Lastly, unlike in neuroblastoma23, we found no difference in DLK1 expression by IHC between pre- and post-ADCT-701 treated ACC PDX tumors (Supplementary Fig. 8D) suggesting that selection and outgrowth of DLK1 negative cells does not contribute to ADCT-701 acquired resistance in ACC. Here, DLK1 is linked to adrenal cortex carcinoma.