Cell Journal (Jan 2012)
Down-regulation of miR-302b, an ESC-specific microRNA, in Gastric Adenocarcinoma
Abstract
Objective: microRNAs (miRNAs) are a new class of non-coding RNAs involved in regulatingvarious biological processes including proliferation, differentiation, and apoptosis,among others. Alterations in miRNA expression are reported in several human cancers,which suggests their potential roles in tumor initiation and progression. Members of themiR-302 cluster are highly expressed in embryonic stem cells (ESC), where they regulatecell self-renewal and pluripotency. Based on the cancer stem cell (CSC) hypothesis,mis-expression of such genes might contribute to tumorigenicity. This study aims to find apotential link between the expression level of human/homo sapiens miR-302b (has-miR-302b) and tumor/grade state of gastric tissues.Materials and Methods: A matched based case-control study was conducted that includedtumor and matched marginal non-tumor surgical specimens from 34 patients diagnosedwith gastric adenocarcinoma. Randomly selected samples were obtained fromthe Iran National Tumor Bank. cDNA synthesis was carried out on total RNA, by usingthe miRCURY LNA™ Universal RT microRNA PCR Kit. Real-time reverse transcriptionpolymerasechain reaction (RT-PCR) assays were performed with specific LNA™ primersand SYBR Green master mix. The human embryonic carcinoma cell line, NTERA2 (NT2)and a human gastric adenocarcinoma cell line, AGS, were used to optimize the PCR reactions.A comparative evaluation of miR-302b expression in tumor and non-tumor gastricsamples was performed by either paired t test or Wilcoxon non-parametric test. The abilityof miR-302b to discriminate tumor from non-tumor gastric samples was evaluated usingthe area under the receiver operating characteristic (ROC) curve.Results: According to our data, miR-302b expression (normalized to that of the U6 snRNAhousekeeping gene) in the pluripotent cell line NT2 was more than 500 times greater thanthat of the AGS cell line. The level of expression was even lower in tumor and non-tumorgastric tissue samples. The data further revealed a down-regulation of miR-302b in gastrictumor samples (p=0.001), particularly in high-grade adenocarcinoma (p=0.009). However,ROC analysis data demonstrated a low sensitivity and specificity of miR-302b expressionto discriminate between the tumor and non-tumor state of the samples (AUC=0.63).Conclusion: Despite the upregulation of some hESC-specific genes in tumors, our datarevealed a down-regulation of miR-302b in high-grade tumors. This data suggested a potentialtumor-suppressor role for miR-302b in tumorigenesis of gastric tissue.
