Hanson Jeffrey A, Gillespie John W, Grover Amelia, Tangrea Michael A, Chuaqui Rodrigo F, Emmert-Buck Michael R, Tangrea Joseph A, Libutti Stephen K, Linehan W Marston, Woodson Karen G
Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
J Natl Cancer Inst. 2006 Feb 15;98(4):255-61. doi: 10.1093/jnci/djj051.
Gene expression can be silenced through the methylation of specific sites in the promoter region. This mechanism of gene silencing has an important role in the carcinogenesis of prostate and other cancers. Although tumor-associated stromal cells also exhibit changes in gene expression, promoter methylation has not been described in these cells.
Tumor epithelia, tumor-associated stroma and normal epithelia, and stroma adjacent to tumor tissues were isolated from whole-mount prostatectomy specimens (two per patient) of patients (n = 5) with localized prostate cancer and from normal epithelia and stroma from benign prostate hyperplasia specimens (two per patient) from men (n = 5) without prostate cancer by using laser capture microdissection or expression microdissection. The methylation status of three genes important in prostate carcinogenesis, GSTP1, RARbeta2, and CD44, were evaluated using quantitative methylation-sensitive polymerase chain reaction.
GSTP1 and RARbeta2 were methylated in the tumor epithelium of all five prostate cancer patients and in the tumor-associated stroma in four of the five patients. CD44 was methylated in the tumor epithelium from four of the five patients but not in the tumor stroma. GSTP1 and RARbeta2 were methylated in normal epithelium of two and four patients, respectively, and in normal stroma of one and two patients, respectively, that were isolated from regions adjacent to the tumors and may have resulted from a tumor-field effect; CD44 methylation was not observed in normal epithelium or stroma. In contrast, normal epithelia and stroma from benign prostate hyperplasia specimens showed no promoter methylation in GSTP1, RARbeta2, or CD44.
The observation of promoter methylation in the non-neoplastic cells of the prostate tumor microenvironment may advance our understanding of prostate cancer development and progression and lead to new diagnostic and prognostic markers and therapeutic targets.
基因表达可通过启动子区域特定位点的甲基化而沉默。这种基因沉默机制在前列腺癌和其他癌症的致癌过程中发挥重要作用。尽管肿瘤相关基质细胞也表现出基因表达的变化，但尚未见这些细胞中启动子甲基化的相关报道。
通过激光捕获显微切割或表达显微切割技术，从5例局限性前列腺癌患者的全前列腺切除标本（每位患者2份）中分离肿瘤上皮、肿瘤相关基质以及正常上皮和肿瘤组织旁的基质，同时从5例无前列腺癌男性的良性前列腺增生标本（每位患者2份）中分离正常上皮和基质。采用定量甲基化敏感聚合酶链反应评估前列腺癌发生过程中3个重要基因GSTP1、RARβ2和CD44的甲基化状态。
在所有5例前列腺癌患者的肿瘤上皮以及5例患者中的4例肿瘤相关基质中，GSTP1和RARβ2发生甲基化。5例患者中的4例肿瘤上皮中CD44发生甲基化，但肿瘤基质中未发生甲基化。分别在2例和4例患者的肿瘤旁正常上皮中，以及1例和2例患者的肿瘤旁正常基质中检测到GSTP1和RARβ2甲基化，这可能是肿瘤场效应所致；正常上皮或基质中未观察到CD44甲基化。相比之下，良性前列腺增生标本中的正常上皮和基质在GSTP1、RARβ2或CD44中未显示启动子甲基化。
前列腺肿瘤微环境中非肿瘤细胞中启动子甲基化的观察结果可能会增进我们对前列腺癌发生发展的理解，并导致新的诊断和预后标志物以及治疗靶点的出现。
