What exactly is Cancer?
Cancer is a complex set of genetic diseases that lead to abnormal cell growth, proliferation, and metastasis of cancer cells to vital organs resulting in death. In other words, cancer is a group of diseases in which some of our body’s cells grow uncontrollably and spread to other parts of the body, damages our critical organs and can ultimately lead to death.
Cancer is the first or second major cause of death before the age of 70 in most countries. (World Health Organization, 2019)
Why is Cancer a Genetic Disease?
Each of our cells contain more than twenty thousand genes. Cancer is caused by changes to some of those genes that control the way our cells function, especially how they grow and divide.
Does it mean that cancer can be passed on to the next generation hereditarily?
Not necessarily. There are some genetic defects which can run through the family. This doesn’t automatically ensure that the next generation will develop cancer, but they certainly increase the risk. They pre-dispose a person to cancer. We need to be careful and screen them regularly. However, most of the cancers happen because of ‘somatic’ mutations during a lifetime. These mutations, or genetic defects, are not hereditary, but accumulated over period of time.
Does Cancer Develop Suddenly?
Cancer develops over time (years to decades) with the gradual accumulation of mutations in genes that control normal growth, proliferation, and differentiation. Normal cells become cancerous by acquiring the following hallmark properties:
Sustained proliferative signalling: Normal cells grow only when they are signalled to grow, not otherwise. They start becoming cancerous when the ‘stop signal’ malfunctions.
Evading growth suppressors: Ignore signals that tell normal cells to stop dividing or growing.
Escaping the immune system: Our immune system normally attacks and eliminates damaged or abnormal cells, but when they become cancerous, they start evading the immune attack. In fact, some cancers trick the immune system into helping cancer cells stay alive and grow.
Endless replicative potential: Cancer cells start replicating endlessly, they just don’t stop.
Escaping natural cell death (apoptosis): When normal cells grow old or become damaged, they die naturally, and new cells replace them. This orderly process breaks down in cancer. Abnormal or damaged cells continue to grow and multiply when they actually shouldn’t.
Invasion and metastasis: Normal cells do not grow when they encounter other cells. Most normal cells do not move around the body. Unfortunately, when they become cancerous, they invade into nearby areas and starts spreading to other parts of the body.
Capability of angiogenesis: Cancer cells signal blood vessels to grow toward tumors. These newly formed blood vessels supply oxygen and nutrients to tumors, providing them further nourishment to grow.
Genome instability: Cancer cells continuously accumulate multiple changes in genes or chromosomes, thereby hampering the normal genome stability.
What Triggers Cancer?
The main triggers of cancer are tobacco use, obesity, poor diet, lack of physical activity, alcohol consumption, exposure to UV light from the sun or tanning devices, and Cancer-associated pathogens such as human papillomavirus (HPV) and Epstein-Barr virus (EBV).
Stages of Cancer
The development of cancer can be identified by stages:
- Stage 1 - Localised tumor
- Stage 2 – Early Locally Advanced Tumor
- Stage 3 – Late Locally Advanced Tumor
- Stage 4- Metastasized Tumors
Cancer can be cured if the tumors are detected and diagnosed at stages 1 and 2. The success of treatment decreases if detected at stages 3 and 4. Most cancer deaths occur due to metastasis. Importantly, cancer is unique to an individual. It is critical to know which therapy suits a particular cancer patient, before actually starting the treatment. Personalisation of cancer treatment to each patient is the key to success.