SMAD9 and neuroblastoma: We employed Tet-on shRNA methods to induce SMAD9 knockdown in BE(2)-C Tet-on-shSMAD9 STCs as a method to validate the function of SMAD9 in MYCN-amplified NB in vivo (Fig. S6A), and found that doxycycline-induced SMAD9 knockdown suppressed NB growth in vitro (Figs. S6B-S6D).