Cancer at the molecular level
The body is made up of trillions of living cells. These cells grow, divide, and die in an orderly fashion. This process is tightly regulated and is controlled by the DNA machinery within the cell. In a baby or a child normal cells divide rapidly to allow for growth. After the person becomes an adult, most cells divide only to replace worn-out or dying cells or to repair injuries.
When cells of the body at a particular site start to grow out of control, they may become cancerous. Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. In addition, these cells can also invade other tissues. This is a property that normal cells do not possess.
Cancer cells originate from normal cells when their DNA (deoxyribonucleic acid) or blue prints within the cell nucleus is damaged. DNA is in every cell and it directs all the cell’s actions, growth, death, protein synthesis etc. when DNA is damaged in a normal cell the cell either repairs the damage or the cell dies.
Normally, the body safeguards against cancer via numerous methods, such as: apoptosis or a process by which abnormal cells die on their own accord, helper molecules (some DNA polymerases), possibly senescence or aging, etc.
In cancer cells, the damaged DNA is not repaired, and the cell does not die. Instead it gives rise to more such abnormal cells with abnormal DNA. These new cells all have the same defective DNA of the original cancer cell.
DNA damage may be inherited from parents or may be a spontaneous problem that occurs during the lifetime of a person. This is called a mutation. DNA damage may also be triggered by exposure to certain environmental toxins such as those present in cigarette smoke. There are, however, multiple factors that may cause cancer and it is difficult to pin point an exact cause.
Mutations may be:
- Those in the error-correcting machinery of a cell. This may cause accumulation of errors rapidly in the cell and its progeny.
- Those in signaling (endocrine) machinery of the cell. This leads transmission of the error signals to nearby healthy cells as well.
- Those that allow the cells to migrate and disrupt more healthy cells away from the primary site of origin.
- Those that make the cell immortal so that the abnormal cell refuses to die.