Humtsoe Joseph O, Kim Hyun-Su, Jones Leilani, Cevallos James, Boileau Philippe, Kuo Fengshen, Morris Luc G T, Ha Patrick
Department of Otolaryngology, Head and Neck Surgery, University of California-San Francisco, Helen Diller Family Comprehensive Cancer Center, San Francisco, CA 94080, USA.
School of Medicine, University of California-San Francisco, San Francisco, CA 94080, USA.
Cancers (Basel). 2022 Apr 30;14(9):2263. doi: 10.3390/cancers14092263.
Adenoid cystic carcinoma (ACC) is the second most common cancer type arising from the salivary gland. The frequent occurrence of chromosome t(6;9) translocation leading to the fusion of MYB and NFIB transcription factor genes is considered a genetic hallmark of ACC. This inter-chromosomal rearrangement may encode multiple variants of functional MYB-NFIB fusion in ACC. However, the lack of an ACC model that harbors the t(6;9) translocation has limited studies on defining the potential function and implication of chimeric MYB-NFIB protein in ACC. This report aims to establish a MYB-NFIB fusion protein expressing system in ACC cells for in vitro and in vivo studies. RNA-seq data from MYB-NFIB translocation positive ACC patients' tumors and MYB-NFIB fusion transcript in ACC patient-derived xenografts (ACCX) was analyzed to identify MYB breakpoints and their frequency of occurrence. Based on the MYB breakpoint identified, variants of MYB-NFIB fusion expression system were developed in a MYB-NFIB deficient ACC cell lines. Analysis confirmed MYB-NFIB fusion protein expression in ACC cells and ACCXs. Furthermore, recombinant MYB-NFIB fusion displayed sustained protein stability and impacted transcriptional activities of interferon-associated genes set as compared to a wild type MYB. In vivo tumor formation analysis indicated the capacity of MYB-NFIB fusion cells to grow as implanted tumors, although there were no fusion-mediated growth advantages. This expression system may be useful not only in studies to determine the functional aspects of MYB-NFIB fusion but also in evaluating effective drug response in vitro and in vivo settings.
腺样囊性癌（ACC）是唾液腺来源的第二大常见癌症类型。导致MYB和NFIB转录因子基因融合的染色体t(6;9)易位频繁发生，被认为是ACC的遗传标志。这种染色体间重排可能在ACC中编码多种功能性MYB-NFIB融合变体。然而，缺乏携带t(6;9)易位的ACC模型限制了对嵌合MYB-NFIB蛋白在ACC中的潜在功能和意义的研究。本报告旨在建立ACC细胞中的MYB-NFIB融合蛋白表达系统，用于体外和体内研究。分析了MYB-NFIB易位阳性ACC患者肿瘤的RNA测序数据以及ACC患者来源异种移植瘤（ACCX）中的MYB-NFIB融合转录本，以确定MYB断点及其发生频率。基于鉴定出的MYB断点，在MYB-NFIB缺陷的ACC细胞系中开发了MYB-NFIB融合表达系统的变体。分析证实了ACC细胞和ACCX中MYB-NFIB融合蛋白的表达。此外，与野生型MYB相比，重组MYB-NFIB融合蛋白表现出持续的蛋白质稳定性，并影响了干扰素相关基因集的转录活性。体内肿瘤形成分析表明，MYB-NFIB融合细胞具有作为植入肿瘤生长的能力，尽管没有融合介导的生长优势。该表达系统不仅可能有助于确定MYB-NFIB融合功能方面的研究，还可用于评估体外和体内环境中的有效药物反应。
