[Inhibition of c-sis protein synthesis and cell growth with antisense oligonucleotides in human glioma cells].

The protein encoded by the proto-oncogene c-sis is over-amplified in human neuroglial tumors and has been hypothesized as playing an important role in tumorigenesis, but this hypothesis remains to be clarified. In order to address this issue, we examined the effect of 18-bp oligodeoxynucleotides complementary to the sense mRNA of c-sis upon glioma cell growth. First, we investigated the expression of c-sis protooncogenes within cultured human glioma cell lines and also fresh glioma specimens by using polymerase chain reaction. We could detect mRNA transcripts of c-sis in 3 out of 4 glioma cell lines (U138MG, U251MG and A172) and two in 5 glioblastoma multiforme specimens. The antisense oligonucleotides complementary to c-sis mRNA were efficiently incorporated into A172 in vitro and the kinetic study showed that maximum uptake occurred after 48 hours of incubation with antisense oligomers. Exposure of human glioma cell lines to antisense oligodeoxynucleotides targeted against first initiation codon inhibited cell proliferation in a time and dose dependent fashion. From the flow cytometric analysis using anti-c-sis sera, it was demonstrated that the antisense oligomers specifically block the de novo synthesis of intracellular c-sis protein by glioma cells dose-dependently. In contrast to this, the corresponding sense oligomers inhibited neither synthesis of c-sis protein nor glioma cell growth. Taken together, these results clearly support a role of c-sis protein in the proliferation process and show that inducible protein expression can be blocked by means of synthetic oligonucleotides complementary to a coding exon.