Biology of Cancer ✅

Question 1

What is cancer?

Answer 1

Uncontrolled cellular proliferation

Question 2

What prevents excessive replication of normal cells?

Answer 2

Most healthy cells have limited potential for replication and their proliferation, differentiation, and death is carefully controlled

Question 3

What happens to cell division during cancer development?

Answer 3

Cells undergo a multi-step process in which they gradually acquire genetic mutations allowing them to escape the normal controls

Question 4

What can cancers be divided into?

Answer 4

• Benign, or low-grade

- Malignant, or high-grade

Question 5

What are the features of low grade tumours?

Answer 5

• Tends to grow locally

- Has not developed the potential to metastasise

Question 6

What are the features of high grade tumours?

Answer 6

• Highly proliferative

- Tends to metastasise

Question 7

How is it determined if a tumour is ‘highly proliferative’?

Answer 7

Has high mitotic index when examined under the microscope

Question 8

When might a benign tumour not have a benign clinical course?

Answer 8

If the tumour is growing close to and impinging on a vital structure

Question 9

What must happen for a cell to become malignant?

Answer 9

Mechanisms designed to prevent cancer development must be overcome

Question 10

What are the key processes by which a cell becomes malignant?

Answer 10

• Self-sufficiency in growth signals
• Insensitivity to anti-growth signs
• Immune escape
• Limitless replicative potential
• Tumour-promoting inflammation
• Tissue invasion and metastasis
• Inducing angiogenesis
• Genetic instability
• Evading apoptosis
• Abnormal cellular metabolism

Question 11

What do normal cells require to trigger them to proliferate?

Answer 11

External signals (growth factors)

Question 12

How can cells develop self-sufficiency in growth signals to become cancerous?

Answer 12

• Mutations in cell surface receptors so that they are constitutionally active even in the absence of growth factors
• Expression of abnormally high levels of cell surface receptors

Question 13

What do normal cells have to prevent excess proliferation?

Answer 13

Multiple anti-proliferative signals

Question 14

Give an example of an anti-proliferative signal

Answer 14

Contact with neighbouring cells

Question 15

What is the purpose of anti-proliferative signals?

Answer 15

Maintain tissue stability and prevent overgrowth

Question 16

How can cells change to overcome anti-proliferative signals to become cancerous?

Answer 16

They can acquire mutations such that they become insensitive to these signals

Question 17

What is meant by a limited replicative potential of cells?

Answer 17

Normal cells are able to divide a limited number of times before they enter a state known as senescence

Question 18

What controls the limited replicative potential of cells?

Answer 18

Successive shortening of telomeres

Question 19

What are telomeres?

Answer 19

Repetitive sequences of DNA base pairs that cap the end of chromosomes

Question 20

What happens to telomeres following each replication?

Answer 20

Some of their base pairs are lost

Question 21

How can cells acquire limitless replicative potential to become cancerous?

Answer 21

They can develop the ability to overcome telomere shortening

Question 22

How can cells develop the ability to overcome telomere shortening?

Answer 22

By re-expressing telomerase that allows them to rebuild lost telomeres, or through other mechanisms

Question 23

What is apoptosis?

Answer 23

Inbuilt mechanisms to trigger programmed cell death

Question 24

Why might a cell trigger apoptosis?

Answer 24

In response to significant DNA damage or other insult

Question 25

How can cells evade apoptosis to become cancerous?

Answer 25

The balance between pro and anti-apoptotic signals is altered

Question 26

What does a cancer cell need to do to in order to metastasise?

Answer 26

Acquire a number of abilities, including;

• The ability to invade into blood vessels or lymphatic system
• The ability to survive as a single detached cell or clump of cells
• The ability to invade the target tissue and survive in this new environment

Question 27

Why is it important for cancer cells to be able to induce angiogenesis?

Answer 27

As tumours grow, they need to ensure the development of new blood vessels to ensure adequate supply of oxygen and nutrients

Question 28

How do cancer cells induce angiogenesis?

Answer 28

They produce various signals, such as vascular endothelial growth factor (VEGF), that stimulate the growth of new blood vessels

Question 29

What is meant by immune escape in cancer cells?

Answer 29

The development of mechanisms by which they can evade detection and elimination by the immune system

Question 30

Why is it important that cancer cells develop the ability to evade the immune system?

Answer 30

There is growing evidence for a role of the immune system in controlling cancer development

Question 31

What is the importance of non-cancer cells within a tumour?

Answer 31

They may play a role in stimulating tumour growth

Question 32

Give an example of when a non-cancer cell within a tumour may play a role in stimulating tumour growth

Answer 32

Inflammatory cells enhancing angiogenesis

Question 33

Why is genetic instability important in the development of cancerous cells?

Answer 33

Cancer cells need to acquire multiple genetic mutations in order to achieve many of the characteristics required to survive, and increased genetic instability helps enhance the acquisition of these mutations

Question 34

Why is abnormal cellular metabolism important in the development of cancerous cells?

Answer 34

Cancer cells must survive in relatively inhospitable tissue environments, and so many cancer cells alter their energy metabolism as an adapation

Question 35

Give an example of when a tumour may have an inhospitable tissue environment

Answer 35

Marked hypoxia at the centre of a large tumour

Question 36

What can genetic abnormalities in cancer be divided into?

Answer 36

• Those that result in the over-activation of a particular gene or pathway
• Those that result in a loss of function

Question 37

Give 2 examples of where gain of function mutations can lead to enhanced malignant progression

Answer 37

• Growth factor receptor signally pathways

- Transcription factors

Question 38

By what mechanisms can a gain of function mutation occur in a proto-oncogene?

Answer 38

• Translocation
• Amplification
• Point mutations

Question 39

How might translocation of a proto-oncogene lead to a gain of function mutation?

Answer 39

Can lead to increased expression of the oncogene driven by the promoter region of another gene, or the formation of a novel fusion protein with abnormal activity

Question 40

How can amplification of a proto-oncogene lead to cancer?

Answer 40

It leads to increased oncogene expression

Question 41

What can point mutations in proto-oncogenes be divided into?

Answer 41

• In promoters (at the beginning of a gene)

- Within a gene

Question 42

How can a promoter point mutation in a proto-oncogene lead to cancer?

Answer 42

Leads to increased oncogene expression

Question 43

How can a point mutation within a proto-oncogene lead to cancer?

Answer 43

It may lead to expression of a protein with abnormal activity

Question 44

In what kind of genes can a loss of function mutation lead to cancer?

Answer 44

Tumour suppressor genes

Question 45

Give 2 examples of functions of tumour suppressor genes

Answer 45

• Trigger apoptosis

- Block cell cycle progression in the presence of DNA damage