Pathology Project for Molecular Targets, The Cancer Institute, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto, Tokyo, 135-8550, Japan.
Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto, Tokyo, 135-8550, Japan.
Mod Pathol. 2018 Jun;31(6):934-946. doi: 10.1038/s41379-018-0008-8. Epub 2018 Feb 6.
MYB-NFIB and MYBL1-NFIB have been reported in ~60% of adenoid cystic carcinoma cases, but driver alterations in the remaining ~40% of adenoid cystic carcinoma remain unclear. We examined 100 adenoid cystic carcinoma cases for MYB and MYBL1 locus rearrangements by fluorescence in situ hybridization (FISH) with originally designed probe sets using formalin-fixed paraffin-embedded materials. Approximately one-third of samples were also analyzed by fusion transcript-specific RT-PCR and capture RNA sequencing. In the 27 cases with frozen materials, MYB-NFIB and MYBL1-NFIB fusion transcripts were detected in 9 (33%) and 6 cases (22%) by RT-PCR, respectively. Meanwhile, high expression of MYB (18 cases, 67%) or MYBL1 (9 cases, 33%) was detected in all 27 cases in a mutually exclusive manner, regardless of its form (full-length, truncation, or fusion transcript). Interestingly, genomic rearrangements around the corresponding highly-expressed gene were observed in all 27 cases by FISH, suggesting a causative relationship between genomic rearrangements and gene expression. Among the 100 cases, including additional 73 cases, 97 harbored genomic rearrangements in the MYB (73 cases) or MYBL1 locus (24 cases) including 10 cases with atypical FISH patterns undetectable through ordinary split FISH approaches: breakpoints far distant from MYB (5 cases) and a small NFIB locus insertion into the MYB (3 cases) or MYBL1 locus (2 cases). In clinicopathological analyses, histological grade, primary tumor size, and lymph node metastasis were identified as prognostic factors, whereas MYB/MYBL1 rearrangements were not, but were associated with histological grade. In the present study, MYB or MYBL1 locus rearrangement was detected in nearly all adenoid cystic carcinoma cases, and therefore it would be a good diagnostic marker for adenoid cystic carcinoma. However, fusion transcript-specific RT-PCR for MYB-NFIB and MYBL1-NFIB and ordinary split FISH assays for MYB and MYBL1 were less sensitive, and thus detection methods should be judiciously designed because of the diversity of rearrangement modes in adenoid cystic carcinoma.
MYB-NFIB 和 MYBL1-NFIB 已在60%的腺样囊性癌病例中报道，但在剩余40%的腺样囊性癌中，驱动突变仍不清楚。我们使用最初设计的探针组通过荧光原位杂交（FISH）检查了 100 例福尔马林固定石蜡包埋材料的腺样囊性癌病例，以检测 MYB 和 MYBL1 基因座重排。大约三分之一的样本还通过融合转录特异性 RT-PCR 和捕获 RNA 测序进行了分析。在 27 例有冷冻材料的病例中，通过 RT-PCR 分别在 9 例（33%）和 6 例（22%）中检测到 MYB-NFIB 和 MYBL1-NFIB 融合转录本。同时，在所有 27 例病例中，无论其形式（全长、截断或融合转录本）如何，均以高表达的 MYB（18 例，67%）或 MYBL1（9 例，33%）的方式检测到高表达。有趣的是，通过 FISH 在所有 27 例病例中均观察到相应高表达基因周围的基因组重排，表明基因组重排与基因表达之间存在因果关系。在包括另外 73 例病例的 100 例病例中，97 例 MYB（73 例）或 MYBL1 基因座（24 例）存在基因组重排，包括 10 例通过普通分裂 FISH 方法无法检测到的非典型 FISH 模式：断点远离 MYB（5 例）和 NFIB 基因座小片段插入 MYB（3 例）或 MYBL1 基因座（2 例）。在临床病理分析中，组织学分级、原发肿瘤大小和淋巴结转移被确定为预后因素，而 MYB/MYBL1 重排则不是，但与组织学分级相关。在本研究中，几乎所有的腺样囊性癌病例都检测到 MYB 或 MYBL1 基因座重排，因此它将成为腺样囊性癌的一个很好的诊断标志物。然而，针对 MYB-NFIB 和 MYBL1-NFIB 的融合转录特异性 RT-PCR 和针对 MYB 和 MYBL1 的普通分裂 FISH 检测的敏感性较低，因此由于腺样囊性癌中重排模式的多样性，应谨慎设计检测方法。
