Specific inhibition of breast cancer cells by antisense poly-DNP-oligoribonucleotides and targeted apoptosis

Two membrane-permeable and RNase-resistant antisense poly-2′-O-(2,4-dinitrophenyl)-oligoribonucleotides (poly-DNP-RNAs) have been synthesized as inhibitors of human breast cancer, with nucleotide sequences complementary to the genes of RI_α subunit of protein kinase A (RI_α/PKA) and erbB-2, respectively. Both compounds inhibit the proliferation of SK-Br-3 breast cancer cells in culture above the concentration of 10 μg/ml, but have no effect on nontumorigenic MCF-10A breast cells. These antisense inhibitors also block the cell colony formation in methylcellulose medium, whereas the control poly-DNP-RNA with either random or sense sequence has no effect. RT-PCR data show that the antisense inhibition decreases the concentration of the mRNA. TdT-mediated dUTP nick-end labeling (TUNEL) fluorescence assay indicates that the targeted antisense inhibition by poly-DNP-RNAs leads to apoptosis of SK-Br-3 cells but does not affect nontumorigenic MCF-10A cells. The control poly-DNP-RNAs with random or sense nucleotide sequence are completely inactive.