New Weapon Against Breast Cancer | Newswise: News for Journalists:
New research from the University of Delaware suggests pairing two forms of minimally invasive, light-triggered therapy may be a powerful new option in combatting a particularly aggressive form of breast cancer.
Newswise — Two University of Delaware researchers have developed a
new approach to attack cancer, using two light-activated treatments that
appear to be more effective together than when applied independently.
More research is needed, but the findings point to promising new
approaches against an especially challenging kind of cancer — triple
negative breast cancer — which was the focus of their recent studies.
Triple
negative breast cancer is a particularly aggressive form of breast
cancer that accounts for 10 to 20 percent of patients. It is called
triple negative because the cancer cells do not have three biomolecules
commonly found on other breast cancer cells – receptors for the hormones
estrogen and progesterone and another receptor known as HER2. This
means there are no targeted treatments for triple-negative breast
cancer, so it is usually managed with surgery, radiation and/or
chemotherapy. Each of these options has negative side effects with less
than ideal patient outcomes.
Now UD researchers Emily Day,
assistant professor of biomedical engineering, and Joel Rosenthal,
associate professor of chemistry and biochemistry, and their labs have
shown that a combination of two minimally invasive therapies could give
doctors a more powerful weapon against this cancer as well as others.
Both
treatments are activated by near-infrared wavelengths of laser light,
but each accomplishes its mission differently. One — called photodynamic
therapy (PDT) — uses light-sensitive agents called photosensitizers to
produce a lethal form of oxygen (singlet oxygen) to accomplish a
combustion-like destruction of the cancer cells. The other therapy —
called photothermal therapy (PTT) — uses light-sensitive gold nanoshells
that heat up when irradiated with light and can essentially ‘cook’
cancer cells to death.
Because the cancer-killing effects of these
treatments are achieved only when the photosensitizers or nanoshells
are combined with light at the tumor site, both phototreatments can be
directly and selectively applied to tumor sites and cancerous tissues.
As a result, they are expected to show fewer side effects than more
conventional radiation or chemotherapy treatment options.
“Photodynamic
and photothermal therapy are not new concepts and there are probes and
nano-based materials that have been developed and used for such
applications, but there are limitations and drawbacks associated with
those existing systems,” Rosenthal said.
Some are not effective
in deeper tissue because the necessary light cannot reach it, while
others can damage white blood cells or cause problems in other nearby
healthy tissue.
When used together, though, the UD team found that
these treatments show powerful synergy, meaning they provide greater
than an additive therapeutic effect when compared to the individual
treatments. Together, they required lower dosages and produced more
natural cell death (apoptosis) than the kind of cell death caused by
injury or disease (necrosis). The latter, which can often trigger
harmful inflammation and lead to recurrence of disease is a cell death
mechanism that Day and Rosenthal were actively trying to avoid.
This
dual approach has not been used in clinical trials yet and more
research is needed before that step can be taken. The agent used in the
photothermal therapy is already in use in clinical trials, Day said. But
the PDT agent — a water-soluble biladiene complex synthesized in
Rosenthal’s lab — is new.
The connection between these two UD labs
started about two years ago when Day heard a presentation by one of
Rosenthal’s doctoral students, Andrea Potocny, during the Biomedical
Engineering Graduate Student Seminar Series. Potocny was discussing
efforts to develop water-soluble molecules to use in photodynamic
therapy.
Photodynamic therapy (PDT) works by turning the regularly
stable oxygen molecules (triplet) within a cell into a more energetic
form (singlet) that rapidly reacts with and degrades organic material.
This therapy has been used to kill viruses and bacteria and treat some
kinds of malignant cancers.
Rosenthal’s lab had developed a
complex that would produce the toxic singlet oxygen that could trigger
destruction of cancer cells. They needed a water-soluble molecule that
could be used in a real tumor in its regular biological context.
Day,
whose lab was working with nanoparticles for photothermal therapy
(PTT), realized she could help. She had extensive experience working
with models of triple-negative breast cancer with which to test the new
PDT approach, as well as examine its combined application with PTT.
It
was a remarkable success – a hat trick of advances, including easy
preparation, biological compatibility and excellent potency. The new
biladiene complex was effective in a small dose and had a much higher
phototoxicity score than PDT agents in current use.
Upon
demonstrating that the biladiene PDT agent developed by the Rosenthal
lab was both extremely safe and effective, another question emerged –
what would happen if they combined the photodynamic therapy with the
photothermal therapy?
That work led to uncharted territory and two publications – one in the journal Inorganic Chemistry on the
new PDT approach and one in the journal
Nanomaterials on
the combined PDT and PTT approach.
To
combine the two approaches, the labs used nanoshells (silica spheres
coated with thin, gold shells) to enable photothermal therapy and used
the biladiene photosensitizer developed by the Rosenthal lab to enable
photodynamic therapy. The treatments were applied either independently
or together to cell culture models of triple-negative breast cancer, and
their safety and efficacy were then examined.
An undergraduate student in Day’s lab — senior Rachel O’Sullivan — noticed unexpected results.
“When
we were testing the treatments, out of the blue I noticed that when we
put them together it was more effective at killing cells than each on
their own,” she said. “I went and talked to Rachel [Riley] in the lab
about it and she was surprised. I asked her if I did something wrong and
she said, ‘No! If it’s working synergistically, that’s really good!’”
Further
studies by the Day and Rosenthal team demonstrated this was indeed the
case. The combined therapies could synergistically inhibit
triple-negative breast cancer cells.
Support for the research came
from the University of Delaware Strategic Initiative Grant, the
Delaware Federal Research and Development Grant Program, the National
Science Foundation, the National Institutes of Health, a University of
Delaware Graduate Fellowship and the American Association of University
Women.
About the researchers
Emily Day is
an assistant professor of biomedical engineering, who earlier won a
National Science Foundation Early Career Award. Her research focuses on
nanomedicine, gene regulation, photothermal therapy and translational
cancer research. She earned her bachelor’s degree in physics at the
University of Oklahoma, her doctorate in bioengineering at Rice
University and worked as a postdoctoral fellow at Northwestern
University before joining the UD faculty in 2013. The students in her
lab who worked on this project include Rachel O’Sullivan (a senior
undergraduate in biomedical engineering) and Rachel Riley (a 2018
doctoral graduate from biomedical engineering who is now a postdoctoral
researcher at the University of Pennsylvania).
Joel Rosenthal
is an associate professor of chemistry and biochemistry and associate
chair of Graduate Studies and Research. He is an expert in
photochemistry and electrochemistry and through his research seeks to
address issues related to catalysis, molecular energy conversion and the
improvement of human health. He earned his bachelor’s degree from New
York University, his doctorate in inorganic chemistry at the
Massachusetts Institute of Technology and served as an NIH postdoctoral
research fellow at MIT before joining the UD faculty in 2010. Among his
awards to date are an NSF Early Career Award, an Alfred P. Sloan
Research Fellowship and selection as a Gerard J. Mangone Young Scholar.
The student in his lab who worked on this project is Andrea Potocny, a
doctoral student in chemistry and biochemistry.