Fransson Susanne, Hansson Magnus, Ruuth Kristina, Djos Anna, Berbegall Ana, Javanmardi Niloufar, Abrahamsson Jonas, Palmer Ruth H, Noguera Rosa, Hallberg Bengt, Kogner Per, Martinsson Tommy
Department of Medical and Clinical Genetics, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden.
Genes Chromosomes Cancer. 2015 Feb;54(2):99-109. doi: 10.1002/gcc.22223. Epub 2014 Sep 23.
Anaplastic lymphoma kinase (ALK) has been demonstrated to be deregulated in sporadic as well as in familiar cases of neuroblastoma (NB). Whereas ALK-fusion proteins are common in lymphoma and lung cancer, there are few reports of ALK rearrangements in NB indicating that ALK mainly exerts its oncogenic capacity via activating mutations and/or overexpression in this tumor type. In this study, 332 NB tumors and 13 cell lines were screened by high resolution single nucleotide polymorphism microarray. Gain of 2p was detected in 23% (60/332) of primary tumors and 46% (6/13) of cell lines, while breakpoints at the ALK locus were detected in four primary tumors and two cell lines. These were further analyzed by next generation sequencing and a targeted enrichment approach. Samples with both ALK and MYCN amplification displayed complex genomic rearrangements with multiple breakpoints within the amplicon. None of the translocations characterized in primary NB tumors are likely to result in a chimeric protein. However, immunohistochemical analysis reveals high levels of phosphorylated ALK in these samples despite lack of initial exons, possibly due to alternative transcription initiation sites. Both ALK proteins predicted to arise from such alterations and from the abnormal ALK exon 4-11 deletion observed in the CLB-BAR cell line show strong activation of downstream targets STAT3 and extracellular signal-regulated kinase (ERK) when expressed in PC12 cells. Taken together, our data indicate a novel, although rare, mechanism of ALK activation with implications for NB tumorigenesis.
间变性淋巴瘤激酶（ALK）已被证明在散发性以及家族性神经母细胞瘤（NB）病例中存在失调。虽然ALK融合蛋白在淋巴瘤和肺癌中很常见，但关于NB中ALK重排的报道很少，这表明ALK在这种肿瘤类型中主要通过激活突变和/或过表达发挥其致癌能力。在本研究中，通过高分辨率单核苷酸多态性微阵列对332个NB肿瘤和13个细胞系进行了筛查。在23%（60/332）的原发性肿瘤和46%（6/13）的细胞系中检测到2号染色体短臂增益，而在4个原发性肿瘤和2个细胞系中检测到ALK基因座的断点。通过下一代测序和靶向富集方法对这些样本进行了进一步分析。同时具有ALK和MYCN扩增的样本显示出复杂的基因组重排，扩增子内有多个断点。在原发性NB肿瘤中鉴定的易位均不太可能产生嵌合蛋白。然而，免疫组织化学分析显示，尽管缺乏起始外显子，但这些样本中磷酸化ALK水平较高，这可能是由于替代转录起始位点所致。在PC12细胞中表达时，预计由这些改变产生的ALK蛋白以及在CLB - BAR细胞系中观察到的异常ALK外显子4 - 11缺失产生的ALK蛋白均显示下游靶点信号转导和转录激活因子3（STAT3）和细胞外信号调节激酶（ERK）的强烈激活。综上所述，我们的数据表明ALK激活存在一种新的、尽管罕见的机制，这对NB肿瘤发生具有重要意义。
