Introduction to Cancer

Question 1

what is cancer?

Answer 1

A group of diseases characterised by unregulated cell growth and the invasion and spread of cells from the site of origin.

Question 2

what is a carcinoma?

Answer 2

a cancer of the epithelial cell

Question 3

what is a sarcoma?

Answer 3

a cancer of the mesoderm cells (e.g. muscle and bone)

Question 4

what is an adenocarcinoma?

Answer 4

a cancer of the glandular tissue (e.g. breast).

Question 5

what are the hallmarks of cancer and what do they mean?

Answer 5

growth signal autonomy (growth signal-independent growth)
evasion of growth inhibitory signals
avoiding immune destruction
unlimited replicative potential (maintain the length of they telomeres)
tumour promoting inflammation
invasion and metastasis
angiogenesis (new blood vessel formation)
genome instability and mutation
evasion of cell death
reprogramming energy metabolism

Question 6

What are the two emerging hallmarks of cancer?

Answer 6

reprogramming energy metabolism and avoiding immune destruction

Question 7

what are the two enabling hallmarks of cancer?

Answer 7

tumour-promoting inflammation and genome instability and mutation

Question 8

what is the difference between benign and malignant tumours?

Answer 8

bengin:
- remains encapsulated 
- non-invasive 
- no metastasis 
- usually not life-threatening 
malignant:
- non-encapsulated 
- invasive and metastasises 
- life-threatening 
- fast growth 
- non-differentiated

Question 9

what are the differences between normal and cancer cells?

Answer 9

normal cells:
- grow in monolayers 
- contact inhibition 
- flat, extended morphology 
- cannot grow in low serum 
- anchorage dependant 
cancer cells:
- grows in piles called 'foci'
- no contact inhibition 
- rounded morphology 
- grows in low serum 
- anchor independant

Question 10

what is the name for an agent that causes cancer?

Answer 10

carcinogen

Question 11

what is a mutagen?

Answer 11

an agent that causes a DNA alteration, mutation.

most carcinogens are mutagens.

Question 12

why is cancer called the ‘disease of ageing’

Answer 12

accumulation of many mutations over time results in cancer formations

Question 13

what is a germline mutation

Answer 13

DNA alterations in the sperm and egg cells that are passed on to offspring. they can increase risk of cancer but never directly induce cancer

Question 14

what is a somatic mutation

Answer 14

a mutation of the body cells (somatic cells) via DNA alterations. This is passed onto daughter cells.

Question 15

what is clonal origin

Answer 15

all cancerous cells arise from a single cell with multiple mutations

Question 16

what are the three key mechanisms affected by mutation that lead to cancer

Answer 16

cell proliferation, differentiation and apoptosis

Question 17

what are proto-oncogenes?

Answer 17

normal genes that can be activated by mutation to be oncogenic

Question 18

what is an oncogene? How do they cause cancer?

Answer 18

a gene mutated such that its protein product is produced in higher quantities or has increased activity and therefore acts in a dominant manner to initiate tumour formation.
an example includes an oncogene that produces a growth factor receptor with increased activity so is therefore constituently active and doesn’t require a GF to send a signal to cells

Question 19

what is a tumour suppressor gene? How can they cause cancer?

Answer 19

codes for proteins that play a role in inhibiting growth and tumour formation, promoting differentiation and triggering apoptosis.
Loss of growth inhibition occurs when mutations cause loss of function of the gene. Mutations are recessive.

Question 20

what is haploinsufficiency?

Answer 20

one mutated allele can lead to cancer phenotype

Question 21

how can environment influence cancer?

Answer 21

exposure to carcinogens.
first seen in 1775, increased nasal and scrotal cancer in chimney sweeps due to chronic exposure to soot.
UVB in sunlight can directly alter DNA by forming pyrimidine dimers and cause mutations.

Question 22

how does reproduction influence cancer?

Answer 22

having children young decreases chance for breast cancer
sexually transmitted human papillomaviruses are involved in cervical cancers.
human herpesvirus type 8 is involved in Kaposi’s sarcomas, linked to AIDS

Question 23

what lifestyle factors can affect cancer risk?

Answer 23

diet and exercise, reproduction, environment, alcohol consumption, smoking

Question 24

what is the main objective of current cancer treatment?

Answer 24

inhibit or eradicate metastasised cells, prevent proliferation, and kill cancer cells (cytostatic and cytotoxic effects)

Question 25

what is the therapeutic index?

Answer 25

value of the difference between the minimum effective dose and the maximum tolerated dose (MTD). The larger the value the safer the drug.
most cancer treatments are given at the MTD