Dual-Specificity Anti-HER-2/neu Antisense DNA Agents for Breast Cancer Therapy

摘要

The high level expression in some breast cancers of HER-2/neu, correlates with poor prognosis. An antisense agent capable of down-regulating expression of this gene should be useful in treating these cancers. To achieve high avidity and specificity, we designed chimeric antisense molecules consisting of a short active DNA fused to a short 'anchor' 2-0-methyl RNA complementary to non-contiguous single-stranded sequences in the 5 -UTR of HER- 2/neu. DNA hexamers were tested for their ability to mediate RNaseH cleavage. The two most potent sequences were chosen as the active and anchor partners, and they were linked using spacers of various lengths. Besides these dimeric antisense agents, we attempted to further increase potency with trimeric oligonucleotides comprising 1 'active' and 2 'anchor' oligonucleotides complementary to 3 non-contiguous sequences. We tested the ability of both dimeras and trimeras to down-regulate expression of the luciferase reporter gene placed downstream of the HER-2/neu 5'-UTR in wheat germ cell- free extracts. While dimeras successfully decreased expression at 1muM, trimeras, surprisingly, were stimulatory at 1muM for luciferase activity. Since both were equally potent in promoting RNA degradation of HER-2/neu mRNA in the RNaseH assay, this finding could be a clue to the mechanism that is responsible for HER-2/neu overexpression. We are now examining this phenomenon in breast cancer cell lines. In separate studies, we have developed and obtained a United States patent on a carrier polymer that can potentially provide oral bioavailability and enhanced cellular/cytosolic uptake into cells for antisense therapeutics.