If you’ve recently been diagnosed with cancer or have recently started anticancer therapy, chances are you’ve had to familiarize yourself with a lot of new words that pertain to your cancer type, the type of treatment you’re receiving, and the challenges of living with cancer. One word you may not have heard before is “biomarker.” As researchers learn more about how cancer cells develop, grow, and spread, more attention is being paid to the role biomarkers play in these processes. It may not seem obvious at first, but the understanding of cancer biomarkers is key to developing a treatment plan that is right for you.
What are biomarkers?
Biomarkers are molecules that indicate normal or abnormal process taking place in your body and may be a sign of an underlying condition or disease. Various types of molecules, such as DNA (genes), proteins or hormones, can serve as biomarkers, since they all indicate something about your health. Biomarkers may be produced by the cancer tissue itself or by other cells in the body in response to cancer. They can be found in the blood, stool, urine, tumor tissue, or other tissues or bodily fluids. Notably, biomarkers are not limited to cancer. There are biomarkers for heart disease, multiple sclerosis, and many other diseases.
Learning some basic facts about DNA, RNA and proteins is helpful for understanding the importance of biomarkers in cancer. DNA, which stands for deoxyribonucleic acid, is a molecule inside the cell that carries genetic information and passes it on from one generation to the next. RNA, or ribonucleic acid, contains information that has been copied from DNA. Body cells make several different types of RNA molecules that are necessary for the synthesis of protein molecules. For example, mRNA, or messenger RNA molecules, serve as templates for the synthesis of proteins from amino acid building blocks, while tRNA, or transfer RNA molecules, bring the amino acid residues to the ribosome. Inside the ribosome – an organelle where the protein is being synthesized – tRNA “reads” the mRNA template in a process called translation.
Proteins help the body function properly and are the basis of body structures such as skin and hair. They have a wide range of functions inside the human body. Certain proteins speed up chemical reactions (enzymes), others affect the functioning of the immune system (cytokines), and yet others, known as antibodies, trigger specific immune responses in response to antigens – harmful substances that the body periodically has to overcome.
Cancer biomarkers can include:
- Gene mutations (changes)
- Gene rearrangements
- Extra copies of genes
- Missing genes
- Other molecules
When people talk about cancer biomarkers they’re usually referring to proteins, genes, and other molecules that affect how cancer cells grow, multiply, die, and respond to other compounds in the body. In recent years, scientists have started to look at patterns of gene expression and changes in DNA as cancer biomarkers. While some cancer biomarkers can be used to predict how aggressively your cancer will grow, and are therefore useful for assessing your prognosis (outlook), the most promising use of biomarkers today is to identify which therapies a particular patient’s cancer may or may not respond to.
Functions of Cancer Biomarkers
There are many types of cancer biomarkers, and they each work differently within the body and react differently to treatments. In general, cancer biomarkers are classified by their different functions:
Biomarkers that Trigger Cells to Grow and Multiply Abnormally
An example of this type of biomarker is the HER2 protein, which helps to control cell growth. If HER2 is “overexpressed” in cancer cells, the cells are considered “HER2-positive,” meaning they produce more of the protein than is normal. This condition can possibly cause the cells to grow more quickly and increase their chances of metastasizing (spreading) to other parts of the body. It also means that treatments known to disrupt the HER2 signaling pathway are likely to help stop the cancer’s growth.
Biomarkers That Support a Treatment’s Cellular or Molecular Action
This type of biomarker is exemplified by a gene called SPARC, which stands for Secreted Protein, Acidic, Cysteine-Rich. SPARC helps bring albumin — a type of protein found in blood, egg whites, milk, and other substances — into cells. Some chemotherapeutic drugs are bound (“packaged”) with albumin to prevent them from being dissolved in the bloodstream before they reach their target cells. Therefore, an overexpression of SPARC helps treatments bound with albumin work more effectively by bringing the treatment right into the cell.
Biomarkers That Disrupt a Treatment’s Cellular or Molecular Action
Some chemotherapeutic drugs are made with platinum to disrupt tumor DNA. However, there is a protein called ERCC1 that repairs tumor DNA. If biomarker testing detects high levels of ERCC1 in a patient’s tumor, platinum-based agents aren’t likely to be very effective for that patient.
Even within the above biomarker categories, there is variety. For example, molecules that trigger abnormal cell growth can come from a gene mutation or from extra copies of an otherwise healthy gene within the tumor’s DNA.
Caution: Your Genes and Your Cancer Biomarkers Are Not Exactly The Same Thing
There are identifiable genes in some people’s DNA that can indicate an increased risk of developing certain cancers. For example, a person who inherits certain mutations in BRCA1 and BRCA2, the so-called “breast cancer genes,” has a higher risk of getting breast, ovarian, prostate, and other types of cancer.
However, most cancers are not inherited and in the majority of cases people who are diagnosed with cancer do not have any of the “cancer genes” — at least none that we can currently identify. But all cancers do have biomarkers, including genetic biomarkers. So, what’s the difference?
Your cancer has a unique version of your DNA that is different from the DNA in your healthy cells. Most of the cancer biomarkers that have been associated with treatments have to do with your tumor’s unique genes and molecular structure, rather than your own genes.
Detecting and Measuring Biomarkers to Develop a Personalized Anticancer Treatment Plan
In order to determine if, and at what levels, certain biomarkers are present in your cancer, your doctor will need to take a sample of tumor tissue or bodily fluid and send it to a laboratory to conduct a series of advanced pathology and molecular profiling tests. Those tests will detect and measure the levels of your cancer’s specific biomarkers. Obtained information will then be matched with published research by the world’s leading cancer researchers to identify which treatments are and are not likely to work. Your doctor will then receive a report that lists all the biomarkers that have been detected in the sample, along with the treatments that have been identified as positively and negatively associated with those biomarkers. This process allows your doctor to personalize your anticancer treatment plan based on your cancer’s unique biomarker profile.