Cancer Biomarkers

A biomarker is defined by the National Institute of Health as "a biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease. A biomarker may be used to see how well the body responds to a treatment for a disease or condition. Also called molecular marker and signature molecule."

Cancer biomarkers are often selected among genetic alterations occurring during cancerous transformation of a normal cell. These genetic alterations are extremely diverse and include deletions, chromosomal rearrangements, gene amplification or expression, chromosome loss and point mutations.

The two main challenges in developing cancer biomarkers are:

• the discovery of candidate markers,
  
  

• the validation of those candidates for specific medical uses.
  
  

The discovery process depends on the technologies available to interrogate the complex biochemistry of health and disease in order to identify biomarkers that can be detected consistently. Recent technological developments, especially in genomics, have made it much easier to examine a large number of potential biomarkers.


The validation process is also laborious and costly, requiring access to patient samples with comprehensive clinical annotations and long-term follow-up. In addition, a biomarker must be validated for each specific application for which it will be used (such as classification, diagnosis, prognosis, drug response prediction or monitoring).