Advancing medicine, layer by layer
Cancer treatment and bone replacement.
DEEPAK KUMAR, Materials
Processing Center
July 1, 2014
July 1, 2014
Morton's work focuses
on developing drug-carrying nanoparticles to target hard-to-treat cancers —
such as triple-negative breast cancer (TNBC) — while Shah develops coatings
that promote better adhesion for bone implants.
Their work shares a
materials-based approach that uses layer-by-layer assembly of nanoparticles and
coatings. This approach provides controlled release of desirable components
from chemotherapy drugs to bone growth factors. Use of natural materials
promises to reduce harmful side effects.
"We have all of
these different areas in which we are seeking to address different problems
related to human health, certainly in the context of cancer research which is a
very big part of the lab now," Shah says. "In addition to that we are
also looking at how we can improve ways in which various patient diseases and
injuries are managed in a way that will improve current clinical
standards."
However it could take
from five to seven years to move from preclinical success in lab animals
through human clinical trials to public availability.
"Layer-by-layer
allows us to introduce very specific materials on the surface of various
substrates, be it a nanoparticle, be it an implant, right from the nanoscale to
the macroscale," Shah explains. "We were able to introduce all kinds
of different properties by depositing very specific materials on substrates, modifying
their surface properties and eventually having them do very specific things in
the context of applications."
Targeting
hard-to-treat cancers
When delivered through
time-staggered release from a liposome-based nanoparticle, the chemotherapy
drugs erlotinib and doxorubicin shrunk tumors in mice, Morton and colleagues
reported in a recent paper. A layer of hyaluronic acid promotes nanoparticle
passage through the body, while folate attached to their shell helps the
nanoparticles bind to receptors on cancer cells. The study targeted
two hard-to-treat cancers: TNBC and non-small cell lung cancer. Morton was lead
co-author with Michael J. Lee in biology professor Michael B. Yaffe's group at
MIT; Shah was one of several other co-authors. Both Hammond, the David H. Koch
Professor in Engineering, and Yaffe, the David H. Koch Professor in Science,
are members of the Koch
Institute for Integrative
Cancer Research at MIT.
For an earlier
study, led by postdoc
associate Zhou J. "Jason" Deng in Hammond's group, Morton was part of
a team that demonstrated progress in fighting TNBC with a layered nanoparticle.
They used biodegradable biopolymers and FDA-approved liposomes to create
nanoparticles made of a drug-carrying core and an outer layer containing short
interfering RNA (siRNA). The siRNA binds to a gene on the cancer cell and
blocks it from producing a protein that kicks out chemotherapy drugs. Shah also
was part of that team.
"We're trying to
design these systems that release therapies in combination that work together
in a fashion that has this enhanced benefit. We're designing these systems with
a focus on materials to release them in ways that will engage a cancer cell and
kill it in a more efficacious fashion, where the drugs work together and do so
with a more potent effect," Morton says.
In several studies
published beginning in 2011, Hammond and colleagues showed how coatings could
be laid down layer-by-layer to target tumor cells and control drug release from
the core. This approach has the advantage of increasing drug strength against
the tumor cell and decreasing harmful side effects. In the siRNA work, Deng,
Morton, and colleagues identified poly-L-arginine (PLA) as a promising
candidate because it offered the ability carry a large amount of siRNA, as well
as offering film stability and low toxicity to normal cells. In the study, they
estimated their nanoparticles contained about 3,500 siRNA molecules per layer
with approximately 95 percent surface coating. An additional layer of
hyaluronic acid gave the nanoparticles "stealth" ability to travel
through blood to the tumor site in live animal studies. "The result here
demonstrates that a target gene within the tumor can be effectively silenced
following a single, systemic administration of siRNA LbL nanoparticles,"
they wrote.
Strengthening
implants, improving drug delivery
Shah was lead author
of several papers on the bone implant studies, showing in a 2013 Science
Translational Medicine report that layered coatings containing bone
morphogenetic protein–2 (BMP-2) and hydroxyapatite (HAP) produced stronger
bonding of implants to bones in mice. Morton also was part of that team.
"In a small
percentage of people, the implant doesn't bond very well with the existing host
bone tissue and it causes the implant to fail," Shah
explains. Significantly, the coatings promoted growth of new bone tissue
directly on the implants, indicating a potential to replace the cement seam
that binds current implants to natural bone. Another step that can be included
in the layer-by-layer technique is adding antibiotics or antimicrobial polymers
that can prevent infection.
Morton says he joined
the Hammond-Yaffe collaboration after Yaffe's group had shown that
administering erlotinib and doxorubicin in a staggered fashion boosted the
effect of each chemotherapy drug against cancer — but when administered
independently, they didn't work as well. "In free form, whenever you apply
it to a biological system such as a mouse or human, the drugs get rapidly
cleared and don't go where they need to go," Morton explains. "We
were trying to find better ways to deliver these drugs in a way that would
promote this nice synergy that they observed in culture."
Morton made the
nanoparticles himself, worked with colleagues to analyze lab cultures and
conducted experiments on mice in the Koch Institute. The experiments showed
tumor shrinkage in mice after 32 days of receiving the nanoparticles releasing
both erlotinib and doxorubicin in time-staggered fashion. In contrast, tumor
growth continued in both untreated mice, as well as mice given just a single
drug, doxorubicin. The animal studies involved injecting human cancer cells
into mice. A fourth-year graduate student, Morton has another year to defend
his thesis and complete his doctorate.
Researchers in the
Hammond lab last year developed a spray-based technique for applying layers on
top of nanoparticles generated by the PRINT (Particle Replication In
Non-wetting Templates) process, which was pioneered by Joseph DeSimone at the
University of North Carolina at Chapel Hill. Morton was the lead author of that paper,
which showed that coating the nanoparticles with hyaluronic acid functionalized
them to adhere to CD44 receptors on TNBC cells (BT-20).
