Antisense oligonucleotide Elk‐1 suppresses the tumorigenicity of human hepatocellular carcinoma cells

Abstract

In previous studies, we showed that reducing Ets-like protein-1 (Elk-1) expression inhibited protein kinase C alpha (PKC alpha) expression and decreased cell migration and invasion in human hepatocellular carcinoma (HCC). In this study, we have investigated the role of Elk-1 in tumorigenesis. SK-Hep-1 HCC cells were transfected with the ElK-1 antisense oligonucleotide (ODN). In the pretreated cells we detected a reduction of mRNA level using RT-PCR. The inhibitory rate of cell growth was measured by MTT assay. Pretreated-SK-Hep-1 HCC cells were implanted subcutaneously into nude mice to observe the tumor growth and calculate tumor inhibitory rate. The results showed that 5 microM of the antisense ODN Elk-1 suppressed both Elk-1 and PKC alpha production by SK-Hep-1 HCC cells after cationic liposome-mediated transfection, to 8% and 1% of control values, respectively, and the growth of SK-Hep-1 HCC cells was inhibited at 2-5 microM doses of the antisense ODN Elk-1. The control reagent, sense ODN Elk-1, showed no effects. In BALB/nude mice, SK-Hep-1 HCC cells transfected with the 5 microM antisense ODN Elk-1 formed tumors much smaller than those of sense ODN Elk-1 pretreated cells. The maximum inhibitory rate of tumor growth was 80.8+/-12.6% and the tumor formation time was prolonged from 13 to 25 days. These findings suggested the usefulness of antisense ODN Elk-1 as a new reagent for liver cancer therapy.

Abnormal expression of TFIIIB subunits and RNA Pol III genes is associated with hepatocellular carcinoma

“…Although the function of Elk-1 in human cancer has not been clearly established, initial results indicate that downregulation of Elk-1 suppresses the tumorigenicity of human hepatocellular carcinoma cells. 50 Although Bdp1 expression is not regulated directly by Elk-1, the resulting Elk-1-mediated change in TBP expression governs Bdp1 promoter activity and cellular Bdp1 concentrations, demonstrating that alterations in cellular TBP levels modulate Bdp1 expression but not Brf1. 8 …”

“…49 Furthermore, these changes regulate c-Jun levels and its activity, which in turn increase proliferation rates. 50 The regulation of Pol III gene transcription by JNKs through its effects on TBP and its associated factors, Brf1 and Bdp1, constitutes a mechanism by which it controls the proliferative capacity of cells.…”

“…8, 49 Although alcohol stimulates Elk-1 and AP-1, its ability to activate TBP and Brf1 is driven primarily by greater c-Jun expression and its recruitment to their promoters. Downregulation of Elk-1 suppresses the tumorigenicity of hepatocellular carcinoma cells, 50 and Elk-1 activation is likely to regulate at least a subset of genes that participate in alcohol-mediated liver disease. Interestingly, we found that Elk-1, c-Jun, and c-Fos occupy sites near the tRNA Leu gene.…”

The JNKs differentially regulate RNA polymerase III transcription by coordinately modulating the expression of all TFIIIB subunits

“…Our previous studies demonstrated that JNK-mediated alterations in cellular TBP expression dictate the proliferation rates of MEFs (19). Furthermore, these changes in TBP concentrations regulate c-Jun levels and its activity, which have been shown to drive the proliferation rates of MEFs (29). Our finding that the JNKs regulate RNA pol IIIdependent transcription through its affects on TBP and its associ- ated RNA pol III factors identifies a mechanism by which it controls the proliferative capacity of these cells.…”

“…JNK-mediated regulation of all 3 TFIIIB subunits is orchestrated through Elk-1. Although a role for Elk-1 in human cancer has not been clearly established, initial results indicate that reduced expression of Elk-1 suppresses tumorigenicity of human hepatocellular carcinoma cells (29). While Bdp1 expression is not directly regulated by Elk-1, the resultant Elk-1-mediated change in TBP expression serves to regulate Bdp1 promoter activity and cellular Bdp1 concentrations.…”