Aljohani Hashim M, Aittaleb Mohamed, Furgason John M, Amaya Peter, Deeb Ayham, Chalmers Jeffery J, Bahassi El Mustapha
Department of Internal Medicine, Division of Hematology and Oncology and UC Brain Tumor Center, Cincinnati, OH, USA.
Department of Molecular Genetics and Biochemistry, Cincinnati, OH, USA.
Mutagenesis. 2018 Apr 13;33(2):137-145. doi: 10.1093/mutage/gey003.
Approximately 90% of all cancer deaths arise from the metastatic spread of primary tumours. Of all the processes involved in carcinogenesis, local invasion and the formation of metastases are clinically the most relevant, but they are the least well understood at the molecular level. As a barrier to metastasis, cells normally undergo an apoptotic process known as 'anoikis', in circulation. The recent technological advances in the isolation and characterisation of rare circulating tumour cells (CTCs) will allow a better understanding of anoikis resistance. Detailed molecular and functional analyses of anoikis-resistant cells may provide insight into the biology of cancer metastasis and help identify novel targets for prevention of cancer dissemination. To uncover the molecular changes that govern the transition from a primary lung tumour to a secondary metastasis and specifically the mechanisms by which CTCs survive in circulation, we carried out whole genome sequencing (WGS) of normal lung, primary tumours and the corresponding brain metastases from five patients with progressive metastatic non-small-cell lung carcinoma. We also isolated CTCs from patients with metastatic cancer and subjected them to whole genome amplification and Sanger sequencing of genes of interest. While the primary tumours showed mutations in genes associated with cell adhesion and motility, brain metastases acquired mutations in adaptive, cytoprotective genes involved in response to cellular stress such as Keap-1, Nrf2 and P300, which are key players of the Keap1-Nrf2-ARE survival pathway. Nrf2 is a transcriptional factor that upon stress translocates into the nucleus, binds to the anti-oxidant response elements (ARE) and drives the expression of anti-oxidant genes. The identified mutations affect regulatory domains in all three proteins, suggesting a functional role in providing a survival advantage to CTCs in the peripheral blood allowing their dissemination to distant organs.
所有癌症死亡病例中约90%是由原发性肿瘤的转移扩散所致。在致癌过程所涉及的所有进程中，局部侵袭和转移灶的形成在临床上最为关键，但在分子水平上却了解最少。作为转移的一道屏障，细胞在循环过程中通常会经历一种名为“失巢凋亡”的凋亡过程。近期在稀有循环肿瘤细胞（CTC）的分离和特征描述方面取得的技术进展，将有助于更好地理解失巢凋亡抗性。对失巢凋亡抗性细胞进行详细的分子和功能分析，可能会为癌症转移生物学提供见解，并有助于确定预防癌症扩散的新靶点。为了揭示从原发性肺肿瘤向继发性转移转变所涉及的分子变化，特别是循环肿瘤细胞在循环中存活的机制，我们对5例进行性转移性非小细胞肺癌患者的正常肺组织、原发性肿瘤及相应脑转移瘤进行了全基因组测序（WGS）。我们还从转移性癌症患者中分离出循环肿瘤细胞，并对其进行全基因组扩增以及对感兴趣的基因进行桑格测序。原发性肿瘤显示出与细胞黏附和运动相关基因的突变，而脑转移瘤则获得了与适应性细胞保护基因相关的突变，这些基因参与对细胞应激的反应，如Keap-1、Nrf2和P300，它们是Keap1-Nrf2-ARE生存途径的关键参与者。Nrf2是一种转录因子，在应激时易位进入细胞核，与抗氧化反应元件（ARE）结合并驱动抗氧化基因的表达。所鉴定出的突变影响这三种蛋白质的调节结构域，表明它们在为外周血中的循环肿瘤细胞提供生存优势从而使其扩散至远处器官方面发挥着功能性作用。
