US scientists have used non invasive radio waves to heat up carbon nanotubes embedded in the cancerous livers of rabbits to kill cancer cells without damaging healthy tissue.

The preclinical study is published in the October 24th early online issue of the journal Cancer and is the work of Dr Steven A Curley, professor of surgical oncology at the University of Texas MD Anderson Cancer Center in Houston, Texas.

Carbon nanotubes are hollow cylinders of pure carbon with a diameter of one nanometer, or one billionth of a meter.

Curley and colleagues said their method completely destroyed the liver cancer tumors in rabbits, with no side effects, but there was some heat damage to neighbouring tissue 2 to 5 mm from the tumors. This was due to nanotube leakage, they said.

"These are promising, even exciting, preclinical results in this liver cancer model," said Curley, who is senior author of the paper.

The challenge is making sure the nanotubes only attach to cancer cells without damaging healthy tissue, said Curley. One way to do this is bind the nanotubes to antibodies, peptides, or other agents that target only cancer cells. But unfortunately it is not as straightforward as it sounds for many of these agents also target healthy tissue.

That's why a clinical trial on humans is at least three to four years away, said the research team.

Curley and colleagues collaborated with experts in nanotechnology from Rice University, also in Houston, and the entrepreneur John Kanzius, a cancer survivor and former radio station owner who inspired this line of research and invented the prototype radiofrequency generator used in this experiment.

The experiment began in "test tubes". Two lines of liver cancer cells and one of pancreatic cancer cells were destroyed after being incubated with nanotubes and exposed to radio waves.

In the next stage, four rabbits with liver cancer had a solution of single-walled carbon nanotubes injected directly into the tumors. They were then exposed to two minutes of radio waves, which heated up the nanotubes and destroyed the liver tumors.

There were also two control groups. One group of rabbits had nanotubes inserted but no radio waves, and the other had the radio waves but no nanotubes. Their tumors remained undamaged.

Radio waves penetrate far into the body so putting nanotubes inside deeply embedded tumors and shining radio waves into them is a way to access these deep seated cancer cells non-invasively. Without the nanotubes or similar devices to pick up the radio frequencies, the waves would pass straight through, harmlessly.

Kanzius said that he felt "humbled" by the results. He said he realized it was early days, but Curley and colleagues have rapidly, but carefully, moved the research on a stage and he looked forward to continuing the collaboration and "hopefully to watching the first person be treated with this procedure".

"Carbon nanotube-enhanced thermal destruction of cancer cells in a noninvasive radiofrequency field."
Gannon CJ, Cherukuri P, Yakobson BI, Cognet L, Kanzius JS, Kittrell C, Weisman RB, Pasquali M, Schmidt HK, Smalley RE, Curley SA.
CancerEarly View: Published Online: 24 Oct 2007
DOI: 10.1002/cncr.23155
click here for Abstract.

Written by: Catharine Paddock