Relationship between the status of cell cycle- and apoptosis-regulatory genes and sensitivity to radio-chemotherapy for malignant astrocytic tumors.

我们对星形细胞肿瘤中p53基因突变的研究揭示了了解低级别肿瘤如何复发和进展为恶性病变的重要性，因为这极大地缩短了患者的生存时间。在低级别星形细胞肿瘤中，带有TP53突变的细胞克隆性地演变为恶性肿瘤，是一个不利的预后因素。TP53、p16/CDKN2A、p14(ARF)、PTEN抑癌基因的频繁共变表明，开发适用于具有广泛基因改变的肿瘤的治疗方法具有重要意义。为了了解P53的功能状态对抗癌药物和放射治疗敏感性的影响，我们分析了34度和37度温敏突变型P53对依托泊苷、紫杉醇、顺铂和ACNU的反应。在LN382细胞中，恢复34度的P53蛋白功能降低了依托泊苷和紫杉醇的细胞毒性，而顺铂的细胞毒性降低，但ACNU没有。细胞周期分析显示，这种敏感性的降低与加入依托泊苷或紫杉醇后向G2M期的转变受损有关。野生型P53功能诱导的细胞周期停滞可能取消依托泊苷和紫杉醇的细胞毒作用，这两种细胞毒作用依赖于G2M相关的细胞凋亡。另一方面，通过恢复p53功能来表达p21可以通过将细胞阻滞在G1期和G2M期来增加胶质母细胞瘤细胞的放射敏感性。为了研究恶性胶质瘤基因治疗的可行性，我们用15个不同的高级别胶质瘤细胞株检测了腺病毒转导的野生型p53抑癌基因的抗增殖作用，发现CAR的表达是决定腺病毒基因治疗恶性胶质瘤转导效率的关键因素。

Our study on p53 gene mutation in astrocytic tumors disclosed the importance to understand how low grade tumors recur and progress to malignant lesions since this dramatically shortens patient survival. Cells with TP53 mutations in low grade astrocytic tumors evolve clonally to malignancy and are an unfavorable prognostic factor. Frequent co-alterations of TP53, p16/CDKN2A, p14 (ARF), PTEN tumor suppressor genes indicate the importance of developing therapeutic approaches applicable to tumors with a broad range of genetic alterations. In order to understand the influence of the functional status of p53 on the sensitivity to anticancer agents and radiotherapy, we analyzed responses of LN382 cells containing a temperature-sensitive mutant p53 at 34 degrees and 37 degrees to etoposide, paclitaxel, cisplatin, and ACNU.Restoration of p53 protein function in LN382 cells at 34 degrees reduced the cytotoxicity of etoposide and paclitaxel, whereas that of cisplatin, but not of ACNU.Transduction of wild-type p53 in LN382 cells also reduced the sensitivity of the cells to etoposide. Cell cycle analysis revealed that this decrease in sensitivity was associated with an impaired transition to the G2M phase subsequent to the addition of etoposide or paclitaxel. The cell cycle arrest induced by wild-type p53 function may abrogate the cytotoxic effects of etoposide and paclitaxel, which are dependent on G2M-associated apoptosis. On the other hand, p21 expression by restoration of p53 function can increase the radiosensitivity of glioblastoma cells by arresting the cells at G1 and G2M phases. To study the feasibility of gene therapy in malignant gliomas, we examined the antiproliferative effect of the adenovirally transduced wild-type p53 tumor suppressor gene by using 15 different high-grade glioma cell lines and found that CAR expression is a critical determinant of transduction efficiencies in adenovirus-based gene therapy for human malignant gliomas.