The human body has many mechanisms to control proliferation and arrest cell cycle to stop DNA damage. Robert Weinberg and Douglas Hanahan wrote in depth about the hallmarks of cancer in two review articles. They summarised the whole concept of cancer that gave a better understanding of the disease progression and opened up ways of management. The original article was published in 2000 described six hallmarks of cancers, followed by the second article which added another four hallmarks, which gives up a total of ten hallmarks of cancer.Cancer cells can alter the signalling pathways that control proliferation, cell cycle and growth to ensure survival.
They can do that by sending signals to other cells to release growth factors, or they can produce the growth factors on their own. They also can bypass the tumour suppressor genes activities, usually due to a gene mutation, which leads to continuous cell cycle progression. Unlike healthy cells, cancer cells can inactivate the machinery of apoptosis and escape cell death. They also gain the ability to be immortal and replicate unlimited numbers of times. As tumour cells grow and replicate, they require more blood supply to deliver oxygen and nutrients. They can keep revascularisation active to ensure they receive all the nutrients essential for their growth.
Due to their abilities to continually proliferate and forming new blood vessels, cancer cells can spread locally to adjacent tissues or systematically through blood and lymphatics to other organs. Moreover, depending on the oxygen status in the environment, They can switch between aerobic and anaerobic metabolism. This ability give the cells the chance to survive in the absence of oxygen. Tumour cells can escape and avoid being detected by the immune system which leads to survival of the cells, although the mechanism is not entirely well understood. The next two hallmarks are enabling characteristics; their presence facilitates the alteration necessary for the cells to become cancerous.
By acquiring and accumulating gene mutations, healthy cells will be genomic unstable and more prone accumulate mutations and to transform into malignant cells. Tumor cells can promote inflammation; cells produce chemicals, reactive oxygen species which promote more mutations and DNA damage. Inflammation also enhances proliferation and cell survival which accelerate cancer progression (Figure 1.1 the hallmarks of cancer).