CANCER is always a dreaded diagnosis.
Even with improvements in treatment results over the last few decades,
cancer is still the second leading cause of death in this country.
for cancer include cutting, burning, and poisoningsurgery,
radiation therapy, and chemotherapyany combination of which
is often highly successful in eradicating cancer cells. However,
cancer that metastasizes, spreading to multiple sites in the body,
has proved to be difficult to treat. Therapy with beams of radiation
is only successful for localized cancers. At the same time, the
5-year survival rate for patients with detectable metastatic cancer
who receive chemotherapy is less than 20 percent for many cancers.
that almost three-quarters of all cancer deaths involve cancers
that have metastasized, finding an effective treatment method is
a top national health priority. Livermore is facing this challenge
head-on with a far-reaching set of projects overseen by medical
physicist Christine Hartmann-Siantar, director of Livermores
Glenn T. Seaborg Institute. In pursuing this work, biochemists,
computational biologists, material scientists, chemists, and physicists
in two Livermore directoratesChemistry and Materials Science
and Biology and Biotechnology Research Programare collaborating
with scientists at the University of California (UC) at Davis Cancer
had been principal investigator for development of PEREGRINE, a
treatment planning program for radiation beam therapy that couples
Livermores storehouse of radiation transport data with powerful
simulation tools and desktop computers. (See S&TR, May
1997, PEREGRINE: Improving Radiation Treatment for Cancer; April
2001, Leading the Attack on Cancer.) PEREGRINE, named for the
patron saint of cancer patients, has since been commercialized and
is now available to hospitals as a tool for accurately targeting
cancer tumors with radiation beams.
couple of years ago, PEREGRINE was in the technology transfer phase,
and the team was asking what we could do to save the next 100,000
cancer patients using radiation, Hartmann-Siantar says. Beam
therapy cannot treat cancer that has metastasized. We wanted to
know how we could address widespread cancer.
(a) Conventional radiation
beam therapy works well for localized cancer but not for cancer
that has metastasized. (b) With molecular targeted radiation
therapy, the proven effectiveness of radiation in curing cancer
can be extended to metastatic cancer.
At about the same time, Livermore and the UC Davis Cancer Center
formed a research collaboration to fight cancer. In part as a result
of that joint venture, the UC Davis Cancer Center was named a designated
cancer center by the National Cancer Institute, one of the National
Institutes of Health. Together, Livermore and UC Davis are seeking
better ways to prevent, diagnose, and treat cancer.
cancer-fighting initiative brought Hartmann-Siantar and others
Livermore together with many experts at the UC Davis Cancer Center,
including physicians Sally and Gerald DeNardo, leaders of the Section
of Radiodiagnosis and Therapy in the Molecular Cancer Institute
at the UC Davis Medical School. The DeNardos are pioneers in the
treatment of cancers with radiation administered internally. They,
together with Hartmann-Siantar and others at Livermore and UC Davis,
envisioned much of the work that goes on today in four projects
that are described here.
team is perfecting a new way to get radiation inside the body and
directed only at cancer cells. New molecules being synthesized
the laboratory will lock on to specific proteins, in a process
known as molecular targeting. When the specially designed molecules
tagged with a radioactive isotope, deadly radiation can be delivered
straight to cancer cells.
problem with chemotherapy is that the toxicity it delivers to tumors
only slightly higher than what it delivers to healthy tissue. The
beauty of targeted radionuclide therapy is that diseased cells
a much higher fraction of drug. The radioactive material is busily
destroying cancerous tissue while normal, healthy tissue stays
This translates to no more nausea or hair loss for the patient.
team is developing a new imaging system that uses molecular targeted
radionuclides to reveal and diagnose breast cancer tumors. A third
project is combining such images with computer software similar
to PEREGRINE to make the planning of molecular targeted radiation
therapy as specific to each patient as possible. Finally, a fourth
project is using subcellular imaging to take snapshots that show
how radioisotopes interact with cells to kill tumors.
none of the systems currently under development will be available
for patients in the immediate future. Says Hartmann-Siantar, Even
if we are wildly successful, it will be at least 10 and more likely
20 years before our advances mean widespread cures for metastatic
cancer. After research and development are done, the phases 1, 2,
and 3 trials take several years. Thats just the way it works.
