PEDF通过促进肺癌血管正常化增强放射治疗作用及分子机制研究

Over the past decade, a host of studies have shown that pigment epithelium derived factor (PEDF) could inhibit the angiogenesis and growth of several types of cancers，including lung cancer. However, the effects of PEDF on tumor vascular normalization remains unknown. Our previous study showed that during PEDF treatment, tumor vascularity decreased, while the basement membrane and pericyte coverage associated with endothelial cells increased, which supported the idea of vessel normalization. Accordingly, the aim of the project is to investigate the anti-tumor growth effects of PEDF combined with radiotherapy. .Furthermore, the mechanism by which PEDF induces vasulcar normalization will be explored. Regulator of G protein 5 (RGS5) was discovered as one of the factors modulated tumor vascular normalization, which is regulated by hypoxia-induced factor 1alpha (HIF-1α). Downregulating of RGS5 induces tumor vessel normalization. Interestingly, our and the others' studies demonstrated that the activity of HIF-1α were inhibited by PEDF. Therefore, we proposed that PEDF might induce vascular normalization by downregulating RGS5 expression via HIF-1α..In summary, the present study focus on the effects and the potential mechanisms of PEDF on tumor vascular normalization in a xenografted model of lung cancer. We aimed to elucidate the "normalizing time window" induced by PEDF, and examined the anti-tumor effects of radiotherapy delivered during or out the "time window". These results are of translational importance because the clinical benefits of PEDF therapy might be increased by more precise treatment scheduling to ensure that radiation is given during periods of peak radiosensitivity.

以往研究证实PEDF可通过抑制肿瘤血管新生抑制肿瘤的生长，但PEDF对肿瘤血管正常化的作用尚无报道。我们的预实验表明PEDF可诱导小鼠肺癌移植瘤血管正常化。RGS5是调控肿瘤血管正常化的重要因子，其表达具有低氧依赖性，受HIF-1α调控。我们前期研究表明PEDF可下调HIF-1α，且在肺癌血管正常化期间，RGS5的表达下降，提示PEDF可能通过HIF-1α调控RGS5进而调控肿瘤血管正常化。诱导血管正常化是血管新生抑制因子增强放疗抗肿瘤作用的重要机制，我们推测PEDF可提高放疗对肺癌的治疗作用。本项目拟观察：PEDF促进肺癌血管正常化的作用并初步探讨其分子机制，明确PEDF促进肺癌血管正常化的时间窗，探讨PEDF联合放疗对肺癌的最佳治疗模式，旨在为肺癌等恶性肿瘤治疗提供新的候选药物及为临床应用提供科学依据和理论基础。

以往研究证实PEDF可通过抑制肿瘤血管新生抑制肿瘤的生长。本课题采用免疫荧光的方法观测了PEDF对肺癌血管正常化的作用并明确其正常化时间窗；采用动物实验观测PEDF联合放疗对肺癌移植瘤的生长抑制作用。我们的研究结果发现：PEDF 治疗后的第3-7天，肿瘤分布更均匀，分布更均匀，直径变小并趋于一致，血管密度逐渐下降。此外，与对照组相比，PEDF组肿瘤血管基底膜覆盖内皮细胞的比例逐渐降低且分布较均匀、周皮细胞覆盖率增加以及肿瘤乏氧细胞的比例下降。综上所述，本研究发现PEDF可诱导肺癌血管正常化，其时间窗为第3至第7天。此外，动物实验发现在PEDF诱导血管正常化时间窗内给予放射治疗可以取得最好的联合治疗作用。此外，本课题研究了G蛋白信号通路调节蛋白5（RGS5）对人肺癌细胞的作用并探讨其可能的分子机制。我们的研究结果：过表达RGS5可显著地降低人肺癌细胞系A549及Calu-3的生长，进一步的研究表明RGS5可通过诱导肺癌细胞的凋亡抑制其生长。此外，过表达RGS5与放射治疗联合，可以显著地增强抑制肺癌细胞的存活能力。综上，本研究发现PEDF可促进肺癌血管正常化并增强放射治疗的抗肺癌生长作用，这将为进一步探索PEDF联合放化疗对肺癌的最佳治疗模式提供依据，从而为肺癌等恶性肿瘤治疗提供新的候选药物及为临床应用提供科学依据和理论基础。此外，进一步研究表明RGS5可显著地抑制人肺癌细胞的生长，并且过表达RGS5可增强放射治疗对肺癌细胞的杀伤作用。这在理论上解释了为什么RGS5的表达水平与肺癌的进展呈负相关，也为RGS5作为肺癌治疗的靶点提供了科学依据和理论基础。