How Cancer Starts?
Normally, cells multiply and die in an orderly way, so that each new cell replaces one lost. Sometimes, however, cells become abnormal and keep growing. In solid cancers, such as breast cancer, the abnormal cells form a mass or lump called a tumour.
For a cancer to start, certain changes take place within the genes of a cell or a group of cells. A tumor develops due to errors in the cell replication process, resulting in flawed replicated cells. The most critical error is their uncontrolled reproduction, persisting endlessly. Moreover, these cells often lack specialization or differentiation, rendering them non-functional and incapable of following the normal life cycle of cells.
Genetic Change that cause uncontrolled divisions of cancer cells
Failure To Respond To 'STOP' signals
Avoidance Of Cell Death
Getting the Blood Supply
Cancer begins when a normal cell undergoes changes in its DNA, disrupting its normal function. A tumour forms, made up of billions of copies of the original cancerous cell.
Cancers of blood cells don't form tumours for example leukaemias. But they make many abnormal blood cells that build up in the blood.
Our cells talk to each other using chemical signals. These signals work like messages that cells use to know what to do. They attach to special spots on the cells called receptors, which then send these messages inside the cell. These messages are like instructions telling the cell what to do, like "grow" or "stop growing." But in cancer, these messages can get mixed up. Sometimes they're sent too many times, or they don't get through at all. Other times, the cells receive the messages even when they shouldn't. Because of these mix-ups, cells don't follow the right instructions. They starts to grow too much or not stop growing when they're supposed to, causing problems in the body.
In normal tissue there is a balance between the generation of new cells via cell division and the loss of cells through cell death. Old cells become damaged over time and death. Normal cells die by cellular suicide (apoptosis) when they behave abnormally. Cancer cells can avoid apoptosis and survive by producing pro-survival protein 'shields'. Cancer cells can also survive by making defective (mutated) 'death' proteins - or not making them at all. Avoidance of cell death, coupled with continued cell division leads to the growth of a tumor.
As a tumor grows larger, it uses more oxygen and nutrients. Eventually it will need to increase the supply of nutrients and oxygen it receives. This is done by causing the growth of new blood vessels. The process is called angiogenesis. Low oxygen levels (hypoxia) trigger the tumor and its surrounding environment to release signals that cause the growth of blood vessels towards and into the tumor. These new vessels supply oxygen and nutrients that allow the tumor to continue growing.
Cancer cells separated and caused metastasis
When cancer cells grew strong and ignored signaling, they can then lose certain molecules on their surface that usually help normal cells stick together properly. This loss makes cancer cells break away from their neighboring cells. When cancer cells break away from their usual place due to losing those sticking molecules, they can travel through the body and settle in other areas, causing cancer to spread. This ability of cancer cells to move to different parts of the body is known as metastasis.
