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轩辕之客金虫 (小有名气)
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Nature：肿瘤抑制因子的功能获得性突变
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正常人类细胞含有来自双亲中每一方的全套染色体，但在某些癌症中，部分特定染色体的两个版本都来自同一亲代——该现象被称为“获得性单亲二体”。对来自从患有髓样肿瘤的患者取来的超过200份骨髓样本的基因组DNA所做研究，发现11号染色体的一部分的两个版本都遗传自单亲的发生率较高，该部分含有肿瘤抑制因子C-CBL的一个功能获得性突变，它使成纤维细胞发生癌变，使造血干细胞对细胞因子刺激更敏感。这些数据支持这样一个观点：c-Cbl是一个肿瘤抑制基因，癌症中所发生的突变能够以功能获得性方式发挥作用，正如以前对肿瘤抑制基因p53所发现的那样。（生物谷Bioon.com） 生物谷推荐原始出处： Nature 460, 904-908 (13 August 2009) | doi:10.1038/nature08240 Gain-of-function of mutated C-CBL tumour suppressor in myeloid neoplasms Masashi Sanada1,5,19, Takahiro Suzuki7,19, Lee-Yung Shih8,19, Makoto Otsu9, Motohiro Kato1,2, Satoshi Yamazaki6, Azusa Tamura1, Hiroaki Honda11, Mamiko Sakata-Yanagimoto12, Keiki Kumano3, Hideaki Oda13, Tetsuya Yamagata14, Junko Takita1,2,3, Noriko Gotoh10, Kumi Nakazaki1,4, Norihiko Kawamata15, Masafumi Onodera16, Masaharu Nobuyoshi7, Yasuhide Hayashi17, Hiroshi Harada18, Mineo Kurokawa3,4, Shigeru Chiba12, Hiraku Mori18, Keiya Ozawa7, Mitsuhiro Omine18, Hisamaru Hirai3,4, Hiromitsu Nakauchi6,9, H. Phillip Koeffler15 & Seishi Ogawa1,5 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 genes1, but also with gain-of-function mutations of proto-oncogenes2. 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 kinases3, 4, 5, 6. 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. [ Last edited by 轩辕之客 on 2009-8-16 at 14:01 ] |
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