cancer

Question 1

Whos law stated that all cells come from other cells? Importance?

Answer 1

Virchow 1858.
Important for stem cells and that cancers must just come from normal cells that have aberrent organisation, lost the ability to assemble and create tissues of normal form and function

Question 2

Tissue growth containing excess number of cells? E.g.

Answer 2

Hyperplasia- e.g. more cells than space allows so ingress into lumen/ chnage shape e.g. carcoma

Question 3

Displaced but otherwise normal cells? E.g.

Answer 3

Metaplasia e.g. Barratts oesophagus- squarmous to columnar

Question 4

Non-Invasive abnormal tissue growth?

Answer 4

Dysplasia- shape/form of cells different

Question 5

Invasive, abnormal tissue growth?

Answer 5

Neoplasia- agressive, often cannot be well removed as not well defined and may be joined to other tissues

Question 6

Tumour definition

Answer 6

created by cells that have lost the ability to assemble and create tissues of normal form and function

Question 7

Major risk factor in cancer development?

Answer 7

AGE
75% of 75yr+ that die have a tumour but just haven’t died from (yet).
e.g. breast cancer during menapause

Question 8

Example of a cancer that decreases with age?

Answer 8

Testis- highest incidence in 30’s
Brain peaks at 60 then decreases massively at 85 same as at birth
Hodgkin lymphoma peaks at 75- and then risk
decreases
(Cancer in WBCs in lymph system)

Question 9

Is cancer increasing?

Answer 9

No but life expectancy is, therefore incidences are.

Question 10

Migration study of cancer?

Answer 10

Japanses to hawaii , 1800’s and early 1900’s
Japanese: Low breast, colon and prostate but high stomach.
Caucasian: High prostate, breast, low stomach
If japanese migrate to hawaii: took to environment.

Question 11

Why the chimney Sweep act in 1788?

Answer 11

Percival Pott noticed link between chimney sweeps and prostate cancer- epidemiology.

Question 12

Who came up with the 20 year lag of smoking an cancer paper?

Answer 12

Richard Doll ‘father of epidemiology’

John Hill initially noticed link between snuff and nasopharyngeal cancer

Question 13

Genetic contribution examples for cancer?

Answer 13

Rb -/+ retinoblastoma- cancer of retina
APC loss, increase wnt which maintains colon crypt stem cells, therefore increase risk of colon cancer (Familial adenomatous polyposis)
PTCH loss- Gorlin syndrome, only 10% dont get BCC
Hereditory breast cancer

Question 14

Cancer can be …….(cancer predisposition)

Answer 14

monogenetic- so certain alleles of genes can give a predisposition
e.g. Rb, APC, BRCA2
Only need one sponatnous somatic mutation

Question 15

Breast cancer genetic component?

Answer 15

BRCA2, constitutionally active. 80% risk if have hereditory breast cancer.

Question 16

Cancer and age graphs?

Answer 16

Sigmoid positive correlation, if log both axis linear y=mx+c

Question 17

Maths behind cancer development?

Answer 17

P(c1) proportional to A
P(T)= (P(c1)A) x (P(c2)A)… where multiple changes are needed for tumour.
P(T)= A^n(P(C1)xP(C2)…)
Take logs
LogP(T)= nlogA+C in form y=mx+c
where number of events needed usually around 6, the slope of the linear line normally 6

P(c1) =probability of a change associated with cancer happening.
P(T)= tumour probability
A=Age

Question 18

WHat is the final equation for P(T)? Slope?

Answer 18

LogP(T)= nlogA+C in form y=mx+c

where number of events needed usually around 6, the slope of the linear line normally 6

Question 19

Cancer is a consquence of…

Answer 19

Metazoan evolution

Multicellular

Question 20

Genetic instability within a cell results in which two different outcomes?

Answer 20

Genetic instability- high frequency of mutations within the genome

Dead cell- mutations in the core machinery
Cancerous- mutation that causes an inhibition in proliferation but promotes differentiation and cellular architecture

Question 21

How many times are chromosomes replciated in our life?

Answer 21

40 copies of the genome- but 2^40= 10^13 times, as all of these cells perform mitosis

Question 22

How experimentally was it found out how long cells are in each stage of mitosis?

