Abstract: 【Abstract】 Objective To evaluate the efficacy and safety of chidamide combined with curcumin in the treatment of cutaneous T-cell lymphoma （CTCL）. Methods Human CTCL cell lines HH and HuT-78 were cultured in vitro and treated with gradient concentrations of chidamide （0.4, 0.8, 1.6, 3.2, and 6.4 μmol/L） and curcumin （1.25, 2.5, 5, 10, and 20 μmol/L） alone or in combination, and the combination index （CI） of chidamide and curcumin for HH and HuT-78 cells was evaluated. Cultured HH/HuT-78 cells were divided into chidamide group （treated with 0.4 μmol/L chidamide）, curcumin group （treated with 10 μmol/L curcumin）, combination group （treated with 0.4 μmol/L chidamide + 10 μmol/L curcumin）, and solvent control group （treated with dimethyl sulfoxide）; after 48-hour treatment, the MTS assay was performed to evaluate the cell viability, flow cytometry to detect cell apoptosis and analyze cell cycle, and real-time quantitative PCR（RT-PCR） and Western blot analysis were conducted to determine the mRNA and protein expression of apoptosis-related genes nuclear factor （NF）-κB p65, B-cell lymphoma 2 （Bcl-2）, and caspase-3, respectively. A tumor-bearing mouse model was established with HH cells in immunodeficient mice. These tumor-bearing mice were randomly divided into 4 groups: chidamide group （gavaged with 10 mg/kg chidamide）, curcumin group （gavaged with 100 mg/kg curcumin）, combination group, and solvent control group. The treatment was administered daily for 12 days, and body weight and tumor size were measured. On day 13, these mice were sacrificed, and tumor tissues were collected. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNEL） staining was performed to detect apoptosis of tumor cells, and RT-PCR and Western blot analysis were conducted to determine the expression of apoptosis-related genes and proteins. Differences among multiple groups were analyzed using one-way analysis of variance, and multiple comparisons were performed using least significant difference-t test. Results The CI values of chidamide （0.4 - 6.4 μmol/L） combined with curcumin （1.25 - 20 μmol/L） were all < 1, indicating a synergistic effect. After 48-hour treatment, the proliferation rates of HH and HuT-78 cells were significantly lower in the combination groups than in the chidamide groups and curcumin groups （all P < 0.05）; HH and HuT-78 cells both showed significantly increased apoptosis rates in the combination groups compared with the chidamide groups, curcumin groups and control groups （HH cells: 70.47% ± 7.87% vs. 31.95% ± 9.43%, 37.23% ± 10.74%, 11.76% ± 5.65%, all P < 0.001; HuT-78 cells: 28.31% ± 1.70% vs. 21.29% ± 3.61%, 18.74% ± 1.82%, 3.18% ± 1.00%, all P < 0.001）; in both HH and HuT-78 cells, the combination groups exhibited significantly increased caspase-3 mRNA expression and cleaved protein levels （all P < 0.05）, but significantly decreased mRNA and protein expression of NF-κB p65 and Bcl-2 compared with the control groups, chidamide groups, and curcumin groups, （all P < 0.05）. On day 13 in the in vivo experiment, the tumor volume was significantly lower in the combination group （107.00 ± 43.10 mm3） than in the control group （1 833.00 ± 281.20 mm3）, chidamide group （453.30 ± 91.71 mm3）, and curcumin group （548.50 ± 90.72 mm3, all P < 0.05）; the apoptosis level of tumor cells detected by TUNEL staining was significantly higher in the combination group than in the chidamide group, curcumin group, and control group （all P < 0.05）; compared with the chidamide group, curcumin group, and control group, the combination group showed significantly increased expression of caspase-3 mRNA and cleaved caspase-3 protein （all P < 0.05）, but significantly decreased mRNA and protein expression of NF-κB p65 and Bcl-2 （all P < 0.05）. During the treatment period, there was no significant difference in the body weight of mice among the 4 groups （P < 0.05）; after sacrifice of the mice, no abnormalities were found in histopathological manifestations of their resected visceral tissues, blood routine test results, or liver and kidney function indicators. Conclusion The combination of chidamide and curcumin had a synergistic antitumor effect on CTCL, which may be related to the inhibition of cell proliferation and induction of tumor cell apoptosis.

Key words: Lymphoma, T-cell, cutaneous, Curcumin, Apoptosis, Chidamide, HH cell, Drug combinations, Tumor cells bearing