Immunohistochemical and genomic profiles of diffuse large B-cell lymphomas: Implications for targeted EZH2 inhibitor therapy?

Abstract

Enhancer of Zeste Homolog 2 (EZH2) plays an essential epigenetic role in Diffuse Large B Cell Lymphoma (DLBCL) development. Recurrent somatic heterozygous gain-of-function mutations of EZH2 have been identified in DLBCL, most notably affecting tyrosine 641 (Y641), inducing hyper-trimethylation of H3K27 (H3K27me3). Novel EZH2 inhibitors are being tested in phase 1 and 2 clinical trials but no study has examined which patients would most benefit from this treatment. We evaluated the immunohistochemical (IHC) methylation profiles of 82 patients with DLBCL, as well as the mutational profiles of 32 patients with DLBCL using NGS analysis of a panel of 34 genes involved in lymphomagenesis. A novel IHC score based on H3K27me2 and H3K27me3 expression was developed, capable of distinguishing patients with wild-type (WT) EZH2 and patients with EZH2 Y641 mutations (p = 10−5). NGS analysis revealed a subclonal EZH2 mutation pattern in EZH2 mutant patients with WT-like IHC methylation profiles, while associated mutations capable of upregulating EZH2 were detected in WT EZH2 patients with mutant-like IHC methylation profiles. IHC and mutational profiles highlight in vivo hyper-H3K27me3 and hypo-H3K27me2 status, pinpoint associated activating mutations and determine EZH2 mutation clonality, maximizing EZH2 inhibitor potential by identifying patients most likely to benefit from treatment.

Next-Generation Sequencing in Diffuse Large B-Cell Lymphoma Highlights Molecular Divergence and Therapeutic Opportunities: a LYSA Study

“…S5B). Interestingly, one PMBL patient presented an EZH2 Y641 mutation, adding to the debate of which DLBCL subtypes might benefit from EZH2 inhibitor treatment (26). CREBBP mutations were identified in 31.3% of GCB patients and 6.2% of ABC patients, corroborating previous studies (17), but were also found in 24.2% of "other" and 11.1% of PMBL ( Fig.…”

“…Ion Torrent Personal Genome Machine (PGM) Sequencing and PGM data analysis was performed as described previously (26) and detailed in Supplementary Methods. Variant analysis was performed using an in-house generated bioinformatics pipeline, detailed in Supplementary Methods and Supplementary Fig.…”

Oncogenic events rather than antigen selection pressure may be the main driving forces for relapse in diffuse large B‐cell lymphomas

“…Thirty four genes relevant to lymphomagenesis (listed in Supporting Information Table V) were analyzed using the multiplexed PCR‐based targeted library Ion AmpliSeq™ technology, as previously described . Sequencing performances and whole nucleotide variations are respectively given in Supporting Information Table VI and Supporting Information Data as a combined .vcf file.…”

Detection and prognostic value of recurrent exportin 1 mutations in tumor and cell-free circulating DNA of patients with classical Hodgkin lymphoma

“…Libraries were prepared from 10 ng of genomic DNA with primers from our previously reported Lymphopanel 21,26 targeting the XPO1 E571K nucleotide variant (Online Supplementary Methods).…”