This diagram shows how a linker molecule
will connect molecules that bind to two sites on a protein.
When two molecules are connected with a linker, they bind
with up to a million times higher affinity than does each
molecule alone. The goal is to develop synthetic high-affinity
ligands (SHALs) that bind to cancer cells. When tagged
with a radioactive substance, the SHAL serves as a delivery
system for cancer-killing treatment.
Delivery System for the Cure
radiation is a proven killer of cancer cells, researchers have been
searching for years for the best way to get radiation inside the
body and directed specifically at tumors.
1985, a team led by the DeNardos was the first to use monoclonal
tagged with a radioisotope to treat cancer patients. Monoclonal
antibodies are laboratory-produced substances that can locate and
bind to cells wherever they are in the body. Many monoclonal antibodies
are used in cancer detection or therapy; each one recognizes a
protein on certain cancer cells. Monoclonal antibodies can be used
alone to stimulate the immune system, or they can be used as a
to directly deliver drugs, toxins, or radioactive material to a
tumor. The first monoclonal antibodies were produced entirely from
the cells of mice, which meant that rejection by the human body
was common. In recent years, methods for humanizing monoclonal
antibodies have greatly reduced the rejection rate.
the years, the DeNardos have treated more than 200 patients with
radionuclide-tagged monoclonal antibodies for non-Hodgkins
lymphoma, prostate, and metastatic breast cancers. Lymphoma is a
cancer of the lymphatic system, a network of thin vessels and nodes
in the body whose function is to fight infection. Lymphoma is a
particularly difficult cancer to treat because its tumors tend to
be small and widespread. Cancers of the prostate and breast are
carcinomas. Accounting for at least 80 percent of all cancers, carcinomas
begin in the lining layerepithelial cellsof organs.
DeNardos patients were typically at the end of the line,
looking only to gain a few more months of life after not responding
chemotherapy and radiation. Despite their grim prognosis, 60 percent
of the patients responded to radionuclide-tagged antibody treatment,
and 30 percent of that number have celebrated with complete remissions.
radiation therapy for cancer was gaining ground in research hospitals,
a project to develop synthetic antibodylike molecules began at Livermore
about three years ago. (See S&TR, June
2002, A Two-Pronged Attack on Terrorism.) The original goal
for this work was to design molecules to bind to and capture proteins
of biowarfare agents for fast, efficient detection. It was Gerald
DeNardo who suggested to Livermore researchers that synthetic molecules
could easily be tagged with radionuclides and used for cancer treatment.
Rod Balhorn heads the team of biologists and chemists at Livermore
who are producing the synthetic high-affinity ligands, or SHALs.
The synthesis of a SHAL in the laboratory is the culmination of
a process that integrates computations and experimental selection.
A SHAL has two ends, each of which is a small molecule selected
for its affinity to bind to a part of a particular protein (as
through computational modeling by Felice Lightstone and other members
of Mike Colvins biomolecular modeling team). The two ends
are combined by a linker molecule to create an entirely new molecule
that will bind to the target protein thousands or even millions
of times more strongly than either one of the original small molecules
first cancer-fighting SHAL, synthesized by Julie Perkins, binds
to a receptor protein known as HLA-DR10 that is found on the surface
of almost all non-Hodgkins lymphoma cells. This SHAL, which
will carry the radioactive isotope yttrium-90, is designed to rapidly
pass through the liver and kidney to minimize the systemic damage
that can occur when antibodies carry radionuclides.
new high-affinity ligands will have the selectivity of monoclonal
antibodies without the baggage that comes with antibodies, says
laboratory testing of the non-Hodgkins lymphoma SHAL at UC
Davis will be to verify that it is selective for cancer. Researchers
are examining the response of many kinds of tissue to the SHAL,
using tissue arrays that have various types of healthy tissueheart,
liver, kidney, breast, and so onas well as some cancerous
tissue. The first SHAL tested has been shown to bind selectively
to human lymphoma cells, and it doesnt bind to normal cells
lacking the HLA-DR10 receptor. Future tests will use mice implanted
with a human cancer to determine if the SHAL selectively localizes
in the tumor, a feature critical for effective tumor targeting.
