Researchers at Wake Forest
University School of Medicine have destroyed prostate cancer tumors in mice
by injecting them with specially-coated, miniscule carbon tubes and then superheating
the tubes with a brief zap of a laser.
The procedure, which used DNA-encased, multi-walled carbon nanotubes (MWCNTs)
to treat human prostate cancer tumors in mice, left only a small burn on the
skin that healed within days.
"That we could eradicate the tumor mass and not harm the tissue is truly
amazing," said principal investigator William H. Gmeiner, Ph.D., a professor
of cancer biology at the School of Medicine.
An advance copy of the study is now available in the online edition of ACS
Nano and the full paper is scheduled to appear in a future print issue.
The researchers envision using the particles not only to kill tumors through
heating, but also to target cancer drugs to the diseased area in patients.
"The long-term goal in the project is to be able to use the DNA-encased
MWCNTs in multi-modality fashion for a variety of types of tumors," Gmeiner
said.
Carbon nanotubes are sub-microscopic particles that have been the subject of
intense cancer research. The MWCNTs used in the current study consist of several
nanotubes that "fit inside one another like Russian dolls," Gmeiner
said. The MWCNTs are injected into a tumor and then heated with laser-generated
near-infrared radiation. For this study, the tubes were injected into human
prostate cancer tumors being grown in mice. The radiation causes the tubes to
vibrate, creating heat. That heat kills the cancer cells near the nanotubes.
If there are enough nanotubes, the amount of heat generated can kill whole tumors.
For this study, researchers used MWCNTs encased with DNA, which prevented them
from bunching up in the tumor, allowing them to heat more efficiently at a lower
level of radiation and leaving the surrounding tissue virtually unharmed.
With funding from the National Cancer Institute and the North Carolina Biotechnology
Center, researchers grew 24 prostate cancer tumors in 12 mice. They then separated
the mice into groups receiving treatment with DNA-encased MWCNTs and laser,
laser only, non-DNA-encased MWCNTs only, or no treatment.
The eight tumors treated with a single injection of DNA-encased MWCNTs and
zapped with a 70-second burst from a three-watt laser were gone within six days
after treatment. While a minor surface burn appeared at the site of laser treatment,
it healed within a few days with antibiotic ointment, Gmeiner said.
The tumors in the other treatment groups showed no distinguishable reduction.
Using the DNA-encased MWCNTs increased heat production two- to threefold –
allowing researchers to use fewer nanotubes and a less powerful laser to kill
tumors – an important consideration as scientists determine potential
issues with the toxicity of nanotubes, since they remain in the body after treatment,
Gmeiner said.
Current thermal ablation, or heat therapy, treatments for human tumors include
radiofrequency ablation, which causes regional heating between two electrodes
implanted in tissue but cannot be used to selectively distinguish cancer cells
from healthy cells, like researchers hope they will be able to do with MWCNTs.
In addition to the DNA-encased MWCNTs used in this study, other nanomaterials,
such as single-walled carbon nanotubes and gold nanoshells, are also currently
undergoing experimental investigation as cancer therapies.
Before treatment with MWCNTs can be tested in humans, studies need to be done
to test the toxicity and safety, looking to see if the treatment causes any
changes to organs over time, as well as the pharmacology of the treatment, to
see what happens to the nanotubes, which are synthetic materials, over time.
Co-investigators for the study were Ralph D'Agostino Jr., Ph.D., John Olson,
M.S., Evan Gomes, Ph.D., and doctoral student Supratim Ghosh, all of the School
of Medicine; Samrat Dutta and Martin Guthold, Ph.D., of the Wake Forest University
Department of Physics, and David L. Carroll, Ph.D., director of the Wake Forest
University Center for Nanotechnology and Molecular Materials.
Posted August 19th, 2009
