Identification of novel gene amplifications in breast cancer and coexistence of gene amplification with an activating mutation of PIK3CA.
Identification of novel gene amplifications in breast cancer and coexistence of gene amplification with an activating mutation of PIK3CA.
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DOI：
10.1158/0008-5472.can-09-0064
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发表时间：
2009-09-15
期刊：
影响因子：
11.2
通讯作者：
Lee MP
中科院分区：
文献类型：
--
作者：
Kadota M;Sato M;Duncan B;Ooshima A;Yang HH;Diaz-Meyer N;Gere S;Kageyama S;Fukuoka J;Nagata T;Tsukada K;Dunn BK;Wakefield LM;Lee MP
为了确定表征癌症进展的基因事件，我们对161个原发乳腺肿瘤进行了全面的基因评估。与突变的“山丘”观点类似，基因放大在乳腺癌中也显示出高频和低频的变化。常见的扩增基因包括众所周知的癌基因ERBB2、FGFR1、MYC、CCND1和PIK3CA，而其他已知的癌基因被扩增的频率较低，包括CCND2、EGFR、FGFR2和NOTCH3。更重要的是，通过对包含≤3基因的最小扩增区域的研究，我们发现了6个新的扩增基因：POLD3、IRAK4、IRX2、TBL1XR1、ASPh和BRD4。我们发现IRX2和TBL1XR1蛋白在恶性细胞系MCF10CA1h和MCF10CA1a中的表达均高于其前体细胞系MCF10A。为了研究TBL1XR1的致癌作用，我们使用shRNA方法进行了基因敲除实验，发现TBL1XR1在MCF10CA1h细胞中的缺失导致细胞迁移和侵袭减少，以及小鼠异种移植瘤的生长受到抑制。有趣的是，我们的突变分析显示，在一组肿瘤中存在PIK3CA基因的激活突变，这些肿瘤的DNA拷贝数也在PIK3CA基因座上增加，这表明共存的激活氨基酸替代和通过扩增而增加的剂量的相加效应。我们对乳腺原发肿瘤的基因扩增和体细胞突变分析提供了一幅关于基因事件的连贯图景，既有佐证的，也有新颖的，为深入了解乳腺癌进展的遗传基础提供了洞察力。
To identify genetic events that characterize cancer progression, we conducted a comprehensive genetic evaluation of 161 primary breast tumors. Similar to the “mountain-and-hill” view of mutations, gene amplification also shows high and low frequency alterations in breast cancers. The frequently amplified genes include the well-known oncogenes, ERBB2, FGFR1, MYC, CCND1, and PIK3CA, whereas other known oncogenes that are amplified, though less frequently, include CCND2, EGFR, FGFR2, and NOTCH3. More importantly, by honing in on minimally amplified regions containing ≤ 3 genes, we identified six new amplified genes: POLD3, IRAK4, IRX2, TBL1XR1, ASPH, and BRD4. We found that both the IRX2 and TBL1XR1 proteins showed higher expression in the malignant cell lines, MCF10CA1h and MCF10CA1a, than in their precursor, MCF10A, a normal immortalized mammary epithelial cell line. To study oncogenic roles of TBL1XR1, we performed knockdown experiments using a shRNA approach and found that depletion of TBL1XR1 in MCF10CA1h cells resulted in reduction of cell migration and invasion as well as suppression of tumorigenesis in mouse xenografts. Intriguingly, our mutation analysis showed the presence of activation mutations in the PIK3CA gene in a subset of tumors that also had DNA copy number increases in the PIK3CA locus, suggesting an additive effect of co-existing activating amino-acid substitution and dosage increase from amplification. Our gene amplification and somatic mutation analysis of breast primary tumors provides a coherent picture of genetic events, both corroborating and novel, offering insight into the genetic underpinnings of breast cancer progression.