The team will also be designing SHALs for prostate cancer and metastatic
breast cancer in the next few years.
The first synthetic high-affinity
ligand (SHAL) for cancer is designed to bind to HLA-DR10,
a receptor protein found on the surface of almost all non-Hodgkin’s
lymphoma cells. The two sites on the HLA-DR10 molecule
that the SHAL binds to were identified by Felice Lightstone.
Imaging to Detect
SHALs or monoclonal antibodies that bind tightly to cells can also
serve as a diagnostic tool for cancer. The gamma rays they emit
can be detected to reveal precisely where cancer cells are located.
A team led by Livermore physicist Kai Vetter is developing a high-resolution
gamma-ray imager designed to improve the odds of detecting breast
a mammogram indicates the presence of a lesion in the breast, a
biopsy must be performed. Yet 80 percent of such biopsies reveal
a benign rather than a malignant lesion. Patients and doctors alike
want to reduce the problem of false-positive mammograms, reduce
the need for invasive biopsies, make mammograms more sensitive,
and generally improve breast cancer detection.
gamma-ray detection systems can only detect lesions greater than
about 10 millimeters across, which is too large to improve detection
and treatment of breast cancer. Livermores new technology
is applying radiation detection systems developed for national
to the detection of breast cancer lesions just 1 to 2 millimeters
isotope detection systems require that radiation emanating from
the tumor source be aligned, or collimated. The new Livermore detector
eliminates this need for collimation. Instead, it relies on recent
developments in segmented semiconductor detectors and digital signal
processing to measure the spatial distribution of the outgoing,
tumor-based gamma rays. Because some gamma-ray energy is lost in
the collimation process, eliminating collimation makes Livermores
new device just that much more efficient. Thus, technology advances
have made it possible to realize the full potential of the gamma-ray
imaging concept in the new detector.
initial demonstration of Livermores gamma-ray imager prototype will
use small radioactive test lesions embedded in material designed
to mimic the tissue of a womans breast. In developing the
prototype, Vetter is working closely with UC Davis physicians and
technical staff to optimize the imagers usefulness in a clinical
new system for detecting breast cancer tumors relies on recent
developments in segmented semiconductor detectors and digital
signal processing. Unlike other gamma-ray detectors, this
system does not require collimation (alignment) of the radiation
emanating from the tumor source. Because some gamma-ray energy
is lost in the collimation process, not requiring collimation
increases system efficiency.
Imaging to Plan the Attack
ability of targeted molecular radionuclides to locate tumors is
being put to another use as well. By taking images of patients after
they have received a small diagnostic radionuclide dose, physicians
can determine exactly where the drug is distributed in the body.
No other cancer treatment can provide that kind of dose information.
of researchers at Livermore, Montana State University, Idaho National
Engineering and Environmental Laboratory (INEEL), and UC Davis is
putting that dose data to work in new treatment planning system
known as Modality-Inclusive Environment for Radiotherapeutic Variable
Analysis, or MINERVA. While the initial emphasis in the development
of MINERVA is on targeted radionuclide therapy, the system can be
used for any kind of external or internal radiotherapy or combination
team is making use of radiation-response data that have been accumulated
over decades of conventional radiation beam therapy. They anticipate
that this valuable data can be used to refine the estimates of what
it will take to make targeted radiation therapy cure metastatic
cancer while avoiding injury to healthy organs.
