New Nanoparticle Cancer Therapy 81
quixote9 tips us to a BBC story on a promising new cancer therapy using targeted nanoparticles. From the article: "The researchers used the nanoparticles to zero in on the network of blood vessels that supply the tumors in mice with nutrients and oxygen... [They] developed a technique for amplifying [the nanoparticles'] homing ability by designing a multifunctional nanoparticle that binds to a protein structure found only in tumors and associated blood vessels... The tests showed that within hours of the injection, the artificial platelets began blocking the supply without harming normal tissues. The scientists believe the nanoparticles could also be used to carry drugs to the tumor."
Re:When (Score:4, Informative)
Two things:
1) As someone else points out, it's relatively easy to kill cancer cells in a dish (see the last "Cure For Cancer!" story from a few days ago) or even in a mouse (as in this case). That's a long, long way from a usable treatment.
2) In fact, some fraction of these do become useful treatments, but you're not aware of them because they're not miracle cure-alls and because they're not advertised on television like Cialis or Clarinex.
Mathematical and Computational Modeling (Score:5, Informative)
Some of my colleagues (e.g., Vittorio Cristini [uci.edu]) have been modeling the potential benefits of nanoparticle drug delivery for a couple of years now. As has been known for some time (e.g., see papers from R.K. Jain), the blood vessels that grow to supply tumors with nutrients (the tumor-induced neo-vasculature) are different than regular, non-pathological vessels. They tend to be more tortuous and leaky, with larger holes than regular vessels.
This is where the nanoparticles come in: one can design nanoparticles that encapsulate cancer drugs in particles that are too large to exit normal blood vessels but can pass through the leakier, tumor-induced blood vessels. This naturally targets cancerous tissues.
However, there are other issues to consider. Due to the high pressure inside tumors (due to the rapid proliferation of cells within a confined area, among other factors), along with the leaky vessels, blood flow can be very poor inside a tumor, and so while the drug may be targeted toward and delivered to the tumor, it may not actually penetrate very far into the tumor. Some great work has been done by Steven McDougall [hw.ac.uk], Sandy Anderson [dundee.ac.uk], and Mark Chaplain [dundee.ac.uk] in this area. In particular, look at their DATIA (dynamic adaptive tumour-induced angiogenesis) papers.
One way around this (suggested by R.K. Jain and Vittorio Cristini, among others) is to use targeted anti-angiogenic therapy to prune out the worse blood vessels and improve flow within the tumors, thereby also improving drug delivery and penetration.
Lastly, on the therapeutic aspect of blocking up tumor blood vessels with the nanoparticles, the work we've done (see this paper [doi.org], which will appear in the Journal of Theoretical Biology soon), indiscriminately cutting off the nutrient supply to a tumor can increase tumor invasiveness by increasing morphological (shape) instability. (See some of the animations here [uci.edu].) So ironically, while more tumor cells may be killed, those that remain may spread farther and initiate new tumors. Given that hypoxic tumor cells are more likely to be resilient to further treatment (e.g., hypoxic breast cancer cells), this is a problem worth keeping in mind when planning anti-angiogenic therapy.
If you're interested in these topics, please do check out the paper above. (You can also download it at my website [uci.edu] without any special memberships.) Even if you don't like it, we have a lot of references you may find handy. -- Paul
Re:Halfway there, maybe (Score:2, Informative)
I'm a chemist that does drug formulations and I have made nanoparticles. The nanoparticles that I made were specifically, solid lipid nanoparticles (SLNs) for an oral formulation to increase bioavailability, but we have also made nanoparticles out of biodegradable polymers. The solid lipid nanoparticles dissolve quickly because of the low melting point of the lipids. The biodegradable polymers are typically poly lactic glycolic acid (PLG), which because of the large surface area of nanoparitcles should cause more rapid hydrolysis of the polymer to it's monomer, Lactic acid or Glycolic acid. Lactic acid is what is produced in your muscles after you work out to cause you to be sore, but both Lactic and Glycolic acid are commonly found in the body.
Nanoparticles are really small so it would take a lot of them to cause a clot. The larger microparticles when they are injected form a depot and are not intended to be in the circulatory system.
I remember hearing something about this technology but I think that there were serious side effects to the "homing ability" of the nanoparticle. I'm assuming that the nanoparticle is a biodegradable polymer with some sort of protein coating.