Intracellular Copy Numbers Quantification of Mirnas Reveals the Expression Characteristics in Different Types of Cancer at Single-Cell Level

Abstract

MicroRNAs (miRNAs) are a class of endogenous non-coding single-stranded RNAs, which play a very important regulatory role in life activities. Abnormal expression levels of miRNAs in cells are associated with various diseases, especially human cancer. Nevertheless, the number of copies of intracellular miRNAs varies from cell to cell, and the number of copies of miRNA molecules in healthy cells is very low. Accurate determination of the number of copies of various miRNA molecules in a single cell is still a great challenge. In order to support cell-to-cell heterogeneity and reveal the expression characteristics of different miRNAs in different types of cancers at the single-cell level, we developed an ultrasensitive single-cell analysis method based on a microchip electrophoresis platform for simultaneous quantification of the number of copies of multiple miRNAs in a single cell. Using miRNA-21 and miRNA-141 as the analytical models of miRNAs, we performed an analysis of 600 randomly acquired human prostate cells (RWPE-1), human prostate cancer cells (22RV1), human breast cancer cells (MCF-7), human normal mammary epithelial cells (MCF-10A), human liver cancer cells (HepG2), and human hepatocytes cells (HL-7702) at the single cell level. We obtained the distribution of absolute copy numbers of miRNA-21 and miRNA-141 in six types of cells. We found that there was absence of exactly the same copy numbers of miRNA-21 and miRNA-141 in all analyzed individual cells. The results of this analysis can help us more accurately understand the relationship between different miRNAs and different types of cancer at the single cell level.