Global Analysis of Gene Expression Pattern in Membrane-transport Inducing Cells

Objectives: The differential expressions of genes between Hoechst^low cells and Hoechst^high cells were analyzed to elucidate the properties of Hoechst^low cells in oral cancer cell lines.
Methods: The human oral cancer cell line SCC-4 was used. Hoechst^low cells were separated with Hoechst 33342 and reserpine by FACS. A GeneChip^® Array (Affymetrix) was used to analyze the expressions of genes in Hoechst^low cells. DAVID functional annotation bioinformatics microarray analysis was carried out on GO enrichment analysis and KEGG pathway enrichment analysis for differentially expressed probes on DAVID v6.7 online tool (p < 0.05). KEGG Mapper Search&Color Pathway analysis was also performed on the KEGG online tool.
Results: Hoechst^low cells accounted for around 1.5% of cells. Among the entire 26,879 distinct probes, microarray analysis in Hoechst^low cells versus Hoechst^high cells revealed that 4,246 probes and 4,474 probes were up-regulated and down-regulated by more than 10%, respectively. As the results of these enrichment analyses, the associated terms significantly detected immune and inflammatory responses, positive regulation of NF-kappa B transcription factor activity, and pattern recognition receptor signaling pathway among the up-regulated probes. The terms related to DNA replication, DNA metabolic processes, and DNA repair were the most highly enriched in the down-regulated probes. The ABC transporters ABCG2/BCRP1 and ABCC2/MRP2, which drain anti-cancer drugs, were also up-regulated. The nucleoside transporter SLC29A1 /ENT1, which uptakes drugs into cells, was down-regulated.
Conclusions: Hoechst^low cells with a strong ability to excrete Hoechst existed in the SCC-4 cell line. Hoechst^low cells in the SCC-4 cell line were characterized to have gene-expression pattern of self-renewal, quiescence at G0/1 phase. These cells might have the possibility possessing the property of the resistance to some anti-cancer drugs, suggesting that cancer stem-like cells exist in SCC-4.