The 3′untranslated region of CCAAT/enhancer binding protein β(C/EBPβ) is a regulation element with tumor suppression activity found in previous study. Here, it is reported that deletion of 3 short sequences in this 3′UTR reduces the tumor suppression activity of it, as demonstrated by slowed-down cell growth, reduced colony formation ability in soft agar and in ordinary culture conditions, as well as the decreased tumorigenicity in nude mice. The cDNA array and real-time RT-PCR analysis showed that the loss of tumor suppression activity for the mutated 3′UTR was due to the change of the gene expression profile of the transfected cells, i.e. the up-regulation of several genes related with malignant phenotype and the down-regulation of some genes related with tumor suppression, compared with the revertant control cells. These results indicate that those short sequences are simultaneous necessary for the tumor suppression activity of the C/EBPβ 3′UTR.