.0001, figure 1A). In multivariate analysis that included, FLT3-status, age at diagnosis, cytogenetics and achievement of CR, the predictive impact of the 4-group division on OS was maintained, HR 2.12 (95%CI 1.04–4.29; p=.037). Moreover, the combination identified a good prognostic patient subgroup (n=15, median OS 39 month) within the intermediate cytogenetic risk group (n=54, median OS 8.3 month), figure 1B. In conclusion, concurrent methylation occurs frequent in AML and is best predicted by ESR1 methylation. Methylation of ESR1 and methylation of other TSGs represent processes with independent predictivity. When combined, they constitute a unique and powerful factor for predicting overall survival, both in the total AML population as well as within the intermediate cytogenetic risk group.
Overall Survival based on the methylation status of ER (ER+/ER) combined with the absence or presence of methylation of TSGs (TSG+/TSG−) for the total population (A) and confined to the intermediate cytogenetic risk group (B)
Overall Survival based on the methylation status of ER (ER+/ER) combined with the absence or presence of methylation of TSGs (TSG+/TSG−) for the total population (A) and confined to the intermediate cytogenetic risk group (B)
Disclosure: No relevant conflicts of interest to declare.
