Contact: Erin Digitale
Stanford University Medical Center
Plants make vaccine for treating type of cancer in Stanford study
STANFORD, Calif. - Plants could act
as safe, speedy factories for growing antibodies for personalized
treatments against a common form of cancer, according to new findings
from the Stanford University School of Medicine. The findings came in
the first human tests of an injectable vaccine grown in genetically
The treatments, which would vaccinate
cancer patients against their malignant cells, could lead to earlier
personalized therapy to tackle follicular B-cell lymphoma, an
immune-system malignancy diagnosed in about 16,000 people each year.
regard follicular B-cell lymphoma as a chronic, incurable disease. The
standard treatment, chemotherapy, has such severe side effects that
patients often opt for watchful waiting in the early stages of illness.
However, plant-grown vaccines, which lack side effects, could allow
earlier, more aggressive management of the cancer.
be a way to treat cancer without side effects," said Ronald Levy, MD,
professor of oncology and the Robert K. and Helen K. Summy Professor in
the School of Medicine, who is the study's senior author. "The idea is
to marshal the body's own immune system to fight cancer."
The findings will appear July 21 in the advance online issue of the
Proceedings of the National Academy of Sciences.
The study was a phase-1 trial that showed plant-grown cancer vaccines
were safe for patients and could be produced quickly and cheaply.
Sixteen newly diagnosed lymphoma patients received the treatment; none
experienced any side effects from plant-grown vaccines.
Future studies will test the vaccine's effectiveness.
cancer vaccines rely on a biological quirk of follicular B-cell
lymphoma, which is a type of non-Hodgkin's lymphoma. The cancer starts
when a single immune cell multiplies uncontrollably, producing many
identical clones of itself. The clones all carry the same antibody on
their exterior, a marker that is unique to the cancer and is not found
on any of the body's healthy cells. Levy's vaccination strategy is to
inject many copies of the cancer-specific antibody into a newly
diagnosed lymphoma patient, stimulating the patient's immune system to
seek and destroy malignant cells.
Previous trials of this
kind of vaccine, produced in animal cells and tested in mice and
humans, have had mixed success, and the vaccines are not yet
commercially available. Growing cancer vaccines in plants could
circumvent some of the hurdles to turning the concept into a real
treatment, Levy said.
Because each person's cancer antibody is
unique, every patient needs a personalized vaccine. Growing
personalized vaccines in animal cells takes months, costs thousands of
dollars per patient and comes with the theoretical risk that a patient
might inadvertently be infected with an animal virus that contaminated
the cells used to grow the vaccine. Personalized vaccines could also be
produced with genetically engineered bacteria, but bacteria-grown
vaccines aren't ideal, either.
"The plant system has some
advantages," said Levy, who is also a member of the Stanford Cancer
Center and a Howard Hughes Medical Institute investigator.
researchers chose tobacco plants that were genetically engineered to
reproduce quantities of the vaccine. To make a tobacco plant churn out
a human antibody, scientists isolate the antibody from the patient's
tumor and put the antibody gene into a modified version of the tobacco
mosaic virus. They infect a tobacco plant with the gene-carrying virus
by scratching the virus on its leaves. The virus takes the gene into
the plant's cells, which then churn out lots of antibody. After a few
days, technicians snip off the plant's leaves, grind them up and purify
the antibody. Only a few plants are needed to make enough vaccine for
"The new manufacturing system allows very rapid
production of a vaccine," said Charles Arntzen, PhD, a professor of
plant biology at the Arizona Biodesign Institute at Arizona State
University, who was not involved in the research. "I think without the
speed, it would be hard to convince a cancer patient to wait for a
vaccine to be developed, rather than going on some other therapy."
pretty cool technology," Levy said. "And it's really ironic that you
would make a treatment for cancer out of tobacco. That appealed to me."
None of the harmful chemicals found in cigarettes end up in the
Not only is the technology fast, cheap and
safe, but Levy said there's reason to expect that the plant-grown
antibodies will generate a stronger immune response than those made in
animal cells. Both plant and animal cells attach sugars to antibodies
and other proteins during biochemical processing, but the plant and
animal sugars are different. The difference might prompt a more robust
immune response to plant-grown antibodies, Levy said.
research step is a phase-2 clinical trial to test the effectiveness of
plant-grown vaccines in a larger group of lymphoma patients, Levy said.
He's optimistic, adding, "We know that if you get the immune system
revved up, it can attack and kill cancer."
research team included scientists from Stanford, Touro University in
Vallejo, Calif., and the biotechnology companies Large Scale Biology
Corp., CBR International Corp., Bayer HealthCare, Integrated
Biomolecule Corp., The Biologics Consulting Group Inc. and Holtz
The study was funded by a grant from the National Institutes of Health and by Large Scale Biology Corp.
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