The Kruppel-like factor 5 (KLF5) transcription factor is highly expressed in high-grade and basal-like breast cancers. However, the mechanism by which KLF5 promotes cell migration and invasion is still not completely understood. In this study, we demonstrate that TNFAIP2, a tumor necrosis factor-α (TNFα)-induced gene, is a direct KLF5 target gene. The expression of TNFAIP2 is highly correlated with the expression of KLF5 in breast cancers. The manipulation of KLF5 expression positively alters TNFAIP2 expression levels. KLF5 directly binds to the TNFAIP2 gene promoter and activates its transcription. Functionally, KLF5 promotes cancer cell proliferation, migration and invasion in part through TNFAIP2. TNFAIP2 interacts with the two small GTPases Rac1 and Cdc42, thereby increasing their activities to change actin cytoskeleton and cell morphology. These findings collectively suggest that TNFAIP2 is a direct KLF5 target gene, and both KLF5 and TNFAIP2 promote breast cancer cell proliferation, migration and invasion through Rac1 and Cdc42.

XAF1 is a newly identified tumor-suppressor gene that can antagonize XIAP and sensitize cells to other cell death triggers. In this study, we utilized ZD55, a conditionally replicative adenovirus (CRAd) similar to ONYX-015 as the vector to transfer XAF1 into the tumor cells to evaluate its antitumor efficacy in vitro and in vivo. Potent and specific cytopathic effect (CPE) was observed upon infection with ZD55-XAF1 in tumor cell lines. Importantly, ZD55-XAF1 exhibited a superior suppression of tumor growth in an animal model of colorectal carcinoma in nude mice compared with Ad-XAF1 (E1-deleted replication-defective viral) and ONYX-015. Complete eradication of the established tumors was observed in four of eight mice. Our data also showed that infection with ZD55-XAF1 resulted in caspase-independent apoptosis. Although caspase-3, poly(ADP-ribose) polymerase were mildly activated in response to ZD55-XAF1 infection, pretreatment with pan-caspase inhibitor hardly influence its apoptosis-inducing activity. In summary, our study strongly suggested that ZD55-XAF1 could serve as an effective gene-virotherapy strategy and has highly potential against human cancers.