Abstract:

Objective To isolate side population（SP）cells and non-SP cells from the MG-63 human osteosarcoma cell line and investigate the mechanism behind SP cell resistance to chemotherapy. Methods MG-63 SP cells were isolated by flow cytometry using the blue fluorescent dye Hoechst 33342．Resistance of SP and non-SP cells to Cisplatin （DDP） were analyzed using the Cell Counting Kit-8，and 50% inhibitory concentration （IC₅₀） was calculated for both subpopulations. Expression of MRP，XRCC1，MGMT and ABCG2 transcripts was assayed by RT-PCR in SP and non-SP cells. Results SP cells accounted for （1.45±0.23）% of MG-63 cells at a density of 9 × 10⁵/ml after staining with 5 μg/ml Hoechst 33342. DDP showed an IC₅₀ of 11.608 g/mL in SP cells，significantly higher than the value in non-SP cells（P<0.05）. Transcript levels were significantly higher in SP cells than in non-SP cells for MRP （1.58-fold higher），XRCC1 （1.61-fold），MGMT （2.36-fold） and ABCG2 （3.14-fold） （P<0.05）． Conclusion MG-63 human osteosarcoma cells contain SP cells， which show higher resistance to DDP than non-SP cells. Up-regulation of MRP，XRCC1，MGMT and ABCG2 in SP cells may play a role in this drug resistance.

Key words: Osteosarcoma neoplasm, Side population cell, Cancer stem cell, Drug resistance