Ultrasound microbubble potentiated enhancement of hyperthermia-effect in tumours

It is now well established that for tumour growth and survival, tumour vasculature is an important element. Studies have demonstrated that ultrasound-stimulated microbubble (USMB) treatment causes extensive endothelial cell death leading to tumour vascular disruption. The subsequent rapid vascular collapse translates to overall increases in tumour response to various therapies. In this study, we explored USMB involvement in the enhancement of hyperthermia (HT) treatment effects. Human prostate tumour (PC3) xenografts were grown in mice and were treated with USMB, HT, or with a combination of the two treatments. Treatment parameters consisted of ultrasound pressures of 0 to 740 kPa, the use of perfluorocarbon-filled microbubbles administered intravenously, and an HT temperature of 43°C delivered for various times (0–50 minutes). Single and multiple repeated treatments were evaluated. Tumour response was monitored 24 hours after treatments and tumour growth was monitored for up to over 30 days for a single treatment and 4 weeks for multiple treatments. Tumours exposed to USMB combined with HT exhibited enhanced cell death (p<0.05) and decreased vasculature (p<0.05) compared to untreated tumours or those treated with either USMB alone or HT alone within 24 hours. Deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining and cluster of differentiation 31 (CD31) staining were used to assess cell death and vascular content, respectively. Further, tumours receiving a single combined USMB and HT treatment exhibited decreased tumour volumes (p<0.05) compared to those receiving either treatment alone when monitored over the duration of 30 days. Additionally, tumour response monitored weekly up to 4 weeks demonstrated a reduced vascular index and tumour volume, increased fibrosis and lesser number of proliferating cells with combined treatment of USMB and HT. Thus in this study, we characterize a novel therapeutic approach that combines USMB with HT to enhance treatment responses in a prostate cancer xenograft model in vivo.

现有研究已充分证实，肿瘤血管系统（tumour vasculature）是肿瘤生长与存活的关键要素。已有研究证实，超声刺激微泡（ultrasound-stimulated microbubble, USMB）治疗可诱导广泛的内皮细胞死亡，进而引发肿瘤血管破坏。后续发生的快速血管塌陷，可全面增强肿瘤对多种治疗方案的应答反应。本研究探讨了USMB在增强热疗（hyperthermia, HT）治疗效果中的作用。本研究以小鼠体内构建的人前列腺肿瘤（PC3）异种移植瘤为实验模型，分别采用USMB、热疗以及二者联合的方式进行干预。本次实验的治疗参数包括：超声压力范围0~740 kPa，经静脉注射的全氟碳填充微泡，以及43℃热疗的处理时长（0~50分钟不等）。研究同时评估了单次治疗与多次重复干预的效果。干预后24小时内监测肿瘤应答情况；对于单次干预组，连续监测肿瘤生长时长超过30天，多次干预组则监测至4周。干预后24小时内，与未处理组、单独USMB干预组或单独热疗干预组相比，USMB联合热疗干预的肿瘤显示出更显著的细胞死亡（p<0.05）与更明显的血管含量降低（p<0.05）。本研究分别采用脱氧核糖核苷酸末端转移酶介导的dUTP缺口末端标记法（deoxynucleotidyl transferase dUTP nick-end labeling, TUNEL）染色与分化簇31（cluster of differentiation 31, CD31）染色，来评估肿瘤细胞死亡情况与血管含量。此外，在30天的监测周期内，与单独接受任一干预的肿瘤相比，单次USMB联合热疗干预的肿瘤体积显著更小（p<0.05）。另外，在长达4周的每周一次的肿瘤应答监测中，USMB联合热疗干预组的血管指数与肿瘤体积均显著降低，纤维化程度升高，增殖细胞数量明显减少。综上，本研究阐明了一种新型治疗策略：将USMB与热疗联合应用，可在体内前列腺癌异种移植瘤模型中增强治疗应答效果。