Rosemary Fisher

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Genetics of Gestational Trophoblastic Disease
Rosemary Fisher Department of Medical Oncology,
Charing Cross Campus,
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Classification of GTD
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Genetics of Hydatidiform Moles
CHM
PHM
Triploid
Diploid
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Genetic Origin of Partial Moles
Two sperm fertilise an egg
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23
23
23
23
69
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This results in a triploid conceptus with 69
chromosomes
PHM are dispermic and may be 69,XXX 69,XXY
69,XYY
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Genetic Origin of Complete Moles
Monospermic Complete Mole - 80
The paternal chromosomes double up
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CHM are 46,XX
Maternal chromosomes are lost
CHM are 46,XX or 46,XY
Two sperm fertilise the egg
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Maternal chromosomes are lost
Dispermic Complete Mole - 20
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Genetic Origin of Complete Moles
HM - two paternal contributions to the genome

• Triploid conceptuses where the extra set is
  maternal
• do not have molar pathology
• greater fetal development

• Diploid germ cells with two maternal sets of
  chromosomes
• do not have molar pathology
• develop as dermoid cysts with mature tissues

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Differential Diagnosis of HM
Incidence of trophoblastic tumours
Normal pregnancy
1 in 40 - 50,000
Complete hydatidiform mole
1 in 8
Partial hydatidiform mole
1 in 200
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Genetic Diagnosis of Hydatidiform moles
Compare DNA in the patient, her partner and the
molar tissue
Microsatellite polymorphisms - short lengths of
repeat sequences which occur throughout the
genome - vary in size between individuals
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Methods
Sections from pathological blocks
Blood
DNA
Polymerase Chain Reaction amplify polymorphic
microsatellite sequences on different chromosomes
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Methods
Fluorescently labelled PCR products
Separate by capillary electrophoresis in a 310
ABI PRISM Genetic Analyser
Compare microsatellite polymorphisms in tissue
DNA with those in patient and her partner
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Microsatellite Polymorphisms
Size (bps)
Arbitrary Units of Fluorescence
Microsatellite
D13S317
D12S391
D18S535

Uninformative allele
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Microsatellite Polymorphisms in PHM and CHM
PHM
CHM
Size (bps)
Arbitrary Units of Fluorescence
D15S659
D13S317
Microsatellite
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Genetic Diagnosis of Hydatidiform Moles
Fluorescent microsatellite genotyping
Examine expression of imprinted genes
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Genomic Imprinting
Parent-of-origin gene expression
A small number of genes are only transcribed from
one allele, may be the maternally inherited or
the paternally inherited
Genomic imprinting may be tissue specific
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Expression of Imprinted Genes in HM
CHM
PHM
Overexpression of paternally expressed genes
Overexpression of paternally expressed genes
Loss of maternally expressed genes
Presence of maternally transcribed genes in PHM
is associated with fetal development
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p57KIP2 Expression in HM
CHM
Placenta
PHM
LP
HP
LP
P57KIP2 - expressed only from the maternally
derived allele
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Genetic Diagnosis of Hydatidiform Moles
Differential diagnosis of HM
Diagnosis of familial recurrent HM
Mosaic pregnancies involving HM
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Mosaic pregnancies involving androgenetic cells
Placenta comprising two distinct cell lines
Androgenetic

Normal, diploid biparental
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Genetic Diagnosis of Mosaic Placenta involving HM
Case history -
Singleton pregnancy
Normal live birth - female
Areas of normal villi
Areas of molar villi
Same sperm involved
Case of confined placental mosaicism
Makrydimas et al 2002
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Androgenetic/Biparental Mosaics
Genetics
Pathology
Biparental villi / androgenetic villi
Mosaic placenta with molar/normal pathology
Biparental cells / androgenetic cells in the
same villi
Placental mesenchymal dysplasia
Androgenetic cells associated with PTD
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Classification of GTD
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Characteristics of Gestational Trophoblastic
Tumours
1. Raised serum hCG
2. Trophoblast morphology
3. Positive hCG staining
4. Good prognosis
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Genetic Diagnosis of Trophoblastic Tumours
Is a tumour gestational in origin?
Which is the causative pregnancy?
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Genetic Diagnosis of Trophoblastic Tumours
Gestational
Non-Gestational
Genome will reflect that of the pregnancy in
which it arose
Genome will reflect that of the host
DNA from the patient
Paternal DNA
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Microsatellite Polymorphisms in Trophoblastic
Tumours
Gestational
Non-Gestational
size (bps)
Arbitrary Units of Fluorescence
D1S1656
D20S418
Microsatellite
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Microsatellite Polymorphisms in Trophoblastic
Tumours
Non-Gestational
size (bps)
Patient
Arbitrary Units of Fluorescence

Tumour
Partner
D20S481
D11S1999
Microsatellite
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Genetic Diagnosis of Trophoblastic Tumours
Case history - LC
57 year old lady
FTND 23 years previously
Presented with uterine mass
Hysteroscopy
Consistent with choriocarcinoma
Gestational tumour
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Genetic Diagnosis of Trophoblastic Tumours
Case history - AW
32 year old lady
FTND 6 years previously
Hysterectomy 2 years later
Presented with liver metastases
Consistent with choriocarcinoma
allele loss
Non-gestational tumour
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Laser Capture Microdissection
H E stained tissue
Tissue before capture
Tissue after capture
Captured cells
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Genetic Diagnosis of Trophoblastic Tumours
Is a tumour gestational in origin?
Which is the causative pregnancy?
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Size (bps)
Causative Pregnancy in GTT
Case history - VP
Arbitrary Units of Fluorescence
June 1997 - CHM plus twin
July 2000 - Termination for Turner
syndrome
Sep 2000 - Choriocarcinoma
D5S816
Microsatellite
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Post - Mole Trophoblastic Tumour
Case history - JS
1990
CHM
1991
Normal delivery
1992
Normal delivery
1997
Termination for Down Syndrome
1998
Choriocarcinoma
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Post - Mole Trophoblastic Tumour
Incidence of trophoblastic tumours
Normal pregnancy
1 in 40 - 50,000
Complete hydatidiform mole
1 in 8
Partial hydatidiform mole
1 in 200
Abnormal imprinting may predispose to tumour
development
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Genetic Diagnosis of Trophoblastic Tumours
Can confirm a tumour is gestational in origin
Identify the causative pregnancy
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Acknowledgements
Charing Cross Hospital, London
Michael Seckl
Delia Short
Philip Savage
Karina Catalano
Neil Sebire
Iain Lindsay
Cancer Treatment and Research Trust