A MYCN-independent mechanism mediating secretome reprogramming and metastasis in MYCN -amplified neuroblastoma.

MYCN amplification ( MNA ) is a defining feature of high-risk neuroblastoma (NB) and predicts poor prognosis. However, whether genes within or in close proximity to the MYCN amplicon also contribute to MNA + NB remains poorly understood. Here, we identify that GREB1 , a transcription factor encoding gene neighboring the MYCN locus, is frequently coexpressed with MYCN and promotes cell survival in MNA + NB. GREB1 controls gene expression independently of MYCN, among which we uncover myosin 1B ( MYO1B ) as being highly expressed in MNA + NB and, using a chick chorioallantoic membrane (CAM) model, as a crucial regulator of invasion and metastasis. Global secretome and proteome profiling further delineates MYO1B in regulating secretome reprogramming in MNA + NB cells, and the cytokine MIF as an important pro-invasive and pro-metastatic mediator of MYO1B activity. Together, we have identified a putative GREB1-MYO1B-MIF axis as an unconventional mechanism promoting aggressive behavior in MNA + NB and independently of MYCN.