(PQA1) The antipsychotic thioridazine protects against medulloblastoma (MB): volu

描述(申请人提供)：自20世纪40年代以来，包括硫代咪嗪在内的吩噻嗪类药物已被广泛用于治疗精神障碍。自20世纪70年代初以来，这些抗精神病药物的抗癌活性就引起了临床医生和研究人员的兴趣。尽管硫代咪嗪和其他几种吩噻嗪可以阻断心脏HERG电压门控钾通道，但它们仍然在市场上销售，因为它们延长心脏QTC间期的风险超过了它们的益处。钾通道阻断是这些抗精神病药物预防癌症的一种分子机制，这一可能性以前从未被考虑过。我们建议测试最初的假设，即硫代咪嗪通过阻断EAG2电压门控钾通道来防止髓母细胞瘤(MB)的生长和转移，EAG2电压门控钾通道在人类患者的MBS亚群中上调，特别是在转移性MBS中。具体地说，我们假设(1)硫代咪嗪阻断EAG2通道可以阻止MB细胞因有丝分裂前凝聚(PMC)而减少体积，从而导致细胞周期停滞--那些越过G2期的MB细胞会遇到有丝分裂的灾难并通过凋亡而死亡，以及(2)Thioridazine阻断EAG2通道可以减少迁移中的MB细胞后缘的水流出，从而通过防止细胞后缘收缩来干扰MB细胞的迁移--这是一种对细胞运动至关重要的局部体积调节。为了验证我们的假设，即硫代咪嗪阻断出现在有丝分裂MB细胞表面和迁移MB细胞后缘的EAG2钾通道以防止MB生长和转移，我们将进行体外和体内研究，以实验验证硫代咪嗪的抗癌活性可以通过阿司咪唑的药物治疗来模拟的预测，阿司咪唑是一种结构上无关的EAG2通道阻滞剂。我们将进一步测试这两种EAG2通道阻滞剂的抗癌活性是否类似于在体外和体内降低人MB细胞EAG2表达的效果-对于携带人MB异种移植的小鼠，以及在小鼠MB模型中敲除Eag2的效果。在小鼠模型中，将进行额外的对照以确认硫代咪嗪因其阻断EAG2通道而产生的抗癌活性被EAG2的shRNA敲除或Eag2的基因缺失所阻断。

DESCRIPTION (provided by applicant): The phenothiazine group of drugs including thioridazine has been widely prescribed for the treatment of psychiatric disorders since the 1940s. The anti-cancer activities of these antipsychotics have intrigued clinicians and researchers since the early 1970s. Whereas thioridazine and several other phenothiazines can block the cardiac hERG voltage-gated potassium channels, they remain on the market because their risk for prolonging the cardiac QTc interval is outweighed by their beneficial effects. The possibility that potassium channel block is one molecular mechanism by which these antipsychotics protect against cancer has never been considered before. We propose to test the original hypothesis that thioridazine protects against medulloblastoma (MB) growth and metastasis by blocking the EAG2 voltage-gated potassium channels that are upregulated in a subset of MBs of human patients, particularly in metastatic MBs. Specifically, we hypothesize that (1) thioridazine block of EAG2 channels prevents MB cell volume reduction for premitotic condensation (PMC) so as to cause cell cycle arrest - those MB cells that venture beyond the G2 phase encounter mitotic catastrophe and perish via apoptosis, and (2) thioridazine block of EAG2 channels reduces water efflux from the trailing edge of migrating MB cells, thereby interfering with MB cell migration by preventing the trailing edge of the cell from shrinking - a local volume regulation essential for cell movement. To test our hypothesis that thioridazine block of EAG2 potassium channels that appear on the surface of mitotic MB cells and on the trailing edge of migrating MB cells to protect against MB growth and metastasis, we will conduct in vitro and in vivo studies to experimentally validate the prediction that the anti-cancer activites of thioridazine can be mimicked by pharmacological treatment with astemizole, a structurally unrelated EAG2 channel blocker. We will further test whether the anti-cancer activities of these two EAG2 channel blockers resemble the effects of reducing EAG2 expression of human MB cells in vitro and in vivo - for mice bearing human MB xenograft, as well as the effects of knocking out Eag2 in mouse MB models. Additional controls will be conducted to confirm that the anti-cancer activities of thioridazine that arise from its block of EAG2 channels are occluded by shRNA knockdown of EAG2 or genetic deletion of Eag2 in mouse models.