Hallmarks of Cancer

Question 1

Hallmark 1: Self Sufficiency in Growth Signals

Answer 1

• Mutations in proto-oncogenes lead to a gain of function. Leads to constant signalling to promote cell proliferation even in absence of growth factors

Question 2

Hallmark 2: Limitless Replicative Potential

Answer 2

• Normally, Telomere shortening following cell division limits the number of times a cell divides (40-60).
• Tumour cells can rebuild telomeres by enzyme Telomerase and are effectively immortal
• Not a mutation but a change in gene expression

Question 3

Hallmark 3: Insensitivity to Antigrowth Signals

Answer 3

• Mutations in tumour suppressor genes lead to a loss of function, making it difficult to develop drugs against them
• 2 hits are required to inactivate a tumour suppressor gene

Question 4

Hallmark 4: Resistance to Apoptosis

Answer 4

• Apoptosis can be triggered in cells by DNA Damage and viral infection. Also mechanism in which radio/chemotherapy kill cancer cells
• Resistance can therefore develop through both gain & loss of function mutations, and changes in gene expression

Question 5

Hallmark 5: Angiogenesis

Answer 5

• Formation of new blood vessels by secreting angiogenic factors causing them to grow into tumour and supply oxygen + nutrients

Question 6

Hallmark 6: Invasion & Metastasis

Answer 6

• Metastasis = Spread of cancer cells to other parts of body
• Many cases metastatic tumours are detected first and it is unknown where primary tumour is
• Acquisition of invasive properties is what distinguishes malignant from benign cells
• Cancer cells travel from tumour into bloodstream where platelets may be recruited to help avoid recognition

Question 7

Hallmark 7: Reprogrammed Energetics

Answer 7

• Cancer cells often have altered energetics where metabolism shifts from oxidative Phosphorylation => Glycolysis (Warburg Effect)
• Since Glycolysis is much less efficient at producing ATP, cancer cells have to significantly increase glucose uptake through glucose transporters
• Process may allow increased biosynthesis of key molecules allowing increased cell proliferation

Question 8

Hallmark 8: Avoiding Immune Destruction

Answer 8

• Mutations can generate new antigens that are recognised as non-self by T Cells. Tumours therefore need to avoid immune destruction

Question 9

Cells signalling in a tumour

Answer 9

• Signalling between cells is important for tumour progression and therapeutic intervention