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Combined analysis of KRAS and PIK3CA mutations, MET and PTEN expression in primary tumors and corresponding metastases in colorectal cancer.

大肠癌原发灶及其对应转移灶中KRAS基因和PIK3CA基因突变、MET和PTEN表达的综合分析

Voutsina A,Tzardi M,Kalikaki A,Zafeiriou Z,Papadimitraki E,Papadakis M,Mavroudis D,Georgoulias V

Abstract

Metastasis is the main cause of mortality in patients with colorectal cancer. However, most of the targeted therapies and predictive molecular biomarkers were developed based mainly on primary tumors. The current study was conducted to determine the degree of discordance between potential predictive and/or prognostic molecular markers in primary colorectal tumors and corresponding metastases, as this could have an impact on the efficacy of targeted therapies in the advanced colorectal cancer. KRAS, PIK3CA and BRAF mutations were determined by Sanger sequencing and mutant-enriched polymerase chain reaction (PCR) assays in 83 paired samples, MET gene copy number by quantitative PCR in 59, MET expression by immunohistochemistry in 73 and nuclear and cytoplasmic expression of PTEN by immunohistochemistry in 78 and 71 pairs, respectively. A certain degree of discordance between primary tumors and corresponding metastases was demonstrated for all examined biomarkers except BRAF mutations. PIK3CA exon 9 mutations in primary tumors and loss of PTEN nuclear expression in metastases correlated with KRAS mutations. KRAS wild-type status in primary tumors was associated with loss of PTEN cytoplasmic expression and high gene copy number of MET. Survival and clinical data were available for 68 patients. The multiple regression analysis revealed that the right-sided tumor localization and overexpression of MET were associated with shorter overall survival.

摘要

转移是大肠癌患者死亡的主要原因。然而,大多数靶向治疗和可预测的分子生物标记物主要基于原发肿瘤。本研究是为了确定原发大肠癌和相应转移灶中潜在预测和/或预后分子标志物之间的不一致程度,因为这可能对晚期结直肠癌的靶向治疗的疗效产生影响。应用Sanger测序和突变富集聚合酶链反应(PCR)检测83例配对样本中的KRAS、PIK3CA及BRAF突变,定量PCR检测59例样本中的MET拷贝数,免疫组化检测73例样本中的MET蛋白表达,78例和71例配对样本中应用免疫组化检测PTEN在细胞核和细胞质中的表达。
除BRAF突变外,其他检测的所有生物标志物在原发和对应的转移肿瘤中都有一定程度的不同。原发灶中PIK3CA第9外显子的突变、转移癌中PTEN核表达的缺失与KRAS突变相关。原发灶中KRAS野生型与PTEN胞质表达缺失及MET基因拷贝数高相关。68名患者有生存和临床数据。
多元回归分析表明,肿瘤位于右侧及MET过表达与较短的生存期相关。

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