Jiye Liu, PhD, on Multiple Myeloma: Genome-Wide CRISPR-Cas9 Screening Identifies KDM6A as a Modulator of Daratumumab Sensitivity

We know that daratumumab is the first in class humanize the monoclonal antibody to target CD38 on myeloma cells. So the daratumumab triggers myeloma cell toxicity through the different molecular mechanisms including ADCC, ADCP and CDC, and the direct killing. And several clinical trials recently using the daratumumab alone and in combination with other agent to treat the newly diagnosed and the relapse, and the refractory myeloma cells then show the high efficacy. However, the relapse of the disease is commonly observed due to the daratumumab resistance. So we are seeking for the molecular mechanism of the daratumumab resistance in our project. We performed the genome-scale CRISPR screening in myeloma cells and find the genes named the KDM6A is most enriched in our daratumumab, positively select the gene list. And we found that the KDM6A is a histone 3 lysine 27 demethylase which activating the gene transcription. Then we found that we knock out the KDM6A in the myeloma cells and can significantly downregulate the CD38 expression level on the myeloma cells. And associated with the increased H3K27me3 level on the CD38 promote area. We found that the KDM-60 knockout cells showed resistance to the DARAmediated ADCC in vitro and the in vivo mass model. Also by analyzing the [inaudible 00:01:55] in the KDM-60 knockout cells, we found that the KDM-60 also regulate CD48 expression, which is thought to be an NK-activating ligand in myeloma cells. So we knock out the CD48 in myeloma cells, attenuate the DARAmediated ADCC. So this data suggests that the KDM6A mediate ADCC not only by regulating CD38, but also modulate NK activity by the CD48 regulation. So how we can overcome the resistance induced by the KDM6A? We know the KDM6A and EZH2 mediate the H3K27me3 level together in the cells and balance the genes transcription in the myeloma cells. So it is challenging to elevate the KDM-60 level in the myeloma patient cells. So we hypothesize that whether we can inhibit EZH2 to restore the CD38 or the CD48 expression level in the myeloma cells. So we used the one that FDA approved, the EZH2 inhibitor, to treat the KDM-60 knockout cells and find the CD38 and the CD48 expression level for restore also enhanced DARAmediated ADCC in these KDM-60 knockout cells. Our funding here identify a novel mechanism underlying the daratumumab sensitivity. This funding provided that the EZH2 inhibitor combined with the daratumumab to overcome the daratumumab resistance and for the translation to the clinical trial and improve the myeloma patient outcome.