射频消融后HIF-1a调控小细胞肺癌移植瘤增殖的机制研究

Accelerated proliferation of small cell lung cancer metastases following radiofrequency ablation induced by HIF-1a

目的探讨射频消融形成的消融灶周边移行区域内缺氧诱导因子1a(hypoxia inducible factor-1a,HIF-1a)的表达情况,以及HIF-1a表达对移行区域内小细胞肺癌微转移瘤增殖及免疫反应的影响。方法骨髓腔注射人NCIH446小细胞肺癌细胞建立转移性人小细胞肺癌裸鼠模型,30 d后经皮穿刺行右肺上叶RFA处理,同时腹腔注射HIF-1a特异性抑制剂3-(5’-羟甲基-2’呋喃基)-1-苯甲基吲唑(YC-1)抑制其表达,7 d后观察各组指标。实验分为未处理组(对照组)、YC-1处理组,RFA处理组、RFA+YC-1组。将消融形成的中央坏死灶移行至正常肺组织2~3 mm的区域定义为移行区域,检测此区域内微转移瘤的负荷率(PRA),免疫组织化学法检测HIF-1a蛋白水平。切取坏死灶周边2~3 mm厚的组织切片,Realtime PCR检测HIF-1a和血管内皮生长因子-A(vascular endothelial growth factor A,VEGF-A)mRNA表达。结果建模成功的裸鼠可见明显的人小细胞肺癌转移瘤分布。RFA组中右肺上叶移行区域内转移瘤的PRA值及HIF-1a,表达水平均明显高于右肺上叶对照区域(P<0.05),亦高于对照组右肺上叶移植瘤组织(P<0.05),此外RFA+YC-1组移行区域内PRA值及HIF-1a明显低于RFA处理组(P<0.05)。虽然RFA+YC-1组移行区域和对照区域内的VEGF-A mRNA表达水平明显均低于RFA组(P<0.05),但是RFA组移行区域及对照区域内的VEGF-A mRNA表达无显著差异(P>0.05)。结论小细胞肺癌在接受射频消融处理后消融灶周边的肿瘤局部复发现象与移行区域内HIF-1a表达密切相关,但这一过程与HIF-1a介导的血管生成效应无明显关系,而与HIF-1a参与调控的肿瘤免疫反应可能存在相关性。

Objective To explore the expression of hypoxia inducible factor-1a (HIF-1a) in transition zone(TZ)around the ablation zone following the RFA treatment and investigate the effect and mechanism of HIF-1a on the proliferation of SCLC metastases in TZ. Methods Nude mouse model with metastatic human small cell lung cancer was established by injection of human NCI-H446 cell suspension into BALB/c-nu nude mouse. The growth of the SCLC metastases was observed. Percutaneous RFA on the right upper lung was conducted after 30 days. At the same time, YC-1, the inhibitor of hypoxia inducible factor-1, was injected intraperitoneally. Mice were randomly separated into four groups: control group, YC-1 group,RFA group and RFA+YC-1 group;7 days later, pulmonary replacement area (PRA) was measured in the area where the central necrotic lesion formed by ablation migrated to 2-3 mm of normal lung tissue, defined as the transitional area. HIF-1a protein level was measured with immunohistrochemistry assay. HIF-1a and vascular endothelial growth factor A(VEGF-A) mRNA level, in 2-3 mm thick tissue sections around the necrotic lesion, were measured with Real-time PCR. Results The growth of SCLC metastases was observed and measured after the nude mouse model was established. PRA value, HIF-1a expression level were significantly higher in TZ than reference zone(RZ) of right upper lobe in RFA group (P<0.05) and control group (P<0.01). In addition, PRA value, HIF-1a expression level were significantly lower in TZ of RFA+YC-1 group than these of RFA group (P<0.05). Although the expression levels of VEGF-A mRNA in the transitional area and control area of the RFA+ YC-1 group were significantly lower than those in the RFA group (P<0.05), there was no significant difference in the expression of VEGF-A mRNA in the transitional area and control area of the RFA group (P>0.05). Conclusion Local recurrence of SCLC around the ablation zone following RFA treatment was induced by HIF-1a expression in TZ but had no significant correlation with angiogenesis which was regulated by HIF-1a. However, tumor immune response meditated by HIF-1a perhaps involved in this process.