PGD2/PTGDR2信号调控自噬对胃癌干细胞的作用及其机制

Previous studies have shown that PGD2/PTGDR2 signal inhibited the tumorigenesis and progression of cancer. However, the role and mechanism of PGD2/PTGDR2 signal in gastric cancer and gastric cancer stem cells is unclear. We found that the expression of PGD2/PTGDR2 signaling-related proteins (PGD2 synthase PTGDS and its receptor PTGDR2) in gastric cancer tissues were significantly lower than adjacent tissue and was associated with prognosis of patients. The expression of PTGDS and PTGDR2 was significantly negatively correlated with gastric cancer stem cell marker molecules (Sall4, Lgr5, etc.). In vitro experiments also showed that PGD2/PTGDR2 signal induced autophagic-death and inhibited stemness of GCSC. In this study, we will investigate the action of PGD2/PTGDR2 signal in autophagy and its mechanism by using Crispr/cas9 gene editing, immunoprecipitation, other cell and molecular biology techniques and PTGDR2 knockout animal model. The completion of this study will explain the new mechanism of GCSCs and provide new ideas and methods for the diagnosis and treatment of gastric cancer.

研究表明PGD2/PTGDR2信号抑制肿瘤的发生发展，然而PGD2/PTGDR2信号对胃癌及胃癌干细胞（GCSC）的作用及机制尚不清楚，我们发现PGD2/PTGDR2信号通路蛋白（PGD2合成酶PTGDS及其受体PTGDR2）在胃癌组织中显著低表达且与胃癌患者的预后相关，它们在胃癌组织中的表达与GCSC标记分子（Sall4、Lgr5等）呈显著负相关，体外实验亦发现PGD2/PTGDR2信号促进胃癌细胞的自噬性死亡并抑制GCSC的干细胞特性，以上结果说明PGD2/PTGDR2信号具备调控GCSC恶性生物学功能的潜力。本研究将采用Crispr/cas9基因编辑、免疫共沉淀等多种细胞与分子生物学技术，结合PTGDR2基因敲除动物模型探讨PGD2/PTGDR2信号对胃癌干细胞自噬的影响及其在胃癌干细胞调控中的作用机制。本课题的完成将揭示调控胃癌干细胞功能的新机制，为胃癌诊疗提供新的思路和方法。

前列腺素D2(PGD2)对胃癌(GC)的抗肿瘤作用早在几十年前就已为人所知。然而，PGD2调控胃癌生长的机制尚不清楚。肿瘤干细胞(CSCs)与肿瘤新生血管、侵袭性和治疗耐药密切相关。此研究中，我们发现PGD2与其受体(PTGDR2)之间的信号转导具有抑制胃癌细胞体外自我更新、抑制体内肿瘤生长和转移的能力。为此，我们首先确定了PGD2合成酶(L-PTGDS)和PTGDR2在胃癌组织中的表达低于癌旁组织，并且与患者的预后有关，胃癌组织中L-PTGDS和PTGDR2的表达与GC-CSC标记物Sall4和Lgr5呈负相关。第二，在CSC样细胞中，L-PTGDS和PTGDR2的表达显著下调，导致CSCs标志物的表达增强，自我更新能力增强。PGD2 的直接刺激和L-PTGDS的过表达则出现相反的现象。第三，PGD2在皮下肿瘤模型中抑制肿瘤生长和发病率，在腹膜转移模型中抑制肝脏和肠系膜转移，在体内干扰PTGDR2的表达逆转了这些作用。最后，机制研究发现PGD2抑制STAT3磷酸化和核表达。进一步实验发现，在STAT3磷酸化(Thr705)位点引入突变后，PGD2对CSC标志物表达的抑制作用消失，证明PGD2/PTGDR2信号通过影响STAT3的磷酸化抑制胃癌CSCs的功能。最后我们还发现，PTGDS和PTGDR2上游是收到YAP蛋白的调控。综上所述，本课题的完成揭示了PGD2/PTGDR2信号在CSC调控中的新功能，为控制胃癌的发生发展提供了新的途径。