It might be at least partially due to the relatively lower background expression level of PBK in H929 compared to ARP1 (Figure 6A), and that H929 cells bearing a confirmed/observed heterozygous G13D mutation in NRAS gene (https://www.keatslab.org/myeloma-cell-lines) may confine and sensitize H929 cell to interact with FHND004. Here, PBK is linked to plasma cell myeloma.