Download The Next Wave of Cancer Cures Could Come From Nasty Viruses

The Next Wave of Cancer Cures Could
Come From Nasty Viruses
“If you put the virus and that agent together, it basically is a
double kill,” Shah says. “One sensitizes the other for therapeutic
efficiency.”
The idea of using viruses to fight cancer isn’t new, but
recent breakthroughs are offering more promising results
While this method requires the bulk of the tumor to be surgically
removed first, Shah says this method can kill the remaining cells,
as well as those that are resistant to other treatments as well.
By Matt Safford
smithsonian.com
May 28, 2014
The notion of using viruses to attack cancer has been
around nearly as long as we’ve known about viruses themselves.
But several roadblocks-- viruses attacking patients’ immune
systems, or, not effectively targeting tumors--have led to slow
growth in this area of research. Until now.
Earlier this month, a team led by Dr. Stephen Russell at
Minnesota’s Mayo Clinic announced that a patient with
previously unresponsive, blood-borne cancer (multiple myeloma)
had gone into complete remission after being treated with a
massive dose of a modified measles virus. A second patient given
a similar dose (10 million times the amount in the
common measles vaccine) didn’t respond as dramatically to the
treatment, but the patient’s tumors did shrink, indicating the
virus was at least attacking the targeted areas.
In a separate study that hasn’t yet made it to human trials, a team
led by Dr. Khalid Shah at the Harvard Stem Cell Institute (HSCI)
at Massachusetts General Hospital has made progress in attacking
brain tumor cells in mice using the herpes virus.
Shah’s team packed the virus inside a type of human stem cell
which, unlike some previous vehicles, is amenable to carrying
modified viruses and doesn’t trigger a significant immune
response. The team’s second trick: They wrapped the herpesloaded stem cells inside a biocompatible gel to help keep the virus
in place and attacking tumor cells for a longer period of time.
According to the team, mice treated in this way had significantly
improved survival.
The victories come more than half a century after work on cancerfighting viruses (known in the field as oncolytic virotherapy)
began in earnest in the 1950s, when scientists began attempting to
engineer the evolution of viruses to make them more effective at
fighting specific types of cancer. But that initial surge of research
mostly fizzled, resulting in little success, and other promising
areas of cancer treatment lured researchers elsewhere.
As for what makes a specific virus fit to fight a particular kind of
cancer, it’s all about how the virus functions in the wild. Russell
says Herpes is a good at tackling brain tumors because it hangs
around in nerve cells (creating cold sores in the process). That
allows it to hide from your immune system—a tactic that keeps
the virus from spreading elsewhere. Measles, on the other hand,
naturally attacks the immune system, which makes it a good
option for fighting cancers in the blood.
But if a patient has already been exposed to a virus that’s being
used for treatment, the body’s immune system will attack the
virus before it can do its job. This will also pose a problem if the
treatment shows initial success, but the cancer eventually returns
(as happened with the second patient in Russell’s trial).
“The only way we know how to use the virus when the patient is
immune,” Russell says, “is to put it inside cell carriers and use
them as Trojan Horses to deliver it to the target site.” He says this
method has worked in mice, but hasn’t yet been tested on
humans.
Both Shah and Russell believe their teams’ recent successes will
lead to increased interest in the field, and likely more
breakthroughs.
As for when this type of treatment will go from research and
limited human testing to approval for widespread use, it's not
clear.
“The biggest player at the moment is Amgen,” says Russell,
“with a herpes virus that is about to be approved by FDA—we
think—for melanoma therapy.”
The measles success is cause for with hope, but cool heads
are calling for caution until more results become available. The
technique will likely encounter other hurdles when it's tried on
more human patients. For something like this to be brought to the
masses, it would have to go through "large randomized clinical
trials," the Washington Post pointed out in its coverage of the
concept—a process that will likely take years.
So what’s behind the recent promising research in cancer-fighting
contagions? For Russell at the Mayo Clinic, the difference has
been incremental, parallel advancements.
For now, Peter Lipson of Forbes Magazine said, the study is
"a promising proof of concept, but a very early one."
“The field has finally reached a stage … where many of the
fundamental problems have been partially addressed,” Russell
says. “The parallel evolution of knowledge in virology, oncology
and immunology have all had a major impact.”
"This has been tried in two patients, neither of whom are cured,
and the therapy was not without dangers," Lipson wrote. It may
not be a cure and instead another step "toward an eventual
treatment."
For Shah and his team, advancements in virology are key to their
success with brain tumors. His team was able to load the herpes
with another agent (TRAIL) that specifically targets the tumor
cells.
"Either way," though, he wrote, "it’s good science."