Site Editors
Shaji K. Kumar, MD
Prashant Kapoor, MD, FACP
Shaji K. Kumar, MD
Prashant Kapoor, MD, FACP
Posted: Friday, December 23, 2022
Patients with multiple myeloma and lower expression levels of CD38 frequently develop resistance to the anti-CD38 monoclonal antibody daratumumab. Jiye Liu, PhD, of Harvard Medical School, Boston, and colleagues found that KDM6A regulates CD38 and CD48 expression, and they suggested combination treatment with an EZH2 inhibitor may overcome daratumumab resistance. These data, which were presented during the 2022 American Society of Hematology (ASH) Annual Meeting and Exposition (Abstract 148), provide the rationale for combination clinical trials.
An in vitro genome-wide CRISPR-Cas9 knockout screen identified 46 single-guide RNAs that seemed to be positively correlated with daratumumab and primary natural killer (NK) cell–triggered multiple myeloma cytotoxicity. A second screening, which was performed using the cells with the lowest expression of CD38, found KDM6A to be the top-ranked gene of those overlapping from the two screenings. Knockout of KDM6A appeared to significantly decrease CD38 expression, and its reintroduction restored the expression level of CD38 and daratumumab-induced cytotoxicity.
KDM6A demethylates lysine 27 on histone 3 (H3K27) to promote gene expression, according to the investigators. To confirm whether CD38 expression is altered by the methylation status of H3K27, the researchers compared the CD38 promoter area between KDM6A knockout and control cells; the level of trimethylated H3K27 was found to be higher in knockout cells. H3K27 is methylated by EZH2; EZH2 inhibition seemed to significantly decrease the level of trimethylated H3K27 in the CD38 promoter area, upregulate both CD38 mRNA and protein expression in knockout cells, and restore the sensitivity of knockout cells to daratumumab-mediated NK cell cytotoxicity in vitro and in vivo.
Reintroduction of CD38 into KDM6A knockout cells was found to partially restore daratumumab sensitivity, suggesting there may be other mechanisms underlying knockout-induced resistance. RNA sequencing in knockout cells revealed downregulation of the NK cell–activating ligand CD48. Overexpression of CD48 in knockout cells appeared to significantly increase granzyme B and perforin secretion, restoring the activity of NK cells and resensitizing knockout cells to daratumumab.
Disclosure: For full disclosures of the study authors, visit ash.confex.com.
2022 ASH Annual Meeting and Exposition
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