肺癌细胞抑癌蛋白PTEN下调机制的研究

Mechanisms of PTEN down-regulation in lung cancer cells

目的:探讨肺癌细胞中抑癌蛋白PTEN低表达的相关机制。方法:Western blot方法检测肺癌细胞和正常人肺上皮细胞BEAS-2BPTEN蛋白的表达;用放线菌酮(1μg/mL)处理人肺腺癌细胞A549和正常人肺上皮细胞BEAS-2B阻断细胞翻译后,Western blot方法检测不同时相PTEN蛋白的表达。RT-PCR检测肺癌细胞与正常肺上皮细胞PTEN mRNA水平;放线菌素D(1μg/mL)处理肺癌细胞与正常肺上皮细胞阻断新生RNA合成,RT-PCR检测不同时相PTEN mRNA的水平。结果:Western blot结果显示,肺癌细胞中PTEN蛋白表达与正常肺上皮细胞比较有不同程度的降低(0.38～1.32倍);使用放线菌酮处理A549和BEAS-2B后,24h内A549及BEAS-2B细胞PTEN蛋白表达无明显改变。RT-PCR结果显示肺癌细胞中PTEN mRNA与正常人肺上皮细胞相比明显降低(0.41～0.68倍);放线菌素D处理显示肺癌细胞PTEN mRNA降解速率比正常肺上皮细胞降解速率明显加快。结论:肺癌细胞中抑癌蛋白PTEN低表达的主要原因是其mRNA降解加速,这为进一步研究PTEN蛋白低表达的详细分子机制提供了线索。

OBJECTIVE：To investigate the mechanisms of low expression of PTEN in lung cancer ceils. METHODS： Western blot was performed to detect the protein expression of PTEN in lung cancer cells and normal human lung epithelial cell. After translation inhibition with cycloheximide （1 μg/mL）, PTEN protein levels were determined during different phases. The levels of PTEN mRNA were determined by RT-PCR in A549 and BEAS-2B. Then, the treatment of actinomycin D （1 μg/mL） for blocking transcription, evaluated PTEN mRNA at indicated time point in A549 and BEAS-2B cells. RESULTS： Western blot showed that the PTEN protein was obviously decreased by approximately 0. 38- 1.32 times in lung cancer cells than normal lung ceil. After using cycloheximide, PTEN protein expression in A549 had not changed significantly during 24 hours as well as BEAS-2B. RT-PCR results showed that PTEN mRNA levels were significantly dropped by 0.41-0.68 times in lung cancer cells, compared with BEAS-2B. The treatment with actinomycin D, PTEN mRNA degradation rate in lung cancer cells was much faster than that in BEAS-2B. CONCLUSION： These data indicates that PTEN mRNA degradation acceleration led to down-regulation of PTEN, which provids some clues for further investigating the PTEN expression molecular mechanisms in lung cancer cells.