Center of Laboratory Technology and Experimental Medicine, China Medical University, Shenyang, China.
BMC Cancer. 2010 Feb 16;10:43. doi: 10.1186/1471-2407-10-43.
Aberrant regulation in the invasion of cancer cells is closely associated with their metastatic potentials. TrkB functions as a receptor tyrosine kinase and is considered to facilitate tumor metastasis. Pyk2 is a non-receptor tyrosine kinase and integrates signals in cell invasion. However, little is known about the expression of TrkB in NSCLC and whether Pyk2 is involved in TrkB-mediated invasion of A549 cells.
The expression of TrkB was investigated in NSCLC by immunohistochemical staining. Both HBE and A549 cells were treated with BDNF. The expression of TrkB, Pyk2 and ERK phosphorylations were assessed by western blot. Besides, A549 cells were transfected with TrkB-siRNA or Pyk2-siRNA, or treated with ERK inhibitor where indicated. Transwell assay was performed to evaluate cell invasion.
40 cases (66.7%) of NSCLC were found higher expression of TrkB and patients with more TrkB expression had significant metastatic lymph nodes (p = 0.028). BDNF facilitated the invasion of A549 cells and the activations of Pyk2 in Tyr402 and ERK. However, the effects of BDNF were not observed in HBE cells with lower expression of TrkB. In addition, the increased Pyk2 and ERK activities induced by BDNF were significantly inhibited by blocking TrkB expression, so was the invasion of A549 cells. Knockdown studies revealed the essential role of Pyk2 for BDNF-induced cell invasion, since the invasion of A549 cells was abolished by Pyk2-siRNA. The application of ERK inhibitor also showed the suppressed ERK phosphorylation and cell invasion.
These data indicated that higher expression of TrkB in NSCLC was closely correlated with lymph node metastasis, and BDNF probably via TrkB/Pyk2/ERK promoted the invasion of A549 cells.
癌细胞侵袭的异常调节与转移潜能密切相关。TrkB 作为受体酪氨酸激酶，被认为有助于肿瘤转移。Pyk2 是一种非受体酪氨酸激酶，整合细胞侵袭中的信号。然而，关于非小细胞肺癌（NSCLC）中 TrkB 的表达情况以及 Pyk2 是否参与 TrkB 介导的 A549 细胞侵袭知之甚少。
通过免疫组织化学染色研究 NSCLC 中 TrkB 的表达。用 BDNF 处理 HBE 和 A549 细胞。通过 Western blot 评估 TrkB、Pyk2 和 ERK 磷酸化的表达。此外，用 TrkB-siRNA 或 Pyk2-siRNA 转染 A549 细胞，或在有需要时用 ERK 抑制剂处理。用 Transwell 测定法评估细胞侵袭。
40 例（66.7%）NSCLC 中发现 TrkB 表达较高，TrkB 表达较高的患者有明显的转移性淋巴结（p=0.028）。BDNF 促进了 A549 细胞的侵袭以及 Pyk2 在 Tyr402 和 ERK 的激活。然而，在 TrkB 表达较低的 HBE 细胞中，BDNF 没有观察到这些作用。此外，BDNF 诱导的 Pyk2 和 ERK 活性增加被阻断 TrkB 表达显著抑制，A549 细胞的侵袭也是如此。敲低研究表明 Pyk2 在 BDNF 诱导的细胞侵袭中起关键作用，因为 Pyk2-siRNA 消除了 A549 细胞的侵袭。应用 ERK 抑制剂也显示出抑制的 ERK 磷酸化和细胞侵袭。
这些数据表明 NSCLC 中较高的 TrkB 表达与淋巴结转移密切相关，BDNF 可能通过 TrkB/Pyk2/ERK 促进 A549 细胞的侵袭。
