Immunotherapy is an emerging technique to kill cancer cells
Written by Dr harold Gunatillake FRCS, FICS, FIACS, AM (Sing), MBBS
Health writer
For decades, cancer has been treated with invasive procedures like surgery, combined with non-invasive- radio and chemo therapy. Some cancers are also controlled through hormone therapy specifically for those hormone dependant cancers of the breast post conventional therapy. If cancer is detected in the early stages excisional surgery could be 100% cure. If the cancer cells have spread beyond its local boundaries, say into the regional lymph glands then regional radiotherapy is planned in addition to primary elective surgery. When spread beyond the regional lymph glands –chemotherapy is added as an adjuvant therapy to kill ‘metastatic cancer cells’ in the distant sites. The problem with non-invasive procedures is that normally functioning healthy cells also get harmed, revealed by hair loss, gastro-intestinal symptoms, tiredness, lethargy loss of appetite, and so on. For some, the therapy cause more issues than the disease.
Immunotherapy is a new emerging science where cancer cells in the body are attacked by certain parts of a person’s immune system to fight cancer within the body sparing ones normally functioning cells.
We need to understand what the immune system means. The human immune system is a powerful natural defence mechanism and is very complex, not well understood. The system is a collection of organs (lymph system); special cells (T cells) and substances that help protect you. This system identifies the foreign enemy (substances), as antigens and destroyed by chemicals and substances produced by the body called antibodies. They are akin to soldiers ever waiting to kill the foreign enemy cells. The advantage of this antigen and antibody reaction is that it destroys mainly the invading cells, sparing more than 30 trillion cells of the healthy body.
In most situations unfortunately the damaged cancer cells may not be detected by the immune system, remain alive and grow unmolested
One way to attack these cancer cells is to find drugs that help to boost the immune system that will destroy cancer cells. Another avenue is to find vaccines that can teach the body to recognise cancer cells.
Like bacteria and viruses entering the body producing antigens and are being neutralised by the antibodies produced by the body, cancer cells also produce antigens. Unfortunately, unlike the antigens produced by germs can be bound by antibodies, the latter don’t seem to bind to cancer antigens and the immune system cannot destroy them. This is because the cancer cells have learnt the art of avoiding the protective immune system and even weaken them.
Drugs stimulating the immune system- Monoclonal antibodies
One promising group of immunotherapy drugs are laboratory-made monoclonal antibodies. Monoclonal antibodies are a specific type of therapy made in a laboratory. These antibodies can bind and attach to specific proteins covering cancer cells. This earmarks the cells for the body’s immune system to recognise and destroy those cells… A good example of monoclonal drug is trastuzumab (Herceptin) that attacks breast cancer cells and kill them through the binding of the cancer antigens and body produced antibodies.
Other types of antibodies work by releasing the brakes on the immune system, so it can destroy the cancer cells. Researchers have identified the PD-1/PD-L1 and CTLA-4 pathways as being critical to the immune system’s ability to control cancer growth.
These drugs also can detect the normal protein coverings of the cancer cells, penetrate and block there further activity. These monoclonal drugs are expensive over US $ 100,000 per tag.
Vaccines
Studies conducted at the Ohio State University Comprehensive Cancer Centre to develop a single-shot vaccine to trigger the same process as the monoclonal drugs, has been successful. A vaccine exposes the immune system to an antigen in cancer cells. This exposure triggers the immune system to recognise and destroy that protein (antigen).
An example is the HER-2 breast vaccine still in the trial stage.
In the above trials terminally ill patients developed antibodies against their own cancers via giving the vaccine. So far one patient has survived more than three years
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Vaccine therapy shows no toxicity and the side effects were minimal.
Viruses attacking cancer cells
Experiments are being done to train viruses through ‘oncolytic viral therapy’ to create a long-term robust defence for the immune system to attack cancer cells. These viruses are called oncolytic viruses and trials have shown that they directly attack the cancerous tumour. These viruses also replicate within the diseased cancer cells causing them to violently explode.
The US. FDA approved the first oncolytic virus therapy to treat melanoma. The virus is a genetically modified version of the herpes simplex virus that causes cold sores.
Combination therapy
There are three categories of treatment to destroy cancer cells- a virus, a cancer drug and an immunotherapy to destroy cancer tumours.
Non-specific immunotherapies
Like monoclonal antibodies, non-specific immunotherapies also help the immune system destroy cancer cells. Two such examples are: Interferons and Interleukins. Most non-specific immunotherapies are given after or at the same time as another cancer treatment, such as chemotherapy or radiation therapy.
Conclusions: When you are faced with having cancer you need to check what type of immunotherapy is recommended to you and why? You need to check on the goals of this treatment. How you will receive treatment and how often will you need immunotherapy treatment. You need to check on the side effects and who should be called when you have problems.
Some Reference to: Live Science- article by Balveen Kaurand Pravin Kaumaya- Ohio State University and Cancer.Net