"Bringing PRINT
and spray-LbL technologies together enables fabrication of medicine with
exquisite control over particle composition, geometry, and surface properties,
providing an exciting platform for large-scale manufacture of highly-controlled
multi-functional particles," they report. Both the spray coat and PRINT
technologies are being commercialized.
Morton and Shah also
collaborated last year on a study of layered nanoparticles targeted against osteosarcoma, a form of bone cancer that
has a low treatment rate. Their experiments showed tumor shrinkage, and in some
cases, elimination, in mice from treatment with nanoparticles carrying a
combination of chemotherapy (doxorubicin) and tumor targeting (alendronate).
"To achieve this, a polyelectrolyte, poly(acrylic acid) (PAA), was
functionalized with a bisphosphonate, alendronate, and subsequently electrostatically
assembled in a nano particle coating," they reported. Using
clinically safe materials, mice treated with nanoparticles targeted at
osteosarcoma tumor cells exhibited reduced tumor volume compared to the
uncoated doxorubicin-loaded liposome control nanoparticles.
Restoring bone growth
Shah, who successfully
defended his PhD thesis in May, uses the layer-by-layer technology for
regenerating tissue damaged by injury or congenital defect, as well as better
bonding of implants — such as in artificial knee or hip bones — to natural
tissues.
"We've also
looked at taking these scaffold constructs that can be put inside the body at
the site of an injury," Shah says. "We've coated the scaffolds using
the layer-by-layer approach, depositing one polymer layer, followed by one
layer of biological drug that can induce the differentiation of stem cells that
are present within the body to form cells that can start secreting very
specific kinds of tissue." Once activated, stem cells can generate blood
vessels or bone, and heal defects in the body.
Hammond and Shah
patented some of their work and a startup, LayerBio, is attempting to
commercialize some aspects of the work in bone tissue engineering and
delivering drugs from bandages. Those bandages could aid diabetic patients or
wounded soldiers. Shah is acting as a consultant to the company. He also will
continue in the Hammond Lab as a postdoc to oversee a new project.
In the lab, Shah
assembled nanoparticles, made bone scaffolds and coated scaffolds and implants
using layer-by-layer technology. An important component is a polymer that
breaks apart in the presence of water, a material property called hydrolytic
degradability. That allows the scaffold to dissolve naturally as new bone forms
to replace it. The polymers can be modified to break down faster or slower.
The next step from a
research perspective is to reproduce the results found in small animal studies
of mice and rabbits and in larger animals, such as dogs or goats. "We're
confident in the technology, so we know what we need to do in order to do these
large animal studies to prove that ultimately we can use them in patients. This
is a necessary step for any therapeutic-based approach," Shah explains.
Morton hopes there
might be enough interest in the folate-decorated nanoparticles with the
dual-drug combo of erlotinib and doxorubicin to jump to human clinical trials
without larger animal studies. "That could be a possibility as well,"
he said.
Continuing
collaborations with Brigham and Women's Hospital and Massachusetts General
Hospital are testing the folate-dual-drug platform against tumors in mice
caused by TNBC cells implanted in them. The primary cancer cells were isolated
from women who've had the cancer.
"There really
isn't a specific therapy for triple-negative breast cancer (TNBC)," Shah
explains. One possibility might be an expedited approval process through the
FDA to get the new approach to clinic even faster (perhaps two years), because
there is a tremendous need for a specific therapeutic strategy for TNBC.
"This would be first in class in that sense," he adds.
Morton has another
year to go to complete his doctorate. Shah and Morton both work a lot with
animals: They use fluorescent labeling of proteins, drugs, nanoparticles, and
substrates to track what happens once they are implanted in test animals,
particularly how they are distributed in the different parts of the body.
"We've looked at that extensively," Shah says. Tumor progress, for
example, is tracked using micro CT — essentially a CAT scan of the animal. The
same imaging can be used to track bone formation.
Although their earlier studies didn't evaluate their
nanoparticles for toxicity to non-cancer cells, one previous study of cancer in
mice showed nanoparticles accumulated in the liver, kidneys, and brain.
"We will be evaluating the off-target toxicity, but it's also allowed us
to engage in collaborations for treating other types of diseases," Morton
says. A new collaboration with a Koch Institute clinical investigator, Scott Floyd,
is looking at glioblastoma, a brain cancer. The researchers will be studying
toxicity and looking for genetic cancer targets in glioblastoma tumors, in
order to deliver inhibitors that are specific to that cancer. "The beauty
of siRNA is that you can target it to essentially any gene. You can modify the
sequence that you incorporate into your siRNA, and then you can target it to
whatever gene you want to shut down or control the expression of," Morton
says. "In combination with traditional chemotherapeutics, for instance,
you can really design a number of different combinations that are pretty
powerful
Delivering a knock-out
punch
It isn't clear how
long the inhibiting effect of siRNA stays active against a target cancer cell,
Morton explains. "That's why these combination therapies are nice,"
he says. "If you can induce this kind short-term loss of protein, or
whatever it is that's causing the problem, then expose it to a second drug for
the knock-out punch that may be all you need. But I think there is still a lot
to be flushed out in the community as to how long different siRNAs and
different gene targets are able to be suppressed."
Because no two cancer patients have the same genetic profile,
they may have the same type of cancer, but with different genes driving the
aggressive growth. Based on genetic screening to identify the specific drivers
for individual patients, siRNA can be engineered to target them specifically.
"Our technology can deliver these drugs very well and it can do so in a
way that will incorporate independently all of these different types of
therapeutics for personalized medicine," Morton says.