Silencing of KIF14 interferes with cell cycle progression and cytokinesis by blocking the p27(Kip1) ubiquitination pathway in hepatocellular carcinoma.
Although it has been suggested that kinesin family member 14 (KIF14) has oncogenic potential in various cancers, including hepatocellular carcinoma (HCC), the molecular mechanism of this potential remains unknown. We aimed to elucidate the role of KIF14 in hepatocarcinogenesis by knocking down KIF14 in HCC cells that overexpressed KIF14. After KIF14 knockdown, changes in tumor cell growth, cell cycle and cytokinesis were examined. We also examined cell cycle regulatory molecules and upstream Skp1/Cul1/F-box (SCF) complex molecules. Knockdown of KIF14 resulted in suppression of cell proliferation and failure of cytokinesis, whereas KIF14 overexpression increased cell proliferation. In KIF14-silenced cells, the levels of cyclins E1, D1 and B1 were profoundly decreased compared with control cells. Of the cyclin-dependent kinase inhibitors, the p27(Kip1) protein level specifically increased after KIF14 knockdown. The increase in p27(Kip1) was not due to elevation of its mRNA level, but was due to inhibition of the proteasome-dependent degradation pathway. To explore the pathway upstream of this event, we measured the levels of SCF complex molecules, including Skp1, Skp2, Cul1, Roc1 and Cks1. The levels of Skp2 and its cofactor Cks1 decreased in the KIF14 knockdown cells where p27(Kip1) accumulated. Overexpression of Skp2 in the KIF14 knockdown cells attenuated the failure of cytokinesis. On the basis of these results, we postulate that KIF14 knockdown downregulates the expression of Skp2 and Cks1, which target p27(Kip1) for degradation by the 26S proteasome, leading to accumulation of p27(Kip1). The downregulation of Skp2 and Cks1 also resulted in cytokinesis failure, which may inhibit tumor growth. To the best of our knowledge, this is the first report that has identified the molecular target and oncogenic effect of KIF14 in HCC.
1] Integrated Research Center for Genome Polymorphism, Department of Microbiology, Catholic University of Korea, College of Medicine, Seoul, Korea [2] Center of Laboratory, Yanbian University Hospital, Yanji, China.
Haidong
H
Xu
Integrated Research Center for Genome Polymorphism, Department of Microbiology, Catholic University of Korea, College of Medicine, Seoul, Korea.
Chungyoul
C
Choe
Integrated Research Center for Genome Polymorphism, Department of Microbiology, Catholic University of Korea, College of Medicine, Seoul, Korea.
Seung-Hun
SH
Shin
Integrated Research Center for Genome Polymorphism, Department of Microbiology, Catholic University of Korea, College of Medicine, Seoul, Korea.
Sung-Won
SW
Park
Department of Biochemistry, Catholic University of Korea, College of Medicine, Seoul, Korea.
Ho-Shik
HS
Kim
Integrated Research Center for Genome Polymorphism, Department of Microbiology, Catholic University of Korea, College of Medicine, Seoul, Korea.
Seung-Hyun
SH
Jung
1] Integrated Research Center for Genome Polymorphism, Department of Microbiology, Catholic University of Korea, College of Medicine, Seoul, Korea [2] Department of Medical Education, Catholic University of Korea, College of Medicine, Seoul, Korea.
Seon-Hee
SH
Yim
MRC Cancer Evolution Research Center, Department of Medical Informatics, Catholic University of Korea, College of Medicine, Seoul, Korea.
Tae-Min
TM
Kim
Integrated Research Center for Genome Polymorphism, Department of Microbiology, Catholic University of Korea, College of Medicine, Seoul, Korea.
Yeun-Jun
YJ
Chung
D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D048749:Cytokinesis; D020868:Gene Silencing; D056945:Hep G2 Cells; D006801:Humans; D016547:Kinesins / Q000235:genetics / Q000378:metabolism*; D008113:Liver Neoplasms / Q000378:metabolism*; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination
D016213:Cyclins; D015513:Oncogene Proteins; D012333:RNA, Messenger; D044786:S-Phase Kinase-Associated Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D046988:Proteasome Endopeptidase Complex; C502598:KIF14 protein, human; D016547:Kinesins