How our gut bacteria affect cancer risk and response to treatment

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How our gut bacteria affect
cancer risk and response to
Gut microbiota is critical to making sure immune system
is in best possible state to fight diseases
The trillions of bacteria living in our gut (called the gut microbiota) can help determine our
risk of cancer, as well as how we might respond to cancer treatment.
Each person’s unique gut microbiota is in constant communication with their immune
system. This ensures good bacteria can thrive in the body, while bad bacteria and foreign
material are eradicated.
The gut microbiota is therefore critical to making sure the immune system is in the best
possible state to fight diseases – from the flu, to serious ones like cancer.
Your gut microbiota
Everyone’s gut microbiota is unique, much like a fingerprint. In the first few years of life, it
is at its most malleable, reflecting factors that occur during birth.
For instance, babies born through caesarean section have been reported to have lower
numbers of good bacteria and higher numbers of pathogenic (bad) bacteria, compared
with babies born vaginally.
Microbiota and cancer risk
The gut and immune system are closely linked. Just as our gut bacteria control our
immune system, our immune system controls our gut bacteria. Research now suggests this
interaction plays a significant role in determining cancer risk.
Mice lacking certain immune molecules that slow the immune response, called anti-
inflammatory cytokines, have more bad bacteria in their gut. This means a strong immune
response ensures bad bacteria do not overpopulate our guts
Microbiota and chemotherapy
A review of research published in the journal Nature also points to the gut microbiota
playing a role in how patients respond to chemotherapy. The review suggests the gut
microbiota determines the effectiveness of chemotherapy in two ways: through activating
chemotherapy drugs, and through its interaction with the immune system.
These mechanisms have been best described in mice that lack a gut microbiota. Such mice,
termed “germ-free” mice, are bred in completely sterile conditions. They are exposed to no
external sources of bacteria and have no bacteria in any part of their body.