Citations

Abstract Background: As a key receptor tyrosine kinase (RTK) regulating tumorigenesis, AXL is overexpressed in multiple different types of cancers. AXL can be activated by homodimerization after binding with its ligand, growth arrest specific 6 protein (Gas6) or by heterodimerization with other RTKs. AXL overexpression and/or activation have been reported to promote cancer cell proliferation, migration/invasion and to induce resistance to targeted therapy. However, the AXL downstream signaling network has not yet been fully elucidated. Methods: We employed a CRISPR-CAS9-based knockout technology to create AXL inducible knockout cells in a human triple negative breast cancer (TNBC) cell line, HCC1395. In order to explore the downstream signaling events driven by AXL, we induced AXL knockout for 72 hours and used a 6-plex TMT-labeling-based quantitative proteomic approach to characterize the protein phosphorylation alterations induced by AXL knockout. IMAC and anti-phosphotyrosine antibody (pY1000)-based phosphopeptide enrichment methods were used to comprehensively quantify the phosphoproteome changes induced by AXL knockout. Results: In this study, we identified 38,525 phospho serine/threonine sites and 1,427 phosphotyrosine sites. In response to AXL knockout, 1,581 phospho serine/threonine sites and 40 phosphotyrosine sites showed significant differences between AXL-KO and AXL-WT groups with >1.5-fold change and p<0.05 as the cutoff. Among them, 982 phosphoserine/threonine sites and 30 phosphotyrosine sites were decreased, while 599 phospho serine/threonine sites and 10 phosphotyrosine sites were increased in AXL-KO cells. Signaling pathway enrichment analysis revealed that suppressing AXL expression could inhibit multiple important cancer related signaling pathways, including cell cycle, focal adhesion, MAPK signaling pathway, p53 signaling pathway and mTOR signaling pathway. Conclusion: Quantitative analysis of the phosphoproteome driven by AXL demonstrated that AXL plays a pivotal role in regulating canonical oncogenic signaling but also signaling pathways involved in RNA processing and DNA repair. Our data also suggest that targeting AXL could suppress these oncogenic signaling pathways and have therapeutic potential to improve clinical outcomes for patients with AXL overexpression. Citation Format: Li Wang, Nicole Pearson, Yuning Xiong, Santosh Renuse, Ran Cheng, Jodi M. Carter, Akhilesh Pandey, Xinyan Wu. Quantitative phosphoproteomic analysis of AXL signaling network in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3913.

Summary Background and Purpose Sprawling ( Swl ) is a radiation‐induced mutation which has been identified to have a nine base pair deletion in dynein heavy chain 1 (DYNC1H1: encoded by a single gene Dync1h1 ). This study is to investigate the phenotype and the underlying mechanism of the Dync1h1 mutant. Methods and Results To display the phenotype of Swl mutant mice, we examined the embryos of homozygous ( Swl/Swl ) and heterozygous ( Swl /+) mice and their postnatal dorsal root ganglion (DRG) of surviving Swl /+ mice. The Swl /+ mice could survive for a normal life span, while Swl/Swl could only survive till embryonic (E) 8.5 days. Excessive apoptosis of Swl/ + DRG neurons was revealed during E11.5–E15.5 days, and the peak rate was at E13.5 days. In vitro study of mutated DRG neurons showed impaired retrograde transport of dynein‐driven nerve growth factor (NGF). Mitochondria, another dynein‐driven cargo, demonstrated much slower retrograde transport velocity in Swl/+ neurons than in wild‐type (WT) neurons. Nevertheless, the Swl , Loa, and Cra mutations did not affect homodimerization of DYNC1H1. Conclusion The Swl/Swl mutation of Dync1h1 gene led to embryonic mal‐development and lethality, whereas the Swl/+ DRG neurons demonstrated deficient retrograde transport in dynein‐driven cargos and excessive apoptosis during mid‐ to late‐developmental stages. The underlying mechanism of the mutation may not be due to impaired homodimerization of DYNC1H1.