EGFR (Epidermal growth factor receptor) ) is a receptor protein found on the surface of cells. Different small molecules (mainly growth factors) bind to this receptor thus activating it. The activated receptor sends signals into the cell which lead to the activation of genes and, finally, to cell division, cell growth, angiogenesis, and metastasis formation. Several processes can lead to abnormal receptor activation including receptor overproduction, different mutations (mentioned above), and other mechanisms. Abnormal high levels of EGFR can be found on the surface of many types of tumour cells
Currently, the most efficient treatment of colorectal and non-small cell lung cancers targets the so called EGFR signalling pathway via its inhibition. Recently, several EGFR inhibitors have been developed that inhibit signalling pathways, improving the survival rates of cancer patients. These medications bind to the EGFR receptor and inactivate it, thus leading to the inhibition of EGFR signalling and halting cell division, metastasis formation, etc. Therefore, the diagnostics of certain regions of the EGFR gene is essential for the selection of an appropriate, efficient tumour therapy. However, these medications are ineffective if a mutation is present in the K-RAS, NRAS, B-RAF, PIK3CA members of the EGFR signalling pathway.
To assess the efficiency of targeted therapy, it is essential to analyse the KRAS, NRAS, BRAF, and PIK3CA genes, because if these genes contain mutations then the EGFR inhibitor therapy will not affect the tumour cells, but the side effects will remain, further weakening the patient.
Tumour tissues for analysis can only be obtained from surgery, which is extremely stressful for the patient, furthermore, in some cases the condition of the patient does not allow invasive intervention.
Non-invasive genetic diagnostics has become an effervescent research area in the past few years. Employing this technique, the DNA of freely circulating cells derived from tumorous tissues can be analysed. Body fluids such as blood plasma, saliva, or urine may contain the genetic material of cancerous cells at an early stage. Thus, we can obtain genetic information about the tumour with a simple blood draw.