Transforming growth factor-β （TGF-β） exerts apoptotic effects on various types of malignant ceils, including liver cancer cells. However, the precise mechanisms by which TGF-β induces apoptosis remain poorly know...Transforming growth factor-β （TGF-β） exerts apoptotic effects on various types of malignant ceils, including liver cancer cells. However, the precise mechanisms by which TGF-β induces apoptosis remain poorly known. In the present study, we have showed that threonine 32 （Thr32） residue of FoxO3 is critical for TGF-β to induce apoptosis via Bim in hepatocarcinoma Hep3B cells. Our data demonstrated that TGF-βinduced FoxO3 activation through specific de-phosphorylation at Thr32. TGF-β-activated FoxO3 cooperated with Smad2/ 3 to mediate Bim up-regulation and apoptosis. FoxO3 （de）phosphorylation at Thr32 was regulated by casein kinase I-ε （CKI-E）. CKI inhibition by small molecule D4476 could abrogate TGF-β-induced FoxO/Smad acti- vation, reverse Bim up-regulation, and block the sequential apoptosis. More importantly, the deregulated levels of CKI-ε and p32FoxO3 were found in human malignant liver tissues. Taken together, our findings suggest that there might be a CKI-FoxO/Smad-Bim engine in which Thr32 of FoxO3 is pivotal for TGF-β- induced apoptosis, making it a potential therapeutic target for liver cancer treatment.展开更多
基金This work was supported by grants from the National Basic Research Program （973 Program） （Nos. 2007CB914800 and 2006CB910102）, the National Natural Science Foundation of China （Grant Nos. 30630038 and 30400098）, a project grant from Chinese Academy of Sciences （KSCX2-YW-R-02） to Q.C. We greatly appreciate the gift of CKI-ε （WT and KD mutant） constructs from Dr. Xiaofan Wang （Department of Pharmacology and Cancer Biol- ogy, Duke University Medical Center, Durham, North Carolina, USA）. XZ, YL, DL and HL designed, performed experiments and ana- lyzed data XZ., DH, JH, ZL and QC designed experiments, analyzed data, directed the whole study and wrote the manuscript. All authors read and approved the final manuscripts.
文摘Transforming growth factor-β （TGF-β） exerts apoptotic effects on various types of malignant ceils, including liver cancer cells. However, the precise mechanisms by which TGF-β induces apoptosis remain poorly known. In the present study, we have showed that threonine 32 （Thr32） residue of FoxO3 is critical for TGF-β to induce apoptosis via Bim in hepatocarcinoma Hep3B cells. Our data demonstrated that TGF-βinduced FoxO3 activation through specific de-phosphorylation at Thr32. TGF-β-activated FoxO3 cooperated with Smad2/ 3 to mediate Bim up-regulation and apoptosis. FoxO3 （de）phosphorylation at Thr32 was regulated by casein kinase I-ε （CKI-E）. CKI inhibition by small molecule D4476 could abrogate TGF-β-induced FoxO/Smad acti- vation, reverse Bim up-regulation, and block the sequential apoptosis. More importantly, the deregulated levels of CKI-ε and p32FoxO3 were found in human malignant liver tissues. Taken together, our findings suggest that there might be a CKI-FoxO/Smad-Bim engine in which Thr32 of FoxO3 is pivotal for TGF-β- induced apoptosis, making it a potential therapeutic target for liver cancer treatment.
