Kawai Hideki, Minamiya Yoshihiro, Ito Manabu, Saito Hajime, Ogawa Junichi
Department of Surgery, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan.
Lung Cancer. 2008 Jan;59(1):41-7. doi: 10.1016/j.lungcan.2007.08.001. Epub 2007 Sep 14.
The sentinel lymph node (SLN) concept is that lymphatic flux from a primary tumor initially flows into a SLN. The mechanism mediating tumor metastasis within SLNs remains largely unknown; however, primary tumors overexpressing vascular endothelial growth factor (VEGF)-A appear to induce SLN lymphangiogenesis prior to metastasis in animal model. Our aim was to further investigate the capacity of VEGFs to induce lymphangiogenesis within SLNs and to assess their role in SLN metastasis in non-small cell lung carcinoma (NSCLC).
Real-time quantitative RT-PCR was used to assess expression of mRNAs encoding several VEGFs (VEGF121, VEGF165, VEGFR1, VEGFR2, VEGFR3, VEGF-C and VEGF-D) in resected lymph node specimens from 35 NSCLC patients, after which we compared their expression SLNs and non-SLNs. In addition, expression of the lymphatic endothelium-specific hyaluronan receptor (LYVE)-1 was used to assess lymphangiogenesis in SLNs and non-SLNs.
Immunohistochemical staining revealed substantial expression of LYVE-1 in SLNs. Moreover, levels LYVE-1 mRNA were significantly higher in SLNs than non-SLNs (P<0.05), as were levels of VEGF121 and VEGFR2 mRNA (P<0.01 and P=0.02, respectively). In addition metastasis-positive SLNs showed significantly higher levels of VEGF121, VEGF-C and VEGF-D mRNA than metastasis-negative SLNs (P<0.001, P=0.01 and P=0.01, respectively), and VEGF121 induced the proliferation of lymphatic endothelial cells (P<0.01).
Our findings suggest that active lymphangiogenesis is ongoing within SLNs from NSCLC patients, even before metastasis. This lymphangiogenesis may be promoted by upregulation of VEGF121, which may in turn act in part via induction of VEGF-C.
前哨淋巴结（SLN）概念是指来自原发性肿瘤的淋巴流最初流入前哨淋巴结。介导前哨淋巴结内肿瘤转移的机制在很大程度上仍然未知；然而，在动物模型中，过表达血管内皮生长因子（VEGF）-A的原发性肿瘤似乎在转移之前诱导前哨淋巴结淋巴管生成。我们的目的是进一步研究VEGF在诱导前哨淋巴结内淋巴管生成的能力，并评估它们在非小细胞肺癌（NSCLC）前哨淋巴结转移中的作用。
采用实时定量逆转录-聚合酶链反应（RT-PCR）评估35例NSCLC患者切除的淋巴结标本中编码几种VEGF（VEGF121、VEGF165、VEGFR1、VEGFR2、VEGFR3、VEGF-C和VEGF-D）的mRNA表达，之后我们比较了它们在前哨淋巴结和非前哨淋巴结中的表达。此外，使用淋巴管内皮特异性透明质酸受体（LYVE）-1的表达来评估前哨淋巴结和非前哨淋巴结中的淋巴管生成。
免疫组织化学染色显示前哨淋巴结中LYVE-1大量表达。此外，前哨淋巴结中LYVE-1 mRNA水平显著高于非前哨淋巴结（P<0.05），VEGF121和VEGFR2 mRNA水平也是如此（分别为P<0.01和P=0.02）。此外，转移阳性前哨淋巴结中VEGF121、VEGF-C和VEGF-D mRNA水平显著高于转移阴性前哨淋巴结（分别为P<0.001、P=0.01和P=0.01），且VEGF121诱导淋巴管内皮细胞增殖（P<0.01）。
我们的研究结果表明，NSCLC患者的前哨淋巴结内即使在转移之前也在进行活跃的淋巴管生成。这种淋巴管生成可能通过VEGF121上调而促进，而VEGF121反过来可能部分通过诱导VEGF-C起作用。
