新的环状RNA circ-0005785靶向PTEN调控胰腺癌细胞增殖和侵袭的分子机制研究

Recent studies indicate that circular RNAs (CircRNAs) play crucial roles in numerous cancers, while their function in pancreatic cancer is rarely elucidated. We keen on identifying functional circRNAs and uncovering their potential mechanisms in pancreatic cancer. Microarray for circRNAs in human pancreatic tissues demonstrated that circ-0005785 is one of the most remarkably downregulated circRNAs in pancreatic cancer tissues, which is tightly involved with poor prognosis. Moreover, suppressed circ-0005785 resulted in promoted proliferative and invasive capacity of pancreatic cancer cell by downregulating the expression of tumor-suppressor gene PTEN. Based on the “miRNAs sponge” hypothesis, co-analysis of circRNA, miRNA and mRNA was performed by using bioinformatics software. Interestingly, the miRNAs target prediction algorithm demonstrated that circ-0005785 harbors two miRNAs response elements (MREs) of miR-181 family, which has already been identified as the direct upstream of PTEN in pancreatic cancer. Hence, we hypothesized that circ-0005785 could regulate the expression of PTEN by competitively binding with miR-181 family as a miRNAs sponge and further modulate proliferation and invasion of pancreatic cancer cells. In this project, we intend to illustrate the functional roles of circ-0005785 in the tumorigenesis of pancreatic cancer, as well as the regulation mechanism of tumor suppressor gene, PTEN, by circ-0005785. Altogether, it is hopeful to clarified the importance of complicated circRNAs-miRNAs-mRNAs network in pancreatic cancer and improves our understanding of pancreatic cancer pathogenesis.

环状RNA（CircRNA）是一类新发现的非编码RNA，其在恶性肿瘤中的作用和机制是研究热点。我们前期发现circRNA-0005785在胰腺癌组织中显著低表达，且离体实验结果提示其可以正向调控抑癌基因PTEN，进而有效抑制胰腺癌细胞增殖和侵袭能力。运用生物信息学软件分析发现，该circRNA与PTEN的直接上游miR-181家族具有直接结合能力。依据“miRNA海绵”理论，我们推测该circRNA通过竞争结合miR-181家族稳定下游PTEN表达进而发挥抑癌作用。本申请项目拟从胰腺癌中表达差异的circRNA入手，从临床数据和离体实验两方面研究该circRNA在胰腺癌中的功能及其对PTEN的调控机制，并在动物模型中进一步验证该circRNA与胰腺癌的关联。该申请项目有助于研究者更为深入地了解circRNA在胰腺癌中的作用与复杂的非编码RNA对基因的调控网络，为胰腺癌的诊治提供新的线索。

胰腺癌是一种恶性程度非常高的消化系统恶性肿瘤，探寻其起病机制及治疗靶点将有助于改善患者的预后。环状RNA（CircRNA）是一类新发现的非编码RNA，其在恶性肿瘤中的作用和机制是研究热点。本研究发现circRNA-0005785在胰腺癌组织中显著低表达，并且在胰腺癌细胞系中人为下调circRNA-0005785后可以观察到肿瘤细胞增殖速度加快、细胞活力和侵袭能力也有不同程度的加强。因而，circRNA-0005785具有抑制胰腺癌的功能，随后研究对circRNA-0005785可能的潜在机制进行了研究。胰腺癌组织中抑癌基因PTEN的表达和circRNA-0005785存在显著的正相关性，并且细胞中也得到了circRNA-0005785正向调控PTEN表达的结果，所以PTEN可能是circRNA-0005785的潜在下游。依据生物信息学软件预测结果，设计实验探索circRNA-0005785-miR-181家族-PTEN三者间的内在关联，miR-181家族可能作为中间媒介参与circRNA-0005785对PTEN的调控。研究发现miR-181家族可以负向调控PTEN的表达，随后通过双荧光实验证实miR-181家族可以和PTEN的mRNA直接结合进而抑制PTEN的蛋白表达，所以miR-181家族确实是PTEN的直接上游。然而在后续的研究中发现miR-181家族并没有和circRNA-0005785序列结合的能力，也无法对circRNA-0005785的表达进行调控，所以circRNA-0005785通过竞争性结合miR-181家族来调控PTEN的表达的假设是不成立的。但是，本研究所得数据仍然说明circRNA-0005785以及miR-181家族在胰腺癌发生发展过程中扮演了一定的作用，至于circRNA-0005785对PTEN的具体调控机制目前还需要更为深入的研究。