Abstract 2593: A MYCN-independent mechanism mediating secretome reprogramming and metastasis in MYCN-amplified neuroblastoma

Abstract MYCN amplification (MNA) is a defining feature of high-risk neuroblastoma (NB) that predicts poor prognosis. However, whether genes within or in close proximity to the MYCN amplicon also contribute to aggressiveness in MNA+ NB remains poorly understood. Here we identify that GREB1, a transcription factor encoding gene neighboring the MYCN locus, is frequently co-expressed with MYCN, and promotes gene expression independently of MYCN in MNA+ NB. We found that GREB1, as a crucial estrogen receptor (ER) regulatory factor, is highly expressed in MNA+ NB comparable to ER+ breast cancer. Among GREB1-regulated genes altered in MNA+ NB, we uncover that Myosin 1B (MYO1B) promotes aggressive features in MNA+ NB, including invasive capacity in vitro, as well as extravasation and distant metastasis in vivo. Global secretome and proteome profiling uncover MYO1B as a major regulator of secretome reprogramming in MNA+ NB cells. Moreover, we identify 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 that promotes the aggressiveness of MNA+ NB, and independently of MYCN. Furthermore, we found that MYO1B is also upregulated in association with other oncoproteins during cellular transformation, and is dramatically increased in multiple human cancer types, suggesting a crucial role of MYO1B in cancers in addition to MNA+ NB. Citation Format: Hai-Feng Zhang, Alberto Delaidelli, Sumreen Javed, Busra Turgu, Christopher S. Hughes, Xiaqiu Yang, Michael Lizardo, Daniel Martinez, John M. Maris, Kristopher R. Bosse, Karla C. Williams, Poul H. Sorensen. A MYCN-independent mechanism mediating secretome reprogramming and metastasis in MYCN-amplified neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2593.