Evolution of AML genome and epigenome with IDH inhibitors and their association with clinical response and resistance [RNA-seq]
Allosteric inhibitors of mutant IDH1 or IDH2 induce terminal differentiation in mutant leukemic blasts and may provide durable clinical responses in approximately 40% of acute myeloid leukemia (AML) patients with the mutations. However, most responders eventually relapse. To understand the molecular underpinnings of clinical resistance, we performed multipronged genomic analyses (DNA sequencing, RNA sequencing and cytosine methylation profiling) in longitudinally collected specimens from 68 IDH1/IDH2-mutant AML patients treated with IDH inhibitors (IDHi), and described the evolution of AML genome and epigenome during the therapy and its association with clinical response and relapse. Co-occurrence of mutations in RUNX1/CEBPA or RAS-RTK pathway genes were associated with poor response to IDHi. The same group of mutations were also frequently selected or acquired at relapse. In addition, acquired mutations in BCOR, reciprocal IDH gene, and TET2 were also implicated at relapse. DNA methylation changes largely mirrored plasma 2HG dynamics and had little association with clinical response to IDHi. The mapping of mutation dynamics and methylation changes in longitudinal samples revealed the interplay between AML genome and epigenome with IDHi therapy. While the alteration in RAS-RTK signaling genes and RUNX1/CEBPA were the key molecular pathways involved in clinical resistance to IDHi, diverse molecular pathways were involved in IDHi resistance. The data highlights the role of clonal heterogeneity in therapeutic resistance in AML and implicates opportunities for novel combination strategies. Overall design: RNA expression profiles were generated by RNA-Seq using HiSeq 2000 platform on longitudinal samples during the IDH inhibitor therapy. BL = baseline REL = relapse