Biomarker can be a protein, carbohydrate or lipid whose presence or absence or its concentration level can be used as an indicator for presence of some kind of disease state. Many biomarkers with potential clinical application are discovered due to the advances in fields like genomics, proteomics and molecular pathology. Biomarkers are also used in cancer staging, prognosis and also in treatment.
Biomarkers or molecular markers are used in traditional tumor classes into subsets. These new cancer subsets behave differently; these new classes can be successfully treated with chemotherapeutic agents. Depending upon the presence and level of expression of a particular biomarker target therapy using agents such as imatinib, gefitinib and cetuximab can be used to treat the cancer. For example in breast cancer oestrogen receptor (ER) and HER2/NEU expression status are used for prognosis and therapy. ER positive tumors are successfully treated with targeted hormonal agents such as tamoxifen or an aromatase inhibitor. ER positivity also improves the prognosis of the cancer.

DNA Biomarker:

DNA based biomarkers are Single Nucleotide Polymorphism (SNP), chromosomal aberrations like translocation of BCR-ABL genes, change in DNA copy number, instability of microsatellite, change in methylation of promoter-region of gene.

RNA Biomarker:

RNA base biomarkers are differentially expressed tran script s and regulatory microRNA.

Protein Biomarker:

Protein biomarkers are cell membrane receptors like CD20, tumor antigens, carbohydrate determinants and also release of peptides by tumors into serum, urine, nipple aspirates and also into other body fluids.

Identification of Biomarkers:

Biomarkers are discovered or identified using genomic, proteiomic techniques and also Metabolomics, Lipidomics and Glycomics methods.

Genomic Technique:

Genomic techniques such as Northern blotting, microarray, SAGE and also expression of genes are used in identifying biomarkers.

Proteomic Technique:

Proteomic techniques such as 2D-PAGE, LS/MS, SELDI-TOF, ab-Microarry and also tissue microarray are used in identification of biomarkers.

Metabolomic Technique:

Metabolomics refers to analysis of metabolic pathway in response to some drugs. In metabolomics altering metabolic pathway is used to identify biomarkers.

Lipidomic Technique:

Lipidomics refers to the analysis of lipids. Mass spectroscopy, chromatography and nuclear magnetic resonance are used to study and analyze lipids.

Biomarker Imaging:

Functional molecular imaging such as magnetic resonance imaging, positron emission tomography or optical imaging are used to detect Biomarkers in the body fluid.

Biomarker Application:

1. Biomarker α-fetoprotein can be used in staging of nonseminometous testicular cancer.
2. Biomarker human chorionic gonadotropin-β can be used in staging of testicular cancer.
3. Biomarker known as CA19-9 can be used in monitoring of pancreatic cancer.
4. CA125 biomarker can be used in monitoring of ovarian cancer.
5. Biomarker CEA can be used in monitoring of colon cancer.
6. Epidermal growth factor receptor can be used as biomarker in selecting the type of therapy for colon cancer.
7. Biomarker thyroglobulin protein can be used in monitoring of thyroid cancer.
8. PSA protein can be used as biomarker for screening and monitoring of prostate cancer.
9. CA15-3 biomarker used in monitoring breast cancer.
10. Oestrogen and progesterone receptor expression can be used as biomarkers in selecting hormonal therapy for breast cancer.

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