Pang Huan, Flinn Rory, Patsialou Antonia, Wyckoff Jeffrey, Roussos Evanthia T, Wu Haiyan, Pozzuto Maria, Goswami Sumanta, Condeelis John S, Bresnick Anne R, Segall Jeffrey E, Backer Jonathan M
Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Cancer Res. 2009 Dec 1;69(23):8868-76. doi: 10.1158/0008-5472.CAN-09-1968. Epub 2009 Nov 10.
Class IA (p85/p110) phosphoinositide 3-kinases play a major role in regulating cell growth, survival, and motility. Activating mutations in the p110alpha isoform of the class IA catalytic subunit (PIK3CA) are commonly found in human cancers. These mutations lead to increased proliferation and transformation in cultured cells, but their effects on cell motility and tumor metastasis have not been evaluated. We used lentiviral-mediated gene transfer and knockdown to produce stable MDA-MB-231 cells in which the endogenous human p110alpha is replaced with either wild-type bovine p110alpha or the two most common activating p110alpha mutants, the helical domain mutant E545K and the kinase domain mutant H1047R. The phosphoinositide 3-kinase/Akt pathway was hyperactivated in cells expressing physiologic levels of helical or kinase domain mutants. Cells expressing either mutant showed increased motility in vitro, but only cells expressing the helical domain mutant showed increased directionality in a chemotaxis assay. In severe combined immunodeficient mice, xenograft tumors expressing either mutant showed increased rates of tumor growth compared with tumors expressing wild-type p110alpha. However, tumors expressing the p110alpha helical domain mutant showed a marked increase in both tumor cell intravasation into the blood and tumor cell extravasation into the lung after tail vein injection compared with tumors expressing wild-type p110alpha or the kinase domain mutant. Our observations suggest that, when compared with kinase domain mutations in a genetically identical background, expression of helical domain mutants of p110alpha produce a more severe metastatic phenotype.
IA类（p85/p110）磷酸肌醇3激酶在调节细胞生长、存活和运动中起主要作用。IA类催化亚基（PIK3CA）的p110α异构体中的激活突变常见于人类癌症中。这些突变导致培养细胞中增殖和转化增加，但它们对细胞运动和肿瘤转移的影响尚未评估。我们使用慢病毒介导的基因转移和敲低来产生稳定的MDA-MB-231细胞，其中内源性人类p110α被野生型牛p110α或两种最常见的激活p110α突变体（螺旋结构域突变体E545K和激酶结构域突变体H1047R）所取代。在表达生理水平螺旋或激酶结构域突变体的细胞中，磷酸肌醇3激酶/Akt途径被过度激活。表达任一突变体的细胞在体外显示出运动增加，但只有表达螺旋结构域突变体的细胞在趋化性测定中显示出方向性增加。在严重联合免疫缺陷小鼠中，与表达野生型p110α的肿瘤相比，表达任一突变体的异种移植肿瘤显示出更高的肿瘤生长速率。然而，与表达野生型p110α或激酶结构域突变体的肿瘤相比，表达p110α螺旋结构域突变体的肿瘤在尾静脉注射后肿瘤细胞进入血液和肿瘤细胞进入肺的外渗均显著增加。我们的观察结果表明，与在基因相同背景下的激酶结构域突变相比，p110α螺旋结构域突变体的表达产生更严重的转移表型。
