OBJECTIVETo investigate the impact of all-trans retinoic acid (ATRA) on chemosensitivity to esophageal squamous cell carcinoma EC9706 cells in vitro and its mechanism.

METHODSEC9706 cells were routinely cultured as the control group. The experimental group was divided into three groups. The ATRA group with ATRA in final concentration of 1 µmol/L; the 5-Fu group with 5-Fu in final concentration of 50 mg/L; the combined treatment group with ATRA in final concentration of 1 µmol/L and 5-Fu 50 mg/L. The cell apoptosis was detected by terminal deoxynucleotidy transferase mediated dUTP nick end labelling (TUNEL). The cell cycle and apoptosis were detected by flow cytometry.

RESULTSThe results of TUNEL showed that in the combined treatment group appeared a large number of apoptotic cells, and their nuclei were stained brown, with a positive rate of 89.7%. There was a significant difference in the comparison with the ATRA group (38.3%) and 5-Fu group (40.3%) (P < 0.05). The flow cytometry showed that the ATRA + 5-Fu group had a significantly higher apoptosis rate (76.9% ± 2.7%) than that in the ATRA group (38.2% ± 2.6%) and 5-Fu group (45.2% ± 2.3%) (P < 0.05). The ratio of cells in G(1) phase increased in the ATRA + 5-Fu group (83.4% ± 3.0%), significantly higher than (48.2% ± 2.5%) in the ATRA group and (53.2% ± 2.6%) in the 5-Fu group (P < 0.05). The ratio of cells in S + G(2)/M phase was decreased in the ATRA + 5-Fu group, with a significant difference (P < 0.05) when compared with other groups. There was no significant difference between the ATRA group and 5-Fu group (P > 0.05) in the apoptosis rate and the proportion of cells at different phases.

CONCLUSIONATRA can induce apoptosis of esophageal carcinoma EC9706 cells in vitro. The combination of ATRA and 5-Fu may enhance the chemotherapeutic efficacy.