Type: Oral
Session: 651. Multiple Myeloma and Plasma Cell Dyscrasias: Basic and Translational: Genomics
Hematology Disease Topics & Pathways:
Translational Research, Plasma Cell Disorders, Clinically Relevant, Diseases, Therapies, Lymphoid Malignancies
Serial BM aspirates (n=24) were collected from 15 relapsed or refractory myeloma patients (RRMM); harboring t(11;14) (n=6 pairs) and 9 without this translocation prior to initiation of salvage therapy and at time of relapse. All t(11;14) MM patients were treated with venetoclax. Unbiased chromatin accessibility and mRNA profiling of CD138pos cells were performed using the chromium single cell ATAC and RNA-Seq 3’ solution (10x Genomics), respectively. Cell Ranger, Seurat and ArchR were used for sample de-multiplexing, barcode processing, single-cell 3’ gene, peaks counting, and data analysis.
We first compared the scATAC-seq and scRNA-seq profiles found in CD138pos MM cell isolated from patients harboring t(11;14) with the one obtained in patients without this translocation. As expected, t(11:14) patients had high chromatin accessibility at the CCND1 locus and high mRNA expression. Differentially accessible chromatin analysis identified 147518 peaks that were specific to t(11;14) patients. Of interest, motifs enrichment analysis of accessible peaks identified a “B cell-like” motifs signature with enriched TFs motifs such as TCF4 and PAX5 in t(11;14) patients compared to non t(11:14) enriched for IRF and STAT family of motifs. The integration of the scATAC-seq and scRNA-seq data confirmed the B cell signature of t(11;14) patients with upregulation of B cell markers such as MS4A1, VPREB3, CD79A, CD19, and down-regulation of plasma cell markers such as TDO2, EFEMP1, CD28, SLAMF7, and IL6R. Additionally, we found PAX1, PAX5, TCF3, TCF5, and SPI1 transcription factors to be highly expressed in t(11;14) while the non t(11:14) were enriched for IRF1-9 transcription factors. Of interest, the clustering analysis performed on scATAC-seq data identified 3 non t(11;14) patients with a chromatin accessibility profile similar to that of t(11;14) patients. They expressed B cell markers (PAX5, VPREB3 or FCRLA), overexpressed BCL2 and we are currently examining whether this B cell-like epigenetic signature determines sensitivity to venetoclax.
In order to define the epigenetic contribution to the acquired resistance to venetoclax in t(11;14) myeloma, we compared the chromatin accessibility profiles of t(11;14) patients pre- vs. post-venetoclax treatment. Enriched motifs within accessible peaks differed significantly between pre- and post-venetoclax with RELA, REL, RELB and EGR1 motifs predominantly enrichmed in the pre-samples in contrast to JUN, JUNB, JUND and FOSL1/L2 motifs enrichment in the post-samples. Of note, integration analysis of scRNAseq (differentially expressed genes) and ATACseq data (differentially accessible peaks) identified MCL1 and ENSA (a gene 60 Kb centromeric to MCL1 on chr1q) as the top enriched genes and peaks in resistant samples suggesting that copy number gain at the MCL1 locus (which we confirmed by single cell CNV analysis) rather than epigenetic modifications is likely the main determinant of acquired resistant to venetoclax in t(11;14) MM.
In the current study we have defined the epigenetic regulome and transcriptome associated with t(11;14) myeloma and its relatedness to B cell rather than plasma cell biology. Our studies also suggest that acquired resistance to venetoclax is largely driven by copy number gain at the MCL1 locus.
Disclosures: Bahlis: Pfizer: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Genentech: Consultancy; Takeda: Consultancy, Honoraria; BMS/Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Janssen: Consultancy, Honoraria. Neri: BMS: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Amgen: Consultancy, Honoraria.
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