House Michael G, Herman James G, Guo Ming Zhou, Hooker Craig M, Schulick Richard D, Lillemoe Keith D, Cameron John L, Hruban Ralph H, Maitra Anirban, Yeo Charles J
Departments of Surgery.
Ann Surg. 2003 Sep;238(3):423-31; discussion 431-2. doi: 10.1097/01.sla.0000086659.49569.9e.
Because histologic features can be unreliable in determining the malignant potential of pancreatic endocrine neoplasms (PENs), we characterized the methylation patterns of PENs to develop a molecular marker system useful for clinical prognosis.
Aberrant promoter methylation of tumor suppressor genes is associated with a loss of gene function that can afford selective growth advantages to neoplastic cells. Gene hypermethylation, coupled with sporadic genetic mutations, defines the heterogeneous biology of human neoplasms.
Forty-eight well-differentiated PENs were subjected to methylation-specific polymerase chain reaction to detect aberrant methylation associated with 11 candidate tumor suppressor genes (INK4a/p16, APC, O6-MGMT, hMLH1, p73, E-cadherin, RAR-beta, p14ARF, GST-pi, TIMP3, and RASSF1A). Methylation differences among PENs, subdivided according to tumor size, lymph node status, or liver metastasis, were analyzed, and the association of gene methylation with tumor recurrence and patient survival was evaluated.
Aberrant hypermethylation of any of the 11 tumor suppressor genes was detected in 87% of the PENs. In decreasing order of frequency, the 5 most commonly methylated genes were: RASSF1A (75%), INK4a/p16 (40%), O6-MGMT (40%), RAR-beta (25%), and hMLH1 (23%). In general, tumors larger than 5 cm and those associated with lymph node or hepatic metastases exhibited a higher frequency of methylation at each promoter site compared with PENs without malignant histologic features. The methylation of specific tumor suppressor genes was an independent predictor of early PEN recurrence and decreased 5-year survival following surgical resection. The accumulation of methylation of multiple tumor suppressor genes was associated with early tumor recurrence and reduced survival among a subpopulation of patients with lymph node-negative PENs.
Aberrant methylation of multiple tumor suppressor genes is associated with advanced tumor stage and identifies molecularly distinct PENs with identical histologic characteristics. The methylation status of specific tumor suppressor genes is predictive of PEN behavior.
鉴于组织学特征在判断胰腺内分泌肿瘤（PENs）的恶性潜能方面可能不可靠，我们对PENs的甲基化模式进行了特征分析，以开发一种有助于临床预后的分子标记系统。
肿瘤抑制基因的异常启动子甲基化与基因功能丧失有关，这可为肿瘤细胞提供选择性生长优势。基因高甲基化与散发性基因突变共同决定了人类肿瘤的异质性生物学特性。
对48例高分化PENs进行甲基化特异性聚合酶链反应，以检测与11个候选肿瘤抑制基因（INK4a/p16、APC、O6-MGMT、hMLH1、p73、E-钙黏蛋白、RAR-β、p14ARF、GST-π、TIMP3和RASSF1A）相关的异常甲基化。分析根据肿瘤大小、淋巴结状态或肝转移进行细分的PENs之间的甲基化差异，并评估基因甲基化与肿瘤复发和患者生存的相关性。
在87%的PENs中检测到11个肿瘤抑制基因中的任何一个存在异常高甲基化。按频率递减顺序，5个最常甲基化的基因依次为：RASSF1A（75%）、INK4a/p16（40%）、O6-MGMT（40%）、RAR-β（25%）和hMLH1（23%）。一般来说，与无恶性组织学特征的PENs相比，直径大于5 cm的肿瘤以及伴有淋巴结或肝转移的肿瘤在每个启动子位点的甲基化频率更高。特定肿瘤抑制基因的甲基化是PEN早期复发的独立预测指标，且与手术切除后5年生存率降低相关。多个肿瘤抑制基因甲基化的累积与淋巴结阴性PENs亚组患者的早期肿瘤复发和生存率降低相关。
多个肿瘤抑制基因的异常甲基化与肿瘤晚期相关，并可识别出具有相同组织学特征但分子特征不同的PENs。特定肿瘤抑制基因的甲基化状态可预测PEN的行为。
