GCS overexpression is associated with multidrug resistance of human HCT-8 colon cancer cells

The cell proliferation and cell toxicity were measured with Cell Counting Kit-8 (CCK-8). The mRNA levels of GCS and MDR1 were detected by semiquantitative reverse transcription-PCR amplification, the protein levels of GCS, caspase-3 and P-gp proteins were indicated by Western blotting. The apoptosis rates of cells were measured with flow cytometry.The relative mRNA levels of GCS in HCT-8, HCT-8/VCR, HCT-8/VCR- sh-mock and HCT-8/VCR-sh-GCS were 71.4 ± 1.1%, 95.1 ± 1.2%, 98.2 ± 1.5%, and 66.6 ± 2.1% respectively. The mRNA levels of MDR1 were respectively 61.3 ± 1.1%, 90.5 ± 1.4%, 97.6 ± 2.2% and 56.1 ± 1.2%. The IC50 of Cisplatin complexes were respectively 69.070 ± 0.253 μg/ml, 312.050 ± 1.46 μg/ml, 328.741 ± 5.648 μg/ml, 150.792 ± 0.967 μg/ml in HCT-8, HCT-8/VCR, HCT-8/VCR-sh-mock and HCT-8/VCR-sh-GCS. The protein levels of caspase-3 were 34.2 ± o.6%, 93.0 ± 0.7%, 109.09 ± 0.7%, 42.7 ± 1.3% respectively. The apoptosis rates of cells were 8.77 ± 0.14%, 12.75 ± 0.54%, 15.39 ± 0.41% and 8.49 ± 0.23% respectively.In conclusion, our research indicated that suppression of GCS restores the sensitivity of multidrug resistance colon cancer cells to drug treatment.Multidrug resistance (MDR) is one of the main impediments to the successful treatment of colon cancer [1]. Furthermore, colorectal tumors which obtain resistance to one drug are often resistant to several other drugs as well [2]. The underlying mechanisms are complicated [3]. One reason for MDR relates to P-glycoprotein (P-gp) and other transporters which are expressed in some cancer cells and could strengthen the efflux of diverse chemotherapeutic agents from cells [2]. Elevated levels of these MDR proteins, which belong to the ATP-binding cassette (ABC) transporter family, strengthen cellular efflux and reduce the effectiveness of anticancer drugs [4]. One method to measure P-glycoprotein efflux has been set up to o determine tumor response to chemotherapy [1]. To conquer drug resistance, inhibitors of MDR protein