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 p27Kip1 protein level specifically increased after KIF14 knockdown. The increase in p27Kip1 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 p27Kip1 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 p27Kip1 for degradation by the 26S proteasome, leading to accumulation of p27Kip1. 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.

Prognostic value of epidermal growth factor receptor and P27 protein expression in colorectal carcinoma

Clinicopathological data and the expression of direct cellular growth, epidermal growth factor receptor [EGFR] and tumor suppressor gene p27 were studied by immunohistochemistry on paraffin-embedded sections of 50 cases of primary colorectal carcinoma [CRC] in Egyptian patients, to evaluate their role in predicting patients prognosis. EGFR was expressed in 26 out of 50 cases [52%]. There is a significant conrrelation between expression of EGFR and tumor differentiation [p < 0.001] and 5-year survival rate [p < 0.001]. EGFR expression had no statistically significant correlation with Clinicopathological parameters including histological type, size, site, and stage. Lack or low p27 expression was noted in 15 out of 50 [30%] cases of CRC [p < 0.05]. This altered expression was significantly higher in proximal cancer [p < 0.05], mucinous tumors [p < 0.001], poorly differentiated histololgy [p < 0.01]. Overall survival was better in the patient group with altered level of p27 expression, although the difference does not reach statistical significance [p > 0.05]. In conclusion, EGFR overexpression has been found to be related to a poor prognosis of CRC, and loss or p27 protein expression was associated with poorly differentiated CRC and may be part of the genetic pathway, which is responsible for the development of some CRC