PCR Analysis of the Absolute Number of Copies of Human Chromosome 18 Transcripts in the Liver and HepG2 Cells

Using reverse transcription in conjunction with the quantitative real-time PCR or digital droplet PCR, the transcriptome profiling of human chromosome 18 has been carried out in liver hepatocytes and hepatoblastoma cells (HepG2 cell line) in terms of the absolute number of each transcript per cell. The transcript abundance varied within the range of 0.006 to 9635 and 0.011 to 4819 copies per cell for the HepG2 cell line and hepatocytes, respectively. There was significant correlation between expression profiles of chromosome 18 genes in hepatocytes and HepG2 cells: the Spearman’s correlation coefficient was 0.81. The frequency distribution of transcripts by their abundance was bimodal for HepG2 cells and unimodal for liver hepatocytes. Bioinformatic analysis of the differential gene expression has shown that chromosome 18 genes, overexpressed in HepG2 cells compared to hepatocytes, are associated with cell division and cell adhesion processes. It is suggested that enhanced expression of these genes is related to proliferative activity of cultured HepG2 cells. The differences in transcriptome profiles should be taken into consideration when cultured HepG2 cells are used as a model of liver hepatocytes.