MEDICAL DEVICE INNOVATION - Medical Device Daily

152
Nanotubes plus radiation may be
the key to a kidney cancer cure
By LYNN YOFFEE
Medical Device Daily Staff Writer
An introductory talk from the director of the Center
for Nanotechnology and Molecular Materials at Wake
Forest University’s (Winston-Salem, North Carolina)
School of Medicine about the value of nanomaterials
sparked an idea among researchers that may now lead to
an effective kidney cancer cure.
Researchers there have just reported using nanotubes
to eliminate cancerous kidney tumors and insure that they
don’t return. Nanotubes are injected into the tumors and
heated with a laser to effectively kill tumors in nearly 80%
of mice tested, suggesting a potential future cancer treatment
for humans.
“Our lab is interested in relationships between iron and
cancer,” Suzy Torti, PhD, a professor of biochemistry at WFU
School of Medicine, told Medical Device Daily. “We came to
study nanotubes because of the proximity of the
Nanotechnology Center. A talk by the director, David
Carroll, got everybody here excited. These particles have
some iron and that can be used as contrast agents and
those were our initial thoughts, but it became clear that
nanomaterials were useful for more than that.”
The work, reported in the August issue of the
Proceedings of the National Academy of Sciences (PNAS)
reports how carbon-based multi-walled nanotubes
(MWCNTs), which contain several nanotubes nested within
each other, were injected into tumors and then zapped with
a 30-second dose of near-infrared radiation.
Rather than delivering the nanotubes systemically,
Torti’s team injected them directly into tumors, so that “. . .
they didn’t have to find the tumors. That was a first step –
just proof that they can be tumor-ablative agents if you can
get them to the right place at the right time.
“Then we exposed it to a near infrared laser radiation,”
she said. “When you do that, nanotubes begin to vibrate
pretty fast, creating heat. It’s localized to where the infrared
radiation hits the tubes causing death of tumor cells.”
For the study, Torti’s team reported that mice who
received no treatment for their tumors died about 30 days
into the study. Those that received the nanotubes alone or
had laser treatment alone survived for a similar length of
time. Tumors disappeared for 80% of mice that received the
MWCNTs combined with laser treatment.
Nine months later, many of the treated mice remained
tumor free.
“Nanotubes are pretty efficient at absorbing light . . . a
broad absorption spectrum relative to other materials,”
Torti said when asked why she chose nanotubes rather
than another nanomaterial. “They can also absorb nearinfrared
radiation. They’re pretty efficient at absorption
MEDICAL DEVICE INNOVATION 2010
and reduce the amount of laser light needed to excite
them.”
Torti and her colleagues chose to try the treatment on
kidney tumors because, “People have tried radio frequency
ablation, which is a similar idea. A tip is inserted into the
kidney to generate heat. But there are shortcomings.
Although ablation is successful, the probe is not the best;
there is seeding of tumors along the tumor trace. Using
MWCNTs plus near-infrared radiation provides more diffuse
heating.”
Thermal ablation treatments for human tumors currently
include radio frequency ablation, which applies a single-point
source of heat to the tumor rather than evenly
heating the tumor throughout, like the MWCNTs can do.
Torti said her team was able to watch the tumors
shrink, day by day, until they disappeared.
“Not only did the mice survive, but they maintained
their weight, didn’t have any noticeable behavioral abnormalities
and experienced no obvious problems with internal
tissues,” she said. “As far as we can tell, other than a
transient burn on the skin that didn’t seem to affect the animals
and eventually went away, there were no real downsides
– that’s very encouraging.”
Torti’s team noted the thermal effects generated by
MWCNTs had added benefits, beyond the ablation of cancerous
tumors. “For example, hyperthermia can increase the permeability
of tumor vasculature, which can enhance the delivery
of drugs into tumors, as well as synergistically enhance
tumor cytotoxicity when combined with chemotherapy or
radiotherapy,” according to the PNAS article.
The next step is to explore systemic delivery and use a
“slightly less contrived system” so that kidney tumors are
actually resident in the kidney, rather than a subcutaneous
placement as was the case for this study, in order to move
closer to clinical applications.
The team will then begin toxicology and pharmacology
studies. It’s unknown what happens to the nanotubes after
they are used. Torti said she observed (anecdotally, but not
reported) that a certain number do remain at the site. It’s
not a bad thing, she said, because it provides an opportunity
for retreatment with additional zaps of radiation if necessary.
A grant from the National Cancer Institute
(Bethesda, Maryland) and a private donation will keep the
wheels turning on this research project for several more
years. Torti estimates that it would take at least “a few more
years” of work to test the new therapy before human trials
could begin, “even if everything worked remarkably well.”
(This story originally appeared in the Aug. 4, 2009, edition
of Medical Device Daily)
To subscribe, please call MEDICAL DEVICE DAILY Customer Service at (800) 888-3912; outside the U.S. and Canada, call (404) 262-5547.
Copyright © 2010 AHC Media LLC. Reproduction is strictly prohibited.