biology of cancer

Question 1

what is sporadic cancer?

Answer 1

cancer that is NOT caused by an INHERITED gene

Question 2

how is cancer somatic?

Answer 2

there mutation occurs after conception

Question 3

what is familial cancer?

Answer 3

cancer occurring in families more than expected by chance.

this would happen due to a combination of genetic and environmental factors.

Question 4

what is telomere shortening?

Answer 4

acts as a tumour suppressor.

it limits the proliferation of a cell to only a few rounds of mitosis.

Question 5

what is angiogenesis?

Answer 5

the formation of new blood vessels

Question 6

what are the 5 characteristics of cancer cells?

Answer 6

• excessive proliferation
• avoids telomere shortening/senescence
• angiogenesis is needed
• metastasizes
• can’t be stopped by apoptosis

Question 7

why are there multiple different driver mutations in multiple different key genes to make a malignant tumour?

Answer 7

as there are more than one key tumour suppressors to overcome to form a malignant tumour.

Question 8

why do carcinogens increase the chance of cancer?

Answer 8

it increases the random rate of mutations

Question 9

what is the difference between driver and passenger mutations?

Answer 9

driver mutations- ones that affect genes that control proliferation, apoptosis, immortality and can actually lead to cancer.
passenger mutations-these mutations are in genes that will not promote cancer.

Question 10

what are proto-oncogenes?

Answer 10

if a gene mutation switches this on- it increases cancer risk by increasing excessive proliferation

Question 11

what happens if there is a mutation in tumour suppressor genes?

Answer 11

TS genes are meant to inhibit events leading to cancer, if there is a loss of their function cancers can arise

Question 12

what are some activities of tumour suppressor genes?

Answer 12

• stop excessive proliferation

- promote cell death

Question 13

how does the excessive proliferation in cancer tumours take place?

Answer 13

normally the cell cycle is controlled by 4 checkpoints.

these are deregulated in cancer cells.

Question 14

what is senescence?

Answer 14

cell can’t proliferate or re-enter the cell cycle.
altered cell function.
cancer cells need to avoid this to become immortal

Question 15

what are telomeres?

Answer 15

the repeat sequences at the end of chromosomes.

Question 16

how does telomere shortening work?

Answer 16

ever time the cell divides, the chromosome loses a telomere.
if all the telomeres are lost the chromosome reaches CRISIS which is bad.
so instead when the number of telomeres get short the P53 tumour suppressor starts senescence of that cell.

Question 17

what happens if the chromosome reaches crisis?

Answer 17

there are no telomeres, so it is just broken, naked DNA ends.
these two ends get fused to form a loop.
the loops complicates during anaphase of mitosis and causes chromosome instability and mutations.
apoptosis needs to destroy this, to avoid destroying the genome.

Question 18

how does inactive telomere shortening lead to cancer?

Answer 18

if P53 is inactive the chromosomes get rearranged (this is fine as they will rearrange until the cell dies) but in some cancer cells the TERT enzyme is activated by another mutation.
it adds telomeres to the damaged chromosomes so they can eep proliferating. and leads to cance.

Question 19

what is the Rb enzyme?

Answer 19

Rb is important at the restriction point at the G1 checkpoint.

Question 20

how do cancer tumours induce angiogenesis?

Answer 20

the release VEGF which induces new vessel growth

Question 21

how do the secondary tumours form from the primary ones?

Answer 21

the tumour cells move in the blood vessels, when leading to the capillary beds the vessel lumen gets too small for the enlarged cancer cells. the cancer cells get stuck in the capillary and metastasise.