Photocarcinogenesis

Question 1

What are the 8 hallmarks of Cancer?

Answer 1

1- sustained growth signalling
2- loss of growth inhibition
3- resisting apoptosis
4- unlimited replicative potential
5- inducing angiogenesis
6- disordered repair mechanisms
7-evasion of the immune system
8-activating invasion and metastases

Question 2

What are cellular proto oncogenes?

Answer 2

Normal genes that stimulate cell division

Question 3

What are oncogenes?

Answer 3

These are abnormal genes changed from proto oncogenes to oncogenes in cancer which allows uncontrolled proliferation. Only 1 copy needs to be activated.

Question 4

What are tumour suppressor genes?

Answer 4

Normal genes that inhibit cell division

Question 5

How many copies of tumour suppressor genes need to be lost to allow cancer to develop?

Answer 5

2

Question 6

Give five examples of tumour suppressor genes

Answer 6

p53, Rb, NF1, APC, WT1

Question 7

Explain what telomeres are and what happens in malignancy?

Answer 7

Telomeres are repeats at the end of chromosomes meaning cells can only divide a certain number of times due to the telomerase repeats decreasing. In malignancy there is often a mutation that reactivates the enzyme telomerase allowing unlimited replicative potential.

Question 8

What are there often abnormalities in cancer cells that allow mutations not to be repaired?

Answer 8

Abnormalities in mismatch repair proteins

Question 9

Sun exposed skins often have extensive amounts of mutations in ___1___ which are usually __2__ tolerated

Answer 9

1) p53

2) well

Question 10

Explain the six fitzpatrick skin types

Answer 10

Skin type I - always burns, never tans
Skin type II - usually burns, can tan
Skin type III - can burn, but usually tans
Skin type IV - always tans, never burns
Skin type V - ‘brown’ skin
Skin type VI - ‘black’ skin

Question 11

There are two different types of melanin, the ____1_______ present in the skin and hair of dark-colored persons and ____2_____present in the skin and hair of light colored persons. It has been reported that ________3_________________

Answer 11

1) eumelanin
2) pheomelanin
3) eumelanin is photo-protective and that pheomelanin is phototoxic in nature

Question 12

Up to 80% sun damage occurs during first ___________

Childhood sunburn increases melanoma risk 4-fold

Answer 12

18 years of life

Question 13

What group of people are also at risk of skin cancer?

Answer 13

Those with auto immune conditions on immuno suppressants

Question 14

What is the difference between UVA and UVB

Answer 14

UVB (290-320nm) causes direct DNA damage
1000x more damaging that UVA when sun directly overhead

UVA (320-400nm) causes indirect oxidative damage
UVA penetrates more deeply into the skin than UVB

Question 15

What does UVA cause wrinkles but UVB less so?

Answer 15

UVA gets down deeper attacking collagen fibres which is what causes wrinkles