Immunotherapy in Cancer


Cancer is a much-feared, devastating disease for which scientists around the world are working hard to find cures and treatments, including immunotherapy.

This brings us to the question: What is immunotherapy for cancer?

Immunotherapy is an unconventional approach to cancer treatment based around helping the body’s immune system to fight the disease. Our immune system consists of an army of specialized cells, chemical substances, tissues, and organs that protect our body by fighting against disease-causing pathogens and can destroy cancer cells.

The immune system targets and fights cancer by using special cells and complex mechanisms. Such mechanisms are becoming more and more understood, opening paths to new and exciting ways to manage cancer. These new cancer treatments are promising to provide better outcomes in terms of increased lifespan, reduced recurrence rate, and a greatly improved quality of life.

How our immune system works


The human body’s immune system is incredible. It can identify and target select foreign invaders that threaten our health, such as bacteria, viruses, parasites, and funghi. Even more remarkably, it leaves healthy cells and tissues unharmed in the process.In one of our previous articles, “Immune System and Pathogens”, we discussed in-depth how the immune system can distinguish between healthy and unhealthy cells. To sum up, foreign invaders contain proteins called antigens which the immune system doesn’t recognize as part of the body and, therefore, attacks and destroys them.

Why does the immune system have limitations in fighting cancer?


The immune system struggles to deal with cancer cells because these cells have developed mechanisms to avoid being attacked. Furthermore, the immune system doesn’t always recognize cancer cells as being foreign, because such cells emerge from our own cells. Cancer occurs when our normal cells become mutated and grow out of control, becoming less and less like our healthy cells.

What’s more, cancer cells can fool our immune system in many ways, avoiding an attack. Therefore, they multiply and spread throughout the body unrestrained, while slipping through the grasp of the immune system.

Scientists have recognized this pattern and have found methods to:
  • Boost the immune system’s response to cancer cells, and
  • Arm the immune system with the ability to recognize and target cancer cells
This is the foundation of immunotherapy for cancer.

Types of cancer immunotherapy


1. Monoclonal antibodies

Monoclonal antibodies work by exposing cancer cells to the immune system, making them more vulnerable to attack. This works by:
  • The immune system targets and attacks foreign pathogens by recognizing specific proteins (antigens)
  • The immune system makes antibodies, specialized proteins that bind to antigens to neutralize the pathogens
  • Scientists can create antibodies in the lab that can target specific antigens found on cancer cells. These are known as monoclonal antibodies or mAbs.
Find more information on monoclonal antibodies here

2. Checkpoint inhibitors

Checkpoint inhibitors are drugs designed to stop cancer cells from evading the immune system’s attack. This works as:
  • Whenever the immune system is in alert mode, the body makes certain checkpoints in immune response, making sure that immune cells don’t mistakenly target healthy cells
  • Cancer cells can recognize such checkpoints and take advantage by stopping immune cells from attacking them
  • Checkpoint inhibitors stop cancer cells from using these checkpoints, but rather they reactivate the immune system’s army of T cells and B cells to fight cancer cells
Drugs such as Pembrolizumab (Keytruda) and Nivolumab (Opdivo) are used to target PD-1, a specific checkpoint protein found on T cells. According to the American Cancer Society, such drugs have proven to be helpful in the treatment of many cancer types, “including melanoma of the skin, non-small cell lung cancer, kidney cancer, head and neck cancers, and Hodgkin lymphoma”.

More information on checkpoint inhibitors can be found here.

3. Adoptive T-cell therapy

The purpose of adoptive T-cell therapy is to increase the numbers and functions of T-cells, helping them to launch more aggressive attacks against cancer. This works by:
  • The doctor extracts T-cells from the patient’s tumour
  • The extracted T-cells are re-engineered in the lab to boost their numbers and ability to recognize and destroy cancer cells
Adoptive T-cell therapy has shown great potential in fighting leukaemia and lymphoma in children and adults [1].

4. Cytokines

Human immune cells release chemicals called cytokines that help to regulate the growth and functions of other immune cells. These chemicals are also crucial in how the immune system responds to cancer. In this kind of therapy, cytokines (also known as interferons and interleukins) are injected into the patients. It works by:
  • Interleukin-2 (IL-2) are chemicals that help immune cells to grow and replicate more quickly. A lab version of IL-2 has been approved to treat melanoma and advanced kidney cancer [3]
  • Interferons help our body to build resistance against cancer and infection. There are three main types of interferons, IFN-alfa, IFN-beta, and IFN-gamma, but only IFN-alfa is used in immunotherapy. It works by increasing the efficiency of the immune system to target cancer cells, and by slowing down the growth of cancer cells. IFN-alfa might also be able to limit the growth of new blood vessels that supply nutrients to the tumor
More information about how cytokines can help treat different types of cancers can be found here.

5. Cancer Vaccines

Cancer vaccines are said to work in the same way that normal vaccines do, by using weakened or killed viruses to kick-start an immune response. It works by:
  • Cancer vaccines are made of cancer cells or antigens which are sometimes created in the lab by extracting a patient’s own immune cells and exposing them to cancer cells
  • These vaccines help the immune system to launch a better response and attack on cancer cells
  • Some cancer vaccines can help to treat cancer and may even prevent cancer from recurring following conventional treatments. It is thought that some vaccines can prevent certain types of cancers
While cancer vaccine therapy has shown potential, it is still in nascent stages, with clinical trials and studies underway to determine the efficacy and side-effects of the treatment. Provenge® is the only approved cancer vaccine in the US, used specifically to treat advanced prostate cancer when hormone therapy does not work as desired [3].

Interestingly, a class action suit is currently underway in Japan in regards to a cervical cancer vaccine, highlighting that there’s a lot more research to be done in this area.

There is a lot of buzz about possible immunotherapy cancer treatment for different kinds of cancer. Cancer immunotherapy is used in clinical trials and administered to patients with advanced-stage cancer or those whose cancer has returned or spread under conventional treatment.

There’s no denying that there are risks involved, as activating or boosting the immune system has the potential to backfire. Immunotherapy side effects may involve the immune system attacking the patient’s healthy cells and tissues.

References:
  1. Is Immunotherapy Right for You? Cancer Support Community.
  2. Cancer Immunotherapy. Non-specific cancer immunotherapies and adjuvants. American Cancer Society
  3. Cancer Immunotherapy. Cancer Vaccines. American Cancer Society