ObjectiveTo determine the expression change of activating transcription factor 5 (ATF5) in human rectal cancer tissue, and analyze the correlation between ATF5 expression and the clinicopathologic parameters of rectal cancer. MethodsNinetytwo paired samples of rectal cancer tissue and more than 5 cm distant normal rectal tissue were obtained from inpatients between March 2009 and October 2009 in this hospital. ATF5 mRNA and protein expressions were detected by quantitative real-time RT-PCR and immunohistochemical staining. ResultsThirty-three (35.9%) cases of rectal cancer showed ATF5 mRNA overexpression; however, the expression level of ATF5 mRNA in the rectal cancer tissue was not statistically different from that in the normal rectal tissue (P=0.363). There was no evidence for the relationship between the ATF5 mRNA expression and the patients’ age, gender, histological type, tumor differentiation degree, invasive depth, lymph node metastasis, distance metastasis, or TNM stage. In contrast, the positive expression rate of ATF5 protein in the rectal cancer tissue was significantly higher than that in the normal rectal tissue (P=0.000). Moreover, the ATF5 protein expression was correlated with the tumor differentiation degree (P=0.013), but not with other clinicopathologic features (Pgt;0.05). ConclusionsThe results suggest that ATF5 protein may be related to the carcinogenesis and differentiation of human rectal cancer. However, further researches are required to prove the correlation.