Chemotherapy, with its side effects, is often the worst part of the cancer treatment process. But what if there were a noninvasive treatment that could target a tumor and leave the healthy tissue alone? Engineers at Rice University in Houston have successfully tested a new cancer therapy based on nanoshells gold-coated quartz spheres roughly 1/500th the width of a human hair. By adjusting the relative size of the two parts of the nanoshell, the core and the shells, they can tune the optical properties of that nanoparticle such that they can control what wavelength of light or color it absorbs. Naomi Halas reported in the journal Cancer Letters in 2004 that the nanoshells' ability to capture light and convert it to heat has, in lab tests on mice, destroyed tumors. She and Rice biomedical engineer Jennifer West coat the nanoshells with a substance that binds them to cancer cells. Once they're in place, infrared light is shined through the skin and down into the tumor site. It's a very simple handheld laser, used only for three minutes. Nanoshells absorb light and convert it to heat extremely efficiently, and three minutes is sufficient to kill the cells in the tumor. Studies Show Promise Halas and West studied 25 mice with tumors that were divided into three groups: one that received no treatment; one that received saline injections and three minutes of exposure to the near-infrared light; and one that received nanoshell injections and a laser applied on the skin above each tumor. While tumors in the other two groups of mice continued to grow, the tumors in the group that got the nanoshell treatment disappeared within 10 days, and those mice remained cancer-free afterward. No Toxic Trail So a process of nontoxic, noninvasive illumination resulted in complete tumor regression. In response to the light, the nanoshells heat up and destroy the tumor that surrounds them. Healthy cells around the tumor do not heat up because they absorb far less energy than the nanoshells do. The approach resembles the process whereby coffee heats up in a microwave oven while the cup remains cool. This is in stark contrast to chemotherapy, which when injected into the bloodstream, will circulate through the body on its way to the tumor, and it will kill everything in its path. It leaves what people call a "toxic trail" through the body. And all of the dead blood cells and all the damage caused by this toxin as it progresses to the tumor site lead to the side effects that we associate with cancer treatment like chemotherapy. In contrast, nanoshells, which are nontoxic, would progress through the bloodstream to the tumor site, and unlike conventional drugs, would leave no toxic trail. No Adverse Reactions We recently began a clinical evaluation of nanoshells in cats with soft tissue tumors. So far, we have never seen any adverse reaction to the nanoshells, and all of the preliminary testing at this point, and all of the results to date, look like they're very safe, non-toxic and bio-compatible. When nanoshells are directly injected into the bloodstream, the body doesn't recognize them. They're coated with specific molecules that essentially make them stealth particles, so they're not recognizable as a foreign object. Also, they're gold, and gold is not recognized as a foreign substance by the human body. If we compare nanoshell-assisted cancer therapy to conventional cancer therapy, such as chemotherapy for example, there's a very high likelihood that the type of side effects would be greatly reduced. If our cat studies prove effective, human trials could begin within another year to 18 months. Kevin A. Hahn, DVM, Ph.D., Dipl. ACVIM (Oncology), is director of Oncology Services at Gulf Coast Veterinary Specialists, Houston (www.gcvs.com/oncology), and is the oncology consultant for YourNetVet (www.yournetvet.com). <HOME>
