The E2F transcription factor 1 transactives stathmin 1 in hepatocellular carcinoma.
BACKGROUND
Through data mining the Stanford Microarray Database, the stathmin 1 (STMN1) transcript was found to be frequently upregulated in the hepatocellular carcinoma (HCC) with low alpha-fetoprotein level. The molecular mechanism of STMN1 upregulation in HCCs remained unclear.


METHODS
Quantitative RT-PCR, immunoblotting, immunohistochemistry, and transfection of expression or small hairpin RNA interference plasmids, chromatin immunoprecipitation (ChIP), and quantitative ChIP assays were performed in HCC specimens or 2 distinct HCC-derived cell lines. Dual luciferase assay and site-directed mutagenesis were applied to analyze the activities of STMN1 proximal promoter region.


RESULTS
STMN1 mRNA and proteins were significantly associated with several clinicopathological features. High STMN1 or E2F1 immunoexpression was predictive of poor overall survival (OS) rate (P < .01). In HCC-derived cell lines, E2F1 was elevated before STMN1 mRNA during the cell cycle. Exogenous expression of E2F1 or both transcription factor DP-1 (TFDP1) and E2F1 genes induced E2F1 and STMN1 mRNA (P < .01). Knockdown of the E2F1 gene suppressed E2F1 and STMN1 mRNA and E2F1 and STMN1 protein levels (P < .05). The promoter activity of STMN1 gene increased with overexpression of both E2F1 and TFDP1 genes (P < .05); however, it decreased when mutations were introduced in the E2F1-binding sites (P < .05).


CONCLUSIONS
Upregulation of E2F1 and STMN1 proteins associate with worse outcomes in patients with HCC. E2F1 significantly correlates with STMN1 protein level in HCC lesions and in vitro transactivation assays, suggesting that STMN1 gene is transactivated by the E2F1 protein.
Institute of Biomedical Science, National Sun Yat-sen University, Kaohsiung, Taiwan.
Yi-Ling
YL
Chen
Yih-Huei
YH
Uen
Chien-Feng
CF
Li
Kuo-Chan
KC
Horng
Lih-Ren
LR
Chen
Wen-Ren
WR
Wu
Hong-Yu
HY
Tseng
Hsuan-Ying
HY
Huang
Li-Ching
LC
Wu
Yow-Ling
YL
Shiue
D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D050687:E2F1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D005500:Follow-Up Studies; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008156:Luciferases / Q000378:metabolism; D008297:Male; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D009367:Neoplasm Staging; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050777:Stathmin / Q000235:genetics* / Q000378:metabolism; D050680:Transcription Factor DP1 / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D000509:alpha-Fetoproteins / Q000235:genetics / Q000378:metabolism
D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C493995:STMN1 protein, human; D050777:Stathmin; C493735:TFDP1 protein, human; D050680:Transcription Factor DP1; D000509:alpha-Fetoproteins; D008156:Luciferases