Tuesday, October 11, 2011

Two-for-one: locate and kill cancer with a single agent

Scientists may have found a way to more accurately locate cancer cells and, at the same time, destroy them. New, nano-sized metal particles can bind to tumor cells, emit a fluorescent glow, and then be heated with a magnetic field to kill nearby cancer cells. By uniting the process of imaging and treatment, therapy becomes more effective and targeted to the cancerous cells.

There are numerous methods of cancer imaging, many of which involve using an identifiable molecule that fits into a cancer cell receptor like a key fits into a lock. This process takes some time (in this study 48 hours), and requires that the molecule does indeed fit into the receptor of a cancerous cell, that the molecule can be distinguished during imaging, and that enough of those molecules are located in close proximity to recognize an increased concentration.

For years, researchers have suspected that nanoparticles are good candidates to improve cancer imaging because of the likelihood that more of them would bind to a tumor. In 2010 Dr. Lukehart, a Chemistry professor at Vanderbilt, showed that this was true by using nanoparticles made of iron and platinum. Each nanoparticle was covered with thousands of peptides,  molecules used to bind to a cancer cell. When the tumor is hit with radiation, the nanoparticles bound to cancer cells fluoresce, giving off light waves not visible to the human eye. A machine able to detect these waves is used to locate where they are coming from, to create an image of where in the body cancer cells are. The image created using nanoparticles was much brighter and easier to analyze than when single molecules were previously used. This improvement is because  when a peptide binds to a receptor, like a key fitting into a lock, there are thousands of metal molecules within the nanoparticle it is attached to. Since each metal molecule is giving off the light waves, the machine is able to detect thousands more light rays coming from each location where a peptide is bound to a cancer cell.

Researchers outside Dr. Lukehart's lab see the advantage of this technique. “This technology is cool,” says Dr. Wright, a bio-inorganic chemist at Vanderbilt who did not participate in the research,“ It let’s us see how well radiation is going.”

Using these nanoparticles to image cancer in the future is likely, not just because of the superior images that result, but also because of the possibilities of treatment using these same nanoparticles. The iron and platinum nanoparticles used are paramagnetic, which means they line up in magnetic environments. By rapidly reversing the polarity of a magnetic field, the nanoparticles will create heat, which can kill the cells located nearby.

The platinum part of this nanoparticle introduces another way that this drug could be used to treat cancer. Platinum has been shown to be an anti-cancer chemical. In fact, the anti-tumor properties of the element are already in use in the platinum-containing chemotherapy drug, Cisplatin, used to treat testicular cancer. By using nanoparticles that both contain platinum and are surrounded by peptides which link to cancer cells, as was done in this study, it is possible that the simple introduction of this imaging agent into the body could serve to treat cancer without any external influence.

Dr. Hallahan, head of the Department of Radiation Oncology at Washington University School of Medicine in St. Louis, suggests, “These nanoparticles will first be used for patients with poor prognosis cancers. These include patients with recurrent disease and patients with [inoperable] cancers.” Treatment with these nanoparticles fills an unmet medical need, as there are “no treatment options for most of these patients.”

In this particular study, only the imaging abilities of nanoparticles were analyzed and only lung cancer was investigated. According to Lukehart, however, this method could be easily adapted for other types of cancer by simply changing the peptide linker to one that binds to the targeted cancer cell.

The largest obstacle in the way of getting this imaging technique and treatment to patients is the creation of these nanoparticles. Scaling up their production  is not only difficult, but expensive, and could hold back the application. Lukehart hopes, however, that “if there are really hot results in future research, we may see it in place in only a couple years.”

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