- There are certain biological capabilities that cells acquire on their path to forming tumors.
- Ultimately, the damage to the DNA of healthy cells leads to the formation of malignant tumors.
Although they may seem like foreign invaders, cancer cells develop out of normal body cells and tissues. Over a period of years, damage to the DNA of healthy cells disrupts their orderly growth, leading to the formation of malignant tumors.
Cancer cells may contain thousands of mutations — alterations in their genetic code — but only a small number of them are crucial “drivers” that trigger runaway growth and allow cancer cells to survive and dominate.
What makes cancer cells so different from their normal predecessors?
Two prominent cancer scientists, Robert Weinberg and Douglas Hanahan, published a much-cited paper in 2000, Hallmarks of Cancer listing six traits cancer cells have in common. In 2011 they added two more in an update, Hallmarks of Cancer: The Next Generation. They described these eight biological capabilities that cells acquired on their path to forming tumors.
- Instead of growing only when stimulated by external signals, cancer cells stimulate their own growth.
- They disable tumor-suppressor genes and ignore external signals ordering them to stop dividing.
- They refuse to destroy themselves through apoptosis – the process of programmed cell death that rids the body of damaged and dangerous cells.
- Unlike normal cells, which can divide a limited number of times, cancer cells can multiply indefinitely, and are said to be “immortal.”
- They simulate the growth of new blood vessels (angiogenesis) to support tumors’ increasing size.
- Cancer cells can break away from their site of origin, enabling them to invade surrounding local tissue and spread to distant parts of the body (metastasis).
- They can make use of abnormal metabolic pathways to generate energy.
- They can evade the body’s immune system by hiding from it or using “checkpoints” to prevent T cells from attacking tumors.
Cancer cells are able to gain these new abilities, the authors said, because of two “enabling characteristics.” One is genomic instability — a kind of chaos in the cells’ DNA marked by broken and extra chromosomes, and the generation of random mutations that can lead to cancer. The second is inflammation in premalignant and malignant cells, which promotes the growth and worsening of tumors.
The authors say the increased understanding of cancer biology will guide the development of treatments such as targeted drugs and immunotherapies.
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