Analysis of oncogenes and tumor-suppressor genes in oral cancers and the application to diagnosis

人类肿瘤是在原癌基因和抑癌基因的多个基因突变后，通过多步过程从正常细胞中产生的。本研究以口腔鳞状细胞癌为研究对象，检测了ras、ErbB1(EGFR)原癌基因和p53抑癌基因的异常。ras突变：检测了29例口腔鳞癌组织中N-、H-K-ras基因第12、13和61密码子的激活突变。用聚合酶链式反应扩增的DNA与等位基因特异的寡核苷酸探针杂交或单链构象多态分析检测突变。结果除两株H-ras基因密码子12(HOC313)和13(Za)发生突变外，未检测到突变。石蜡包埋切片分析表明，HOC313的肿瘤标本在最初诊断时已发生突变。虽然在用于L…细胞的肿瘤组织中检测到ZA突变正常上皮和白斑病变多为阴性。结果表明，口腔鳞癌组织中ras基因突变的发生率明显低于腺瘤组织，提示ras基因突变在口腔鳞状细胞癌的发生发展中可能不起重要作用。结果在14个细胞系中发现了p53基因突变，并定位于从Cadon 126到Cadon 305。在248密码子(3例)和外显子6的剪接供体序列(2例)中发现了两个突变热点。14个突变中有13个是点突变，其中10个是错义突变。EGFR分析：4例口腔鳞状细胞癌中均发现EGF结合量增加。从这些结果可以推测，P53基因突变和EGF结合量增加在口腔鳞癌的发生中起重要作用，提示两者都将是诊断口腔鳞癌的良好标记物。较少

Human cancers emerge from a normal cell after multiple genetic changes of protooncogenes and tumor suppressor genes by multistep process. In the present research we focused on squamous cell carcinomas (SCC) in the oral cavity and examined abnormalities of ras and erbB1 (EGFR) protooncogenes, and p53 tumor suppressor gene.ras mutation : 29 tumor lesions of oral SCC were examined for the activational mutations of codons 12, 13, and 61 of N-, H- K-ras genes. Mutations were detected by hybridization of PCR (polymerase chain reaction)-amplified DNA with allele specific oligonucleotide probes or by PCR-SSCP (single strand conformation polymorphysm) analysis. As a result we could not detect mutation except for two cell lines which had mutations of codons 12 (HOC313) and 13 (ZA) of H-ras. Analysis of parafin-embedded sections showed that the tumor sample of HOC313 had the mutation at the time of initial diagnosis. Although the mutation of ZA was detected in the tumor tissue used for the cell l … More ine establishment, the normal epithelium and leukoplakia lesion were negative. From these results frequency of ras mutation in oral SCC is considerablly low compared with those of adenomas, thus suggesting that ras mutation may not important in tumorigenesis of oral SCC.p53 gene mutation : 15 oral SCC cell lines were examined for the presence of the mutation by cDNA-SSCP and exon-SSCP anlaysis, followed by direct sequencing. As a result, p53 gene mutations were found in 14 cell lines and were localized from cadon 126 to cadon 305. Two mutational hot-spots were found in codon 248 (3 cases) and the spliincg donor sequence of exon 6 (2 cases). Thirteen out of 14 mutations were point mutations including 10 missense mutations.Analysis of EGFR : increased capacity for EGF binding was observed in all the examined 4 cases of oral SCC.From these results it is anticipated that p53 gone mutations and increased capacity for EGF binding play important roles in the genesis of oral SCC, thus suggesting that both will be good diagnostic markers for SCC. Less