SSTR2调控Rho亚家族信号通路对胰腺癌生物学行为影响的分子机制和治疗靶点的探索

The loss of SSTR2 expression occurred in more than 90% of pancreatic cancer, and it is a potential pancreatic cancer treatment site. However, it has been unable to be applied into clinic for security constraints of biological agents. Aimed to explore SSTR2 effective downstream targets, our research group found that SSTR2 could regulate Rho subfamily protein activity, which not depend on classic ROCK pathway ,but might through certain spcific protein location to regulate the biological behavior of pancreatic cancer. Rho subfamily is a hot spot in anti-cancer drug development, and it's significantly meaningful to go a step further clarify the relationship between the SSTR2-Rho and figure out the key proteins location for applying SSTR2 into clinical practice. Based on the previous work, our project propose to detect Rho subfamily specific expression in pancreatic cancer, and clarify the relationship between SSTR2 and Rho subfamily signaling pathway by co-immunoprecipitation, and figure out SSTR2-Rho downstream key proteins by DNA microarray and proteomics technology, and clarify the Rho subfamily signaling pathway downstream key proteins affect the biological characteristics of pancreatic cancer by viral vectors and inhibitors. Furthermore, we propose to determine the therapeutic effect of SSTR2 by intervening the key target proteins location in vivo and in vitro.The project is expected to go a step further clarify the mechanism of how SSTR2 affect the malignant biological behavior in pancreatic cancer and establish the foundation for developing novel anti-pancreatic cancer drugs.

SSTR2在90%以上的胰腺癌中缺失表达，是胰腺癌潜在治疗位点,但受生物制剂安全性的制约，该位点一直无法用于临床治疗。在探索其下游有效治疗靶点的研究中，我们发现SSTR2调控Rho亚家族蛋白活性，但不依赖经典ROCK途径，可能通过特殊的蛋白位点调控胰腺癌生物学行为。Rho亚家族是肿瘤药物开发的热点蛋白家族，进一步阐明SSTR2与Rho亚家族的关系并明确其关键蛋白位点，对实现SSTR2临床应用转化具有重要意义。本项目拟在前期研究基础之上：检测Rho亚家族信号通路在胰腺癌中的特殊表达，免疫共沉淀技术阐明SSTR2与Rho亚家族信号通路的关系；基因芯片和蛋白质组学技术明确SSTR2-Rho亚家族下游关键蛋白；病毒载体及相关阻滞剂阐明它们对胰腺癌生物学特性的影响；对关键蛋白位点进行体内外干预明确其治疗作用。本项目将有望阐明SSTR2在胰腺癌生物学行为中的作用机制，为开发新的胰腺癌治疗药物奠定基础。

胰腺癌被称为“癌中之王”，至今仍处于“无药可治”的尴尬现状。探索胰腺癌关键缺失分子SSTR2下游靶点和开发其治疗性药物一直是国内外研究的热点。我们课题组在国际上率先采用荧光差异蛋白质组学技术结合生物信息学分析，发现SSTR2可能通过Rho族信号通路调控胰腺癌恶性生物学行为。然而使用Rho激酶阻滞剂作用于胰腺癌细胞后并不能起到治疗作用。为阐明这一现象的具体机制，通过本次研究，我们发现抑制Rho通路后胰腺癌细胞的自噬过程被强烈激活，并导致其化疗逃逸。随后我们研究发现自噬--溶酶体融合过程在胰腺癌细胞中均异常增强，并在国际上首次发现针对融合过程中关键结构SNAREs复合体的新型阻滞剂withaferin A（WA）。通过体内外研究证实，WA能通过扰乱SNAREs复合体阻断自噬--溶酶体融合进而抑制自噬，且能有效抑制胰腺癌细胞增殖、侵袭和迁移能力，同时增加胰腺癌细胞对多种化疗药物的敏感性。但进一步研究发现WA对动物模型的肝、肾有明显毒副作用。最后，我们通过化学修饰和空间改型，得到与WA生物学活性相似但对肝、肾毒副作用较小的脂质体衍生物。通过本次项目的研究，不仅为我们在国际领域抢占SSTR2靶点治疗的话语权提供契机，也为胰腺癌的药物治疗起到推动作用，同时也为其他恶性肿瘤的研究开辟新的思路和方法。