光动力疗法联合贝伐珠单抗治疗裸鼠U87胶质瘤的实验研究

Combination of Photodynamic Therapy with Bevacizumab for Nude Mouse Bearing U87 Glioblastoma

目的观察光动力疗法(PDT)联合贝伐珠单抗治疗裸鼠原位U87脑胶质瘤的效果并探讨其作用机制。方法裸鼠颅内种植U87脑胶质瘤细胞7 d后,随机分为对照组、PDT组(ALA300 mg/kg,能量密度80 J/cm2)和联合治疗组(PDT+贝伐珠单抗)。种植后第21天处死动物并取出脑组织。HE染色切片计算肿瘤体积;免疫组化染色检测Ki67、VEGF表达,分析肿瘤细胞的增殖和VECF地表达;TUNEL染色分析肿瘤细胞的凋亡。结果与对照组比较,治疗组的肿瘤体积明显减小,细胞的凋亡也明显增加;与PDT组相比,联合治疗组的作用更为明显。单用PDT并不能抑制肿瘤细胞的增殖,但联合治疗的抑制作用非常明显。PDT的照射可诱导肿瘤周围组织中VEGF的表达增高,此作用可被贝伐珠单抗所抑制。结论 PDT联合贝伐珠单抗可明显抑制脑胶质瘤的生长,作用效果优于单用PDT,其作用机制为促进肿瘤细胞的凋亡、抑制细胞的增殖及PDT引起的肿瘤局部血管形成,本研究结果为临床联合应用PDT和贝伐珠单抗治疗脑胶质瘤提供了可靠的实验依据。

Objective To evaluate the effects of combination of photodynamic therapy（PDT） with bevacizumab on intracranial glioblastoma xenografts in nude mice.Methods Nude mice bearing intracerebral U87 glioblastoma were treated with PDT and its combination（PDT＋bevacizumab）.Tumor volume was analyzed to evaluate the outcome of different treatment modalities.In addition,the immunohistochemical expression of VEGF in the brain adjacent to the tumor;and in the tumor area TUNEL and immunohistochemical stainings were used to measure apoptosis and proliferation.Results Compared with control,both of treatment methods could reduce the tumor volume and stimulate apoptosis;furthermore,compared with PDT alone,the combined treatment significantly increased apoptosis and reduced the tumor size.At the same time,Ki67 expression（a marker to indicate cells proliferation） in PDT had no change,while it significantly been decreased in combination.PDT treatment markedly increased the expression of VEGF level,which could be inhibited by bevacizumab.Conclusions Combination of PDT with bevacizumab significantly decreases glioma growth which is better than PDT alone in mice,this effect is mediated by promotion of apoptosis,inhibition of cells proliferation and PDT-induced VEGF expression.This finding suggests that the combination therapy be a promising strategy to improve clinical outcomes of glioblastoma.