Sorensen D M, Lewark T M, Haney J L, Meyers A D, Krause G, Franklin W A
Department of Otolaryngology--Head and Neck Surgery, University of Colorado Health Sciences Center, Denver 80262, USA.
Arch Otolaryngol Head Neck Surg. 1997 May;123(5):503-6. doi: 10.1001/archotol.1997.01900050051006.
Although carcinoma of the tongue usually occurs in patients older than 60 years, up to 4% of these tumors may occur in patients younger than 40 years. Many of the younger patients with this tumor have had no exposure or brief exposure to tobacco smoke or alcohol consumption, to which oral carcinoma is usually attributed. The molecular mechanism responsible for carcinogenesis in this group of patients is not known.
To assess the role of p53 gene mutation in oral carcinogenesis in a group of patients younger than 40 years with squamous carcinoma of the tongue.
Squamous carcinoma cells were isolated from paraffin blocks by microdissection. DNA extracted from these cells was tested for the presence of p53 mutations by polymerase chain reaction and single-stranded conformational polymorphism analysis. Mutations identified by this procedure were directly sequenced. Sections of the tumors were also stained using an immunoperoxidase immunohistochemical technique for expression of p53 protein.
Eleven patients were selected on the basis of 2 criteria: presence of squamous cell carcinoma and age younger than 40 years. Six of the 11 patients had no history of measurable tobacco or alcohol exposure.
Two mutations were detected among 11 tumors by single-stranded conformational polymorphism analysis, one in exon 4 and a second in exon 7. The former mutation consisted of G:C to C:G (guanine:cytosine to cytosine:guanine) transition in codon 72 (CGC to CCC), which would have resulted in the substitution of a proline residue for arginine. With the immunoperoxidase immunohistochemical technique for p53 protein, strong, diffuse nuclear staining was observed only in this tumor. The second mutation was a G:C to A:T (guanine:cytosine to adenine:thymine) transition in codon 248 (CGG to CGA), which would have resulted in no amino acid change since both mutant and wildtype codon sequences encode arginine. Weaker and more variable anti-p53 immunostaining was noted in this and 4 other tumors. Five tumors were negative for p53 protein by the immunoperoxidase immunohistochemical technique.
Our results suggest that p53 gene mutations are less frequent in squamous carcinomas occurring in nonsmoking young patients who do not drink alcohol than in young smokers or in the general population. Paucity of p53 mutations may be explained by the absence of exposure to tobacco smoke or alcohol. These data leave unanswered the question of the molecular mechanism responsible for oral carcinogenesis in this group of patients and suggest that this group may be a suitable population in which to study genetic susceptibility to aerodigestive carcinoma isolated from the confounding factors of tobacco and alcohol exposure.
尽管舌癌通常发生在60岁以上的患者中，但高达4%的此类肿瘤可能发生在40岁以下的患者中。许多患有这种肿瘤的年轻患者没有接触过烟草烟雾或饮酒，或仅有短暂接触，而口腔癌通常被认为与接触烟草烟雾或饮酒有关。这组患者致癌的分子机制尚不清楚。
评估p53基因突变在一组40岁以下舌鳞状细胞癌患者口腔致癌过程中的作用。
通过显微切割从石蜡块中分离鳞状癌细胞。从这些细胞中提取的DNA通过聚合酶链反应和单链构象多态性分析检测p53突变的存在。通过该程序鉴定的突变进行直接测序。肿瘤切片也使用免疫过氧化物酶免疫组织化学技术染色以检测p53蛋白的表达。
根据两个标准选择了11名患者：存在鳞状细胞癌且年龄小于40岁。11名患者中有6名没有可测量的烟草或酒精接触史。
通过单链构象多态性分析在11个肿瘤中检测到两个突变，一个在外显子4，另一个在外显子7。前一个突变是密码子72处的G:C到C:G（鸟嘌呤:胞嘧啶到胞嘧啶:鸟嘌呤）转换（CGC到CCC），这将导致精氨酸被脯氨酸残基取代。使用p53蛋白的免疫过氧化物酶免疫组织化学技术，仅在该肿瘤中观察到强的、弥漫性核染色。第二个突变是密码子248处的G:C到A:T（鸟嘌呤:胞嘧啶到腺嘌呤:胸腺嘧啶）转换（CGG到CGA），由于突变型和野生型密码子序列都编码精氨酸，因此不会导致氨基酸变化。在这个肿瘤和其他4个肿瘤中观察到较弱且更可变的抗p53免疫染色。5个肿瘤通过免疫过氧化物酶免疫组织化学技术检测p53蛋白为阴性。
我们的结果表明，在不吸烟、不饮酒的年轻患者中发生的鳞状细胞癌中，p53基因突变的频率低于年轻吸烟者或一般人群。p53突变的稀少可能是由于没有接触烟草烟雾或酒精。这些数据没有回答这组患者口腔致癌的分子机制问题，并表明这组患者可能是一个合适的人群，可用于研究从烟草和酒精接触的混杂因素中分离出来的气消化道癌的遗传易感性。
