What is cancer?

Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. All cancer begins in cells, the body’s basic unit of life. The body is made up of many types of cells. These cells grow and divide in a controlled way to produce more cells as they are needed to keep the body healthy. When cells become old or damaged, they die and are replaced by new cells. However, sometime this orderly process goes wrong. The genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens (by complex processes that in some way cause a disruption of immuno-functioning), cells do not die when they should and new cells form when the body does not need them. The extra cells may form a mass of tissue called a tumour. Cancer cells can spread to other parts of the body through the blood and lymph systems.

Cancer is not just one disease but many diseases. There are more than 100 types of cancer, usually being named by the organ or type of cell in which they start.

The main categories of cancer are:

1. Carcinoma – cancer that begins in the skin or in tissues that line or cover internal organs
2. Sarcoma – cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue
3. Leukemia – cancer that starts in blood-forming tissue such as the bone marrow
4. Lymphoma and myeloma – cancer that begins in the cells of the immune system
5. Central nervous system cancers – cancers that begin in the tissues of the brain and spinal cord.

Key Factors in Cancer Development
More than many other age-related diseases, cancer results from the cumulative effect of years of discrete, small-scale assaults on the body. Oxidation, inflammation, stress, infection and other physiological damages take their toll, inflicting lethal damage over time, and setting abnormal cell proliferation in motion. The following are ten of the key causative factors identified by cancer researchers.

DNA damage
Numerous biomolecular assaults strike at the “blueprint” that cells need in order to replicate themselves accurately. DNA damage is often referred to as the “initiator” or the first step in the onset of most cancers and cancer development.

Excessive or chronic inflammation
Inflammatory processes trigger the release of a host of disruptive cytokines (cell-signalling molecules) that affect virtually all cellular functions. Inflammation is referred to as a cancer “promoter” for this reason.

Disruption of cell signalling pathways
Normal communication within and between cells assures proper regulation of their healthy function. These pathways are easily disrupted by adverse events such as inflammation.

Alterations in the cellular reproductive cycle
Cells undergo a four-stage process as they prepare to replicate themselves. The cell cycle is controlled by signalling pathways that can be altered or disrupted at each of these stages.

Abnormal regulation of apoptosis
Apoptosis is the process of naturally “pre-programmed” cell death that prevents the overgrowth of tissue. When apoptosis fails, cells may undergo uncontrolled reproduction.

Altered survival pathways
The flip side of unregulated apoptosis: survival of too many healthy cells, paradoxically, can endanger the host by permitting a cancer to take hold by increasing the odds of mutation and proliferation.

Excessive cellular proliferation
Certain hormones and other stimuli can directly trigger cells to reproduce without safe limits, especially when the preceding regulatory mechanisms have failed.

Aggressive invasion of healthy tissue
This is accomplished by excessive production of enzymes and adhesion molecules that “dissolve” tissue and allow the tumour to literally take root. The word “cancer” itself is derived from the crab-like appearance of fully-developed malignancies, which extend tendrils in all directions into healthy tissue.

Rapid angiogenesis
Tumours require growth of new blood vessels for nourishment. They are endowed with the capacity to spontaneously generate blood vessels just like healthy tissue. Angiogenesis in cancer tissue is a primary means by which tumours grow.

Metastasis
This is the migration of cancerous cells to regions of the body beyond the primary tumor. Metastases are the distinguishing features of most malignant cancers, and typically herald the onset of end-stage disease because they disrupt otherwise healthy tissues.