Hexahydrocurcumin enhances inhibitory effect of 5-fluorouracil on HT-29 human colon cancer cells.
OBJECTIVE
To investigate the ability of hexahydrocurcumin (HHC) to enhance 5-fluorouracil (5-FU) in inhibiting the growth of HT-29 cells by focusing on cyclooxygenase (COX)-2 expression.


METHODS
Antiproliferative effects of HHC and 5-FU, alone and in combination, on growth of HT-29 human colon cancer cells were assessed using 5-diphenyltetrazolium bromide (MTT) reduction assay. In combination treatment, low doses of 5-FU were used combined with various concentrations of HHC to minimize the toxicity and side effects of 5-FU. The therapeutic effects of these drugs on down-regulation of COX-2 mRNA and protein expression were examined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting analysis.


RESULTS
MTT reduction assay indicated that HHC alone markedly decreased the viability of HT-29 human colon cancer cells compared to control. Semi-quantitative RT-PCR analysis indicated that HHC is a selective COX-2 inhibitor. This finding was supported by the observation that HHC significantly down-regulates COX-2 mRNA expression compared to the control (control: 100.05% ± 0.03% vs HHC: 61.01% ± 0.35%, P < 0.05) but does not alter COX-1 mRNA. In combined treatment, addition of HHC to a low dose of 5-FU exerts a synergistic effect against the growth of HT-29 cells by markedly reducing cell viability to a greater degree than monotherapy. Semi-quantitative RT-PCR indicated that 5-FU at the concentration of 5 μmol/L in combination with HHC at the concentration of 25 μmol/L significantly down-regulates COX-2 mRNA expression when compared with values in cells treated with 5-FU or HHC alone (HHC + 5-FU: 31.93% ± 5.69%, 5-FU: 100.66% ± 4.52% vs HHC: 61.01% ± 0.35%, P < 0.05).


CONCLUSIONS
HHC together with 5-FU exerts a synergistic effect and may prove chemotherapeutically useful in treating human colon cancer.
Department of Anatomy, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand.
Khanitta
K
Srimuangwong
Chainarong
C
Tocharus
Pornphrom
P
Yoysungnoen Chintana
Apichart
A
Suksamrarn
Jiraporn
J
Tocharus
D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D003474:Curcumin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D051546:Cyclooxygenase 2 / Q000032:analysis / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects*; D004357:Drug Synergism; D005472:Fluorouracil / Q000494:pharmacology; D019073:HT29 Cells; D006801:Humans; D012333:RNA, Messenger / Q000032:analysis / Q000187:drug effects
D000970:Antineoplastic Agents; D012333:RNA, Messenger; C569902:hexahydrocurcumin; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D003474:Curcumin; D005472:Fluorouracil