Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, Mizuho-cho, Mizuho-ku, Japan.
BMC Cancer. 2012 May 30;12:205. doi: 10.1186/1471-2407-12-205.
Membrane-anchored heparin-binding epidermal growth factor-like growth factor (proHB-EGF) yields soluble HB-EGF, which is an epidermal growth factor receptor (EGFR) ligand, and a carboxy-terminal fragment of HB-EGF (HB-EGF-CTF) after ectodomain shedding. We previously reported that HB-EGF-CTF and unshed proHB-EGF which has the cytoplasmic domain of proHB-EGF (HB-EGF-C), translocate from the plasma membrane to the nucleus and regulate cell cycle after shedding stimuli. However, the significance of nuclear exported HB-EGF-C in human gastric cancer is unclear.
We investigated the relationship between intracellular localization of HB-EGF-C and clinical outcome in 96 gastric cancer patients treated with gastrectomy. Moreover, we established stable gastric cancer cell lines overexpressing wild-type HB-EGF (wt-HB-EGF) and mutated HB-EGF (HB-EGF-mC), which prevented HB-EGF-C nuclear translocation after shedding. Cell motility between these 2 gastric cancer cell lines was investigated using a transwell invasion assay and a wound healing assay.
Of the 96 gastric cancer cases, HB-EGF-C immunoreactivity was detected in both the nucleus and cytoplasm in 19 cases (19.8 %) and in the cytoplasm only in 25 cases (26.0 %). The nuclear immunoreactivity of HB-EGF-C was significantly increased in stage pT3/4 tumors compared with pT1/2 tumors (T1/2 vs. T3/4: 11.1 % vs. 36.4 %, P < 0.01). The growth of wt-HB-EGF- and HB-EGF-mC-expressing cells significantly increased compared with control cells, but the growth of HB-EGF-mC-expressing cells was significantly decreased compared with wt-HB-EGF-expressing cells. Gastric cancer cell invasion obviously increased in wt-HB-EGF-expressing cells, but invasion in HB-EGF-mC-expressing cells showed a slight increase compared with control cells. Moreover, wt-HB-EGF overexpression increased the effectiveness of wound healing, but had no significant effect in HB-EGF-mC-expressing cells.
Both the function of HB-EGF as an EGFR ligand and a novel signal for HB-EGF-C nuclear translocation induce gastric cancer growth, whereas HB-EGF-C nuclear translocation independently plays a critical role in gastric cancer invasion. The present study demonstrated that HB-EGF-C nuclear translocation might be crucial in gastric cancer invasion. HB-EGF-C nuclear translocation may offer a prognostic marker and a new molecular target for gastric cancer therapy.
膜锚定的肝素结合表皮生长因子样生长因子（proHB-EGF）产生可溶性 HB-EGF，后者是表皮生长因子受体（EGFR）的配体，在细胞外结构域脱落之后成为 HB-EGF 的羧基末端片段（HB-EGF-CTF）。我们之前曾报道，HB-EGF-CTF 和未脱落的 proHB-EGF（具有 proHB-EGF 的细胞质结构域的 HB-EGF-C）在脱落刺激后从质膜转位到核内并调节细胞周期。然而，在人类胃癌中核输出的 HB-EGF-C 的意义尚不清楚。
我们在 96 例接受胃切除术治疗的胃癌患者中研究了 HB-EGF-C 细胞内定位与临床结局之间的关系。此外，我们建立了稳定过表达野生型 HB-EGF（wt-HB-EGF）和突变型 HB-EGF（HB-EGF-mC）的胃癌细胞系，后者可防止 HB-EGF-C 在脱落后向核内转位。使用 Transwell 侵袭测定法和划痕愈合测定法研究了这两种胃癌细胞系之间的细胞迁移。
在 96 例胃癌病例中，19 例（19.8%）的细胞核和细胞质中均检测到 HB-EGF-C 免疫反应性，25 例（26.0%）仅在细胞质中检测到 HB-EGF-C 免疫反应性。与 pT1/2 肿瘤相比，pT3/4 肿瘤中 HB-EGF-C 的核免疫反应性显著增加（T1/2 与 T3/4：11.1%与 36.4%，P < 0.01）。与对照组相比，wt-HB-EGF 和 HB-EGF-mC 表达细胞的生长明显增加，但 HB-EGF-mC 表达细胞的生长明显低于 wt-HB-EGF 表达细胞。wt-HB-EGF 表达细胞的胃癌细胞侵袭明显增加，但 HB-EGF-mC 表达细胞的侵袭与对照组相比略有增加。此外，wt-HB-EGF 过表达增加了伤口愈合的效果，但在 HB-EGF-mC 表达细胞中没有显著影响。
HB-EGF 作为 EGFR 配体的功能和 HB-EGF-C 核转位的新信号均诱导胃癌生长，而 HB-EGF-C 核转位独立在胃癌侵袭中发挥关键作用。本研究表明 HB-EGF-C 核转位可能在胃癌侵袭中至关重要。HB-EGF-C 核转位可能是胃癌侵袭的一个预后标志物和新的分子靶点。
