Does every person have oncogenes?
According to the present global statistics, every 1 in 100 people suffers and dies from cancer. Every year, 1 out of 5 people that die is taken by cancer. In the coming 20 years the situation is not likely to change, thus we should prepare and learn how to fight it.
Oncogenes are split into viral and cellular, these two have the potential to induce malignant transformation of cell characteristics. Under normal circumstances, there will be no viral oncogene activity; once the viral oncogenes receive impact of the radiation, or are affected by chemical carcinogens, they will wholly or partly cause activation-induced tumorigenesis. And cellular oncogenes – oncogenes present in regular cells – will be then turned into tumor-causing cellular oncogenes, e.g. EGFR, K-RAS, B-RAF, C-KIT, etc. It is presently confirmed that ray radiation, chemical carcinogens and viral infections can lead to activation of oncogenes. Several activation modes are:
- Point mutation
- Gain exogenous promoters
- Reduction of methylation level
- Increased oncogene copy number
- Gene translocation or rearrangement
The cellular oncogenes discovered up to now are closely related to normal cell growth and proliferation, differentiation and apoptosis and the very conservative “housekeeping genes.” Their expression products can be: growth factors, growth factor receptors, G protein or small molecule, protein kinases, transcription factors, or, in short, they are the key molecules in various signal transduction pathways, focused on physiological functions.
Now, what about the tumor suppressor genes?
Scientists have discovered the existence of tumor suppressor genes. They are present in a class of genes that inhibit cell growth in normal cells, also owing a potential tumor suppressor role. When this type of gene mutates, is deleted or inactivated, this can cause malignant transformation of cells and lead to tumorigenesis, such as tp53, pten, etc.
Oncogenes – a storyline as old as the history of multicellular organisms.
Now that we understand the non-negotiable existence of oncogenes in human cells, a new question arises – how can we predict when the oncogenes are going to start causing trouble? Recently, scientists have found some evidence that cancer genes, genes that cause tumor formation, can be traced back to the earliest true metazoans.
Therefore we can say that oncogenes and tumor suppressor genes have always existed in the human body. However, cell carcinogenesis is definitely not the only function of cellular oncogenes. In the normally functioning cells, some of the tasks that the cellular oncogenes are busy with are: the protein products of the oncogenes are involved in normal cell growth, differentiation and multiplication. It would be most precise to say that the normal cellular oncogenes help with the normal physiological cellular functions, but under certain conditions it will cause the appearance of cancerous cell genes. In addition, strong evidence that speaks about the normal functioning of the oncogenes is the discovery of its conservative existence in yeast, fruit flies, mice and human genomes.
So, what are those ‘certain conditions’ that cause cancer development?
Proto-oncogenes are activated by three major factors: physical (most often ionizing radiation or ultraviolet radiation), chemical (aflatoxin, nitrites) and biological (e.g. HPV causing cervical cancer). Normally, once proto-oncogenes are activated, intracellular oncogene p53 would immediately lead to de-activation of proto-oncogenes. In case of P53 gene damage, we will not be immediately facing death, because our immune systems are subject to monitoring the state of the body cells: once cancer cells are found, the immune system immediately starts to promote cancer cell lysis. Therefore, we can conclude that three conditions are necessary for the appearance of cancer: 1. exposure to carcinogenic factors causing oncogene activation; 2. Unsatisfactory functioning of tumor suppressor genes; 3. The immune system monitoring function defects. Thus, to prevent cancer, it is crucial to avoid contact with carcinogenic factors, ensure adequate nutrition, diligent exercise routine and enhance the body immunity.
Detection of oncogenes and curing rate.
If cancer is detected early, the cure rate is high. Currently, more than 100 of cancer genes and tumor suppressor genes have been found. Following in-depth studies of oncogenes, a variety of methods for detection of gene and cancer oncogene products, namely, the Southern blot, PCR, in situ hybridization, ELISA and immunohistochemistry technology, have been used in clinical diagnosis.
Tomislav Domazet-Lošo, Alexander Klimovich, Boris Anokhin, Friederike Anton-Erxleben, Mailin J. Hamm, Christina Lange, Thomas C.G. Bosch. Naturally occurring tumours in the basal metazoan Hydra. Nature Communications, 2014; 5 DOI: 10.1038/ncomms5222
BERNARD W. STEWART and CHRISTOPHER P. WILD. World Cancer Report 2014. WHO