靶向超声造影评估血小板衍生生长因子在甲状腺乳头状癌血管生成中作用的初步研究

Evaluation of the role of platelet derived growth factor in papillary thyroid carcinoma by targeted ultrasound contrast agent

目的评估靶向血小板衍生生长因子受体α（PDGFRα）超声造影剂对裸鼠甲状腺乳头状癌（PTC）血管生成的超声分子成像效果，并探讨血小板衍生生长因子（PDGF）在肿瘤血管生成中的作用。方法通过生物素一亲和素桥接法构建靶向PDGFRα的超声造影剂，空白微泡作为对照组。分别将正常PTC细胞株（BCPAP）（正常组）及构建成功的siRNA—PDGF—BCPAP细胞株（下调组）注射至裸鼠背部，密切观察瘤体的生长情况。分别对正常组及下调组裸鼠PTC进行超声造影检查和时间一强度曲线分析。检查完毕处死裸鼠后，利用CD31染色观察肿瘤中的微血管数，利用WesternBlot检测血管内皮生长因子（VEGF）和PDGF的蛋白表达量。结果PDGFRα靶向超声造影剂可以在裸鼠PTC体内显影，下调组超声造影峰值强度明显低于正常组[（43．085±13．244）％对（57．428±10．952）％，P=0．004]，下调组瘤体微血管数明显小于正常组[（23．200±6．017）个／视野对（35．000±8．456）个／视野，P=0．012]，WesternBlot实验结果显示下调组PDGF和VEGF蛋白含量灰度比值均小于正常组（0．142±0．058对0．269±0．102，P=0．002；0．096±0．036对0．158±0．072，P=0．016）。结论PDGF在PTC的血管生成中起着较重要的作用，有可能成为监测肿瘤血管生成的超声分子成像新方法。

Objective To explore the role of targeted ultrasound contrast agent in the evaluation of angiogenesis in papillary thyroid carcinoma （PTC） in nude mice by constructing platelet derived growth factor receptor a （PDGFRa）-targeted ultrasound contrast agents, and to explore the effect of platelet derived growth factor （PDGF） on angiogenesis in PTC. Methods PDGFRa-targeted ultrasound contrast agents were constructed through biotin-avidin linkage, and blank micro-bubbles were served as control group. After the siRNA-PDGF BCPAP cell line was established, well prepared BCPAP cells or siRNA-PDGF-BCPAP cells were injected subcutaneously into the back of male BABL/C nude mice. The growth of the tumors was observed closely. All tumors of the normal group and the siRNA-PDGF group were examined by PDGFRa- targeted ultrasound contrast agents or blank micro bubbles, and the dynamic images were analyzed quantitatively by QontraXt software. All mice were sacrificed after ultrasonography. Microvessels density （MVD） in the tumors was counted by CD31 staining and the expressions of vascular endothelial growth factor（VEGF） and PDGF were detected by Western Blot. Results PTCs in nude mice were enhanced well by PDGFRa-targeted ultrasound contrast agent or blank micro-bubbles. The peak of tumors in siRNA- PDGF group was significantly lower than that in the normal group [（43. 085 ± 13. 244）% vs （57. 428 ±10.952）G, P =0.004%;MVD of the siRNAPDGF group was significantly less than that of the normal group [（23.200±6.（H7）strips/view vs （35.000±8.456）strips/view, P =0.012]. The protein expression of PDGF and VEGF in siRNA-PDGF group were significantly lower than those in the normal group, respectively （0.142±0.058 vs 0.269±0.102, P =0.002;0.096±0.036 vs 0.158±0.072, P =0.±16）. Conclusions PDGF plays an important role in angiogenesis of PTC, it maybe a new ultrasound molecular imaging method for monitoring tumor angiogenesis.