MINERVA, INEELs computational dosimetry system for neutron radiotherapy
is being merged with Livermores fast, three-dimensional Monte
Carlo PEREGRINE simulations for photonelectron therapy. Montana
State is writing most of the user interface, and UC Davis is providing
its expertise in targeted radiotherapy.
Two-dimensional planar or three-dimensional single photoemission
computed tomography (SPECT) images taken over time after
a patient ingests a small diagnostic dose of a synthetic
high-affinity ligand tagged with a radionuclide. Those images
and (b) computed tomography (CT) images of the patient’s
anatomy are the basis for MINERVA’s Monte Carlo radiation
simulations. (c) MINERVA’s simulations result in verifiable
quantitative data on the amount of radiation that the patient
has absorbed and where the radiation dose is distributed
in tumors and critical normal organs. (d) The physiology
of an individual patient determines how much radiation dose
radiation physicist Joerg Lehmann, who directs Livermores
part of the effort, Targeted radiotherapy has been in trials
for many years and there are other planning programs around. But
their dosimetry data are less accurate than MINERVAs will
dosimetry is based either on the patients body surface alone
or on risk assessment approaches used in diagnostic nuclear medicine.
At the same time, treatment planning is not based on the patients
particular anatomy. The end result is that most patients are undertreated
as doctors strive to avoid damage to normal organs. No one wants
the cure to kill the patient.
contrast, MINERVA is designed to produce a customized treatment
plan for each
patient. When the system is up and running, it will reveal the
time-dependent activity of radiation in the body. First, an initial
test dose of
radiation in a SHAL or monoclonal antibody is administered to the
patient. Then a series of images is taken of the radioisotope in
the body over time using either two-dimensional planar images or
three-dimensional single photoemission computed tomography (SPECT)
images. The distribution of radiation activity in the body is based
on these images and a set of computed tomography (CT) scans of
patients body that show the location of organs. Monte Carlo
radiation simulations will provide verifiable quantitative data
on the amount of radiation that the patient has absorbed and where
the radiation dose is distributed in tumors and critical normal
comes decision time for the oncologist: Will this patient benefit
from this kind of therapy? If so, how much dose should be administered
to the particular patient?
present, the resolution in available isotope imaging technologies
than that of a CT scan. Isotope images also tend to be time-consuming
to obtain. But as Livermores collimatorless technology becomes
available, the image and resolution will improve markedly, leading
to even better data on the activity of the radiopharmaceutical.
Secondary ion images of Raji cells
showing the distribution of (a) nitrogen (imaged as the
12C14N ion) and (b) phosphorus (31P). These images were
obtained with Livermore’s new NanoSIMS and have a
spatial resolution of approximately 50 nanometers. The
ovoid-shaped bright regions in the center of the cell indicate
nitrogen and phosphorus are concentrated in nucleoli. The
membrane separating the cell nucleus is also clearly visible
in the phosphorus image. The cell diameter is approximately
A Look Inside Cancer Cells
a tagged monoclonal antibody or SHAL attaches itself to a cancer
cell, how does the radionuclide attack the cell and work its deadly
magic? Researchers elsewhere have attached three different radioactive
nuclides (iodine-131, copper-67, and yttrium-90) to Lym-1, a monoclonal
antibody used to treat non-Hodgkins lymphoma, with varying
degrees of clinical effectiveness. The reasons for the differences
in effectiveness are currently unknown.
the specific effects radionuclides have on cells, a Livermore team
recently began using a novel form of mass spectrometry with unprecedented
spatial resolution to study the distribution of isotopes within
individual cells. A goal is to determine the toxicities of various
radioisotope-tagged molecules in both cancer and normal tissues
and whether or not the localization of the drug can be correlated
to its effectiveness.
secondary-ion mass spectrometry (SIMS), ions with a few kiloelectronvolts
bombard a solid sample in a vacuum chamber. In this process, called
sputtering, surface atoms are ejected from the sample, ionized,
and sent into a mass spectrometer for analysis. The secondary ions
provide a direct measure of the elemental, isotopic, and molecular
composition of the uppermost atomic layers of the samples
surface. SIMS has been used at Livermore for more than 17 years
for high-precision analyses of many kinds of samplesweapons
materials, radioactive waste to be stored at Yucca Mountain, meteorites,
and even counterfeit money.
two years ago, we wanted to be able to characterize biological materials
with SIMS, says physicist Ian Hutcheon, who has been working
with SIMS for 25 years. But cells are very small, from 1 to
10 micrometers in size, and the spatial resolution with conventional
SIMS wasnt good enough.
