Background: Human YB-1 is a transcription factor that binds to the inverted CCAAT box in the promoter region of a variety of genes such as PCNA, DNA polymerase and MDR. In this study we evaluated the effect of YB-1 antisense oligonucleotides on tumor cell growth.
Methods: Chang liver, HepG2 and CT-26 cells were cultured as immortalized cell lines. The MTT (3-[4,5-dimethylthiazol-2-yl] 2,5-diphenyltetrazolium bromide) assay, Northern blot and flow cytometric analyses were used to determine cell growth, gene expression and cell cycle changes. In an animal model, CT-26 cells were injected into Balb/c mice to induce tumor; YB-1 antisense oligonucleotides were injected into the tail vein or tumor tissue of the mice; change of tumor size was then measured.
Results: Phosphorothioated YB-1 antisense oligonucleotides suppressed the proliferation of the immortalized liver cells (Chang liver cells) and a variety of cancer cells (HepG2 and CT-26 cells); however, it did not inhibit normal cell growth. The DOTAP/antisense oligonucleotide mixture showed stronger effects on cell proliferation than did the antisense oligonucleotide alone. The YB-1 antisense oligonucleotide decreased specific expression of the YB-1 mRNA in the immortalized cancer cell lines. Flow cytometric analysis revealed that the inhibition of cell proliferation might have been due to a decrease in the S phase of the cell cycle. We found that in an animal tumor model, the administration of the YB-1 antisense oligonucleotide, in the vein or tumor tissues, decreased the tumor size significantly.
Conclusion: These results suggest that the YB-1 antisense oligonucleotide may inhibit growth of a variety of cancer cells.
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