Curcumin Reverses 5-Fluorouracil Resistance by Promoting Human Colon Cancer HCT-8/5-FU Cell Apoptosis and Down-regulating Heat Shock Protein 27 and P-Glycoprotein

ObjectiveTo investigate the potential mechanisms that curcumin reverses 5-fluorouracil (5-FU) multidrug resistance (MDR).MethodsCell growth and the inhibitory rate of curcumin (2-25 g/mL) and/or 5-FU (0.05-1000 g/mL) on human colon cancer HCT-8 and HCT-8/5-FU (5-FU-resistant cell line) were determined using cell counting kit-8 (CCK-8) assay. Apoptosis and cell cycle after 5-FU and/or curcumin treatment were detected by flow cytometry (FCM) and transmission electron microscopy (TEM). The expression of the multidrug resistance related factors p-glycoprotein (P-gp) and heat shock protein 27 (HSP-27) genes and proteins were analyzed by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting (WB), respectively.ResultsThe inhibitory rate of curcumin or 5-FU on HCT-8 and HCT-8/5-FU cells proliferation at exponential phase were in a dosedependent manner, HCT-8 cell line was more sensitive to curcumin or 5-FU when compared the inhibitory rate of HCT-8/5-FU. The 50% inhibitory concentration (IC50) of combination 5-FU and curcumin (4.0 g/mL) in HCT-8/5-FU was calculated as 179.26 g/mL, with reversal fold of 1.85. Another IC50 of combination 5-FU and curcumin (5.5 g/mL) in HCT-8/5-FU was calculated as 89.25 g/mL, with reversal fold of 3.71. Synergistic effect of 5-FU and curcumin on HCT-8 and HCT-8/5-FU cells were found. The cell cycle analysis performed by FCM showed that HCT-8 and HCT-8/5-FU cells mostly accumulated at G(0)/G(1) phase, which suggested a synergistic effect of curcumin and 5-FU to induce apoptosis. FCM analysis found that the percentage of apoptosis of cells treated with curcumin, 5-FU and their combination were significantly increased compared to the control group (P<0.05), and the percentage of apoptosis of the combination groups were slightly higher than other groups (P<0.05). The mRNA levels of P-gp (0.280.02) and HSP-27 (0.28 +/- 0.09) in HCT-8/5-FU cells treated with combination drugs were lower than cells treated with 5-FU alone (P-gp, 0.48 +/- 0.07, P=0.009; HSP-27, 0.57 +/- 0.10, P=0.007). The protein levels of P-gp (0.25 +/- 0.06) and HSP-27 (0.09 +/- 0.02) in HCT-8/5-FU cells treated with combination drugs were decreased when compared to 5-FU alone (P-gp, 0.46 +/- 0.02, P=0.005; HSP-27, 0.43 +/- 0.01, P=0.000).ConclusionsCurcumin can inhibit the proliferation of human colon cancer cells. Curcumin has the ability of reversal effects on the multidrug resistance of human colon cancer cells lines HCT-8/5-FU. Down-regulation of P-gp and HSP-27 may be the mechanism of curcumin reversing the drug resistance of HCT-8/5-FU to 5-FU.