Effect Of IFN-α And Antisense C-myc Oligonucleotides On The Telomerase Activity Of SMMC-7721 Hepatocarcinoma Cells

Objective: Telomerase is a ribonucleoprotein enzyme with reverse transcription activity that is composed of RNA component and protein and it is crucial and essential for the continued growth or progression of cancer cells, so telomerase is regard as a realitic target that can repress the proliferation of carcinoma and impel the apoptosis of carcinoma. At present, people are trying to apply a variety of methods to repress telomerase activity, which is to treat carcinoma. Recently, it is reported that IFN- a , in some carcinoma cells such as some malignant hematopoietic cells, can repress telomerase activity while c-myc may activate telomerase activity. However, there is no report that if IFN- a. and antisense c-myc oligonucleotides could repress the telomerase activity of SMMC-7721 hepatocarcinoma cells and how IFN- a and antisense c-myc oligonucleotides do it. In this study, our aims are to study the effect and mechanism of IFN- a and antisense c-myc oligonucleotides on the telomerase activity of SMMC-7721 hepatocarcinoma cells primarily and to observe furtherly the effect of combined treatment of IFN- a and antisense c-myc oligonucleotides on it by the anti-cancer principle of cytokine and antisense gene, which is to explore the anti-cancer mechanism of IFN- a and antisense c-myc oncogene and to supply the theory base for the more efficient biotherapy of hepatocarcinoma.Methods : The antisense c-myc oligonucleotides, IFN- a 2b which were used alone or combined delivered to cultured SMMC-7721. Using immunohistochemistry, RT-PCR and PCR-ELISA, we observed the change of c-myc protein expression, telomerase-related major subunits hTRN hTERT, TP1 mRNA and telomerase activity.Results: Antisense c-myc, at concentration of 10 u mol/L , and IFN- a 2b, 5000u/mL, can successfully inhibit the expression of c-myc protein , hTERT mRNA and telomerase activity in SMMC-7721 hepatocarcinoma cells (p<0.05 or p<0.01) but can not inhibit the expression of TP1 and hTR, which the contrast do not have these effects (p>0.05) .Moreover, these effects were more obvious in the group of combined treatment than in the groups treated with EFN- a or antisense c-myc oligonucleotides alone (p<0.05 or p<0.01), there are no difference between EFN- a and antisense c-myc oligonucleotides (p>0.05) .Conclusion: 1) The data suggested that IFN- a and antisense c-myc oligonucleotides all can inhibit the telomerase activity of SMMC-7721 hepatocarcinoma cells, so telomerase activity was inhibited, which could be the one of anti-cancer mechanism of IFN- a and antisense c-myc oncogene.2) IFN- a and antisense c-myc oligonucleotides inhibiting the telomerase activity in SMMC-7721 hepatocarcinoma cells could be associated with suppression of hTERT mRNA but be no correlation with the expression of hTR and TP1, which could illustrate that hTR and TP1 are the crucial ingredient of telomerase but be no relation to telomerase activity.3 ) The mechanism of IFN- a and antisense c-myc oligonucleotides inhibiting the telomerase activity in SMMC-7721 hepatocarcinoma cells could be that they repress the expression of c-myc oncogene firstly, and then repress the expression of telomerase subunit hTERT mRNA , and last result in the drop of telomerase activity, which may be a pathway.4) The results demonstrated that the telomerase activity was inhibited much more effect in the combined treatment of IFN- a and antisense c-myc oligonucleotides than that in IFN- a or antisense c-myc oligonucleotides alone. The reason could be that IFN- a and antisense c-myc oligonucleotides can inhibitthe expression of c-myc oncogene together by the principle of combination or coordination. So the effect of the combined treatment of IFN- a and antisense c-myc oligonucleotides on treating carcinoma is more efficient than that in IFN- a or antisense c-myc oligonucleotides alone,...