Identification of PFTAIRE protein kinase 1, a novel cell division cycle-2 related gene, in the motile phenotype of hepatocellular carcinoma cells

Metastasis is a major cause of cancer morbidity and mortality in individuals with hepatocellular carcinoma (HCC), yet little is known about the underlying molecular basis. Using genetic information derived from chromosome-based comparative genomic hybridization, we have reported previously on regional chromosome 7q21-q22 gains in dose association with HCC progression. In this study, we undertook cDNA microarray-based comparative genomic hybridization, to examine the 7q21-q22 region for the involved gene(s) in HCC. High-resolution mapping analysis highlighted 7 candidates, namely PFTAIRE protein kinase 1 (PFTK1), ODAG, CDK6, G4S1, PEX1, SLC25A, and PEG10, within the region. Quantitative reverse transcription (RT)-PCR evaluation further indicated upregulation of a single candidate gene, PFTK1, that correlated significantly with both advanced metastatic HCCs (P = 0.032) and tumor microvascular invasion (P = 0.012). Given that little is known about the function(s) of PFTK1, which is a novel cell division cycle (Cdc) 2-related gene, we examined its potential role in the motile phenotype of HCC cells by both ectopic expression and knockdown investigations. RNA-interference knockdown of PFTK1 in invasive Hep3B cells resulted in a significant reduction in cell invasion, chemotactic migration, and cell motility (P < 0.001). Conversely, ectopic expression of PF7K1 in noninvasive HKCI-C3 cells induced substantial cellular invasion and migration (P <= 0.007). In neither cell line was there any effect on cell viability. Immunofluorescence showed marked filamentous actin polymerizations in PFTK1-expressing cells. Conclusion: In this study, we have thus provided preliminary evidence that overexpression of PFTK1 may confer a motile phenotype in malignant hepatocytes that accounts for the association of upregulation of this gene in metastatic HCC.