Analysis of molecular mechanisms of chemoresistance in malignant glioma cells

细胞周期检查点防止从细胞周期的一个阶段过渡到下一个阶段，直到当前阶段的所有过程完成。检查点功能的缺陷导致基因突变和染色体损伤，从而促进肿瘤的发生和发展。然而，一些癌细胞中检查点功能的丧失被认为与它们对化疗和放疗等抗肿瘤治疗的敏感性有关。包括恶性胶质瘤在内的大多数癌细胞都缺乏G_1检查点功能，因此在暴露于基因毒性物质时不能在G_1期阻滞。相反，它们暂时聚集在G_2相。然而，考虑到G_2检查点在癌细胞中也部分受损，它们无法维持G_2阻滞，最终在进入有丝分裂时死亡。这个过程被称为有丝分裂灾难。诱导有丝分裂突变是癌症治疗的一个重要目标。在本项目中，我们描述了p53缺陷癌细胞中DNA损伤诱导的有丝分裂灾难的动力学。大多数细胞进入有丝分裂时DNA损伤在中期停止，随后发生细胞死亡。此外，灾难发生前的中期停滞被清楚地证明是由于纺锤体检查点的激活造成的，而使用RNA干扰抑制检查点功能允许癌细胞逃避有丝分裂灾难。我们的研究结果表明，纺锤体检查点功能是用dna损伤抗肿瘤药物治疗的癌细胞诱导突变所必需的。我们推测胶质母细胞瘤的化疗耐药可能是由于这些肿瘤的纺锤体检查点功能受损。

Cell cycle checkpoints prevent transition from one phase of the cell cycle to the next until all processes of the present phase are completed. Defects in the checkpoint functions result in gene mutations and chromosome damages, which contribute to the development and progression of tumors. However, loss of checkpoint function in some cancer cells is considered to be associated with their sensitivity to antineoplastic treatments such as chemotherapy and radiation. Most cancer cells including malignant gliomas are deficient in G_1 checkpoint function and therefore fail to arrest in G_1 phase on exposure to genotoxic agents. Instead, they accumulate temporarily in G_2 phase. However, given that the G_2 checkpoint is also partially impaired in cancer cells, they are unable to maintain G_2 arrest and eventually die as they enter mitosis. This process is known as mitotic catastrophe. The induction of mitotic catastrophe is an important goal of cancer therapies. In the present project, we characterized the dynamics of mitotic catastrophe induced by DNA damage in p53-deficient cancer cells. Most cells entering mitosis with DNA damage arrested at metaphase and subsequently underwent cell death. Furthermore, metaphase arrest prior to the catastrophe was clearly shown to result from activation of the spindle checkpoint, and inhibition of checkpoint function using RNA interference allowed cancer cells to escape mitotic catastrophe. Our findings suggest that the spindle checkpoint function is required for the induction of catastrophe in cancer cells treated with DNA-damaging antineoplastic agents. We speculate that chemoresistance of glioblastomas may be due to the impairment of spindle checkpoint function in those tumors.