What Is the Main Idea?

The authors of the review article ‘Immune System Efficiency in Cancer and the Microbiota Influence’ in the journal Pathobiology investigate the role of the immune system during cancer and how microorganisms affect the treatment process. This review helps to understand the role of microbiota (community of microorganisms) in the immunotherapy treatment of cancer.

What Else Can You Learn?

  • The immune system is an integral part of curing diseases, including cancer.
  • Boosting the immune system through immunotherapy has gained momentum in recent years.
  • The immune system is complex with multiple modalities, with some deterring and others promoting tumor progression.
  • Providing the appropriate microbiota modulates the tumor microenvironment, leading to more effective immunotherapy treatment.

Cancer and the Immune System

Cancer is the second leading cause of death worldwide. It occurs due to changes in DNA that accumulate and cause aberrant cell growth, causing a tumor to grow. The most common treatments for cancer are surgery, radiotherapy, and chemotherapy.

The immune system is the complex defense mechanism that the body has developed to combat anything perceived as foreign to the body. This is done by constant patrolling, recognizing aberrant or foreign cells and recruiting specific defense molecules and cells to destroy them. When it comes to cancer, the body’s immune system usually recognizes these errors and impairs their development. Based on the nature of the tumor, sometimes the immune system fails or can even aid tumor progression.

How does the immune system interact with cancerous growth? The area around the tumor is called the tumor microenvironment which includes blood vessels, immune cells and signaling molecules. These molecules mediate communication between the cells. Based on the type of molecules present, the immune cells in the tumor microenvironment can change their characteristics. In some cases, they suppress the tumor growth but in other cases they can promote it. Therefore, knowing the tumor microenvironment is of significance to deliver any intervention to suppress cancer.


Advances in research and understanding of the immune system have led to the development of a new class of cancer treatment called immunotherapy. Immunotherapy is a technique used to boost the immune system by utilizing and modulating the components of the immune system. It aids by directly limiting or eliminating cancerous growth or preventing cancer from spreading. To achieve this, substances that are either produced by the body or manufactured in a laboratory are used. They are applied to improve how the body recognizes, suppresses, and destroys cancer cells.

An immunotherapy that has been approved for clinical use utilizes immune checkpoint inhibitors. Immune checkpoints are proteins that stop immune cells from attacking the body’s own normal cells, thus preventing issues like autoimmune diseases. Tumors utilize this same mechanism to evade the immune system from attacking them by introducing checkpoint proteins in the tumor microenvironment. Immune checkpoint inhibitors are drugs that block the checkpoint proteins and allow the immune cells to carry out their function, like attacking and destroying tumor cells. Recent research has gone further to study the composition of the tumor microenvironment to understand factors that affect immune checkpoint inhibitor mechanism. A factor identified is the microbiota.


From the time we are born, microorganisms colonize all surfaces of the body exposed to external environment. This microbiota (community of microorganisms) is commonly known to aid in digestion. Recent data show that it also plays a role in the function of the immune system. The microbiota releases molecules known to have anti-tumor effects. At the same time, there are certain other microorganisms (if present in the body) that release molecules that promote tumors. Therefore, it is crucial to understand the microbiota composition and its effect on the tumor microenvironment. It is important to see how it can be modulated to benefit tumor suppression.

Microbiota in Immunotherapy

Microbiota, depending on its composition, can be an important modulator of success of anti-cancer treatments such as immunotherapy. Two recent preclinical studies on the use of immune checkpoint inhibitors tested how the microbiota modulates the outcome of the therapy. In one study, it was found that when mice were germ-free or treated with antibiotics, the therapy failed. Upon administering a cocktail of certain bacteria, the efficacy of the therapy was restored. In another study, the efficacy of a different immune checkpoint inhibitor was tested in mice having different microbiota. While the treatment worked in one, it failed in the other. Introducing the microbiota in the non-responsive mice with Bifidobacterium species, which was present in the responsive mice, restored the efficacy of the treatment.
While the research is still in its infancy, the data and the importance of appropriate microbiota in modulating the immunotherapy treatment is undeniable. This requires future studies to look at modulating the gut microbiome (by introducing probiotics, fecal microbial transplants, or with specific diets) in cancer patients while administering different immunotherapy treatments.


Immunotherapy in treating cancer has gained a lot of traction in recent years. Learning how to modulate current therapies to make them more effective is key to the health outcome in the patient. Recently, the microbiome has been shown to play a significant role in general health and in cancer, too. In the age of personalized medicine and therapy, understanding a patient’s microbiome and then utilizing it to provide better treatments will be the way forward.

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