Overexpression of activating transcription factor 5 in human rectal cancer.

The aim of this study was to investigate the relationship between the expression of activating transcription factor 5 (ATF5) and clinicopathological features in human rectal cancer. Relative quantitative real-time RT-PCR and immunohistochemical staining were used to detect ATF5 mRNA and protein expression in 92 paired samples of rectal cancer and distant normal tissues. Immunohistochemical staining of the matched rectal tissue samples revealed that the positive expression rate of the ATF5 protein in rectal cancer was significantly higher compared to that in the normal tissue. Furthermore, the expression of ATF5 in poorly differentiated cancers was higher compared to that in well to moderately differentiated cancers (P=0.013). However, there was no significant association between ATF5 protein expression and patient age, gender, histological tumor type, cell differentiation, invasive depth, lymph node metastasis or distant metastasis (P>0.05). However, to our surprise, there was no difference in the relative mRNA expression levels of ATF5 between normal tissues and rectal cancers. Our findings indicate that overexpression of ATF5 protein may be an important biomarker of the degree of malignancy, and increased expression may be related to the post-transcriptional regulation of ATF5 in rectal cancer tissues.