Thomas S, Brennan J, Martel G, Frazer I, Montesano R, Sidransky D, Hollstein M
Queensland Institute of Medical Research, Brisbane, Australia.
Cancer Res. 1994 Jul 1;54(13):3588-93.
Seventy-five % of the world's oral cancers arise in developing countries. In high incidence areas of Southeast Asia such as Papua New Guinea (PNG) the major region-specific risk exposure is betel quid chewing. While it has been shown that p53 gene mutations in the conserved midregion (exons 5-9) are a common feature of oral cancers in the developed world, there is no information on this type of genetic lesion in betel quid-associated oral cancers. We examined 50 oral squamous cell carcinomas, 20 from Baltimore, MD and 30 from PNG, for mutations in exons 5-9 of the p53 gene. DNA extracted from frozen biopsies was amplified by polymerase chain reaction, the purified product was sequenced directly, and mutations were confirmed by repeating the entire procedure. Mutations were found in 3 of 30 tumors from PNG (10%), whereas 9 mutations were detected among the 20 tumors (45%) from Baltimore, MD. This difference in frequency is statistically significant (P < 0.01) by chi 2 analysis. Nuclear accumulation of p53 protein, determined by immunohistochemistry with the CM-1 antiserum, was observed in the PNG cases harboring a missense mutation of the p53 gene. In agreement with the low number of PNG cancers with mutations, only 17% of the cases from PNG were immunostain positive. To explore whether less conserved regions of the gene are preferential targets for alterations in this patient group, sequence analysis in tumors from PNG was extended to outlying regions of the gene (all of exons 4 and 10, and splice sites), but mutations in only two additional tumors were identified. The presence of human papillomavirus DNA in PNG cases was examined with a polymerase chain reaction-based procedure, and viral sequences (human papillomavirus strains 11/16) were detected in two tumors. Human papillomavirus-triggered degradation of the tumor suppressor protein is thus unlikely to be a typical pathway to p53 dysfunction in tumors from PNG.
全球75%的口腔癌发生在发展中国家。在东南亚等口腔癌高发地区，如巴布亚新几内亚（PNG），主要的地区特异性风险暴露因素是嚼槟榔。虽然已有研究表明，发达国家口腔癌的一个常见特征是保守的中间区域（外显子5 - 9）存在p53基因突变，但关于槟榔相关口腔癌中此类基因损伤的信息却未见报道。我们检测了50例口腔鳞状细胞癌，其中20例来自美国马里兰州巴尔的摩，30例来自巴布亚新几内亚，检测p53基因外显子5 - 9的突变情况。从冷冻活检组织中提取的DNA通过聚合酶链反应进行扩增，纯化产物直接测序，并通过重复整个过程来确认突变。在巴布亚新几内亚的30例肿瘤中有3例（10%）发现了突变，而在来自美国马里兰州巴尔的摩的20例肿瘤中有9例（45%）检测到突变。通过卡方分析，这种频率差异具有统计学意义（P < 0.01）。通过使用CM - 1抗血清进行免疫组织化学检测，在携带p53基因错义突变的巴布亚新几内亚病例中观察到p53蛋白的核内积聚。与巴布亚新几内亚突变癌症数量较少一致，来自巴布亚新几内亚的病例中只有17%免疫染色呈阳性。为了探究该基因较少保守的区域是否是该患者群体基因改变的优先靶点，对来自巴布亚新几内亚肿瘤的序列分析扩展到该基因的外围区域（所有外显子4和10以及剪接位点），但仅在另外两个肿瘤中鉴定出突变。采用基于聚合酶链反应的方法检测巴布亚新几内亚病例中人类乳头瘤病毒DNA的存在情况，在两个肿瘤中检测到病毒序列（人类乳头瘤病毒11/16株）。因此，在巴布亚新几内亚肿瘤中，人类乳头瘤病毒引发的肿瘤抑制蛋白降解不太可能是p53功能障碍的典型途径。
