Role of ABCG2 gene in proliferation and invasion of colorectal cancer stem cells

Sun Feng

doi:10.3969/j.issn.2095-4344.0503

Abstract：BACKGROUND: ABCG2 transporter can mediate multidrug resistance. ABCG2 overexpression can enhance the tolerance of stem cells to chemotherapeutic drugs. However, the mechanism of ABCG2 gene in the proliferation and invasion of colorectal cancer stem cells has not been confirmed. OBJECTIVE: To investigate the role of ABCG2 gene in the proliferation and invasion of colorectal cancer stem cells. METHODS: Colorectal cancer cell lines HCT116 were routinely isolated and cultured, and were randomly divided into four groups. CD133 positive cells were isolated by immunomagnetic beads method, and were transfected with ABCG2-siRNA and ABCG2 overexpression plasmids to construct colorectal cancer stem cell models with ABCG2 low expression and overexpression, and were set as low expression group and overexpression groups, respectively. The remaining HCT116 cells were set as normal and empty plasmid transfected control groups. The proliferation and invasion of colorectal cancer stem cells in different models were determined by MTT assay and Transwell assay, respectively. Expressions of matrix metalloproteinase 9 (MMP-9) mRNA and protein were detected by enzyme linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), respectively. RESULTS AND CONCLUSION: (1) Flow cytometry results showed that: CD133 positive cells in colorectal cancer cell line HCT116 accounted for 2.4%, while increased to 94.51% of the cell line after being sorted by immunomagnetic beads, suggesting that isolated and cultured cells were colorectal cancer stem cells. (2) MTT assy showed no significant difference between the four groups of cells prior to the cell transfection (P > 0.05). However, MTT value in the low expression group was significantly lower than that in the overexpression group after cell transfection (P < 0.05). (3) Results from the Transwell assay showed that the cells in the low expression groups did not have the ability of migration; on the contrary, in the overexpression group, the number of cells crossing the basement membrane was relatively increased and the ability of cell migration and invasion was enhanced significantly (P < 0.05). (4) The MMP-9 protein level was lower in the low expression group than in the overexpression group (P < 0.05). Similar results were yielded in the PCR detection. To conclude, down-regulation of ABCG2 protein expression can inhibit colorectal cancer stem cell proliferation and invasion. ABCG2 gene can change the viability of colorectal cancer stem cells by regulating the MMP-9 expression.