A methylated oligonucleotide inhibits IGF2 expression and enhances survival in a model of hepatocellular carcinoma.
IGF-II is a mitogenic peptide that has been implicated in hepatocellular oncogenesis. Since the silencing of gene expression is frequently associated with cytosine methylation at cytosine-guanine (CpG) dinucleotides, we designed a methylated oligonucleotide (MON1) complementary to a region encompassing IGF2 promoter P4 in an attempt to induce DNA methylation at that locus and diminish IGF2 mRNA levels. MON1 specifically inhibited IGF2 mRNA accumulation in vitro, whereas an oligonucleotide (ON1) with the same sequence but with nonmethylated cytosines had no effect on IGF2 mRNA abundance. MON1 treatment led to the specific induction of de novo DNA methylation in the region of IGF2 promoter hP4. Cells from a human hepatocellular carcinoma (HCC) cell line, Hep 3B, were implanted into the livers of nude mice, resulting in the growth of large tumors. Animals treated with MON1 had markedly prolonged survival as compared with those animals treated with saline or a truncated methylated oligonucleotide that did not alter IGF2 mRNA levels in vitro. This study demonstrates that a methylated sense oligonucleotide can be used to induce epigenetic changes in the IGF2 gene and that inhibition of IGF2 mRNA accumulation may lead to enhanced survival in a model of HCC.
Yao
Xiaoming
X
Medical Service, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, USA.
Hu
Ji-Fan
JF
Daniels
Mark
M
Shiran
Hadas
H
Zhou
Xiangjun
X
Yan
Huifan
H
Lu
Hongqi
H
Zeng
Zhilan
Z
Wang
Qingxue
Q
Li
Tao
T
Hoffman
Andrew R
AR
D001483:Base Sequence; D019175:DNA Methylation; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000037:antagonists & inhibitors* / Q000235:genetics; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000401:mortality; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000494:pharmacology / Q000627:therapeutic use*; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured
D009841:Oligonucleotides; D012333:RNA, Messenger; D007335:Insulin-Like Growth Factor II