胶质瘤细胞c-fos基因表达水平对其增殖和凋亡的影响

Effects of the expression level of c-fos gene on the proliferation and apoptosis in human glioma cells

目的原癌基因c-fos属快反应即刻早期应答基因,其编码蛋白是真核细胞内重要的转录因子,可诱导下游报道基因mRNA的转录和蛋白表达,参与细胞增殖和凋亡的调控,当其表达异常增加时可干扰细胞增殖和凋亡的动态平衡,诱导细胞转化和肿瘤形成。通过检测胶质瘤c-fos基因的表达水平观察c-fos基因与肿瘤恶性程度的关系以及对胶质瘤细胞增殖活性和凋亡程度的影响。方法用原位杂交、原位细胞凋亡检测和免疫组织化学染色方法观察73例不同级别人胶质瘤组织标本。结果73例胶质瘤均不同程度地表达c-fos mRNA和c-Fos蛋白(100%),这两种阳性肿瘤细胞密度均随肿瘤恶性程度的升高而相应增加,Ⅰ～Ⅱ级组、Ⅲ级组及Ⅳ级组间比较,差异均有统计学意义(均P<0.01)。73例胶质瘤标本的增殖细胞核抗原阳性肿瘤细胞和凋亡肿瘤细胞的检出率均为100%,增殖细胞核抗原阳性肿瘤细胞密度随肿瘤恶性程度的升高而相应增加,Ⅰ～Ⅱ级组低于Ⅲ级组,Ⅲ级组低于Ⅳ级组,3组间比较差异均有统计学意义(P<0.05或P<0.01);凋亡肿瘤细胞密度随肿瘤恶性程度的升高而相应减低,Ⅰ～Ⅱ级组高于Ⅲ级组,Ⅲ级组高于Ⅳ级组,3组间比较差异均有统计学意义(均P<0.01)。直线相关分析证实,c-fos mRNA阳性肿瘤细胞密度、c-Fos蛋白阳性肿瘤细胞密度及增殖细胞核抗原阳性肿瘤细胞密度彼此间均呈显著性正相关(r=0.648～0.917,P<0.001),这3种阳性肿瘤细胞的密度均与凋亡肿瘤细胞密度呈显著性负相关(r=%0.727～%0.775,P<0.001)。结论c-fos基因表达水平对评价胶质瘤生物学行为有重要参考价值。胶质瘤细胞c-fos基因表达异常增加可能是促进肿瘤细胞增殖和抑制其凋亡的重要因素,并在胶质瘤发生及恶性进展过程中起重要作用。

Objective The c-fos proto-oncogene is described as an immediate early response gene （IEG）, and its encoded protein is an important transcription factor in eucaryotic cell. It can induce the transcription and protein expression of downstream reporter gene mRNA and regulate cell proliferation and apoptosis. The c-fos gene overexpression can interfere the dynamic equilibrium of cell proliferation and apoptosis, and induce cell transformation and tumor formation. This study was undertaken to investigate the relationship between the expression level of c-fos gene in human glioma and its malignant degree and effects on cell proliferative activity and apoptosis of the tumor. Methods Seventy-three human glioma specimens with different grades of malignancy were studied by in situ hybridization, in situ apoptosis detection （TUNEL method） and immunohistochemistry. Results All of the 73 gliomas expressed c-fos mRNA and c-Fos protein in different degree （100%）. The densities of positive cells, c-fos mRNA and c-Fos protein increased with the aggravation of tumor, the differences among grade Ⅰ -Ⅱ, In and Ⅳ groups were significant （P〈0.01, for all）. The detective rates of proliferating cell nuclear antigen （PCNA） positive and the apoptotic of the tumor ceils in 73 cases were all 100%. The density of PCNA positive tumor cell increased with the enhancing of the tumor malignancy, the density was lower in grade Ⅰ -Ⅱ glioma than in grade Ⅲ and was also lower in grade Ⅲ than in grade Ⅳ, the differences were all significant（P〈 0.05 or P〈 0.01）. However, the density of apoptotic tumor cell decreased with the enhancing of tumor malignancy, the density was higher in grade Ⅰ - Ⅱ than in grade Ⅲ and was also higher in grade IV, the differences were significant （P〈 0.01, for all）. In straight line correlation analysis, positive cell densities of c-fos mRNA, c-Fos protein and PCNA were all correlated positively （r = 0.648-0.917, P〈 0.001）, but each of them was correlated negatively with the density of apoptotic tumor cells respectively （r = -0.727- -0.775, P〈0.001）. Conclusion The results suggest that the expression level of c-fos gene has significant reference value in the evaluation of biological behavior of glioma. The overexpression of c-fos gene in glioma cells is possibly a major factor for promoting cell proliferation and inhibiting apoptosis, and plays an important role in the genesis and malignant progression of glioma.