儿童急性淋巴细胞白血病中的突变型p53蛋白、Bcl-2/Bax比率与细胞凋亡
Mutant p53 protein, Bcl-2/Bax ratios and apoptosis in paediatric acute lymphoblastic leukaemia.
作者信息
Srinivas G, Kusumakumary P, Nair M K, Panicker K R, Pillai M R
机构信息
Division of Laboratory Medicine, Regional Cancer Centre, Kerala, India.
出版信息
J Cancer Res Clin Oncol. 2000 Jan;126(1):62-7. doi: 10.1007/s004320050010.
PURPOSE
The Bcl-2 family of proteins regulates a late step in the apoptosis pathway. Bcl-2 protein is believed to be involved in imparting resistance to programmed cell death or apoptosis induced by chemotherapeutic agents and radiation. The anti-apoptotic function of the Bcl-2 protein appears to be modulated by its ability to heterodimerize with other members of the gene family, predominantly Bax, a protein favouring induction of apoptosis. Susceptibility to undergoing apoptosis may, therefore, be dependent on the ratio between Bcl-2 and Bax. Both Bax and Bcl-2 are regulated by the tumour-suppressor protein p53. The present study therefore aims to study the significance of the Bcl-2:Bax ratio, p53 expression and apoptosis in paediatric acute lymphoblastic leukaemia (ALL).
METHODS
Expression of Bax, Bcl-2 and p53 was determined by immunocytochemistry, and apoptosis was evaluated by an enzymatic end-labelling technique using biotin-dUTP and further confirmed by annexin binding. The presence of mutant p53 was determined using a mutant-p53-specific enzyme-linked immunosorbent assay (ELISA).
RESULTS
A total of 32 cases and 20 controls were evaluated. Bcl-2 was found to be expressed in 22/32 of the ALL cases. Pretreatment (spontaneous) apoptosis was observed in 23/32 cases. The mean pretreatment apoptotic index was 11.34 +/- 2.04% with a median value of 7.5%.
CONCLUSIONS
There was a positive correlation between apoptosis and Bax expression (r = 0.5044; P = 0.0038). There was good correlation between the immunoreactivity of p53 and detection of mutant p53 by ELISA (r = 0.4605; P = 0.0079). The apoptosis index showed a negative borderline correlation to the expression of Bcl-2 protein (r = -0.3181; P = 0.076). There was an inverse correlation between extent of apoptosis and the presence of mutant p53 protein (r = -0.4732; P = 0.006). p53 protein expression also showed a correlation with both Bcl-2 (r = 0.4647; P = 0.007) and Bax (r = 0.4128; P = 0.018). The Bcl-2/Bax ratio, however, showed no significant correlation with apoptosis (r = -0.3131; P = 0.08) or with p53 expression. No significant association was evident between clinical and laboratory parameters with the Bcl-2/Bax protein expression except lymphadenopathy (r = 0.5774; P = 0.03). However, Bax expression showed a borderline correlation with the immediate tumour response to chemotherapy (r = -0.338; P = 0.0628). These patients are being followed-up to look for any association between clinical outcome, Bcl-2/Bax ratio and apoptosis.
目的
Bcl-2蛋白家族调控细胞凋亡途径的后期步骤。Bcl-2蛋白被认为参与赋予对化疗药物和辐射诱导的程序性细胞死亡或凋亡的抗性。Bcl-2蛋白的抗凋亡功能似乎受其与基因家族其他成员（主要是Bax，一种促进凋亡诱导的蛋白）形成异二聚体能力的调节。因此，发生凋亡的易感性可能取决于Bcl-2与Bax的比例。Bax和Bcl-2均受肿瘤抑制蛋白p53的调控。因此，本研究旨在探讨Bcl-2:Bax比例、p53表达及凋亡在儿童急性淋巴细胞白血病（ALL）中的意义。
方法
采用免疫细胞化学法测定Bax、Bcl-2和p53的表达，采用生物素-dUTP酶促末端标记技术评估凋亡，并通过膜联蛋白结合进一步证实。使用突变型p53特异性酶联免疫吸附测定（ELISA）法测定突变型p53的存在情况。
结果
共评估了32例病例和20例对照。发现32例ALL病例中有22例表达Bcl-2。32例病例中有23例观察到预处理（自发）凋亡。预处理凋亡指数的平均值为11.34±2.04%，中位数为7.5%。
结论
凋亡与Bax表达呈正相关（r = 0.5044；P = 0.0038）。p53的免疫反应性与ELISA法检测突变型p53之间具有良好的相关性（r = 0.4605；P = 0.0079）。凋亡指数与Bcl-2蛋白表达呈负的临界相关性（r = -0.3181；P = 0.076）。凋亡程度与突变型p53蛋白的存在呈负相关（r = -0.4732；P = 0.006）。p53蛋白表达也与Bcl-2（r = 0.4647；P = 0.007）和Bax（r = 0.4128；P = 0.018）均相关。然而，Bcl-2/Bax比例与凋亡（r = -0.3131；P = 0.08）或p53表达均无显著相关性。除淋巴结病外，临床和实验室参数与Bcl-2/Bax蛋白表达之间无明显关联（r = 0.5774；P = 0.03）。然而，Bax表达与化疗后肿瘤的即时反应呈临界相关性（r = -0.338；P = 0.0628）。这些患者正在接受随访，以寻找临床结局、Bcl-2/Bax比例与凋亡之间的任何关联。
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