Hexahydrocurcumin enhances inhibitory effect of 5-fluorouracil on HT-29 human colon cancer cells

Figure 1 Chemical structures of curcumin (A) and hexahydrocurcumin (B).

Figure 2 Antiproliferative effect of hexahydrocurcumin and 5-fluorouracil on HT-29 human colon cancer cells. HT-29 cells were exposed to different concentrations of 5-fluorouracil (5-FU) (A) and hexahydrocurcumin (HHC) (B) for 24-48 h and then cell viability was measured by 5-diphenyltetrazolium bromide assay. 5-FU or HHC significantly decreased cell viability concentration-dependently. Data are expressed as mean ± SE. ^aP < 0.05 vs control (n = 3).

Figure 3 Combination effects of 5-fluorouracil and hexahydrocurcumin on proliferation of HT-29 colon cancer cells. The HT-29 cells were exposed to 5-fluorouracil (5-FU) (5 and 25 μmol/L), hexahydrocurcumin (HHC) (5 and 25 μmol/L) and their combination for 24 h (A) and 48 h (B) and then harvested for 5-diphenyltetrazolium bromide assay. Combination treatment of 5-FU and HHC significantly decreased cell viability compared to the 5-FU or HHC monotherapy. Data are expressed as mean ± SE. ^aP < 0.05 vs 5-FU or HHC monotherapy (n = 3).

Figure 4 Combination effects of hexahydrocurcumin and 5-fluorouracil on cyclooxygenase-2 mRNA expression in HT-29 colon cancer cells. The HT-29 cells were exposed to 5-fluorouracil (5-FU) (5 μmol/L), hexahydrocurcumin (HHC) (25 μmol/L) and their combination for 24 h. Cells from different experimental groups were subjected to semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). A: RT-PCR showed that the expression of cyclooxygenase (COX)-2 (305 bp) was significantly decreased in HHC or combination of HHC and 5-FU-treated group; B: The expression of COX-2 was determined by normalizing the band intensity of COX-2 with glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Values are expressed as percentage of control (mean ± SE), ^aP < 0.05 vs control; ^cP < 0.05 vs 5-FU or HHC monotherapy (n = 3).

Figure 5 Combination effects of hexahydrocurcumin and 5-fluorouracil on cyclooxygenase-2 protein expression in HT-29 colon cancer cells. A: Western blotting with polyclonal anti-cyclooxygenase (COX) 1 (70 kDa) and anti-COX2 (72 kDa), and anti-β actin (43 kDa) antibodies; B: Fold changes of proteins as represented below, each band was measured by Lab Image software. Combination treatment of 5-fluorouracil (5-FU) and hexahydrocurcumin (HHC) significantly decreased the expression of COX-2 protein with no effect on the expression of COX-1 protein. Values are expressed as percentage of control (mean ± SE), ^aP < 0.05 vs control; ^cP < 0.05 vs 5-FU or HHC monotherapy (n = 3).