Epigenetic priming of AML blasts for all-trans retinoic acid-induced differentiation by the HDAC class-I selective inhibitor entinostat.

All-trans retinoic acid (ATRA) has only limited single agent activity in AML without the PML-RARα fusion (non-M3 AML). In search of a sensitizing strategy to overcome this relative ATRA resistance, we investigated the potency of the HDAC class-I selective inhibitor entinostat in AML cell lines Kasumi-1 and HL-60 and primary AML blasts. Entinostat alone induced robust differentiation of both cell lines, which was enhanced by the combination with ATRA. This "priming" effect on ATRA-induced differentiation was at least equivalent to that achieved with the DNA hypomethylating agent decitabine, and could overall be recapitulated in primary AML blasts treated ex vivo. Moreover, entinostat treatment established the activating chromatin marks acH3, acH3K9, acH4 and H3K4me3 at the promoter of the RARβ2 gene, an essential mediator of retinoic acid (RA) signaling in different solid tumor models. Similarly, RARβ2 promoter hypermethylation (which in primary blasts from 90 AML/MDS patients was surprisingly infrequent) could be partially reversed by decitabine in the two cell lines. Re-induction of the epigenetically silenced RARβ2 gene was achieved only when entinostat or decitabine were given prior to ATRA treatment. Thus in this model, reactivation of RARβ2 was not necessarily required for the differentiation effect, and pharmacological RARβ2 promoter demethylation may be a bystander phenomenon rather than an essential prerequisite for the cellular effects of decitabine when combined with ATRA. In conclusion, as a "priming" agent for non-M3 AML blasts to the differentiation-inducing effects of ATRA, entinostat is at least as active as decitabine, and both act in part independently from RARβ2. Further investigation of this treatment combination in non-M3 AML patients is therefore warranted, independently of RARβ2 gene silencing by DNA methylation

Integrative study of EZH2 mutational status, copy number, protein expression and H3K27 trimethylation in AML/MDS patients

Background!#!Mutations in the EZH2 gene are recurrently found in patients with myeloid neoplasms and are associated with a poor prognosis. We aimed to characterize genetic and epigenetic alterations of EZH2 in 58 patients (51 with acute myeloid leukemia and 7 with myelodysplastic or myeloproliferative neoplasms) by integrating data on EZH2 mutational status, co-occurring mutations, and EZH2 copy number status with EZH2 protein expression, histone H3K27 trimethylation, and EZH2 promoter methylation.!##!Results!#!EZH2 was mutated in 6/51 acute myeloid leukemia patients (12%) and 7/7 patients with other myeloid neoplasms. EZH2 mutations were not overrepresented in patients with chromosome 7q deletions or losses. In acute myeloid leukemia patients, EZH2 mutations frequently co-occurred with CEBPA (67%), ASXL1 (50%), TET2 and RAD21 mutations (33% each). In EZH2-mutated patients with myelodysplastic or myeloproliferative neoplasms, the most common co-mutations were in ASXL1 (100%), NRAS, RUNX1, and STAG2 (29% each). EZH2 mutations were associated with a significant decrease in EZH2 expression (p = 0.0002), which was similar in patients with chromosome 7 aberrations and patients with intact chromosome 7. An association between EZH2 protein expression and H3K27 trimethylation was observed in EZH2-unmutated patients (R!##!Conclusions!#!Perturbations of EZH2 activity in AML/MDS occur on different, genetic and non-genetic levels. Both low EZH2 protein expression and, by trend, EZH2 gene mutations predicted inferior overall survival of AML patients receiving standard chemotherapy

Evaluating the impact of genetic and epigenetic aberrations on survival and response in acute myeloid leukemia patients receiving epigenetic therapy

Treatment with hypomethylating agents such as decitabine, which results in overall response rates of up to 50%, has become standard of care in older patients with acute myeloid leukemia (AML) who are not candidates for intensive chemotherapy. However, there still exists a lack of prognostic and predictive molecular biomarkers that enable selection of patients who are likely to benefit from epigenetic therapy. Here, we investigated distinct genetic (FLT3-ITD, NPM1, DNMT3A) and epigenetic (estrogen receptor alpha (ERα), C/EBPα, and OLIG2) aberrations in 87 AML patients from the recently published phase II decitabine trial (AML00331) to identify potential biomarkers for patients receiving hypomethylating therapy. While FLT3-ITD and NPM1 mutational status were not associated with survival or response to therapy, patients harboring DNMT3A R882 mutations showed a non-significant association towards shorter overall survival (hazard ratio (HR) 2.15, 95% confidence interval (CI) 0.91-5.12, p = 0.08). Promoter DNA methylation analyses using pyrosequencing also revealed a non-significant association towards shorter overall survival of patients with higher levels of methylation of ERα (HR 1.50, CI 0.97-2.32, p = 0.07) and OLIG2 CpG4 (HR 1.52, CI 0.96-2.41, p = 0.08), while DNA methylation of C/EBPα showed no association with outcome. Importantly, in multivariate analyses adjusted for clinical baseline parameters, the impact of ERα and OLIG2 CpG4 methylation was conserved (HR 1.76, CI 1.01-3.06, p = 0.05 and HR 1.67, CI 0.91-3.08, p = 0.10, respectively). In contrast, none of the investigated genetic and epigenetic markers was associated with response to treatment. Additional to the previously reported adverse prognostic clinical parameters such as patients' age, reduced performance status, and elevated lactate dehydrogenase levels, DNMT3A R882 mutation status, as well as ERα and OLIG2 CpG4 DNA methylation status, may prove to be molecular markers in older AML patients prior to hypomethylating therapy