Cancer cells continue to grow in the body because they resemble normal cells enough to evade being targeted by the immune system. The immune system continuously looks for foreign cells and proteins and attempts to destroy them. There are no ‘strong’ and ‘weak’ immune systems, only systems that are able to recognize a cell as foreign.
For a long time research has focused on making the immune system ‘see’ or recognize the cancer cell. Once seen, the cells will be destroyed by the body’s immune system without any side effects on other normal cells. The theory is basic, logical and attractive but putting it into practice is highly complex.
Scientists are increasingly been able to target specific proteins on a cancer cells that are not present in normal cells. Such proteins are identified and tagged with another molecule so that the immune system can ‘see’ them. This immunotherapy is a recent development with promising future.
The number of cases where immunotherapy has been tested is still relatively small, but the results have been encouraging. And, as Jennifer Couzin-Frankel wrote in Science, “Immunotherapy marks an entirely different way of treating cancer—by targeting the immune system, not the tumour itself.”
A number of drugs have been developed and are now in use for kidney and lung cancers, and a type of skin cancer called melanoma. There are promising results in cancers of the breast ovary and large intestine. Long term data on recurrence is awaited.
It is hoped that the recent developments in nanotechnology will allow scientists to tune the body’s immune system to weed out cancer cells without damaging normal cells.