Cancer has been around for thousands of years, but only in recent times, for the last century has cancer started to be a major cause of death in the industrialised world. Cancer has many different causes, both internal and external. A major player in the development of cancer is unwanted changes in the DNA that cannot be repaired by the DNA repair system. These changes can be inherited or acquired. Nevertheless, lots of money is being put into cancer research all around the world in the hopes of finding better treatments and even a cure. Nowadays people with cancer have a much greater chance of survival compared to 50 years ago and things are improving as each day passes.
Key words: cancer history, metastasis, tumour, treatment
•What is cancer?
•History of cancer
•Causes of cancer
•Survival rates then and now
Cancer – an introduction
Cancer is a leading cause of death in the industrialised world, second only to heart disease. Approximately one in three people will be diagnosed of some form of cancer throughout their life and one in four people will die of cancer. An overwhelming 47% of cancer deaths are caused by only four types of cancer: lung, bowel, breast and prostate, therefore more energy and money is concentrated on finding a treatment for these main four killers2. Cancer is a class of many diseases in which one or more cells from our body start to divide uncontrollably (far beyond normal limits) and start to invade and destroy the normal tissues surrounding them. This out of control growth then causes a tumour in most cases (some cancers like leukaemias don’t cause tumours) which can spread to other distant locations and organs in the body via the circulatory system and cause secondary tumours (metastasis). Damaged genes due to errors in DNA (deoxyribonucleic acid) are the main causes for the development of cancer (Figure 1). In order for a normal cell to be transformed into a cancer cell, genes which regulate the growth, differentiation and death of the cell must be altered. Genetic changes can occur at many levels, from losing entire chromosomes (an organised structure of DNA and proteins found in cells) to a mutation affecting only a very small part of the DNA 2,3.
Figure 1. – The link between DNA, proteins and cancer 4
Genetic variation is a crucial part of evolution, without it life as we know it would probably not be possible, but in order for an individual to survive, genome (all of the DNA belonging to an organism) stability is essential. Still, many lesions are caused to the DNA every single day by numerous internal and environmental factors. To respond to these threats and help maintain genetic stability, mechanisms that strictly control DNA replication, detect DNA damage and repair it have evolved. These mechanisms help prevent disease and protect the individual’s life and genetic inheritance2. DNA repair is a process that refers to each cell’s ability to rapidly identify and correct any abnormalities that may have occurred in its genome. This process is extremely effective in humans, because out of the thousands of errors and lesions in DNA that occur in cells every day, only a very small percentage result in a permanent DNA mutation. If the majority of these errors wouldn’t be repaired, the viability of the cell or organism would be threatened. There are multiple studies that have linked a variety of human diseases (such as colon cancer, skin cancer, leukaemia and lymphoma) with a decreased ability to repair DNA damage. DNA damage can be due to many factors 7. The rate of DNA repair is dependent on many factors, including the type of the cell, the age of the cell, and the environment outside the cell. A cell that has accumulated a large amount of DNA damage that cannot be repaired by the repair mechanism, can enter one of these path: the ageing of...