Antisense oligodeoxynucleotide against c-myc mRNA induces differentiation of human hepatocellular carcinoma cells

We have previously demonstrated that the human liver-specific antigen (HLSA) expression was enhanced and c-myc levels were reduced during sodium butyrate-induced differentiation in human hepatoma cells. To further elucidate a linkage between the reduction of c-myc levels and an increase in the HLSA expression, antisense oligodeoxynucleotide against c-myc mRNA was transferred into human hepatoma cells. Human hepatoma cell lines, HCC-M, HCC-T and PLC/PRF/5 were transfected with antisense oligodeoxynucleotide and changes in the cell cycle, expression of the HLSA, albumin, and alpha-fetoprotein were examined. Antisense oligodeoxynucleotide was successfully induced into cells visualized by a confocal microscope using fluorescein-labeled oligodeoxynucleotides, and Northern blot analysis revealed that c-myc expression was reduced three and six hours after the transfection. Following these changes, cell proliferation was inhibited and flow cytometric analysis showed that cell number in the G1 phase significantly increased. Increased expression of the HLSA and albumin, and decreased expression of alpha-fetoprotein was observed by flow cytometry in accordance with those changes. These results showed similar changes to those induced by butyrate-treatment obtained in our previous studies. The present study indicates that the reduction of c-myc transcription increases HLSA expression levels through intracellular changes similar to those induced by butyrate, a differentiation inducer.