We have a remarkable immune system, capable
of detecting rogue cells and foreign invaders, destroying them on impact. Tumor cells, however, have developed ways to
not only evade the immune response, but also to co-opt it for its own advantage
(Hallmarks of Cancer). With a
deeper understanding of these processes, cancer immunotherapy is one of the newest
tricks in our cancer treatment bag. It
is also a major topic at conferences both in Canada (Conferences) and globally. Immunotherapy even pops up in the mainstream
news and on social media frequently. Whether
you’re a patient currently treated using immunotherapy or are just curious
about the latest cancer research news, you’ve come to the right place! This
article is a stepping-stone to a better understanding of cancer
immunotherapy.
More than 100 years ago, William B Coley,
the father of immunotherapy and a New York surgeon, injected bacteria into a
patient with cancer. Such an experiment
was the first to suggest that a bacterial injection could mount an inflammatory
response, bringing immune cells in contact with the tumor and subsequently killing
these tumor cells. 100 years ago, this
practice was rudimentary and not necessarily advantageous to the patient. Now, with our advanced knowledge of the
immune system and tumor biology, we can offer several immunological approaches
to kill cancer cells.
Immunotherapy can refer to any one of
several different types of therapies that use different aspects of immunology. There are four main categories:
Monoclonal
Antibodies
Antibodies are used by the immune system to
recognize foreign bodies in the body.
Monoclonal antibodies come from a single source and are highly specific
for their target. In cancer therapy,
monoclonal antibodies are given to the patient exogenously. These antibodies can target different
components of cancer cells or immune systems and alter the activity of the
target cells. For example, Her2+ breast
cancer can be treated with Herceptin; Ipilimumab enhances the anti-tumor immune
response by binding to and inhibiting an inhibitor of the immune system. Because
these antibodies are targeted they can also be used to specially act as
carriers for more non-specific drugs (chemotherapy) or radiation, directing the
action of these less specific forms of therapy.
Interferons
and Interleukins
Interferons and interleukins are cytokines,
or messengers, that are secreted by immune cells to elicit a desired
effect. Without going into specific
details, interferons and interleukins essentially act as activators of the
immune system. Therefore, to jumpstart
the immune system or increase its activity in a cancer setting, extra interferons
or interleukins can be administered as therapy.
This type of therapy will function in a non-specific manner, activating
the immune system’s response to not only the cancer cells present but
throughout all areas of the body.
Treatment
vaccine is a vaccine that trains the immune system
to recognize cancer. These vaccines include portions of cancer or cancer cells,
priming the immune system to recognize and destroy cancer cells. These vaccines may also contain additional
substances, such as the interleukins that we’ve already discussed, that can
further enhance the immune response. A
current example of this type of therapy is sipuleucel-t, which has shown
benefit in prostate cancer.
Oncolytic
vaccine is type of treatment vaccine, but in addition
to activating the immune system, an oncolytic vaccine also contains a specific
type of oncolytic virus that can also specifically kill cancer cells. Literally defined, oncolytic refers to the
ability to lyse or split open – in this case, cancer cells. Therefore, oncolytic vaccines are composed of
viruses that specifically target cancer cells, and upon entering them, rupture
the cancer cells. Such rapid cell death
initiates an immune-stimulating inflammatory response. In addition, these vaccines are also designed
to prime the immune system to detect and kill cancer. Such a system can provide a longer, more
sustained response and may be particularly important in preventing disease
recurrence. The world’s first clinical
trial assessing the feasibility and effectiveness of this type of therapy was
launched in Canada by renowned researcher John Bell in late 2015 (Clinical Trial).
The field of cancer immunotherapy is
constantly evolving and the types of therapies are ever increasing. With more research, we will better understand
how this type of therapy works and how to maximize its impact by combining immunotherapy
with existing therapeutic options. Stay tuned for more exciting details as we uncover the intricacies behind this new therapeutic!
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