Sugg S L, Ezzat S, Rosen I B, Freeman J L, Asa S L
Department of Pathology and Laboratory Medicine, Mount Sinai Hospital and the University of Toronto, Ontario, Canada.
J Clin Endocrinol Metab. 1998 Nov;83(11):4116-22. doi: 10.1210/jcem.83.11.5271.
Rearrangements involving the RET protooncogene have been implicated in the development of papillary thyroid carcinoma (PC). Transgenic mice, expressing thyroid-targeted RET/PTC-1, develop PC; but the clinical significance of this oncogene remains uncertain. We examined the expression of RET/PTC-1, -2, and -3 in human thyroid microcarcinomas and clinically evident PC to determine its role in early stage vs. developed PC and to examine the diversity of RET/PTC in multifocal disease. RNA was extracted from paraffin-embedded microcarcinomas and clinically evident PCs; the results obtained from paraffin-embedded tissue were confirmed on RNA from corresponding snap-frozen tissue of clinically evident PCs. RT and PCR was performed using primers for RET/PTC-1, -2, and -3; PGK-1 (the housekeeping gene) analysis was used to ensure integrity of the RNA and efficiency of the RT reaction. PCR products were resolved by gel electrophoresis, and Southern hybridization was performed with RET/PTC-1, -2, and -3 probes. A polyclonal antibody to the carboxyterminus of RET was used for immunohistochemistry on paraffin sections. Thirty-nine occult papillary thyroid microcarcinomas from 21 patients were analyzed. Of the 30 tumors (77%) positive for RET/PTC rearrangements, 12 were positive for RET/PTC-1, 3 for RET/ PTC-2, 6 for RET/PTC-3, and 9 for multiple RET/PTC oncogenes. In clinically evident tumors, 47% had RET/PTC rearrangements. Immunohistochemistry demonstrated close correlation with RT-PCR-derived findings. RET/PTC expression is highly prevalent in microcarcinoma and occurs more frequently than in clinically evident PC (P < 0.005). Multifocal disease, identified in 17 of the 21 patients, exhibited identical RET/PTC rearrangements within multiple tumors in only 2 patients; the other 15 patients had diverse rearrangements in individual tumors. Our results indicate that RET/PTC oncogene rearrangements may play a role in early-stage papillary thyroid carcinogenesis, but they seem to be less important in determining progression to clinically-evident disease. In multifocal disease, the diversity of RET/PTC profiles, in the majority of cases, suggests that individual tumors arise independently in a background of genetic or environmental susceptibility.
涉及RET原癌基因的重排与甲状腺乳头状癌（PC）的发生发展有关。表达甲状腺靶向性RET/PTC-1的转基因小鼠会发生PC，但这种癌基因的临床意义仍不明确。我们检测了RET/PTC-1、-2和-3在人甲状腺微小癌及临床显性PC中的表达，以确定其在早期与进展期PC中的作用，并研究多灶性疾病中RET/PTC的多样性。从石蜡包埋的微小癌及临床显性PC中提取RNA；从临床显性PC相应的速冻组织RNA中证实了从石蜡包埋组织获得的结果。使用针对RET/PTC-1、-2和-3的引物进行逆转录和聚合酶链反应（RT-PCR）；采用磷酸甘油酸激酶-1（PGK-1，管家基因）分析来确保RNA完整性及RT反应效率。PCR产物通过凝胶电泳分离，并用RET/PTC-1、-2和-3探针进行Southern杂交。用针对RET羧基末端的多克隆抗体对石蜡切片进行免疫组织化学检测。分析了来自21例患者的39个隐匿性甲状腺乳头状微小癌。在30个（77%）RET/PTC重排阳性的肿瘤中，12个RET/PTC-1阳性，3个RET/PTC-2阳性，6个RET/PTC-3阳性，9个存在多种RET/PTC癌基因阳性。在临床显性肿瘤中，47%存在RET/PTC重排。免疫组织化学结果与RT-PCR结果密切相关。RET/PTC表达在微小癌中高度普遍，且比临床显性PC中更常见（P<0.005）。在21例患者中的17例发现多灶性疾病，仅2例患者的多个肿瘤中出现相同的RET/PTC重排；其他15例患者的各个肿瘤存在不同的重排。我们结果表明，RET/PTC癌基因重排在早期甲状腺乳头状癌发生中可能起作用，但在决定进展为临床显性疾病方面似乎不太重要。在多灶性疾病中，大多数情况下RET/PTC谱的多样性表明，在遗传或环境易感性背景下，各个肿瘤是独立发生的。
