Lecture 16- Chromosomes in Cancer

Question 1

Philadelphia Chromosome

Answer 1

Myeloid Leukaemia

Question 2

Haematopoiesis

Answer 2

all arises from haematopoetic stem cell

Question 3

Leukaemia -

Answer 3

Stem Cell cancers and then problems arise further down

Question 4

2 types of Leukaemia

Answer 4

Either lymphoid or myeloid

-Lymphomas or myeloproliferative disorders

Question 5

What dictates the cancer and the prognosis ?

Answer 5

Stage in the cell it matures in dictates the cancer and the prognosis the later it occurs in the cell the worse the prognosis

Question 6

Multiple Myeloma

Answer 6

of the plasma cells

Question 7

What is the more common form of Leukaemia ?

Answer 7

Myeloid leukaemia more common – more cell types involved > granulocytes eg eosinophils, basophils, neutrophils
-Accumulation of the immature cell types – myeloid progenitor induced to produce more cells but they don’t mature – blasts are cells that haven’t matured

Question 8

Genetic Changes in Leukaemia

Answer 8

 Loss of chromosome material
 Gain of chromosome material – duplication, amplification and trisomy
 Altered gene expression – gene fusion, juxtaposed (next to new gene control)
 DNA mutation – point, splice, frameshift, deletion, duplication

Question 9

Testing for Chromosome Abnormalities

Answer 9

 Cytogenetics – study of genetic material and chromosome level
 Karyotype – whole genome scan
 Fish

Question 10

Preparation of the karyotype

Answer 10

Want chromosomes at metaphase – add colcemid

Sample > Culture medium > Incubate 37> Add colcemid > Add hypotonic sol > Fix cells > stain> Banding > Karotyping

Question 11

Dark bands

Answer 11

AT rich, late replication, gene poor, heterochromatic

Question 12

Light Bands

Answer 12

GC rich early replicating, gene rich

Euchromatic

Question 13

Trypsin produces…

Answer 13

Dark and light bands

Question 14

Karyotype analysis

Answer 14

Analysis- count and pair chromosomes

Match up bands look for absent/extra

Question 15

Types of chromosome abnormalities

Answer 15

• Trisomy
• Monosomy
• Inversion
• Insertion – chunk of one chromosome into another
• Translocation – swap of chromosome from one to the other

Question 16

Chromosome nomenclature

Answer 16

	Long arm q 
	Short arm p 
	Each band assigned a number e.g 3p21 
	46 chromosomes 
	Autosomes 1-22
and sex chromosomes – XX or XY 
total number, sex ,abnormality

Question 17

Fusion genes

Answer 17

breakpoint occurs with the two genes and forms a hybrid

Question 18

Deregulation

Answer 18

juxtaposition to a regulating gene altered regulation

Question 19

Detection –

Answer 19

• Translocation and inversions via karyotype
• Some gene fusions are caused by subkarotypic rearrangements
• Clinical need for rapid confirmation of gene fusion – prognostic and treatment implication
• FISH

Question 20

FISH

Answer 20

 Fluorescently labelled DNA probes
 Detect monosomy trisomy deletions duplication, amplification and rearrangement s
 Probe is ssDNA probe
 Probe on slide cover with cover slip and then hybridise over night

Question 21

Types of FISH probe

Answer 21

• Whole chromosome paints
• Locus specific
• Break a part probes – detect gene fusion > Dual colour probe – abnormal translocation, probe broken apart
  KMT2A – doesn’t matter what its fused with just the translocation isn’t good

Question 22

Digital Droplet PCR

Answer 22

very sensitive > probe for mutant and Wt added to PCR action components – partitioned into oil droplets one PCR reaction per droplet
WT probe only binds to WT and same for mutant
Measured by fluorescent detection
- Can predict relapse

Question 23

Next generation sequencing

Answer 23

look at technique used for myeloid panel look for specific mutation s not shown in karyotyping
- More at once

Question 24

Purpose of genetic testing

Answer 24

 Prognostic
 Diagnostic
 Monitoring

Question 25

Real time quantitative PCR

Answer 25

quantify DNA molecules present- used to monitor response to therapy

Question 26

BCR-ABL Quantitation

Answer 26

Q-PCR is used to measure BCR/ABL transcript in monitoring of disease during treatment in CML

Question 27

Chronic Myeloid Leukaemia (CML)

Answer 27

1960 Nowell and Hungerford
Small chromosome named the Philadelphia chromosome (Ph)
First evidence for a consistent chromosome change

1970 introduction of banding

Question 28

PH Translocation

Answer 28

Fusion of two genes:
ABL1 (9q34)
BCR (22q11)

ABL1 is a cellular oncogene and encodes a nuclear tyrosine kinase protein
BCR/ABL1 gives an abnormal fusion protein with increased tyrosine kinase activity
Is a positive regulator of cell growth and leads to increased proliferation and malignant growth
Alone, is sufficient to cause CML

Question 29

Targeted therapy for BCR-ABL1

Answer 29

2001- introduction of Imatinib
Specific inhibitor of of tyrosine kinase domain of ABL1
Blocks the binding site for ATP and inhibits phosphorylation
Prevents activation of the signal transduction pathways