Andarawewa Kumari L, Erickson Anna C, Chou William S, Costes Sylvain V, Gascard Philippe, Mott Joni D, Bissell Mina J, Barcellos-Hoff Mary Helen
Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Cancer Res. 2007 Sep 15;67(18):8662-70. doi: 10.1158/0008-5472.CAN-07-1294.
Transforming growth factor beta1 (TGFbeta) is a tumor suppressor during the initial stage of tumorigenesis, but it can switch to a tumor promoter during neoplastic progression. Ionizing radiation (IR), both a carcinogen and a therapeutic agent, induces TGFbeta activation in vivo. We now show that IR sensitizes human mammary epithelial cells (HMEC) to undergo TGFbeta-mediated epithelial to mesenchymal transition (EMT). Nonmalignant HMEC (MCF10A, HMT3522 S1, and 184v) were irradiated with 2 Gy shortly after attachment in monolayer culture or treated with a low concentration of TGFbeta (0.4 ng/mL) or double treated. All double-treated (IR + TGFbeta) HMEC underwent a morphologic shift from cuboidal to spindle shaped. This phenotype was accompanied by a decreased expression of epithelial markers E-cadherin, beta-catenin, and ZO-1, remodeling of the actin cytoskeleton, and increased expression of mesenchymal markers N-cadherin, fibronectin, and vimentin. Furthermore, double treatment increased cell motility, promoted invasion, and disrupted acinar morphogenesis of cells subsequently plated in Matrigel. Neither radiation nor TGFbeta alone elicited EMT, although IR increased chronic TGFbeta signaling and activity. Gene expression profiling revealed that double-treated cells exhibit a specific 10-gene signature associated with Erk/mitogen-activated protein kinase (MAPK) signaling. We hypothesized that IR-induced MAPK activation primes nonmalignant HMEC to undergo TGFbeta-mediated EMT. Consistent with this, Erk phosphorylation was transiently induced by irradiation and persisted in irradiated cells treated with TGFbeta, and treatment with U0126, a MAP/Erk kinase (MEK) inhibitor, blocked the EMT phenotype. Together, these data show that the interactions between radiation-induced signaling pathways elicit heritable phenotypes that could contribute to neoplastic progression.
转化生长因子β1（TGFβ）在肿瘤发生的初始阶段是一种肿瘤抑制因子，但在肿瘤进展过程中可转变为肿瘤促进因子。电离辐射（IR）既是一种致癌物也是一种治疗剂，可在体内诱导TGFβ激活。我们现在表明，IR使人类乳腺上皮细胞（HMEC）对TGFβ介导的上皮-间质转化（EMT）敏感。非恶性HMEC（MCF10A、HMT3522 S1和184v）在单层培养贴壁后不久接受2 Gy照射，或用低浓度TGFβ（0.4 ng/mL）处理或双重处理。所有双重处理（IR + TGFβ）的HMEC都经历了从立方形到纺锤形的形态转变。这种表型伴随着上皮标志物E-钙黏蛋白、β-连环蛋白和ZO-1表达的降低、肌动蛋白细胞骨架的重塑以及间质标志物N-钙黏蛋白、纤连蛋白和波形蛋白表达的增加。此外，双重处理增加了细胞运动性，促进了侵袭，并破坏了随后接种在基质胶中的细胞的腺泡形态发生。单独的辐射或TGFβ都不会引发EMT，尽管IR增加了慢性TGFβ信号传导和活性。基因表达谱分析显示，双重处理的细胞表现出与Erk/丝裂原活化蛋白激酶（MAPK）信号传导相关的特定10基因特征。我们假设IR诱导的MAPK激活使非恶性HMEC易于发生TGFβ介导的EMT。与此一致的是，照射可短暂诱导Erk磷酸化，并在用TGFβ处理的照射细胞中持续存在，而用MAP/Erk激酶（MEK）抑制剂U0126处理可阻断EMT表型。总之，这些数据表明，辐射诱导的信号通路之间的相互作用引发了可导致肿瘤进展的可遗传表型。
