抑制Hedgehog通路导致微血管完整性破坏促进胰腺癌转移的机制研究

Pancreatic cancer (mainly pancreatic ductal adenocarcinoma) ranks the fifth most frequent cause of cancer-related death, with a 5-year overall survival rate less than 5%. Chemotherapy is the major choice, whereas the efficacy is limited owing to the hypovasculature but with abundant stroma of tumor. Thus, depletion of stroma treatments may enhance the efficacy of chemotherapy. The Hedgehog (Hh) signaling pathway plays a pivotal role in the development of stroma, and inhibition of it leads to stromal depletion substantially. However, the superimposed efficacy is also unsatisfactory, suggesting that the negative effects may of existence. Our preliminary experiments revealed that treatment of stromal depletion increased the peritoneal dissemination and liver metastasis of tumor-bearing mice. In addition, our previous study found that PDGFR-β was the shared molecule/biomarker between stromal cells and pericytes in pancreatic cancer, and that microvessel integrity was more critical to patients outcome than microvessel density. Therefore, inhibition of Hh pathway may reduce the microvessel integrity and accordingly induce metastasis; nonetheless, the internal mechanism is still unclear. On the basis of our previous work, in the present study, we firstly aim to confirm that inhibition of Hh pathway would probably promote metastasis. Furthermore, we need to verify that whether this role of promotion is associated with the decrease of microvessel integrity, through examining the vascular morphology. Moreover, by using of various interventions in vivo and in vitro, we will clarify that the downregulation of PDGFR-β in pericytes after Hh inhibition is the crucial regulatory mechanism of microvessel integrity. Finally, we also plan to explore whether the tanshinone IIA, an herbal monomer which has the potential activity of promoting vascular normalization, could impede metastasis when combined with stromal depletion therapy. In conclusion, if we got the expected results, we will first report that depletion of stroma in pancreatic cancer can promote metastasis through impairing microvessel integrity. Most importantly, we will obtain the desirable medication which may inhibit the prometastatic effects of stromal depletion, and ultimately improving efficacy.

胰腺癌是世界第5大癌症死因，5年生存率低于5%。化疗是主要手段，但效果不佳，肿瘤富间质而乏血管是主因，去间质化因而可提高疗效。Hedgehog是间质化进展的关键信号，抑制该通路产生显著去间质作用，然其疗效并不理想，提示存在负面作用。我们的预实验显示去间质治疗可增加荷癌小鼠的腹腔播散及肝转移；前期发现，PDGFR-β是间质细胞和血管周细胞的共有功能分子，微血管完整度较其密度更重要。因此，抑制Hh可能同时降低微血管完整度诱导转移，然其机制未明。为此，本课题拟首要确证抑制Hh会增加转移，进而通过形态学检测揭示其主要由微血管完整度下降所导致，随后应用体内外干预阐明下调周细胞PDGFR-β为完整度的关键调节机制，最后探索具促血管正常化的药物丹参酮ⅡA能否阻抑转移。本项目如达预期，将首次揭示去间质可促转移，其机制与破坏微血管完整性密切相关，同时找到具潜在抑转移的药物，可能降低该负面作用，最终提高疗效。

胰腺癌恶性程度极高，近年来已成为世界第4大癌症死因，患者的5年生存率低于7%。手术切除是提高患者长期生存的主要手段，然而超过85%的患者初诊时已为晚期而不适合手术，系统化疗是该类患者的主要疗法，但其效果向来不佳。胰腺癌含有丰富的间质，肿瘤微血管被高度压缩，肿瘤细胞往往处于乏血供状态，使得化疗药物不能有效灌注肿瘤局部，可能是其疗效不佳的主要原因。去间质化因而可能提高疗效。Hedgehog信号转导是胰腺癌间质化进展的关键机制，抑制该通路产生显著的去间质作用，然而其临床疗效却并不理想，提示起效的同时存在负面作用。我们的前期实验结果显示去间质药物可增加小鼠胰腺癌模型的腹腔播散及肝转移；此外还发现PDGFR-β是间质细胞和血管周细胞的共有标记和功能分子，微血管的完整度较其密度更加重要。提示抑制Hedgehog通路可能同时降低微血管的完整度诱导转移，然而其确切机制未明。在前期研究的基础上，本项目首先应用遗传性小鼠胰腺癌模型以及裸鼠胰腺原位移植瘤模型，通过给予Hedgehog通路抑制剂，证实去间质化显著增加循环血肿瘤细胞含量、促进腹腔播散以及肝转移（均P<0.05），进而通过形态学检测揭示其主要由微血管完整度下降所导致。随后应用在体及体外细胞干预实验，揭示胰腺癌间质细胞和血管周细胞具有共性特征，PDGFR-β是两者的共有标记和功能分子；并进一步阐明下调周细胞PDGFR-β为Hedgehog抑制破坏微血管完整性的关键调节机制。最后应用具促血管正常化的药物丹参酮ⅡA，发现它可在一定程度上阻抑去间质药物促转移的负面作用，其机制与上调血管内皮细胞PDGF-BB表达、增强内皮细胞与周细胞耦联密切相关。本项目首次揭示胰腺癌去间质治疗可同时带来促转移的负面作用，其机制与破坏微血管完整性密切相关，同时找到具潜在抑转移的药物丹参酮ⅡA，可降低该负面作用，从而最终提高化疗疗效，具有重要的临床参考价值。