Answer 22

Functional in vivo assays using morphological markers
Collect cells
Add 32P radioactive phosphate label, so cells emit B particles which can be detected
This encorporates into the sugar phosphate backbone of newly created chromosomes during DNA replication (use the phosphate to make their backbone)
Therefore can see when cells undergone DNA synthesis.
Can count and work out the percentage of cells in different stages. 35% of cells were in M stage, therefore 35% of the cells life in mitosis

Question 23

How are morphological markers used to learn about cell cycle?

Answer 23

GFP-Tubulin/Tubulin dye visuallised by fluorescence microscopy.
If can visuallise the tubulins in microtubules, can see as form and pull chromosomes apart etc.
In drosophila shows up until cell cycle 14 all syncronised

Question 24

How can individual bases be visuallised to study cell cycle.

Answer 24

BrDU thymidine analogue (bromodeoxyuridine)- antibodies can then be used to detect(immunohistochemistry/ immunofluorescence) show cells replicating DNA.

ClDU (Chlorodeoxyuridine) and antibody to

Question 25

Time for cell cycles?

Answer 25

M phase aorund 1hour in humans

In drosophila whole cell cycle in 15mins (only S and M)

Question 26

How can fluropores be used to tell the relative times spent in phases of mitosis?

Answer 26

DNA stain and the amount of DNA proportional to laser excitment.
E.g. G1- DNA f1
G2 and M -DNA 2f
if between then interphase.

Question 27

How was yeast used to inform us about cell cycle?

Answer 27

Look for mutations and differences, and mutate to see impact or irradiate DNA- want to get temperatire sensitive mutants. Have restrictive temperature (dont function) and permissive temperature.
As restrictive some proteins may have a confomational change, can see how far get in the cell cycle (arrest) to see when these needed etc = Execution point.

Question 28

WHy Xenopus good model organism for cell cycle?

Answer 28

Infect with progesterone and can lay eggs , whereas most toads only can in March.
Traditionally used as a pregnancy test- will have progesterone in urine if pregnant and this will induce the xenpus to lay eggs if you are pregnant.

Question 29

How can mitosis be seen from xenopus in a test tube?

Answer 29

1. Centifuge eggs to separate up.
2. Add sperm nucleus
3. Will do mitosis

Question 30

How did we find out about cyclins and cdks? Experiment:

Answer 30

Rao and Johnson 1970
If fuse interphase cells and cells in mitosis, the interphase chromosomes will be induced prematurely into mitosis. E.g. even if no sister chromatids have formed yet as DNA hasnt replicated, the chromosomes will condense.

Question 31

WHat does Rao and Johnsons 1970 experiment also prove as well the existance of cyclins?

Answer 31

That M cyclins are dominant over G1/s and S cyclins, as can induce cells in interphase into Mitosis

Question 32

Xenopus experiment by Masui in 1970’s? (upto find protein)

Answer 32

If take out the cytoplasm of an egg arrested in meiosis (before fertilisation) and insert into a fully grown (fertilised) oocyte (which is in arrested G2), can induce the oocyte to undergo meiosis. Nuclear disassembly and chromosome condensation happens.
called these cytoplasmic components ‘Maturation promoting factor’

Question 33

Why are xenopus good for meiosis experiments?

Answer 33

A little white dot appears on the top of the oocyte when enters meiosis.

Question 34

Xenopus experiment by Lohka and Masui in 1970’s? (find protein)

Answer 34

‘Maturation promoting factor’
Fractionated and purified the cytoplam and injected all the different components individually to see what induced a response, ‘biochemical assay’
Found the protein had kinase activity (used histone to study as its readily P by many kinases and radioactive ATP so see phosphate on an autoradiogram) so likely had two components one P another.
(CDK’s and cyclins)

Question 35

Tim Hunt 1983 experiment?

Answer 35

Sea Urchin. Saw that a protein periodically accumulated but then disappeared just before mitosis, and the waves syncronised with the eggs dividing
CYCLINS isolate mRNA

Question 36

Nurse 1983 experiment? Found?

Answer 36

Temperature sensitive mutants stained to see nucleus and cleavage zone.
At restrictive temperature cdc2 mutants fail to enter mitosis. 
Wee1 mutant (short- premature division-no inhibition) and Cdc25 (Long- divide for long time) mutants etc look at length of the cells (grow during mitosis before cytokinesis) 

Found: Cdc25-> cdc2 (yeast- human homologue is CDK1) and wee1 -I cdc2
so Wee1 negative regulator (P) and cdc25 positive.