p55PIK特异性抑制剂N24在胃肠道间质瘤耐药中的作用及机制研究

Gastrointestinal stromal tumor (GIST), is associated with the abnormal activation of KIT/PDGFR. Though the application of imatinib in metastatic GIST led to tremendous therapy response, the inevitable secondary drug resistance during treating session serverly impaired treatment effect, rendering an obstacle the treatment of imatinib-resistant patients of GIST. Previous reseach indicated that, p55PIK, the regulatory subunit of PI3K, was highly expressed in drug resistant GIST, and the ihibition of p55PIK resulted in declined growth pattern of imatinib-resistant cell lines and tumors transplanted subcutaneously in nude mice. For this purpose, we are set to verify the associations between p55PIK and drug resistance through series of experiments,and uncover the molecular mechanisms of p55PIK to promote GIST drug resistant by techniques like gene chip. In the mean time, the effect to the growth pattern of imatinib-resistant GIST and transplanted tumors in nude mice will be observed closely through the application of imatinib with or without N24, the specific inhibitor of p55PIK, in order to demonstrate the reversible treatment effect in imatinib-resistant GIST patients by N24. The project may offer a brand new train of thought in the treatment of these GIST patients, promising a sound prospect in clinical application.

胃肠道间质瘤（GIST）的发病与KIT/PDGFRA的异常活化有关。虽然伊马替尼用于治疗转移性GIST取得了惊人的成果，但是治疗过程中不可避免的继发耐药严重影响了其疗效，使临床伊马替尼耐药患者的治疗成为一个难题。我们前期研究发现PI3K调节亚基之一p55PIK在耐药GIST组织中表达显著增高，抑制p55PIK可以显著抑制伊马替尼耐药的GIST细胞及裸鼠移植瘤生长。为此，我们希望通过设计一系列实验来证实p55PIK与耐药的关系，并通过基因芯片等技术筛查p55PIK促进GIST耐药的分子生物学机制。观察p55PIK的特异性抑制剂N24单用或联合伊马替尼使用对耐药GIST细胞及裸鼠移植瘤的生长的影响，证实p55PIK的特异性抑制剂N24能使临床发生耐药的GIST患者对伊马替尼重新获益，有可能为治疗伊马替尼耐药的GIST患者提供新的思路，具有很好的临床应用前景。

p55PIK是IA型PI3K家族的调节亚基之一，本实验室前期研究发现p55PIK在结直肠癌发生、发展中发挥着重要的作用。通过本项目的研究，我们进一步论证了p55PIK在胃肠道间质瘤（GIST）伊马替尼耐药中的重要作用，丰富了p55PIK的功能。通过一系列实验，我们证实：p55PIK在GIST伊马替尼耐药细胞和临床组织标本中呈明显高表达状态，其表达与KIT的表达呈正相关。过表达p55PIK能够导致GIST细胞对伊马替尼耐药，而低表达p55PIK或应用其特异性抑制剂TAT-N24能够使GIST耐药细胞恢复对伊马替尼的敏感性。机制研究发现，p55PIK通过激活NKκB-p65介导的信号通路，促进KIT及KIT磷酸化水平，从而导致GIST的耐药，低表达p55PIK或应用TAT-N24能够通过抑制NKκB-p65介导的信号通路，减少KIT及磷酸化KIT的水平，从而恢复细胞对伊马替尼敏感性。最后，我们在体内实验中发现低表达p55PIK或应用TAT-N24，联用伊马替尼，能够对伊马替尼耐药的移植瘤起到明显抑制作用。项目的实施有可能为GIST耐药患者提供新的、有效的治疗靶点。