by Chris Kok
Scientific studies have found a correlation between DNA damage and cause of Cancer.
All Cancer cases have pointed to the mutations of cells resulting from unrepaired DNA damage in cells. Our body’s DNA is susceptible to damage from external environmental and internal metabolic/psychological factors. Studies have shown that it is when our body’s DNA repair system gets impaired that damaged DNA remains unresolved thus promoting continuous cell mutations and uncontrolled multiplication of such mutated cells – consequently resulting in tumor growth and ultimately Cancer.
The entire duration from cell mutation to full blown Cancer may be long but the results are devastating.
WHAT IS DNA?
The human genome is the complete set of genetic information for humans. This information is located as DNA (Deoxyribonucleic acid) sequences within the 23 chromosomes pairs in the nucleus of every human cell and in small DNA molecule found within individual mitochondria. The DNA in each human cell contains the unique information that basically tells the cell what protein to make in the body. DNA is inherited by every human being from their parents, which is why everyone will find themselves sharing traits of their parents. Apart from that it is common to find individuals sharing similar traits with other blood related individuals such as those of grandparents, great grandparents, uncles, aunts, cousins and so on.
DNA damage and various forms of DNA repair mechanisms undertaken by the body.
A PLETHORA OF DAMAGES IN DNA
Unknown to most of us, the human DNA constantly gets damaged. This is a natural phenomenon because the physiochemical constitution of our genes does not guarantee life-long stability or proper function of the genes. Damage to DNA is caused by a plethora of factors (refer to Fig. 1 & Fig.2 ) including but not limited to the following:
• Cosmic ionizing radiation from UV light (Sun rays)
• Ionizing radiation from electromagnetic waves (e.g. mobile phones, computers,
telecommunication towers, high-tension electrical cables, poor discharge of electrical
waves from home power supply etc)
• Cumulative radiation exposure from computed tomographic scanning (CT Scan), X-rays
and other fluoroscopic imaging)
• Genotoxic chemicals (that may be contained in food and beverages)
• Normal cellular metabolism (which produces harmful free radicals inside the body)
DNA DAMAGE REPAIR SYSTEM
Through evolution, the human body has its innate DNA repair mechanism that deals with DNA damage. The body’s DNA repair system involves NER (Nucleotide excision repair), BER (Base excision repair) and MMR (mismatch repair). NER deals with the wide class of helix-distorting lesions that interfere with base pairing whilst BER deals with the chemical alterations of bases and thus prevent mutagenesis. MMR is a repair system that recognizes and repairs erroneous insertion, deletion and mis-incorporation of bases that arises during DNA replication and recombination.
HOW DNA IS DAMAGED AND ITS EFFECTS ON CELL FUNCTIONS
During cell division (mytosis) which involves the formation of a new cell, the DNA is first duplicated prior to cell division. This process ensures that the new cell is formed with an exact copy of the DNA inside its nucleus and mitochondria.
Different stages of DNA damage and cell mutation resulting in development of Cancer
Without a proper copy of the DNA, the newly formed cell would not be a proper functioning cell. An easy way to understand this is to look at the hiring of a new factory worker which has not been given a clear set of work instructions. When such ill-informed factory worker is assigned to the factory floor, he is likely to perform poorly or not perform at all as a result of this. Now, imagine the factory has many new workers that have not been given clear instructions – the consequence would be severe and result in a disruption in production. Under the constant bombardment of external and internal factors (such as ionizing radiation, genotoxic chemicals and free radicals), the chemical bonds in the DNA tends to spontaneously disintegrate. As a result, during cell division, the damaged DNA is duplicated.
HOW CANCER OCCURS?
In the body, there are two genes that are responsible to maintain the equilibrium of cell growth – the tumor suppressor gene and the Proto-oncogene. Proto-oncogene is the gene that directs cell growth (i.e. determines how often the cell divides). On the other hand, tumor suppressor genes (or anti-oncogene) regulate cell growth by slowing down cell division, repair DNA mistakes and determines cell death (a process known as apoptosis or programmed cell death). The easiest way to understand this is to view Oncogene as the foot that presses the car accelerator paddle and the tumor suppressor gene as the foot that presses the car brakes.
To avoid over-speeding and undesired accident, the foot on the brakes would slow the car down to avoid over-speeding. DNA damage leads to development of Cancer because it causes cell mutations and uncontrolled multiplication of mutated cells. It is important to understand that DNA damage is responsible for formation of dysfunctional cells which not only results in mutated cells but cells that carries distorted Oncogenes and Tumor Suppressor Genes.
As a result, mutated cells continue to multiply uncontrollably forming tumor growth. At the same time, as a result of DNA damage, tumor suppressor genes fail to carry out its function of controlling division of mutated cells.
Continuous cell mutations and distortions to tumor suppressor genes leads to further impairment in the body’s DNA damage repair system. Over time, it is this condition that eventually results in a full blown Cancer. It is important to understand that damaged DNA in reproductive cells (such as Ovary cells and Sperm cells) will be passed on to the offspring which explains why some children are born with a high risk of contracting Cancer.
WHAT CAUSED OUR DNA DAMAGE REPAIR SYSTEM TO FAIL?
This is the key question to ask in tackling the issue of the increasing incidences of Cancer in our modern day society at present. What actually caused our DNA damage repair system to fail in protecting against replication of damaged DNA and cell mutations? To understand this, we need to examine the facts surrounding how our body cell functions are largely determined by our mind and its psyche. Look out for our next bulletin on “The Psychology of Cancer”.
Further reading on DNA damage and Cancer Distress and DNA Repair in Human Lymphocytes
Janice K. Kiecolt-Glaser, Ralph E. Stephens, Philip D.
Lipetz, Carl E. Speicher and Ronald Glaser
Role of oxygen radicals in DNA damage and cancer incidence
Marian Valko, Mario Izakovic, Milan Mazur, Christopher
J. Rhodes, Joshua Telser
An Oncogene-Induced DNA Damage Model for
Thanos D. Halazonetis1, Vassilis G. Gorgoulis, Jiri
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