Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York, United States of America.
PLoS One. 2012;7(3):e33421. doi: 10.1371/journal.pone.0033421. Epub 2012 Mar 23.
Wnt/ß-catenin signaling is strongly implicated in neoplasia, but the role of this pathway in human breast cancer has been controversial. Here, we examined Wnt/ß-catenin pathway activation as a function of breast cancer progression, and tested for a relationship with HER2/neu expression, using a human tissue microarray comprising benign breast tissues, ductal carcinoma in situ (DCIS), and invasive carcinomas. Cores were scored for membranous ß-catenin, a key functional component of adherens junctions, and for nucleocytoplasmic ß-catenin, a hallmark of Wnt/ß-catenin pathway activation. Only 82% of benign samples exhibited membrane-associated ß-catenin, indicating a finite frequency of false-negative staining. The frequency of membrane positivity was similar in DCIS samples, but was significantly reduced in carcinomas (45%, P<0.001), consistent with loss of adherens junctions during acquisition of invasiveness. Negative membrane status in cancers correlated with higher grade (P = 0.04) and estrogen receptor-negative status (P = 0.03), both indices of poor prognosis. Unexpectedly, a substantial frequency of nucleocytoplasmic ß-catenin was observed in benign breast tissues (36%), similar to that in carcinomas (35%). Positive-staining basal nuclei observed in benign breast may identify putative stem cells. An increased frequency of nucleocytoplasmic ß-catenin was observed in DCIS tumors (56%), suggesting that pathway activation may be an early event in human breast neoplasia. A correlation was observed between HER2/neu expression and nucleocytoplasmic ß-catenin in node-positive carcinomas (P = 0.02). Furthermore, cytoplasmic ß-catenin was detected in HER2/neu-induced mouse mammary tumors. The Axin2(NLSlacZ) mouse strain, a previously validated reporter of mammary Wnt/ß-catenin signaling, was utilized to define in vivo transcriptional consequences of HER2/neu-induced ß-catenin accumulation. Discrete hyperplastic foci observed in mammary glands from bigenic MMTV/neu, Axin2(NLSlacZ) mice, highlighted by robust ß-catenin/TCF signaling, likely represent the earliest stage of mammary intraepithelial neoplasia in MMTV/neu mice. Our study thus provides provocative evidence for Wnt/ß-catenin signaling as an early, HER2/neu-inducible event in breast neoplasia.
Wnt/β-catenin 信号通路在肿瘤发生中起着重要作用，但该通路在人类乳腺癌中的作用一直存在争议。在这里，我们研究了 Wnt/β-catenin 通路的激活作为乳腺癌进展的一个功能，并通过包含良性乳腺组织、导管原位癌（DCIS）和浸润性癌的人类组织微阵列检测了与 HER2/neu 表达的关系。核心被膜 β-catenin评分，黏附连接的关键功能成分，核质 β-catenin评分，Wnt/β-catenin 通路激活的标志。只有 82%的良性样本显示膜相关β-catenin，表明假阴性染色的频率有限。DCIS 样本中的膜阳性率相似，但在癌组织中显著降低（45%，P<0.001），与侵袭性获得过程中黏附连接的丧失一致。癌症中的阴性膜状态与较高的分级（P=0.04）和雌激素受体阴性状态（P=0.03）相关，这两个都是预后不良的指标。出乎意料的是，在良性乳腺组织中观察到相当大比例的核质 β-catenin（36%），与癌组织相似（35%）。良性乳腺中观察到的阳性核基底可能是潜在的干细胞。在 DCIS 肿瘤中观察到核质 β-catenin 的频率增加（56%），表明通路激活可能是人类乳腺癌发生的早期事件。在淋巴结阳性癌中观察到 HER2/neu 表达与核质 β-catenin 之间存在相关性（P=0.02）。此外，在 HER2/neu 诱导的小鼠乳腺肿瘤中检测到细胞质 β-catenin。利用 Axin2（NLSlacZ）小鼠品系，一种以前验证的乳腺 Wnt/β-catenin 信号的报告基因，来定义 HER2/neu 诱导的 β-catenin 积累的体内转录后果。从双基因 MMTV/neu，Axin2（NLSlacZ）小鼠的乳腺中观察到离散的增生焦点，由强烈的β-catenin/TCF 信号标记，可能代表 MMTV/neu 小鼠乳腺上皮内瘤变的最早阶段。因此，我们的研究为 Wnt/β-catenin 信号作为乳腺癌发生中的早期、HER2/neu 诱导事件提供了有启发性的证据。
