Department of Burns and Plastic Surgery, Children's Hospital of Soochow University, Suzhou 215025, PR China; Suzhou Key Laboratory of Congenital Structural Deformities, Suzhou 215025, Jiangsu, PR China.
Suzhou Key Laboratory of Congenital Structural Deformities, Suzhou 215025, Jiangsu, PR China; Department of Urology, Children's Hospital of Soochow University, Suzhou 215025, PR China.
Int Immunopharmacol. 2023 Sep;122:110617. doi: 10.1016/j.intimp.2023.110617. Epub 2023 Jul 19.
This study aims to discern the possible molecular mechanism of the effect of ubiquitin-specific peptidase 18 (USP18) on the resistance to BRAF inhibitor vemurafenib in BRAF V600E mutant melanoma by regulating cyclic GMP-AMP synthase (cGAS). The cancer tissues of BRAF V600E mutant melanoma patients before and after vemurafenib treatment were collected, in which the protein expression of USP18 and cGAS was determined. A BRAF V600E mutant human melanoma cell line (A2058R) resistant to vemurafenib was constructed with its viability, apoptosis, and autophagy detected following overexpression and depletion assays of USP18 and cGAS. Xenografted tumors were transplanted into nude mice for in vivo validation. Bioinformatics analysis showed that the expression of cGAS was positively correlated with USP18 in melanoma, and USP18 was highly expressed in melanoma. The expression of cGAS and USP18 was up-regulated in cancer tissues of vemurafenib-resistant patients with BRAF V600E mutant melanoma. Knockdown of cGAS inhibited the resistance to vemurafenib in A2058R cells and the protective autophagy induced by vemurafenib in vitro. USP18 could deubiquitinate cGAS to promote its protein stability. In vivo experimentations confirmed that USP18 promoted vemurafenib-induced protective autophagy by stabilizing cGAS protein, which promoted resistance to vemurafenib in BRAF V600E mutant melanoma cells. Collectively, USP18 stabilizes cGAS protein expression through deubiquitination and induces autophagy of melanoma cells, thereby promoting the resistance to vemurafenib in BRAF V600E mutant melanoma.
本研究旨在通过调节环鸟苷酸-腺苷酸合酶（cGAS）来探究泛素特异性肽酶 18（USP18）对 BRAF V600E 突变型黑色素瘤对 BRAF 抑制剂vemurafenib 耐药的影响的可能分子机制。收集 BRAF V600E 突变型黑色素瘤患者在 vemurafenib 治疗前后的癌组织，检测 USP18 和 cGAS 的蛋白表达。通过过表达和敲低 USP18 和 cGAS 检测 BRAF V600E 突变型人黑色素瘤细胞系（A2058R）对 vemurafenib 的耐药性，检测细胞活力、凋亡和自噬。将异种移植瘤移植到裸鼠体内进行体内验证。生物信息学分析显示，cGAS 的表达与黑色素瘤中的 USP18 呈正相关，USP18 在黑色素瘤中高表达。BRAF V600E 突变型黑色素瘤耐药患者的癌组织中 cGAS 和 USP18 的表达上调。体外敲低 cGAS 抑制了 A2058R 细胞对 vemurafenib 的耐药性和 vemurafenib 诱导的保护性自噬。USP18 可以通过去泛素化作用稳定 cGAS 蛋白，促进其蛋白稳定性。体内实验证实，USP18 通过稳定 cGAS 蛋白促进 vemurafenib 诱导的保护性自噬，从而促进 BRAF V600E 突变型黑色素瘤细胞对 vemurafenib 的耐药性。总之，USP18 通过去泛素化稳定 cGAS 蛋白表达，并诱导黑色素瘤细胞自噬，从而促进 BRAF V600E 突变型黑色素瘤对 vemurafenib 的耐药性。
