METHYLATION PROFILING AND RISK OF COLORECTAL CANCER

描述（由申请人提供）：结直肠癌（CRC）是美国最常见的胃肠道恶性肿瘤，非裔美国人（AA）的CRC发病率是白人的1.5倍。分子医学领域的最新进展导致微卫星不稳定性（MSI）、杂合性缺失（洛）和甲基化特异性PCR技术的使用，这些技术允许检测结肠粘膜细胞的染色体和基因改变。标记物的使用有助于预测疾病进展和预后。表观遗传变化是导致CRC的遗传改变序列的早期。随后的变化通常包括部分或整个染色体的丢失。肿瘤中的MSI在某些基因的编码区内的微卫星中积累突变。这些数据表明，MSI，洛和甲基化谱可能会增加一个重要的信息层的恶性肿瘤的分子表型的预后目的。我们假设MSI-H（DNA修复基因hMHL 1、p16的基因沉默）和APC、p53的洛杂合性缺失（LOH）以及结直肠癌（DCC）中的缺失（已知它们调节结肠粘膜中的细胞增殖）可能会改变肿瘤转化途径中的染色体行为。将使用五个微卫星位点测量MSI，并且将通过粘膜活检中的免疫组织化学来确定p53、APC和DCC蛋白的水平。通过检测250例AA患者的甲基化和突变/缺失谱，我们明确：（1）阐明p16和hMLH 1基因甲基化在AA患者的正常和癌组织中的肿瘤转化途径中的作用，（二）为了确定结肠粘膜中MSI的诱导，其可以反映在肿瘤转化和细胞增殖的生物标志物的表达中，AA患者有结肠腺瘤病史、无腺瘤病史和有结直肠癌切除史。这些实验可以帮助鉴定处于发展腺瘤和/或CRC风险中的人，（3）确定CRC患者的正常和癌组织中的APC、p53和DCC基因中是否发生洛或等位基因缺失，并鉴定处于发展另外的腺瘤和/或CRC风险中的人，（4）分析已用氟尿嘧啶治疗的患有III期和高危II期CRC的AA患者的肿瘤组织，以及MSI和洛标记物预测存活和/或对治疗的反应的能力。这些研究将有助于检测和分析AA中CRC途径的遗传变化。

DESCRIPTION (provided by applicant): Colorectal carcinoma (CRC) is the most common gastrointestinal malignancy in the U.S and the rate of CRC is 1.5 times higher in African Americans (AA) than Caucasians. Recent advances in the field of molecular medicine has led to the use of microsatellite instability (MSI), loss of heterozygosity (LOH), and methylation specific PCR techniques which permit detection of chromosomal and gene alterations of colonic mucosal cells. The use of markers has helped to predict disease progression and prognosis. Epigenetic changes are early in the sequence of genetic alterations leading to CRC. Subsequent changes often include the loss of portions or whole chromosomes. MSI in neoplasms accumulates mutations in microsatellites within the coding region of certain genes. These data suggest that MSI, LOH and methylation profiling may add an important layer of information in the molecular phenotyping of malignances for prognostic purposes. We postulate that MSI-H, gene silencing for DNA repair gene hMHL1, p16 and LOH of APC, p53 and deleted in colorectal cancer (DCC), which are known to modulate cellular proliferation in colonic mucosa, may alter chromosome behavior in the pathway of neoplastic transformation. MSI will be measured using five microsatellite loci, and the level of p53, APC and DCC protein will be determined by immunohistochemistry in mucosal biopsies. By determining the methylation and mutation/deletion profiles of 250 cases, we determine specifically (1) to elucidate the effect of p16 and hMLH1 gene methylation in the pathway of neoplastic transformation in normal and cancer tissue of AA patients with CRC, (2) to determine the induction of MSI in colonic mucosa that may be reflected in the expression of biomarkers of neoplastic transformation and cellular proliferation from AA patients history of colonic adenomas, those with no history of adenomas, and those with a history of resected CRC. These experiments may assist in identifying persons at risk of developing adenomas and/or CRC, (3) to determine whether LOH or allelic loss occurs in APC, p53, and DCC genes in normal and cancer tissue of CRC patients and identify persons at risk of developing additional adenomas and/or CRC, (4) to analyze tumor tissue in AA patients with stage III and high-risk stage II CRC who had been treated with fluorouracil, and the ability of MSI and LOH markers to predict survival and/or response to treatment. These studies will help in the detection and profiling of genetic changes in the pathway of CRC in AA.