Fas-associated death domain protein enhance inhibitory effect of 5-fluorouracil on growth of human colorectal carcinoma cells / 中华消化杂志

ABSTRACT

Objective To examine the sensitivity of human colorectal carcinoma cells to 5-fluorouracil treatment by stable transfection of extrinsic Fas-associated death domain protein(FADD) gene，both in vitro and in vivo，so as to investigate the feasibility of combination therapy of FADD gene and 5-fluorouracil in human colorectal carcinoma.Methods①RT-PCR and Western blotting were used to detect the expressions of both mRNA and protein of FADD gene in SW480／FADD (stably transfected with FADD)，SW480／neo and SW480 cells.②After treatment with 5-fluorouracil as an apoptotic inducer，in vitro cell growth activities were investigated by MTT assay.Cell apoptosis and its rates were determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling(TUNEL)assay and flow cytometry of annexin V-FITC／PI staining.The expressions of caspase-8 and caspase-3 were examined by Western blotting.③To examine the inhibitory effect of FADD gene combined with 5-fluorouracil, tumor xenograft model was prepared for in vivo study.Results ① Compared with SW480 and SW480/neo cells, FADD mRNA and protein levels of SW480/FADD cells were higher (P<0.05). ② Inhibitory rate of SW480/FADD cells was remarkably higher than SW480 and SW480/neo cells (P＜0.05 ). ③ Forty-eight hours after treatment with 5-fluorouracil (10 mg/L), the apoptotic rate of SW480/FADD cells was (33.3 ± 4.5)%, which was higher than SW480 [(13. 9 ± 3. 2)%3 and SW480/neo [(14. 1 ± 3. 4)%], with significant difference (P< 0.05).④ Forty-eight hours after treatment with 5-fluorouracil (10 mg/L),procaspase-8 and procaspase-3 expressions of SW480 and SW480/neo cells were higher than SW480/FADD cells, whereas their cleaved caspase-8 and cleaved caspase-3 expressions were lower than SW480/FADD cells (P＜0. 05).⑤ In in vivo study, SW480/FADD cells increased the efficacy of fluorouracil-induced inhibition of tumor growth in nude mice. ConclusionsStable overexpression of FADD increases sensitivity of the cells to 5-fluorouracil and combination of FADD with 5-fluorouracil will he a promising alternative in colorectal cancer treatment.