Livermore purchased the NanoSIMS, a new instrument designed specifically
for quantitative imaging of biological materials. Livermores
NanoSIMS, only the eighth instrument of its kind in the world,
a spatial resolution of better than 50 nanometers, roughly 100
times better than that of conventional SIMS. The unit arrived in
2002, and installation began in January. Although the NanoSIMS
is not yet fully operational, the first studies have already provided
a glimpse of cellular microstructure with remarkable clarity.
before the NanoSIMS was delivered, Hutcheon and his team began
develop procedures and standards for using SIMS on biological samples.
Traditionally, SIMS has been used primarily on inorganic substances.
Unlike inorganic materials, biological samples are largely water
and behave badly in the high vacuum of a SIMS instrument. But Hutcheons
team overcame this problem by developing a biological sample-preparation
technique that removes the water while preserving the biochemistry
and composition of the sample as well as its microstructure and
isotopically labeled monoclonal antibodies in both normal and cancer
cells, the team began studying the distribution of yttrium-89 and
iodine-127stable surrogates for the radioisotopes often used
in cancer therapyin kidney, liver, and tumor samples of a
mouse infected with lymphoma. The NanoSIMS images reveal for the
first time just how yttrium-89 delivered by the molecule accumulates
in a mouses kidney. The yttrium is not found in the kidney
tubules but rather is concentrated in spaces in between tubules.
The images also show that the amount of yttrium is quite variable
from one tubule to another. Data such as these offer great promise
in understanding the toxic effect to the kidneys of different radionuclides.
This examination of the cellular distribution of various molecular
targeting radionuclides will help to determine the effectiveness
of various radiopharmaceuticals in treating tumor cells as well
as what, if any, effect that the pharmaceuticals have on normal
SIMS to examine biological samples is very new, adds Hutcheon.
Our NanoSIMS is only the second one in the country with full-blown
Two views of tubules in the cortex
of an yttrium-treated mouse kidney. (a) Transmitted light
photomicrograph. The tubule diameter is approximately 30
micrometers. (b) Secondary ion image showing the distribution
of yttrium-89 in mouse kidney. Yttrium is not found in
tubules but is concentrated in the spaces between tubules.
The concentration of yttrium is highly variable from one
tubule to another. Understanding how targeted radiopharmaceuticals—represented
here by yttrium-89—are distributed in cells can lead
to more effective cancer treatment.
One Patient at a Time
expects that by the end of five years, phase 1 clinical trials
Livermores customized cancer-fighting SHALs will be under
way while the collimatorless gamma-ray imaging device, MINERVA,
and NanoSIMS will be in use in research settings.
high-resolution images from the collimatorless imager will begin
to diagnose not only breast cancer but other cancers and diseases
whose presence can be revealed with radioisotopes. MINERVA will
be available to assist physicians in providing individualized treatment
decisions, while the images from NanoSIMS will be offering cellular-level
explanations for drug behavior in both mice and patients.
each of us is unique, one-size-fits-most medical treatments should
not be the norm. In a more perfect world, we would be offered treatment
options tailored to our own physiology. These new technologies are
helping to bring that world a bit closer.
Key Words: gamma-ray detection, Modality-Inclusive Environment for
Radiotherapeutic Variable Analysis (MINERVA), non-Hodgkins
lymphoma, PEREGRINE, radiation treatment, radiopharmaceuticals,
secondary-ion mass spectrometry (SIMS), synthetic high-affinity
For further information contact Christine Hartmann-Siantar (925)
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