A cancer biomarker is a substance or process that signposts the presence of a cancerous tumor in the body. It can be genetic, glycomic, proteonic, or epigenetic. Imaging biomarkers and processes like apoptosis, proliferation, and angiogenesis may also be used to detect tumors. Typical biomarkers are produced by tumor cells or healthy cells in response to tumorous growths in the body and can be found in tissues, fluids, and cell lines. According to the Cancer institute (NCI), a biomarker can be used to detect a normal or abnormal process in the body or to study how well the body reacts to treatment for condition. The use of biomarkers is established on the fact that each cell has a unique molecular composition with specific traits like proteins, genes, and molecules.
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Thus, biomarkers can aid in the identification of cancerous cells and diagnosis of cancer in patients. Although numerous drawbacks hinder the application of biomarker research in clinical practice, clinicians have already used various biomarkers at the point of care. Examples include BCR-ABL for Chronic Myeloid Leukemia, AFP for Liver Cancer, BRAF V600E for Colorectal Cancer, CA-125 for ovarian Cancer, CA19.9 for Pancreatic Cancer, CEA for Colorectal Cancer, KIT for Gastrointestinal stromal tumor, and BRCA2 for Ovarian Cancer, among others. A good biomarker is easily measurable, reliable, and cost-effective.
The first reference to biomarkers is attributed to ancient Egyptians who attempted to find biomarkers for malignancy. They wanted to distinguish between breast cancer and mastitis. However, the use of cancer biomarkers in clinical practice was not achieved until roughly two centuries ago when Sir Bence Jones identified a protein in the urine of myeloma patients in 1847.3 The protein, which has since been named Bence-Jones protein, was identifiable through its special heat coagulation properties. It was a tumor-produced light chain antibody of antibody of immunoglobulin G. The next significant attempt at identifying a biomarker occurred in 1867 when Sir Michael Foster introduced amylase as a potential biomarker for patients with pancreatic cancer. It was later ascertained that production of large amounts of amylase enzyme can occur in large tumors that impinge on acinar cells. In the next century, research on biomarkers continued. Researchers studied hormones like catecholamines in neuroblastoma and pheochromocytoma, chorionic gonadotropin in choriocarcinoma and enzymes such as alkaline phosphatase in bone tumors and acid phosphatase in prostate cancer. The creation of the term immunoassays in the 1950s further fueled the pursuit of knowledge in the field of cancer biomarkers using polyclonal antibodies. What ensured was the introduction of several immunoassays and tumor antigens in testing. These, along with recent molecular biology breakthroughs, have contributed to the discovery and realization of putative functions of cancer biomarkers as tumor suppressor oncogenes, genes, telomerase, and nuclear proteins. Emerging technologies such as proteomics and genomics are expected to yield new information on biomarkers.
Key Uses of Biomarkers
Biomarkers have a range of uses in oncology among which include risk assessment, diagnosis, prognosis, treatment predictions, pharmacodynamics and pharmacokinetics, monitoring of treatment responses, and recurrence. Cancer biomarkers, especially those connected to epigenetic alterations and genetic mutations, are a practical way of determining when an individual is exposed to cancer risk. Biomarkers are also useful in diagnosis of specific types of cancers. Diagnostic biomarkers have been remarkably used to differentiate the origin of tumors as either primary or metastatic. To identify the difference researchers usually screen chromosomal alterations that are found in the cells at the primary tumor site versus those found at the secondary location. Matching alterations are interpreted as metastatic while differing alterations are considered as distinct primary tumors.
Another key use of biomarkers is for cancer prognosis which usually takes place after a positive diagnosis.2 Here, doctors use biomarkers to assess the severity and aggressiveness of a cancer and its likely response to a certain treatment. Tumors that show specific biomarkers might be responsive to treatment options that are related to the presence of those biomarkers. Examples include elevated estrogen receptor (ER) expression which is linked to better survival in breast cancer patients and elevated metallopeptidase inhibitor 1 (TIMP1) which is linked to aggressive multiple myeloma. The use of biomarkers in pharmacodynamics and pharmacokinetics are connected with the identification of the most effective treatment solution for a particular cancer.1 Differences in genetic makeup of individuals means that different people react differently to different chemical structures of drugs. In some cases, certain drugs can create dangerous conditions upon metabolizing slowly. Screening for such biomarkers is therefore necessary. Biomarkers also have a potential in monitoring the progress of treatment program. This role of biomarkers is currently under research since cancer biomarkers could significantly reduce costs in patient care. Currently, CT and MRI technologies have proven highly costly in monitoring tumor status. Finally, biomarkers can help in the prediction of recurrence of a tumor.
Biomarkers play a critical role in oncology, especially in clinical risk assessment, screening, diagnosis, prognosis, response treatment, and other diagnostic tools. They also have a potential significance in enabling the much sought-after molecular definition of cancer. However, it is necessary for healthcare providers and clinicians to have a comprehensive understanding about the molecular characteristics of each biomarker in order to identify circumstances under which it could become useful in clinical care. Biomarkers are definitely a prospective solution in personalized medicine.