Sanada Masashi, Suzuki Takahiro, Shih Lee-Yung, Otsu Makoto, Kato Motohiro, Yamazaki Satoshi, Tamura Azusa, Honda Hiroaki, Sakata-Yanagimoto Mamiko, Kumano Keiki, Oda Hideaki, Yamagata Tetsuya, Takita Junko, Gotoh Noriko, Nakazaki Kumi, Kawamata Norihiko, Onodera Masafumi, Nobuyoshi Masaharu, Hayashi Yasuhide, Harada Hiroshi, Kurokawa Mineo, Chiba Shigeru, Mori Hiraku, Ozawa Keiya, Omine Mitsuhiro, Hirai Hisamaru, Nakauchi Hiromitsu, Koeffler H Phillip, Ogawa Seishi
Cancer Genomics Project, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
Nature. 2009 Aug 13;460(7257):904-8. doi: 10.1038/nature08240. Epub 2009 Jul 20.
Acquired uniparental disomy (aUPD) is a common feature of cancer genomes, leading to loss of heterozygosity. aUPD is associated not only with loss-of-function mutations of tumour suppressor genes, but also with gain-of-function mutations of proto-oncogenes. Here we show unique gain-of-function mutations of the C-CBL (also known as CBL) tumour suppressor that are tightly associated with aUPD of the 11q arm in myeloid neoplasms showing myeloproliferative features. The C-CBL proto-oncogene, a cellular homologue of v-Cbl, encodes an E3 ubiquitin ligase and negatively regulates signal transduction of tyrosine kinases. Homozygous C-CBL mutations were found in most 11q-aUPD-positive myeloid malignancies. Although the C-CBL mutations were oncogenic in NIH3T3 cells, c-Cbl was shown to functionally and genetically act as a tumour suppressor. C-CBL mutants did not have E3 ubiquitin ligase activity, but inhibited that of wild-type C-CBL and CBL-B (also known as CBLB), leading to prolonged activation of tyrosine kinases after cytokine stimulation. c-Cbl(-/-) haematopoietic stem/progenitor cells (HSPCs) showed enhanced sensitivity to a variety of cytokines compared to c-Cbl(+/+) HSPCs, and transduction of C-CBL mutants into c-Cbl(-/-) HSPCs further augmented their sensitivities to a broader spectrum of cytokines, including stem-cell factor (SCF, also known as KITLG), thrombopoietin (TPO, also known as THPO), IL3 and FLT3 ligand (FLT3LG), indicating the presence of a gain-of-function that could not be attributed to a simple loss-of-function. The gain-of-function effects of C-CBL mutants on cytokine sensitivity of HSPCs largely disappeared in a c-Cbl(+/+) background or by co-transduction of wild-type C-CBL, which suggests the pathogenic importance of loss of wild-type C-CBL alleles found in most cases of C-CBL-mutated myeloid neoplasms. Our findings provide a new insight into a role of gain-of-function mutations of a tumour suppressor associated with aUPD in the pathogenesis of some myeloid cancer subsets.
获得性单亲二倍体（aUPD）是癌症基因组的一个常见特征，会导致杂合性缺失。aUPD不仅与肿瘤抑制基因的功能丧失突变有关，还与原癌基因的功能获得性突变有关。在此，我们展示了C-CBL（也称为CBL）肿瘤抑制基因独特的功能获得性突变，这些突变与具有骨髓增殖特征的髓系肿瘤中11q臂的aUPD紧密相关。C-CBL原癌基因是v-Cbl的细胞同源物，编码一种E3泛素连接酶，并对酪氨酸激酶的信号转导起负调节作用。在大多数11q-aUPD阳性的髓系恶性肿瘤中发现了纯合的C-CBL突变。虽然C-CBL突变在NIH3T3细胞中具有致癌性，但c-Cbl在功能和遗传上表现为肿瘤抑制因子。C-CBL突变体没有E3泛素连接酶活性，但抑制了野生型C-CBL和CBL-B（也称为CBLB）的活性，导致细胞因子刺激后酪氨酸激酶的持续激活。与c-Cbl(+/+)造血干/祖细胞（HSPCs）相比，c-Cbl(-/-) HSPCs对多种细胞因子表现出更高的敏感性，将C-CBL突变体转导到c-Cbl(-/-) HSPCs中进一步增强了它们对更广泛细胞因子的敏感性，包括干细胞因子（SCF，也称为KITLG）、血小板生成素（TPO，也称为THPO）、IL3和FLT3配体（FLT3LG），这表明存在一种功能获得性，不能简单地归因于功能丧失。C-CBL突变体对HSPCs细胞因子敏感性的功能获得性效应在c-Cbl(+/+)背景中或通过共转导野生型C-CBL时基本消失，这表明在大多数C-CBL突变的髓系肿瘤病例中发现的野生型C-CBL等位基因缺失具有致病重要性。我们的发现为与aUPD相关的肿瘤抑制基因功能获得性突变在某些髓系癌亚群发病机制中的作用提供了新的见解。
