Journal Article

Down-regulation of c-<i>myc</i> and <i>Cyclin D1</i> genes by antisense oligodeoxy nucleotides inhibits the expression of E2F1 and <i>in vitro</i> growth of HepG2 and Morris 5123 liver cancer cells

Maria M. Simile, Maria R. De Miglio, Maria R. Muroni, Maddalena Frau, Giuseppina Asara, Silvia Serra, Maria D. Muntoni, Maria A. Seddaiu, Lucia Daino, Francesco Feo and Rosa M. Pascale

in Carcinogenesis

Volume 25, issue 3, pages 333-341
Published in print March 2004 | ISSN: 0143-3334
Published online March 2004 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgh014
Down-regulation of c-myc and Cyclin D1 genes by antisense oligodeoxy nucleotides inhibits the expression of E2F1 and in vitro growth of HepG2 and Morris 5123 liver cancer cells

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A number of genetic interactions are involved in the control of cell cycle, but their role and nature have not been completely clarified. The knowledge of the behavior of these interactions in hepatocellular carcinoma, could optimize preventive and therapeutic strategies based on cell cycle restraint. We studied downstream events following c-MYC and CYCLIN D1 gene inhibition, by lipoplex-delivered MYC and CYCLIN D1 antisense oligodeoxy nucleotides (aODNM, aODND1), in in vitro cultured human HepG2 and rat Morris 5123 hepatoma cells. 0.5–20 µM aODNM and aODND1 inhibited in vitro growth of both cell types. Scramble oligomer (SCR) and sense ODNs had no or relatively poor effect. Ten micromolar aODNM and aODND1, but not SCR, also induced a significant increase in the apoptotic index of HepG2 and 5123 cells, and inhibited colony formation in soft agar by HepG2 cells. Treatment of the cells with aODNM plus aODND1 had no additive effect on growth and apoptosis. aODNM and aODND1 induced >50% decrease in c-MYC and CYCLIN D1 gene expression, respectively, at both mRNA and protein level. The inhibition of gene expression by aODNs was highly specific, and SCR was without effect. The reduction in c-MYC and CYCLIN D1 expression by aODNs, was associated with a >50% decrease in E2F1 mRNA and protein production, without changes in CYCLIN A and CYCLIN E expression. These results suggest the involvement of both c-MYC and CYCLIN D1 on E2F1 gene function, and indicate that aODNM and aODND1 may inhibit hepatoma cell growth through down-regulation of the E2F1 gene. The inhibition of E2F1 gene expression by E2F1 aODN, was associated with strong growth restraint of HepG2 cells. Thus, interactions of c-MYC and CYCLIN D1 with E2F1 gene are essential for cell cycle activity in hepatoma cells, and their inhibition may have a therapeutic effect.

Keywords: aODN, antisense oligodeoxy nucleotide; aODND1, Cyclin D1 aODN; aODNE, E2F1 aODN; aODNM, c-MYC aODN; CDK, cyclin-dependent kinase; D, DOTAP; FCS, fetal calf serum; HCC, hepatocellular carcinoma; SCR, scramble oligomer; sODN, sense oligodeoxy nucleotide

Journal Article.  7048 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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