Nathakan Klinhom-On1, Wunchana Seubwai2, Kanlayanee Sawanyawisuth3, Sumalee Obchoei4, Panupong Mahalapbutr1, Sopit Wongkham5. 1. Department of Biochemistry, Center for Translational Medicine, Faculty of Medicine, Khon Kaen University, 40002, Thailand. 2. Department of Forensic Medicine, Faculty of Medicine, Khon Kaen University, 40002, Thailand; Cholangiocarcinoma Research Institute, Khon Kaen University, 40002, Thailand. 3. Department of Biochemistry, Center for Translational Medicine, Faculty of Medicine, Khon Kaen University, 40002, Thailand; Cholangiocarcinoma Research Institute, Khon Kaen University, 40002, Thailand. 4. Department of Biochemistry, Faculty of Science, Prince of Songkla University, 90110, Thailand. 5. Department of Biochemistry, Center for Translational Medicine, Faculty of Medicine, Khon Kaen University, 40002, Thailand; Cholangiocarcinoma Research Institute, Khon Kaen University, 40002, Thailand. Electronic address: sopit@kku.ac.th.
Abstract
AIMS: 5-Fluorouracil (5-FU), a thymidylate synthase (TS) inhibitor, has been used as the first-line chemotherapeutic drug for cholangiocarcinoma (CCA). The side effects and drug resistance have developed the limits of the clinical application of 5-FU in CCA treatment. Upregulation of Forkhead box M1 (FOXM1) and TS were shown to play a significant role in 5-FU resistance. In this study, the effect of Siomycin A (SioA), a FOXM1 inhibitor, on enhancing 5-FU cytotoxicity and reversing 5-FU resistance in CCA cell lines were demonstrated. MAIN METHODS: Human CCA cell lines, KKU-100 and KKU-213A were used. Cell viability was determined using MTT assay. Expression of FOXM1 and TS proteins were determined using Western blotting. FOXM1 mRNA expression was quantitated using real-time PCR. The combination and dose reduction (DRI) were analyzed according to the Chou and Talalay method. KEY FINDING: Single drug treatment of 5-FU and SioA effectively inhibited CCA cell growth in dose and time dependent fashions. The two CCA cell lines had different responses to 5-FU but exhibited similar sensitivity to SioA. FOXM1 and TS expression were increased in the 5-FU treated cells but were suppressed in the SioA treated cells. A direct binding of SioA, to TS and 5,10-methylene-tetrahydrofolate as an inactive ternary complex was simulated. The combined treatment of 5-FU with SioA showed a synergistic effect with a high DRI and restored 5-FU sensitivity in the 5-FU resistant cells. SIGNIFICANCE: Targeting FOXM1 using SioA in combination with 5-FU might be a strategy to overcome the 5-FU resistance in CCA.
AIMS: 5-Fluorouracil (5-FU), a thymidylate synthase (TS) inhibitor, has been used as the first-line chemotherapeutic drug for cholangiocarcinoma (CCA). The side effects and drug resistance have developed the limits of the clinical application of 5-FU in CCA treatment. Upregulation of Forkhead box M1 (FOXM1) and TS were shown to play a significant role in 5-FU resistance. In this study, the effect of Siomycin A (SioA), a FOXM1 inhibitor, on enhancing 5-FU cytotoxicity and reversing 5-FU resistance in CCA cell lines were demonstrated. MAIN METHODS: Human CCA cell lines, KKU-100 and KKU-213A were used. Cell viability was determined using MTT assay. Expression of FOXM1 and TS proteins were determined using Western blotting. FOXM1 mRNA expression was quantitated using real-time PCR. The combination and dose reduction (DRI) were analyzed according to the Chou and Talalay method. KEY FINDING: Single drug treatment of 5-FU and SioA effectively inhibited CCA cell growth in dose and time dependent fashions. The two CCA cell lines had different responses to 5-FU but exhibited similar sensitivity to SioA. FOXM1 and TS expression were increased in the 5-FU treated cells but were suppressed in the SioA treated cells. A direct binding of SioA, to TS and 5,10-methylene-tetrahydrofolate as an inactive ternary complex was simulated. The combined treatment of 5-FU with SioA showed a synergistic effect with a high DRI and restored 5-FU sensitivity in the 5-FU resistant cells. SIGNIFICANCE: Targeting FOXM1 using SioA in combination with 5-FU might be a strategy to overcome the 5-FU resistance in CCA.