Abstract 4665: USP18 promotes anlotinib resistance in medullary thyroid carcinoma by stabilizing aurora B kinase

Abstract Targeted therapy resistance is the main cause of disease progression in advanced medullary thyroid carcinoma (MTC). However, the key molecules and mechanisms remain unclear. We previously performed a genome-wide in vitro screen of Anlotinib resistance-related genes in human MTC cell line TT using CRISPR-dCas9-SAM system and identified ubiquitin-specific protease 18 (USP18) as a key molecule mediating Anlotinib resistance in MTC. However, its downstream mechanism needs further clarification. Based on the high-throughput DNA sequencing results of the control group and the Anlotinib screening group, a group of key genes related to Anlotinib resistance in MTC was screened through the MAGeCK algorithm and the enrichment ratio of sgRNA in the Anlotinib screening group. Among them, USP18 ranked first in the enrichment results. Analysis of the correlation between the expression level of USP18 in MTC patient specimens and survival revealed that patients with high USP18 expression in tumor cells had poorer prognosis. Overexpression of USP18 in MTC tumor cells significantly promoted the growth of subcutaneous xenograft tumors in NOD/SCID mice treated with Anlotinib. In vitro cell experiments also showed that overexpression of USP18 promoted the proliferation of MTC tumor cells and significantly inhibited the proportion of cell apoptosis after Anlotinib treatment. Further research found that USP18, as a deubiquitinating enzyme that can specifically remove ISG15-like ubiquitin-like proteins from substrate proteins, can improve the kinase stability of Aurora B by removing ISG15-like ubiquitin modification and promote MTC tumor cell proliferation through the activation of PI3K-Akt signaling regulated by Aurora B kinase. Application of Aurora B kinase inhibitor in Anlotinib-resistant MTC cell lines significantly inhibited tumor cell proliferation, and Aurora B kinase inhibitor significantly increased the proportion of cell apoptosis in MTC tumor cells overexpressing USP18. In the subcutaneous xenograft tumor model of MTC in NOD/SCID mice, the growth of xenograft tumors in the Anlotinib combined with Aurora B kinase inhibitor treatment group was also significantly inhibited. In summary, overexpressed USP18 can activate PI3K-Akt signaling and promote tumor cell proliferation by increasing the stability of Aurora B kinase, ultimately leading to the formation of Anlotinib resistance in MTC patients. Combined use of Aurora B kinase inhibitor is a potentially effective combined treatment strategy for Anlotinib-resistant MTC patients. Citation Format: Xuan Qin, Xing Wan, Dapeng Li, Yimeng Liu, Xianhui Ruan, Fangkun Luan, Kejia Xu, Jia Li, Rong Xiang, Yongjun Piao, Yi Shi, Xiangqian Zheng. USP18 promotes anlotinib resistance in medullary thyroid carcinoma by stabilizing aurora B kinase [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4665.