Rac1 in human breast cancer: overexpression, mutation analysis, and characterization of a new isoform, Rac1b
Rac1 in human breast cancer: overexpression, mutation analysis, and characterization of a new isoform, Rac1b
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DOI：
10.1038/sj.onc.1203621
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发表时间：
2000-06-15
期刊：
影响因子：
8
通讯作者：
Lengyel, E
中科院分区：
文献类型：
--
作者：
Schnelzer, A;Prechtel, D;Lengyel, E
Rac1是小鸟苷三磷酸酶（gtpase） Ras超家族的成员，作为分子开关控制细胞骨架重排和细胞生长。与Ras类似，Rad的组成性激活点突变引起细胞系的致瘤性转化。然而，Rad在体内是否也会发生突变尚无相关信息。在Rad的RT-PCR之后，对7个良性乳腺癌组织和10个恶性乳腺癌组织的多个克隆以及8个乳腺癌细胞系进行了测序。只有Rad的单核苷酸多态性可以被检测到，并且这些都不对应于在细胞系中用于转化的组成性激活点突变。在对乳腺组织中的Rad进行测序时，发现了一个新的Rad异构体，在Rad的阅读框中插入19个密码子，靠近开关区II，并命名为Rac1b。在GTP结合和水解实验中，Rac1b蛋白的作用类似于快速循环的GTPase，在Northern和Western blot实验中，Rad RNA和Rad蛋白在乳腺癌组织中的表达明显高于正常乳腺组织样品。免疫组化染色显示Rad在乳腺良性疾病中表达较弱，而在导管原位癌、原发性乳腺癌和淋巴结转移中表达较高。此外，来自复发性乳腺癌患者的乳腺肿瘤细胞在质膜处有Rad表达，表明在侵袭性乳腺癌患者中Rad被激活。
Rac1 is a member of the Ras superfamily of small guanosine triphosphatases (GTPases) that act as molecular switches to control cytoskeletal rearrangements and cell growth. Analogous to Ras, constitutively activating point mutations of Rad cause tumorigenic transformation of cell lines. However, there is no information about whether Rad is also mutated in vivo, After RT-PCR of Rad, several clones of seven benign and 10 malignant breast cancer tissues as well as eight breast cancer cell lines were sequenced. Only single-nucleotide polymorphisms of Rad could be detected, and none of these corresponded to constitutively activating point mutations that have been used in cell lines for transformation. While sequencing Rad in breast tissues, a new Rad isoform with an insertion of 19 codons within the reading frame of Rad close to switch region II was identified and named Rac1b, The Rac1b protein acts like a fast cycling GTPase in GTP binding and hydrolysis assays, In Northern and Western blot experiments both Rad RNA and Rad protein had a significantly higher expression in breast cancer tissues compared to normal breast tissue samples. Immunohistochemical staining of Rad showed weak Rad expression in benign breast disease but high expression level in ductal carcinoma-in-situ, primary breast cancer, and lymph node metastases. In addition, breast tumor cells from patients with recurrent disease had Rad expression at the plasma membrane, suggesting activation of Rad, in patients with aggressive breast cancer.