To test whether the antitumor activity of indisulam in neuroblastoma is an RBM39-dependent effect rather than due to off-target activity, we engineered each of three neuroblastoma cell lines (SIMA, BE2C, and SK-N-AS), using CRISPR-Cas9 knock-in, to create indisulam-resistant RBM39 variants (RBM39 G268V) (Fig. 3A). Here, RBM39 is linked to neuroblastoma.