目的 探讨P53基因突变、p16基因缺失、肿瘤细胞增殖活性(PCMNA)和凋亡在胶质瘤发生发展中的作用、相互关系及其与临床病理特征的相关性.方法 应用LSAB免疫组化法检测96例不同类型胶质瘤中P53, P16蛋白表达及其肿瘤细胞增殖活性(PCNA);应用非同位素PCR-SSCP技术检测p53基因5-8外显子突变.应用PCR-DNA测序技术检测SSCP阳性标本中p53基因5-8外显子碱基突变谱和氨基酸顺序改变.应用TUNEL技术检测肿瘤细胞中凋亡的改变.结果 结果显示96例不同类型胶质瘤中P53蛋白阳性表达率为41.7%(40/96),其中Ⅱ级肿瘤阳性率为27.3%(13/53),Ⅲ、Ⅳ级肿瘤阳性率分别为62.5%(20/32)、63.6%(7/11),低分级与高分级胶质瘤中P53蛋白阳性表达率有显著性差异 (χ2 = 4.88, P＜0.05).SSCP检测结果显示34/96(35.4%)例胶质瘤出现p53基因异常移动的单链DNA电泳带,主要分布在5,7,8外显子.在40例P53蛋白阳性的病例中有32例呈现该基因的单链构象多态性改变,两种方法检测的符合率基本一致.DNA序列分析显示,17例SSCP有异常电泳带的标本中均存在p53基因突变,而且主要发生在5-8外显子,突变类型多数为点突变或碱基缺失,突变位点多分布在第5外显子130-175号密码子之间,第8外显子270-291密码子之间,突变类型主要为错义突变,且多为单碱基的改变,碱基突变以G→A或A→G最多.p16蛋白的表达缺失率为60.4%(58/96),其中Ⅱ级肿瘤为39.6%(21/53),Ⅲ、Ⅳ级肿瘤为81.2%(26/32)、100%(11/11),在高级别胶质瘤中P16表达缺失率均显著高于低级别的肿瘤.复合表达研究显示,p53蛋白的表达与p16缺失之间存在负相关性(P＜0.05).96例胶质瘤细胞增殖活性及凋亡检测显示,PCNA 标记指数(PCNA Label Index, PCNA LI)随着肿瘤分级的升高而递增,而凋亡指数 (Apoptosis Index, AI)随着肿瘤分级的升高而递减, PCNA LI/AI之比随着肿瘤分级的升高而递增.结论 p53异常表达和突变是胶质瘤中最常见的基因改变,与胶质瘤的组织学分级呈显著正相关;p53突变更常位于5、7、8外显子,突变类型主要为错义突变,且多为单碱基的改变,碱基突变以G→A或A→G最多.p53基因突变可以通过p53蛋白的表达来间接反映,p53基因的异常表达及突变与胶质瘤的发生和进展密切相关.p16的缺失更多见于高级别的胶质瘤,与胶质瘤的发生和进展密切相关.胶质瘤发生、发展与PCNA的高表达和细胞凋亡的抑制密切相关,PCNA LI/AI比PCNA LI或AI单独检测更能反映胶质瘤的病理特征及恶性行为.p53基因突变、p16基因表达的缺失及PCNA LI的增高和细胞凋亡的抑制在胶质瘤发生、发展中可能起着重要协同作用并与肿瘤的分化和异常增生显著相关,而胶质瘤细胞凋亡的发生受p53、p16基因的调控,p53及p16抑癌基因的失活,是胶质瘤逃逸凋亡的重要原因之一.%Objective To investigate P53 gene mutation, abnormal expression of p16 gene, proliferation (PCNA)and apoptosis of tumor cells, as well as their roles and their relationships with each other in tumorigenesis of gliomas. Thses results are contacted with clinicopathological data of gliomas (grade, tumor size, site, age, sex, prognosis).Methods LSAB immunohistochemical staining method were respectively used to detect expression of P53, P16 and the activities of cellular proliferation (PCNA)in 96 cases of gliomas. The base mutations in exon 5～8 of p53 gene were detected by using non-isotopic PCR-SSCP technique. PCR-sequencing was directly used to detect DNA mutations in exon 5～8 of cases with positive SSCP. Apopotosis in 96 cases of gliomas was investigated by using TUNEL technology.Results Results showed that the expression rate of P53 protein was 41.7%(40/96)in glioma samples. Immunoreactivity to the p53 gene product was observed 27.3%(13/53)in grade Ⅱ and 62.5%(20/32)in grade Ⅲ and 63.6% (7/11)grade Ⅳ gliomas respectively. There was a significant difference in expression rate of p53 protein between low grade and high grade gliomas (χ2=4.88, P＜0.05). p53 mutations (aberrant band)were detected in 34 out of 96 cases (35.42%), distributing mainly in exon 5,7,8. Significant electrophoretic mobility shifts were detected in 32 out of 40 gliomas of p53 protein positive. The correlative rate of two methods was 85.0% (32/40). Analysis of DNA sequences indicated that all of p53 mutations in 17 of positive SSCP cases occured in it's exon 5～8, and most of them were p53 gene point mutation or base pair (bp)deletion. The mutations of p53 gene mostly occured in 130～175 codons of exon 5 and 270～291 codons of exon 8. The type of mutation was mainly the missense mutation (mostly the alteration of single bp). G→A or A→G were at most observed in bp mutations.The absence rate of p16 expression was 60.4%(58/96).The absence rate of p16 expression showed 39.6%,81.2%,100% in grade Ⅱ,Ⅲ and Ⅳ gliomas respectively. P16 deletion was singnificantly higher in high grade gliomas than that in low grade gliomas. There was a significant negative correlation between p53 expression and p16 deletion (P＜0.05).The detections of PCNA and apoptosis of 96 cases indicated that PCNA Label Index(PCNA LI)increased progressively along with grade of gliomas steping up, but Apoptosis Index (AI)decreased,PCNA LI/AI also increased progressively.Conclusion The expression and mutation of p53 gene were most commonly genetic alteration in gliomas, which were significantly associated with the grade of tumor differentiation. P53 mutations are mainly located in exon 5, 7 and 8. The type of mutation was mainly the missense mutation ( mostly the alteration of single bp). G→A or A→G were at most observed in bp mutations. p53 protein accumulation would indirectly reflect p53 mutation. The abnormal expression and mutation of P53 gene were significantly related to the tumorigenesis and development of gliomas. p16 deletion were singnificantly higher in high grade than that in low grade gliomas and related to the tumorigenesis and development of gliomas. The high expression of PCNA and the inhibitation of apoptosis were significantly associated with the tumorigenesis and development of gliomas. Detecting PCNA LI/AI was more significant than doing PCNA LI or AI respectively in determing clinicopathlogic features and malignant behaviors. P53 mutation , p16 deletion, PCNA LI increasing and AI decreasing might play an important congenerous roles in the pathogenesis of gliomas and were significantly associated with the differentiation and abnormal proliferation of gliomas. The cellular apoptosis of glioma might be controled by p53 and p16 genes. The inactivation of p53 and p16 might be one of the important causes in escaping apoptosis of gliomas.
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