Abstract 1223: KDM6A orchestrates NK cell response via CD38/48 regulation in multiple myeloma
Authors: Liu Jiye , Xing Lijie , Li Jiang , Wen Kenneth , Liu Ning , Liu Yuntong , Gulla Annamaria , Munshi Nikhil , Hideshima Teru , Anderson Kenneth Carl 
Published: March 2024

Daratumumab (Dara), a first-in-class humanized monoclonal antibody targeting CD38, demonstrates notable efficacy in both newly diagnosed and relapsed/refractory multiple myeloma (MM) when administrated alone or in combination with other agents. However, the development of Dara resistance and subsequent relapse is common.To identify the tumor-intrinsic genes involved in resistance to NK-mediated cytotoxicity in the presence of Dara in MM cells, we conducted an in vitro genome-wide CRISPR-Cas9 knockout (KO) screen and found 433 genes exhibiting a positive correlation with MM cytotoxicity elicited by Dara and primary NK cells. Remarkably, 16 of these genes demonstrated a consistent correlation with cytolytic activity across the majority of the 36 cancer types in the TCGA database.The efficacy of Dara is closely linked to the expression of CD38, with nonresponders exhibiting low CD38 expression. Therefore, we conducted another CRISPR screen to identify the genes whose KO resulted in diminished CD38 expression. The genes that overlapped in these two screens are implicated in regulating both Dara-mediated ADCC and CD38 expression. Our focus turned to KDM6A among the overlapping genes. We validated that KDM6A KO significantly decreased CD38 expression and that reintroducing KDM6A into KDM6A KO cells restored the expression of CD38 and Dara-induced cytotoxicity.KDM6A demethylates lysine 27 of histone H3 (H3K27) to promote gene expression. Our ChIP-seq data unveiled that KDM6A-KO cells exhibited an increased H3K27me3 level at the CD38 promoter area than control cells. Remarkably, this pattern was consistent with Dara-resistant cell lines, which displayed reduced CD38 expression alongside elevated levels of H3K27me3 at the CD38 promoter. Interestingly, we found that CD38 overexpression only partially restored the sensitivity of KDM6A KO cells to Dara treatment, implying the existence of an additional mechanism. We performed RNA-seq in

KDM6A KO cells and found CD48, an NK-activating ligand, was significantly repressed. Overexpression of CD48 in KDM6A KO cells resulted in a substantial increase in the secretion of Granzyme B and Perforin by NK cells and restored the activity of NK cells and re-sensitized KDM6A KO cells to Dara treatment. These data suggest that KDM6A mediates Dara-mediated ADCC sensitivity through the dual regulation of CD38 and CD48. KDM6A acts to oppose the EZH2/PRC2 complex by demethylating H3K27me3, and we found that Tazemetostat (Taze), an FDA-approved EZH2 inhibitor, increased the expression of CD38 and CD48, especially in KDM6A-KO cells. Importantly, Taze also restored the sensitivity of KDM6A KO cells to Dara-mediated NK cell cytotoxicity. In summary, our findings illuminate the dual role of KDM6A in enhancing the efficacy of Dara in MM. Imitating KDM6A function using an FDA-approved inhibitor holds promise in overcoming Dara resistance and improving patient outcomes in MM.

Citation Format: Jiye Liu, Lijie Xing, Jiang Li, Kenneth Wen, Ning Liu, Yuntong Liu, Annamaria Gulla, Nikhil Munshi, Teru Hideshima, Kenneth Carl Anderson. KDM6A orchestrates NK cell response via CD38/48 regulation in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1223.