RNA-Loaded Nanoparticles Fight Cancer

DirkDaring writes "It's been promised for years: that nanoparticles offer a treatment to many forms of cancer. Today, an important first step has been announced. In a new human trial, nanoparticles carrying RNA have successfully reached cancer cells and silenced the target gene. 'The researchers developed a nanoparticle carrying a molecular marker that binds to the surface of cancer cells, triggering the cells to absorb it. The siRNA carried within the particle was designed to silence a gene called ribonucleotide reductase M2 (RRM2), which regulates DNA synthesis and repair and is known to be an anticancer target. Because it was the first trial using targeted RNAi delivery for cancer, says Mark Davis, a professor of chemical engineering at Caltech and the study's lead author, "we wanted to choose a gene that was suspected to be hugely upregulated in a broad spectrum of cancers" in order to increase the likelihood of being able to observe the novel therapy's effect. The researchers analyzed biopsy samples from three melanoma patients in the trial who had received different doses of the therapy. They tracked the particles in the different samples, finding that the amounts they could see in the tumor cells correlated with the doses the patients received.'"

Re:most isn't good enough

[mcgrew]

That's the beauty of this technique. With other therapies like chemo, surgery, or radiation, there is damage to non-cancerous tissue, and those don't kill 100% of the cancer, either. With this you could theoretically continue treatment, as with traditional treatments you can't.

There is still the problem of diagnosing the cancer early enough; this wouln't have helped Linda. [slashdot.org]

Re:Great... not filtered out by the body

[Orga]

Gene specific targeting actually.

Re:Something doesn't add up here.

[reverseengineer]

Well, yes and no. You are absolutely right in that this isn't a permanent effect, in the sense that the DNA of the cancer cells is not altered at all. RNA interference is like putting a defender in the game to intercept a pass; if the defender leaves the field, the receiver will be open again. Translation of the ribonucleotide reductase gene will only be blocked as long as the interfering RNA is there to block the messenger RNA. However, ribonucleotide reductase is incredibly important; it's the enzyme that tears a hydroxyl group off of ribonucleotides and makes them deoxyribonucleotides. A cell cannot make DNA without it. The notion is that cancer cells being treated with RNAi will die during the course of treatment, with no way to replace them. If you get all the cancer, there is no way for it to "bounce back," and if you miss some, then at least progression has been seriously slowed.

On the point of receptors, that raises an interesting point. The nanoparticles used in this experiment target transferrin receptor, a cell surface receptor for the iron-carrying protein transferrin. Transferrin is highly upregulated in cancer cells because iron is required by many enzymes important to cell division (including ribonucleotide reductase, incidentally). Because it is so vital, cancer cells probably cannot just stop making transferrin. Developing a mutant form of transferrin that the nanoparticles cannot adhere to is a possibility, but there'd be a very narrow window of success (success from the cancer's POV). After all, cancer develops a transferrin receptor because it needs to get iron from transferrin- the same transferrin floating in your bloodstream your healthy cells uses. So whatever stealth transferrin receptor cancer cells come up to hide from nanoparticles still has to be compatible with real transferrin, or the cancer cells will be unable to divide.