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

描述（由申请人提供）：自20世纪40年代以来，包括噻嗪在内的吩噻嗪类药物已被广泛用于治疗精神疾病。自20世纪70年代初以来，这些抗精神病药物的抗癌活性引起了临床医生和研究人员的兴趣。尽管硫噻嗪和其他几种吩噻嗪类药物可以阻断心脏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间期的风险大于它们的有益作用。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，这种可能性以前从未被考虑过。我们提出通过阻断EAG2电压门控钾通道（在人类髓母细胞瘤患者中，特别是在转移性髓母细胞瘤中上调）来验证硫噻嗪对髓母细胞瘤（MB）生长和转移的原始假设。具体地说，我们假设(1)硫噻嗪阻断EAG2通道阻止MB细胞体积缩小以进行有丝分裂前冷凝（PMC），从而导致细胞周期阻滞-那些超越G2期的MB细胞遇到有丝分裂灾难并通过凋亡而死亡；(2)硫噻嗪阻断EAG2通道减少迁移MB细胞尾缘的水流出。从而通过阻止细胞的后缘收缩来干扰MB细胞的迁移-这是细胞运动所必需的局部体积调节。为了验证我们的假设，即巯基噻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，以保护MB的生长和转移，我们将进行体外和体内研究，实验验证巯基噻嗪的抗癌活性可以通过与结构无关的EAG2通道阻滞剂阿斯咪唑的药物治疗来模拟的预测。我们将进一步测试这两种EAG2通道阻滞剂在体外和体内对人MB异种移植小鼠的抗癌活性是否类似于降低人MB细胞EAG2表达的作用，以及在小鼠MB模型中敲除EAG2的作用。在小鼠模型中，我们将进行额外的对照，以证实硫硝嗪的抗癌活性是由其阻断EAG2通道而产生的，其抗癌活性被EAG2的shRNA敲低或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.