Scientists have created a new class of cancer drug that combines the targeting strength of one type of ribonucleic acid (RNA) therapy with the therapeutic potency of another. Bruce Sullenger and colleagues have created a hybrid drug molecule that not only precisely targets diseased prostate cancer cells but also reduces levels of proteins that normally protect cancer cells from self destructing. The cancer agent is shown to effectively kill prostate tumors in mice, in a paper to be published in the August issue of Nature Biotechnology.
Aptamers are short nucleic acids with highly specific shapes that enable them to bind tightly to specific protein targets. There is already one aptamer drug on the market for the treatment of the eye disease age-related macular degeneration. Small-interfering RNAs, which specifically block the formation of proteins, are also making headlines as they progress through to the clinic.
The team's new type of RNA therapy combines the exquisite targeting capacity of an aptamer, which binds to a protein expressed specifically on the surface of prostate cancer cells, with the ability of two siRNA molecules to destroy RNA messages within the cancer cells that promote their survival.
Until now, approaches for delivering siRNA therapies to patients have been hampered by poor efficiency, a lack of specificity and unwanted immune responses in patients. It is hoped that the incorporation of aptamers into other siRNA therapies may overcome some of these problems and provide an effective means of targeting and killing diseased cells, although this will clearly require further experiments and studies to establish long-term side-effects and benefits.
Bruce Sullenger (Duke Center for Translational Research, Durham, NC, USA)
Abstract available online.
(C) Nature Biotechnology press release.
Message posted by: Trevor M. D'Souza