Nasu Masaki, Emi Mitsuru, Pastorino Sandra, Tanji Mika, Powers Amy, Luk Hugh, Baumann Francine, Zhang Yu-An, Gazdar Adi, Kanodia Shreya, Tiirikainen Maarit, Flores Erin, Gaudino Giovanni, Becich Michael J, Pass Harvey I, Yang Haining, Carbone Michele
*University of Hawai'i Cancer Center, University of Hawai'i, Honolulu, Hawaii; †Hamon Center for Therapeutic Oncology Research and Department of Pathology, UT Southwestern Medical Center, Dallas, Texas; ‡Department of Biomedical Sciences and Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California; §Department of Biomedical Informatics, University of Pittsburgh, Pittsburgh, Pennsylvania; and ‖Department of Cardiothoracic Surgery, New York University Langone Medical Center, New York, New York.
J Thorac Oncol. 2015 Apr;10(4):565-76. doi: 10.1097/JTO.0000000000000471.
Breast cancer 1-associated protein 1 (BAP1) is a nuclear deubiquitinase that regulates gene expression, transcription, DNA repair, and more. Several findings underscore the apparent driver role of BAP1 in malignant mesothelioma (MM). However, the reported frequency of somatic BAP1 mutations in MM varies considerably, a discrepancy that appeared related to either methodological or ethnical differences across various studies.
To address this discrepancy, we carried out comprehensive genomic and immunohistochemical (IHC) analyses to detect somatic BAP1 gene alterations in 22 frozen MM biopsies from U.S. MM patients.
By combining Sanger sequencing, multiplex ligation-dependent probe amplification, copy number analysis, and cDNA sequencing, we found alteration of BAP1 in 14 of 22 biopsies (63.6%). No changes in methylation were observed. IHC revealed normal nuclear BAP1 staining in the eight MM containing wild-type BAP1, whereas no nuclear staining was detected in the 14 MM biopsies containing tumor cells with mutated BAP1. Thus, IHC results were in agreement with those obtained by genomic analyses. We then extended IHC analysis to an independent cohort of 70 MM biopsies, of which there was insufficient material to perform molecular studies. IHC revealed loss of BAP1 nuclear staining in 47 of these 70 MM biopsies (67.1%).
Our findings conclusively establish BAP1 as the most commonly mutated gene in MM, regardless of ethnic background or other clinical characteristics. Our data point to IHC as the most accessible and reliable technique to detect BAP1 status in MM biopsies.
乳腺癌1相关蛋白1（BAP1）是一种核去泛素化酶，可调节基因表达、转录、DNA修复等。多项研究结果强调了BAP1在恶性间皮瘤（MM）中明显的驱动作用。然而，报道的MM中BAP1体细胞突变频率差异很大，这种差异似乎与不同研究中的方法学或种族差异有关。
为了解决这一差异，我们对来自美国MM患者的22份冷冻MM活检样本进行了全面的基因组和免疫组织化学（IHC）分析，以检测BAP1基因的体细胞改变。
通过结合桑格测序、多重连接依赖探针扩增、拷贝数分析和cDNA测序，我们在22份活检样本中的14份（63.6%）中发现了BAP1改变。未观察到甲基化变化。免疫组化显示，在8例含有野生型BAP1的MM中，核BAP1染色正常，而在14例含有BAP1突变肿瘤细胞的MM活检样本中未检测到核染色。因此，免疫组化结果与基因组分析结果一致。然后，我们将免疫组化分析扩展到一个由70份MM活检样本组成的独立队列，其中没有足够的材料进行分子研究。免疫组化显示，在这70份MM活检样本中的47份（67.1%）中BAP1核染色缺失。
我们的研究结果最终确定BAP1是MM中最常发生突变的基因，无论种族背景或其他临床特征如何。我们的数据表明，免疫组化是检测MM活检样本中BAP1状态最便捷、最可靠的技术。
