食管鳞癌TP53基因突变及其瘤内异质性分析

Analysis of TP53 gene mutation and its intratumoral heterogeneity in esophageal squamous cell carcinoma

目的 探讨食管鳞癌瘤内多个取材位点中TP53基因突变异质性状态及其与临床病理特征的相关性。方法对食管鳞癌原发肿瘤及其配对的手术切端组织,采用聚合酶链式反应（PCR）法和直接测序法检测TP53基因第2~11号外显子突变状态,评估各病例瘤灶内4个不同位点TP53基因突变与临床病理参数的相关性及其在瘤内的异质性。结果 在30例被测食管鳞癌肿瘤中,发现18例患者存在TP53基因突变,占60%（18/30）。16例为点突变,其中3例为无义突变,13例为错义突变;另2例为导致移码的缺失突变。大部分突变集中于TP53基因5~8号外显子,其中5号外显子的突变率最高,为23.3%（7/18）。在2例肿瘤中检测到第282位密码子突变（R282W）,3例检测到第175位密码子突变（R175H）。观察每例肿瘤各位点突变等位基因峰高与正常等位基因峰高之比（relative intensity,RI值）,发现在有点突变的16例中,12例的4个肿瘤位点的RI之间存在很大差异,其余4例瘤内各位点RI值也不一致。结论 食管鳞癌存在较高频率的TP53基因突变,而且每例肿瘤均存在不同程度的瘤内异质性。

Objective To explore the correlation between TP53 gene mutation heterogeneity state of esophageal squamous cell carcinoma（ESCC） tumor and clinicopathologic features. Methods The primary tumor of Esophageal Squamous Cell Carcinoma （ESCC） and its operational end cutting issues were prepared. PCR and direct sequencing were performed to de- tect TP53 genc exon No. 2 - 11 mutation status and assesse the correlation of TP53 gene mutation and clinicopathological parameter of 4 different locations of tumor lesions and its intratumoral heterogeneity. Results Among 30 cases of Esopha- geal Squamous Cell Carcinoma（ESCC） tumors, 18 cases were with TP53 mutations with a proportion of 60% （18/30）, which including 16 cases of point mutations,3 cases of nonsense mutations, 13 cases of missense mutations, and 2 cases of deletion mutation that lead to frame shift. Most mutations were focused on the TP53 gcne No. 5 - 8 exons, while No. 5 was with the highest mutation rate of 23.3 % （ 7/18 ）. The 282th exons codon mutation （R282W） was found in 2 cases, 175 exons codon mutations（R175H） in 3 cases. By comparing the ratio of mutant allele peak height and normal allele peak height（ relative intensity, RI）, we found that there was obvious differences in 4 tumor location RI in 12 of 16 cases, the remaining 4 cases were also with different location RI. Conclusion The high frequency of TP53 gene mutation in e- sophageal squamous cell carcinoma（ESCC） and each tumor is with different degree of intratumoral heterogeneity.