Cancer is an Inevitability for the Immortal Quiz

Answer: Tumours

The term "tumour" is used to describe a growth of abnormal cells. Unlike the term "cancer", "tumour" can refer to both benign and malignant growths. Though "cancer" is often used in place of "tumour", cancer is medically defined as being malignant. Many scientists reserve the term "cancer" for when cells extravastate from their primary location and spread throughout the body, often leading to death.

Answer: Neoplastic

A range of terms are used to describe cells that behave abnormally. Cells which proliferate more/faster than normal are called hyperplastic. Cells which exist in inappropriate tissues (for example an epithelial cell found in non-epithelial tissue) are called metaplastic. Cells which are cytologically abnormal are called dysplastic. Neoplastic is a term often reserved for abnormal cell masses which constitute a cancer and refers to cells that are both dysplastic and metaplastic.

Answer: Carcinoma

Epithelia refers to cells that are exposed to the environment, with "environment" here referring to either our surroundings, or lumena within the body such as the ducts in the breast or the cavity in the stomach. Sarcomas are cancers of mesenchymal origin (such as muscle or cartilage). Leukemia is a term for cancer of the blood cells and bone marrow. Glioma is a specific cancer of cells which form part of the brain.

Answer: Normal cells depend on signalling from neighbouring cells to proliferate

Cancer can be viewed as being caused by selfish behaviour of cells. In normal circumstances, cells make consensus decisions by communicating with the cells which surround them and the decision to divide or die is made for the good of the tissue. In cancer, cells make their own decisions and drive their own proliferation independently of what is best for the tissue.

Answer: Apoptosis

Apoptosis may seem like an unfriendly term, since it refers to the death of our cells, but it is one of the major defences against cancer. Hyperproliferative cells are usually prevented from reaching large (tumour-scale) sizes by apoptosis.

Answer: p53

This question may seem obscure (mainly because it is), but it shouldn't be. p53 is arguably the most important single protein in understanding the molecular biology of cancer. It performs many tasks in the cells (i.e. it is pleiotropic) that are directly involved in promoting death in abnormal cells, therefore preventing cancer. Additionally, p53 is important in halting the cell cycle and inducing cell repair mechanisms. Loss of p53 therefore has the multi-hit effect of making cells resistant to death, removing the breaks on cell proliferation, and allowing cells to continue dividing after acquiring damage. For these reasons, p53 has been described as "the Guardian of the Genome".

The importance of p53 is seen in people who inherit a faulty gene coding for this protein, and who have a high predisposition to developing numerous tumours - this is called Li-Fraumeni syndrome.

Answer: Cell immortality

Cells may acquire mutations in their genome which results in activation of an otherwise quiescent enzyme known as telomerase. Telomerase extends the ends of chromosomes and so effectively extends the cell lifespan. The normal cell lifespan is set at around 60-70 divisions and is known as the Hayflick limit.

Answer: Oncogenes

Cancer is primarily a genetic disease - the majority of its molecular characteristics can be explained by observing mutations to the cell genome. Tumour suppressor genes normally prevent cancer formation, for example by preventing hyperproliferation or preventing cell death. Conversely, oncogenes promote cancer formation by promoting proliferation and preventing cell death.

Their over-activity therefore induces cells to become cancerous.

Answer: The spread of cancer cells from their primary site of origin to secondary sites in the body

Benign tumours rarely cause death, though it is not unknown. If large enough, benign tumours can press on vital organs, compromising their normal function. Metastasis requires cells to become free from their primary site and travel, often via the blood, to secondary sites.

This invasive spread is characteristic of cancer that has acquired so many mutations so as to become aggressive and seriously reduces the chances of survival.

Answer: Stabilisation of the cell genome

Cells that have impaired cell-cell adhesions are more likely to become free from their normal position, and increased motility allows them to move into other parts of the tissue. In order to "clear the path" for these migratory cells, cancer cells often coerce surrounding (otherwise normal) cells to produce proteases which degrade the extracellular matrix.

As well as providing a route for cell migration, degradation of the matrix releases important growth factors for the cancerous cells. Cells may then enter the circulation and travel to numerous sites around the body.