What is a “Biomarker”?

Virginia Hanson Paul, BS, MBA; virgiepaul@aol.com & Terry W. Osborn, Ph.D., MBA; twosborn@aol.com

Biomarkers are measurable characteristics that indicate normal biologic processes, pathogenic processes, or pharmacologic responses to therapy. Traditional biomarkers encompass:

•    Physiological measurements such as heart rate, blood pressure and performance status;
•    Clinical chemistry measurements of metabolites such as cholesterol and many other blood tests;
•    Individual protein measurements such as prostate-specific antigen (PSA) or thyroid stimulating hormone (TSH); and
•    Clinical images such as x-ray, mammograms, computed tomography (CT), magnetic resonance imaging (MRI) or Positron emission tomography (PET).

The Renaissance in Biomarker Development

As a result of the human genome project, the frontier of “biomarkers” has exploded in providing new biomarkers at the molecular level. The project sequenced the three billion parts (nucleotides) of DNA (DeoxyriboNucleic Acid) which is organized into the double helix structures called chromosomes. In the genome there are some 25,000 genes made up only four different nucleotides. It is the sequence, or “spelling”, of these nucleotides that makes us all different.

The DNA sequences generated now provide scientists with a “parts lists” containing instructions for how cells builds, operates, maintains, and reproduces itself while responding to various environmental conditions. In the past, researchers studied one or a few genes or proteins at a time, such as PSA or TSH where quantity rather than function was the goal. Because biological processes are intertwined, these strategies provided incomplete—and often inaccurate—views. Researchers now can approach questions systematically and on a much grander scale study all the genes expressed in a particular environment or all the gene products in a specific cell, tissue, organ, or tumor.

On the technical side, DNA is transcripted into RNA (RiboNucleic Acid) which is the “blueprint” for the protein synthesis. Proteins are essential parts of organisms and participate in every process within cells. Biomarkers can be at the:
•    DNA level (sequence variation occurs such as deletions, polymorphisms, single nucleotide polymorphism-SNPs) or
•    Epigenomics level (methylated DNA – turns a gene on or off) or
•    RNA level (transcriptional alterations, splicing, editing, quantity) or
•    Proteins and peptides level (functional, nonfunctional or quantity).

The true “Daniel Boone’s” of this frontier exploration are those who are using these advancements to venture into the arena of “no known biomarker” for the definitive diagnosis of disease such as neurodegenerative diseases or psychiatric disorders. These include Alzheimer’s, ALS (Amyotrophic Lateral Sclerosis or Lou Gehrig's disease), autism, Multiple Sclerosis (MS), Parkinson’s, Bipolar Disorder, Schizophrenia and others. To date, these diseases are diagnosed by observing the patient’s decline until observation alone definitively diagnoses the disease. The discovery of gene-related biomarkers will provide the first quantitative physiological diagnosis of these diseases. Thus, early therapeutic intervention as well as more specifically targeted drug development will ensue.

The Future of “Biomarkers” is Personalized Medicine

The perspective of disease is now evolving from simply the difference between non-disease and disease states to recognition of the progression from non-disease, potential genetic risk, diagnosis, disease staging, disease stratification, therapeutic selection, recurrence and outcome as elements of disease progression. There is a need to understand the relationship between biomarkers and their association with these components of disease to optimize their utility in both research and clinical settings and for both therapeutic and diagnostic application.

Biomarkers are leading medicine to personalized medicine which offers many potential benefits — from safer, more efficient drugs to huge health care savings. These new “biomarkers” will provide the capability to screen for genetic predisposition for a disease, to treat a disease earlier, to select most likely responders to a new drug as well as prescreen for potential side effects of a drug on a personal level. As well, there can be significant savings to the medical community, both hospitals and insurance carriers, if they know in advance how successful drug treatments will be before wasting a lot of money on ineffective drugs



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