Abstract 3544: ALK signaling activity stabilizes SLC3A2 protein levels in neuroblastoma tumorigenesis
Authors: Lai Wei-Yun , Chuang Tzu-Po , Borenäs Marcus , Palmer Ruth , Hallberg Bengt 
Published: April 2023

Abstract
Background: Neuroblastoma is the most common childhood tumor that grows in the adrenal glands or sympathetic ganglia. Approximately 10% of pediatric neuroblastoma patients harbor mutations in anaplastic lymphoma kinase (ALK). In a previous study, we identified SLC3A2 as a potential interacting partner with ALK using BioID-based in vivo proximity labeling. SLC3A2 is a multifunctional protein that mediates integrin-dependent signaling, acts as a trafficking chaperone for amino acid transporters, and regulates polyamine transport. No previous link to ALK signaling has been reported and the underlying mechanisms and functional consequences of a SLC3A2-ALK interaction in ALK-driven neuroblastoma are unclear.
Materials & Methods: The interaction of SLC3A2 and ALK initially detected with BioID-based in vivo proximity labeling was validated by immunoprecipitation. The effect of ALK signaling on SLC3A2 expression and protein stability was evaluated by quantitative PCR and immunoblotting. The functional effect of SLC3A2 on cell viability were investigated by siRNA and inhibitor treatments in both human and mouse ALK-driven neuroblastoma cells.
Results: SLC3A2 was confirmed to interact with ALK in both anti-ALK and anti-SLC3A2 antibody co-immunoprecipitations from NB1 cells (ALK-wild-type) and CLB-GE (ALK-F1174V). Moreover, this interaction was decreased by ALK inhibitor (lorlatinib) treatment. Upon ALKAL2 ligand treatment, ALK signaling increased the protein levels of SLC3A2 and this was abrogated by lorlatinib treatment in NB1 cells. Furthermore, lorlatinib treatment suppressed SLC3A2 expression and significantly affected protein stability in neuroblastoma cells with different ALK mutations including CLB-BAR (ALK exon4-11 deletion), CLB-GAR (ALK-R1275Q), and CLB-GE (ALK-F1174V) during cycloheximide chase analysis. Knockdown of SLC3A2 significantly inhibited cell growth and down-regulated the amino acid transporter SLC7A5 (LAT1) expression in CLB-GE cells (ALK-F1174V). While mono treatment of either lorlatinib (ALK TKI) or AMXT-1501 (polyamine transport inhibitor) only showed moderate effects, combinatorial treatment exhibited a synergistic effect on cell growth in ALK-driven primary-cultured mouse neuroblastoma #9883 (Th-MYCN; Alk-F1178S) and #111 (Th-MYCN; Rosa26_Alkal2) cells.
Conclusions: SLC3A2 protein stability and its interaction with ALK is dependent on ALK signaling in an ALK-driven neuroblastoma context. The synergistic effect of combined ALK and polyamine transport inhibitors suggests a potential therapeutic option for ALK-driven neuroblastoma.
Citation Format: Wei-Yun Lai, Tzu-Po Chuang, Marcus Borenäs, Ruth Palmer, Bengt Hallberg. ALK signaling activity stabilizes SLC3A2 protein levels in neuroblastoma tumorigenesis. [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 3544.