Wednesday, October 11, 2017

What is Cancer Immunotherapy

Cancer is a disease that can impact any tissue in the body.  When normal tissue cells become cancerous (malignant), they lose some of the fundamental properties of the tissue cells they originated from.  They also grow out of control and ultimately spread (metastasize) to other parts of the body where they bring chaos and instability.  The transformation that normal cells undergo when they become cancerous is known to be a result of genetic changes to the cells complement of DNA.  In some types of cancer there is a definitive hereditary genetic component as in certain types of breast cancer, for example.  A widely accepted model for the transformation of normal cells to the cancerous state involves spontaneous somatic mutation(s).  There are many man-made organic chemicals in the environment that are known to initiate the onset of cancers; these are collectively referred to as carcinogenic compounds.  Carcinogens have also been shown to be mutagens – chemical agents that cause genetic mutations.

The conventional therapies that are applied to a patient that presents with cancer has generally involved the use of chemotherapeutic drugs and/or radiation treatment.  The therapies that employ these agents are referred to as a shotgun approach; since, they do not discriminate between normal and cancer cells   Chemotherapeutic drugs target any cell that is actively dividing and radiation damages cellular DNA that results in cell death.  Although these techniques have become refined over the years, they still suffer from this serious limitation.

This is where Immunotherapy offers an important advantage; because, treatments that use immunotherapy specifically target cancerous cells.  What follows is a discussion of the rationale of some of these approaches.

Succinctly stated, “Immunotherapy is treatment that uses certain parts of a person’s immune system to fight diseases such as cancer.” This can be accomplished in a number of ways.  The patient’s natural immune system can be enhanced to better target cancerous cells.  This is possible; because, an important component of the immune system is referred to as, “the cancer surveillance system.”  Certain subsets of cells in the immune system are designed to target any cell that possesses antigens on their cell surface that are indicative of the fact that it has been transformed,  These antigens indicate to the immune system that the cell is no longer self and thereby becomes subject to destruction.  Another approach involves the addition of human manufactured immune system – related proteins.  This capability is possible on account of the fact the cellular manufacture of unique proteins depends upon a particular gene   Technologies are in wide use that can insert a particular human gene into bacteria in culture and have the bacteria manufacture the human protein product.  This approach has made possible the mass production of human insulin and human growth hormone, for example.  In addition, some types of immunotherapy are also referred to as biologic therapy or biotherapy.

The methodologies that are currently being tested and employed can be classified in the following way –

·        Monoclonal Antibodies  - Once an antigen specific for a certain type of cancer has been isolated, antibodies can be manufactured that are specific to that antigen.  This antibody can then be introduced into the patient with that cancer.  Once the circulating monoclonal antibodies bind to cancer cells, this triggers the immune system to target those cells and destroy them.
·        Immune Checkpoint Inhibitors – The immune system is a very powerful system that has built-in safeguards to keep it under rigorous control i.e. to make it possible to destroy transformed cancerous cells leaving normal cells intact.  This is accomplished by immune checkpoint factors.  These factors are on certain cells in the immune system and need to be activated or inactivated to trigger the immune response.  Some cancer cell types can use this system to prevent it from being used against them.  For these cancers, checkpoint inhibitors are designed to interact with these factors and render them ineffectual; thereby, improving the potency of the immune system targeting cancerous cells.
·        Cancer Vaccines - Cancer vaccines are being developed to treat or even prevent the onset of certain types of cancer.

The following is a table that summarizes some of these data –

Type of Cancer
Methodology Employed
Chronic Lymphocytic Leukemia (CLL)
Monoclonal Antibodies
The monoclonal antibody that has been used targets the CD 20 cell-surface antigen that is in high concentration in some forms of this disease.
Advanced Colorectal Cancer (CRC)
Immune Checkpoint Inhibitors
Many inhibitors are currently being produced and tested.  Some benefit has been shown with certain cancers that are particularly difficult to treat.
Cervical, Advanced Prostate and Bladder Cancer
Cancer Vaccine
Cervical cancer, for example, is known to be caused by the human papilloma virus (HPV).   Therefore, a vaccine that targets this virus can prevent the onset of cervical cancer

It should be remembered that the use of immunotherapy in treating cancer remains in its infancy and requires additional research efforts to improve its efficacy and diminish known side-effects.  However, it is an exceedingly promising approach and is worthy of continued research efforts and support.

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