靶向mTORC2联合抑制Hsp90治疗恶性嗜铬细胞瘤的作用及分子机制研究

Our studies have shown that mTORC2 is emerging as a promising therapeutic target in the treatment of malignant pheochromocytoma (PCC), because its activity is essential for the transformation and vitality of malignant PCC. The Western blot analysis showed that targeting of mTORC2 could inhibit phosphorylation of Akt (Ser473), an mTORC2 phosphorylation site, but could not inhibit phosphorylation of Akt (Thr308), which plays an important role in the pathogenesis of malignant PCC. Thus, it is very important to investigate how to decrease the expression of p-Akt(Thr308) in order to get more effective anti-tumor activity when targeting of mTORC2 in the treatment of malignant PCC. In another study, we have found that the expression of heat shock protein 90 (Hsp90) is associated with the malignant PCC, and plays an important role in the pathogenesis of malignant PCC. However, the mechanism is not clear. We speculate that the reason why targeting of mTORC2 could not inhibit phosphorylation of Akt (Thr308) is due to that the Akt was regulated by the Hsp90. Thus, we think that combination therapy with targeting of mTORC2 and inhibiting HSP90 would be more effective in the treatment of malignant of PCC. Therefore, based on our previous studies, we would like to explore the role and mechanism of combination therapy with targeting of mTORC2 and inhibiting HSP90 for malignant PCC.

我们发现，mTORC2在促进嗜铬细胞瘤恶性化中起重要作用，靶向mTORC2能降低p-Akt（Ser473）水平而具有抗肿瘤作用；但我们也发现，靶向mTORC2并不能降低p-Akt（Thr308）水平，其在继续维持肿瘤细胞生存中可能起重要作用，因而靶向mTORC2时，如何降低p-Akt（Thr308）水平，使得Akt彻底失去功能，从而达到更有效的抗肿瘤作用有待进一步研究。我们还发现，恶性嗜铬细胞瘤中Hsp90呈过度激活，并且在维持肿瘤的存活中起一定作用，但机制不明。我们推测，Akt极可能受Hsp90的调节，致使靶向mTORC2不能有效降低p-Akt（Thr308）水平。我们设想，能否联合抑制Hsp90的活性，这样将导致p-Akt（Thr308）功能丧失，势必达到更有效的抗肿瘤效果。因此，本项目拟在我们前期研究基础上，进一步研究靶向mTORC2联合抑制Hsp90治疗恶性嗜铬细胞瘤的作用及机制。

恶性嗜铬细胞瘤易复发、浸润和转移，治疗比较棘手，目前分子靶向治疗成为恶性嗜铬细胞瘤的重要治疗手段。靶向mTORC2能抑制Akt的Ser473 位点磷酸化降低p-Akt（Ser473）蛋白水平而具有抗肿瘤作用，但靶向mTORC2并不能降低p-Akt（Thr308）蛋白水平。在靶向mTORC2治疗恶性嗜铬细胞瘤时，由于p-Akt（Thr308）蛋白水平并未受影响，而p-Akt（Thr308）仍具有部分功能，其在继续维持肿瘤细胞的生存中可能起着重要的作用，从而靶向mTORC2可能并不能达到非常有效的抗肿瘤作用。.本研究通过构建慢病毒载体，下调PC12细胞Rictor的表达，建立Rictor低表达的PC12细胞；观察靶向mTORC2联合抑制Hsp90对PC12细胞生物学行为的影响；分子水平分析靶向mTORC2联合抑制Hsp90对Akt功能变化的影响；建立裸鼠恶性嗜铬细胞瘤动物模型；观察靶向mTORC2联合抑制Hsp90对裸鼠恶性嗜铬细胞瘤的抑制作用；获取肿瘤标本进行TUNEL分析；提起蛋白，分子水平分析Akt功能变化。.本项目研究发现，Akt受Hsp90的调节，致使靶向靶向mTORC2时不能有效降低p-Akt（Thr308）蛋白水平。本项目研究发现靶向mTORC2联合抑制Hsp90能有效降低p-Akt（Thr308）蛋白水平，使得Akt彻底失去功能，从而达到更有效的抗肿瘤作用。.本项目阐明了靶向mTORC2联合抑制Hsp90治疗恶性嗜铬细胞瘤的作用及分子机制，进一步完善恶性嗜铬细胞瘤靶向治疗的策略，为恶性嗜铬细胞瘤靶向治疗提供新方法，具有较广泛的应用前景。