Wang Fang, Sloss Callum, Zhang Xiaobo, Lee Sam W, Cusack James C
Division of Surgical Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Cancer Res. 2007 Sep 15;67(18):8486-93. doi: 10.1158/0008-5472.CAN-07-0498.
Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a member of the EGF growth factor family. Initially synthesized as a membrane-bound precursor (pro-HB-EGF), it is cleaved at the juxtamembrane domain to release the soluble form of HB-EGF (s-HB-EGF) by sheddases, including matrix metalloproteinases (MMP) and a disintegrin and metalloproteinases. This is a process referred to as ectodomain shedding and is implicated in the process of all ligands of the EGF receptor (EGFR) family. The tumorigenic potential of s-HB-EGF has been studied extensively; however, the role of pro-HB-EGF in tumor progression is unknown, despite the fact that a considerable amount of pro-HB-EGF remains on the cell membrane. Our data here clearly indicated the distinct role of pro-HB-EGF in the regulation of E-cadherin expression and the epithelial-mesenchymal transition. We showed here that the expression of pro-HB-EGF was associated with the differentiation status in pancreatic tumors and cell lines. Expression of noncleaved pro-HB-EGF in pancreatic cells resulted in the up-regulation of E-cadherin through suppression of ZEB1, which is a transcriptional repressor of E-cadherin. Inhibition of HB-EGF shedding using a MMP inhibitor, GM6001, also dramatically augmented the E-cadherin expression while suppressing the EGFR activation. Moreover, up-regulation of E-cadherin by pro-HB-EGF not only resulted in cellular morphologic change but also decreased cell motility and enhanced apoptotic sensitivity in response to gemcitabine-erlotinib treatment. Collectively, our data defined a distinct role of pro-HB-EGF in the regulation of E-cadherin, suggesting that inhibition of shedding may be a novel approach to suppress pancreatic metastasis and sensitize cells to cancer therapy.
肝素结合表皮生长因子样生长因子(HB-EGF)是表皮生长因子(EGF)家族的成员。最初它作为膜结合前体(pro-HB-EGF)合成,通过包括基质金属蛋白酶(MMP)、解整合素和金属蛋白酶在内的蛋白酶在近膜结构域处切割,释放出可溶性形式的HB-EGF(s-HB-EGF)。这一过程被称为胞外域脱落,与表皮生长因子受体(EGFR)家族的所有配体的过程有关。s-HB-EGF的致瘤潜力已得到广泛研究;然而,尽管大量的pro-HB-EGF保留在细胞膜上,但pro-HB-EGF在肿瘤进展中的作用尚不清楚。我们这里的数据清楚地表明了pro-HB-EGF在调节E-钙黏蛋白表达和上皮-间质转化中的独特作用。我们在此表明,pro-HB-EGF的表达与胰腺肿瘤和细胞系的分化状态相关。胰腺细胞中未切割的pro-HB-EGF的表达通过抑制E-钙黏蛋白的转录抑制因子ZEB1导致E-钙黏蛋白上调。使用MMP抑制剂GM6001抑制HB-EGF的脱落,也显著增强了E-钙黏蛋白的表达,同时抑制了EGFR的激活。此外,pro-HB-EGF引起的E-钙黏蛋白上调不仅导致细胞形态改变,还降低了细胞运动性,并增强了对吉西他滨-厄洛替尼治疗的凋亡敏感性。总体而言,我们的数据确定了pro-HB-EGF在调节E-钙黏蛋白中的独特作用,表明抑制脱落可能是一种抑制胰腺转移和使细胞对癌症治疗敏感的新方法。