Abstract 3467: Growth factor receptor trafficking in neuroblastoma differentiation

Abstract

Abstract Background/Objectives: UBE4B is an E3/E4 ubiquitin ligase involved in growth factor receptor (GFR) trafficking. The UBE4B gene is located in the chromosome 1p36 region commonly deleted in high-risk neuroblastoma tumors. We have previously identified associations of UBE4B expression with neuroblastoma patient outcomes. However, the functional roles of UBE4B in neuroblastoma tumor differentiation are not known. Design/Methods: We analyzed the association of UBE4B gene expression with expression of known markers of neuroblastoma tumor differentiation using publicly available databases and screened cell lines and neuroblastoma tumor samples for UBE4B protein expression using Western blot and quantitative immunohistochemistry. We measured UBE4B expression by Western blot in cell lines before and after induction of differentiation with 13-cis-retinoic acid treatment and determined the effects of UBE4B overexpression and depletion on retinoic acid-induced differentiation using continuous live-cell imaging of neurite morphology, immunohistochemistry, and Western blot for markers of differentiation. Effects on signaling through the Ras/MAPK pathway were measured using Western blots. Results: UBE4B expression was associated with neuroblastoma differentiation in patient tumors, and UBE4B gene and protein expression were associated with expression levels of known markers of neuroblastoma differentiation. Retinoic acid treatment resulted in increased UBE4B expression in retinoic acid-sensitive, but not -resistant, neuroblastoma cells, and UBE4B depletion was associated with increased ERK phosphorylation, increased proliferation, and inhibition of retinoic acid-induced neuroblastoma differentiation. Conclusion: We have demonstrated associations between UBE4B expression and tumor differentiation in gene expression databases and in neuroblastoma tumor samples, and our data suggests that UBE4B expression is required for retinoic acid-induced differentiation, potentially through effects on activation of the Ras/MAPK pathway. These associations between UBE4B and neuroblastoma differentiation combined with the established role of UBE4B in GFR trafficking suggest that UBE4B-mediated receptor trafficking may contribute to the responses of neuroblastoma tumors to therapy and to the outcomes of patients with neuroblastoma. Citation Format: Jacqueline Lesperance, Divya Subramonian, Sarah Woodfield, Rongjun Guo, Andrew Bean, Dolores Lopez-Terrada, Michael Ittmann, Sara Hakim, Peter E. Zage. Growth factor receptor trafficking in neuroblastoma differentiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3467.