IKZF1 and plasma cell myeloma: Thus, to test the hypothesis that IKZF1 regulates IgL we performed IKZF1 ChIP-seq in three myeloma cell lines including ARP-1 (IgK-expressing), MM.1S (IgL-expressing), and RPMI-8226 (IgL-expressing and translocated) (Supplementary Fig. 8a).