PIK3CA Cooperates with KRAS to Promote MYC Activity and Tumorigenesis via the Bromodomain Protein BRD9
PIK3CA Cooperates with KRAS to Promote MYC Activity and Tumorigenesis via the Bromodomain Protein BRD9
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DOI：
10.3390/cancers11111634
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发表时间：
2019-11-01
期刊：
影响因子：
5.2
通讯作者：
Vogt, Peter K.
中科院分区：
文献类型：
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作者：
Bell, Catherine M.;Raffeiner, Philipp;Vogt, Peter K.
肿瘤形成通常与获得两个或更多个驱动基因有关，所述驱动基因导致正常细胞从增殖进展到异常扩增和恶性。为了了解这一过程中涉及的遗传改变，我们比较了非转化或含有PIK 3CA（H1047 R）或KRAS（G12 V）的单或双敲入（DKI）的乳腺上皮细胞系的等基因组的转录组。基因集富集分析显示，DKI细胞相对于单个突变细胞富集表征MYC靶基因特征的基因。这种基因特征部分由含溴结构域蛋白9（BRD 9）介导，该蛋白9在SWI-SNF染色质重塑复合物中发现，与MYC超级增强子位点结合。BRD 9的小分子抑制降低MYC转录物水平。关键的是，只有DKI细胞具有在半固体培养基中进行锚定非依赖性生长的能力，并且CRISPR-Cas9操作显示PIK 3CA和BRD 9表达对于该表型是必需的。相反，KRAS是DKI细胞迁移所必需的，BRD 9过表达诱导KRAS单突变细胞在半固体培养基中生长。这些结果为癌蛋白协同驱动的最早转化事件提供了新的见解，并表明BRD 9是突变型PIK 3CA/KRAS驱动的致癌转化的重要介质。
Tumor formation is generally linked to the acquisition of two or more driver genes that cause normal cells to progress from proliferation to abnormal expansion and malignancy. In order to understand genetic alterations involved in this process, we compared the transcriptomes of an isogenic set of breast epithelial cell lines that are non-transformed or contain a single or double knock-in (DKI) of PIK3CA (H1047R) or KRAS (G12V). Gene set enrichment analysis revealed that DKI cells were enriched over single mutant cells for genes that characterize a MYC target gene signature. This gene signature was mediated in part by the bromodomain-containing protein 9 (BRD9) that was found in the SWI-SNF chromatin-remodeling complex, bound to the MYC super-enhancer locus. Small molecule inhibition of BRD9 reduced MYC transcript levels. Critically, only DKI cells had the capacity for anchorage-independent growth in semi-solid medium, and CRISPR-Cas9 manipulations showed that PIK3CA and BRD9 expression were essential for this phenotype. In contrast, KRAS was necessary for DKI cell migration, and BRD9 overexpression induced the growth of KRAS single mutant cells in semi-solid medium. These results provide new insight into the earliest transforming events driven by oncoprotein cooperation and suggest BRD9 is an important mediator of mutant PIK3CA/KRAS-driven oncogenic transformation.