2022 Fiscal Year Research-status Report
Dissecting the tumor suppressive role of Utx in multiple myeloma
| Project/Area Number |
22K16318
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| Research Institution | The University of Tokyo |
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Principal Investigator |
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| Project Period (FY) |
2022-04-01 – 2024-03-31
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| Keywords | myeloma / mouse model / Epigenetics / UTX / BRAF V600E / KDM6A |
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| Outline of Annual Research Achievements |
Our study shows that the conditional deletion of Utx/Kdm6a in germinal center (GC) B cells, post-GC B cells and plasma cells collaborates with the activating BrafV600E mutation to induce GC/post-GC B cell malignancies including multiple myeloma (MM)-like disease in mice. Mice that developed MM-like neoplasms showed expansion of clonal plasma cells in the bone marrow and extramedullary organs, serum M proteins, and anemia. We developed a murine cell line from plasmacytic ascites derived from a moribund compound Utx homozygous female that developed myeloma like disease. We successfully performed serial transplantation of our new cell line into sub-lethally irradiated immunodeficient recipient mice.
Add-back of either wild-type UTX or a demethylase-inactive mutant UTX impaired the growth of UTX-null human MM cell line RPMI8226, while a mutant UTX lacking cIDR domain, that forms phase-separated liquid condensates, failed to suppress the growth. This suggests that cIDR domain is largely responsible for the catalytic activity-independent tumor suppressor function of UTX in MM.
Utx loss together with BrafV600E slightly induced MM-like profiles of transcriptome, chromatin accessibility, and H3K27 acetylation.
Our results uncover a tumor suppressor function of UTX in MM and suggest that its loss leads to transcriptional reprogramming of plasma cells towards myelomagenesis.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Transduction of UTX-null human MM cells RPMI8226 with WT or a demethylase-inactive mutant UTX impaired the growth of the cells. While a UTX mutant lacking cIDR mostly failed to suppress the growth of the cells. These results suggest that UTX acts as a tumor suppressor in a demethylase activity-independent manner and that the cIDR domain is largely responsible for the tumor suppressor function of UTX in MM.
Clustering analysis of RNA seq data from BMPCs from our mice showed that Utx loss together with BrafV600E induced moderate transcriptomic reprogramming of plasma cells towards MM-like transcriptome at the beginning, and eventually established full transformation after a long latency.
Gene set enrichment analysis revealed that genes related to multiple myeloma, Myc, cell cycle and ribosomes were positively enriched, while gene sets associated with B lymphocytes and CD40 signal were downregulated in compound mice that developed MM and to a moderate degree in compound mice before overt disease onset.
Next, we performed ATAC-seq in plasma cells from young control mice, young homozygous Utx KO mice, and our murine cell line. UMAP analysis of ATAC-seq data revealed that the murine cell line had largely different chromatin accessibility from control plasma cells, while the changes in homozygous Utx KO plasma cells were mild. These data suggest that epigenomic reprogramming gradually proceeds in the absence of UTX and/or plasma cell clones that acquire myeloma-like properties are selected over time.
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| Strategy for Future Research Activity |
We are planning to write a paper about this project and submit it for publication soon.
We will be aiming for a high impact factor hematology/oncology journal.
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