Department of Pathology, School of Medicine, Keio University, Tokyo, Japan.
Pathology Division, National Cancer Center Research Institute, Tokyo, Japan.
Lab Invest. 2014 Jun;94(6):683-91. doi: 10.1038/labinvest.2014.53. Epub 2014 Apr 7.
In pancreatic ductal adenocarcinoma (PDAC), features of epithelial-mesenchymal transition (EMT) are often seen in tumor tissue, and such features correlate with poor prognosis. Solitary infiltration of tumor cells represents a morphological phenotype of EMT, and we previously reported that a high degree of solitary cell infiltration correlates with EMT-like features, including reduced E-cadherin and elevated vimentin levels. Using solitary cell infiltration to evaluate the degree of EMT, gene-expression profiling of 12 PDAC xenografts was performed, and SMAD3 was identified as an EMT-related gene. Immunohistochemistry using clinical specimens (n=113) showed that SMAD3 accumulated in the nuclei of tumor cells, but was not detected in most epithelial cells in the pancreatic duct. Moreover, SMAD3 upregulation correlated with malignant characteristics, such as higher tumor grade and lymph node metastasis, as well as with EMT-like features. SMAD4, which plays a key role in transforming growth factor-β (TGF-β) signaling, is inactivated in approximately half of PDAC cases. In this study, the nuclear accumulation of SMAD3 was immunohistochemically detected even in SMAD4-negative cases. SMAD3 knockdown resulted in upregulated E-cadherin, downregulated vimentin, and reduced cell motility in pancreatic cancer cells regardless of SMAD4 status. In addition, TGF-β-treatment resulted in EMT induction in cells carrying wild-type SMAD4, and EMT was suppressed by SMAD3 knockdown. Patients with upregulated SMAD3 and a high degree of solitary cell infiltration had shorter times to recurrence and shorter survival times after surgery, and multivariate analysis showed that both factors were independent prognostic factors linked to unfavorable outcomes. These findings suggest that SMAD3 in PDAC is involved in the promotion of malignant potential through EMT induction in tumor cells regardless of SMAD4 status and serves as a potential biomarker of poor prognosis.
在胰腺导管腺癌（PDAC）中，肿瘤组织中常可见到上皮-间质转化（EMT）的特征，且这些特征与预后不良相关。肿瘤细胞的单一浸润代表 EMT 的一种形态表型，我们之前曾报道过，高度的单一细胞浸润与 EMT 样特征相关，包括 E-钙黏蛋白水平降低和波形蛋白水平升高。我们使用单一细胞浸润来评估 EMT 的程度，对 12 个 PDAC 异种移植物进行了基因表达谱分析，结果鉴定出 SMAD3 是一个与 EMT 相关的基因。使用临床标本（n=113）进行免疫组织化学检测显示，SMAD3 积聚在肿瘤细胞的核内，但在胰腺导管中的大多数上皮细胞中未检测到。此外，SMAD3 的上调与恶性特征相关，如更高的肿瘤分级和淋巴结转移，以及 EMT 样特征。SMAD4 在转化生长因子-β（TGF-β）信号通路中发挥关键作用，大约有一半的 PDAC 病例中 SMAD4 失活。在这项研究中，即使在 SMAD4 阴性的病例中，也通过免疫组织化学检测到 SMAD3 的核内积聚。SMAD3 敲低导致胰腺癌细胞中 E-钙黏蛋白上调、波形蛋白下调和细胞迁移能力降低，无论 SMAD4 状态如何。此外，TGF-β 处理导致携带野生型 SMAD4 的细胞发生 EMT 诱导，而 SMAD3 敲低抑制 EMT。SMAD3 上调和高度单一细胞浸润的患者在手术后复发时间更短、生存时间更短，多变量分析显示，这两个因素都是与不良预后相关的独立预后因素。这些发现表明，SMAD3 在 PDAC 中无论 SMAD4 状态如何，都通过诱导肿瘤细胞发生 EMT 而参与促进恶性潜能，并可作为预后不良的潜在生物标志物。
