Preimplantation Genetic Diagnosis for Brca1 and Brca2 Mutations

Abstract

Hereditary breast and ovarian cancer syndrome is an inherited cancer-susceptibility syndrome with multiple family members with breast cancer or ovarian cancer or both, the presence of both breast cancer and ova-rian cancer in a single individual, and early age of breast cancer onset. BRCA1 and BRCA2 tumor suppressor gene mutations are responsible for the vast majority of inheritance of breast and ovarian cancers. App-roximately 10% of ovarian cancer patients and approximately 3-5% of breast cancer patients have predomi-nating BRCA1 and BRCA2 gene mutations. Preimplantation genetic diagnosis (PGD) is an alternative to conventional prenatal diagnostic techniques such as amniocentesis and chorionic villus sampling. Prenatal diagnosis for BRCA mutation in an ongoing pregnancy and pregnancy termination brings some ethical and psychological questions together. Hence, it may be favorable to perform PGD for patients with BRCA muta-tions. Eventually, PGD may be recommended at least to the infertile patients with BRCA mutation who sho-uld already undergo in vitro ifertilization IVF (in vitro fertilization).

Full text

Preimplantation Genetic Diagnosis for Brca1 and Brca2
Mutations
Brca1 ve Brca2 Mutasyonları İçin Preimplantasyon Genetik Tanı
Yavuz Emre Șükür1, Batuhan Özmen2, Cem Somer Atabekoğlu2
1 Keçiören
Research
and
Training
Hospital,
Department
of
Obstetrics
and Gynecology, Ankara, Turkey
2
A
nkara
University
School
of
Medicine,
Department
of
Obstetrics
an
d
Gynecology, Ankara, Turkey
Hereditary breast and ovarian cancer syndrome is an inherited cancer-susceptibility syndrome with multiple
family members with breast cancer or ovarian cancer or both, the presence of both breast cancer and ova-
rian cancer in a single individual, and early age of breast cancer onset. BRCA1 and BRCA2 tumor suppressor
gene mutations are responsible for the vast majority of inheritance of breast and ovarian cancers. App-
roximately 10% of ovarian cancer patients and approximately 3-5% of breast cancer patients have predomi-
nating BRCA1 and BRCA2 gene mutations. Preimplantation genetic diagnosis (PGD) is an alternative to
conventional prenatal diagnostic techniques such as amniocentesis and chorionic villus sampling. Prenatal
diagnosis for BRCA mutation in an ongoing pregnancy and pregnancy termination brings some ethical and
psychological questions together. Hence, it may be favorable to perform PGD for patients with BRCA muta-
tions. Eventually, PGD may be recommended at least to the infertile patients with BRCA mutation who sho-
uld already undergo in vitro ifertilization IVF (in vitro fertilization).
Key Words:
BRCA1/2 Mutations; Hereditary Breast and Ovarian Cancer; in Vitro Fertilization; Preimp-
lantation Genetic Diagnosis
Herediter meme ve over kanseri sendromu meme, over veya her ikisinin birden kanserine sahip birden fazla
aile üyesinin bulunduğu, bir bireyde hem meme hem de over kanserinin görüldüğü, ve erken bașlangıçlı
meme kanseri görülen kalıtsal bir kanser yatkınlık sendromudur. Meme ve over kanseri kalıtımının büyük
çoğunluğundan BRCA1 ve BRCA2 tümör süpresör gen mutasyonları sorumludur. Over kanserlerinin yaklașık
%10’unda ve meme kanserlerinin yaklașık %3-5’inde büyük oranda BRCA1 ve BRCA2 mutasyonları görülür.
Preimplantasyon genetic tanı (PGT) amniyosentez ve koryon villüs örneklemesi gibi geleneksel prenatal tanı
tekniklerinin bir alternatifidir. Devam etmekte olan bir gebelikte BRCA mutasyonunun prenatal teșhis edil-
mesi ve gebeliğin sonlandırılması konusu beraberinde bazı etik ve psikolojik soruları da tașımaktadır. Bu
nedenle, BRCA mutasyonu olanlarda PGT uygulanması daha uygun olabilir. Nihayetinde, PGT en azından
BRCA mutasyonu olan ve zaten IVF uygulanacak infertil hastalara önerilebilir.
Anahtar Sözcükler:
BRCA1/2 Mutasyonları; Herediter Meme ve Over Kanseri; in Vitro Fertilizasyon;
Preimplantasyon Genetik Tanı
Preimplantation genetic diagnosis is a
recent and emerging technique with
its advantages and disadvantages.
Although the true indications for this
new technique are still controversial,
it may be very helpful in prevention
of some mortal diseases such as inhe-
rited late onset cancers. Hereditary
breast and ovarian cancer syndrome
is an inherited cancer-susceptibility
syndrome with multiple family mem-
bers with breast cancer or ovarian
cancer or both, the presence of both
breast cancer and ovarian cancer in a
single individual, and early age of
breast cancer onset. BRCA1 and
BRCA2 tumor suppressor gene mu-
tations are responsible for the vast
majority of inheritance of breast and
ovarian cancers. Approximately 10%
of ovarian cancer patients and app-
roximately 3-5% of breast cancer pa-
tients have predominating BRCA1
and BRCA2 gene mutations. Altho-
ugh being BRCA1/2 mutation carrier
just expresses an increased cancer
risk, some ethical issues arise about
the prenatal diagnosis. Preimplanta-
tion genetic diagnosis gives the chan-
ce of selecting embryos without
BRCA1/2 mutations. But, for a ferti-
le couple this procedure brings an
exhausting and expensive in vitro fer-
tilization attempt together. However,
preimplantation genetic diagnosis
may be a good option for infertile
BRCA1/2 mutation carriers who are
already candidates for in vitro fertili-
zation.
A
nkara Üniversitesi Tıp Fakültesi Mecmuası 2016, 69 (2)
DOI: 10.1501/Tıpfak_000000933
Received : July 13, 2015  Accepted: July 11, 2016
Corresponding Author
Uz. Dr. Yavuz Emre Șükür
E-mail:yesukur@yahoo.com, yesukur@gmail.com
Ankara Keçiören Research and Training Hospital Department
of Obstetrics and G
y
necolo
gy
CERRAHİ
TIP BİLİMLERİ
/
SURGICAL SCIENCES
Davetli Derleme/
Invited Paper

Ankara Üniversitesi Tıp Fakültesi Mecmuası 2016, 69 (2)
Preimplantation Genetic Diagnosis for Brca1 and Brca2 Mutations
134
Preimplantation Genetic Diagnosis
and Genetic Counseling
Preimplantation genetic testing refers to
a technique for prenatal diagnosis of
cytogenetic and mendelian disorders
via biopsy of one or two cells from
an in vitro embryo at the 6 to 8 cell
stage (developmental day 3) or from
a polar body (1,2). The term preimp-
lantation genetic diagnosis (PGD) is
used when testing is performed to
identify a known heritable chromo-
somal abnormality or a gene muta-
tion. PGD is an alternative to con-
ventional prenatal diagnostic tech-
niques such as amniocentesis and
chorionic villus sampling. The advan-
tage of PGD is avoidance of intraute-
rine transfer of affected embryos. It
may have additional value for impro-
ving pregnancy rates associated with
assisted reproductive technologies
(ART), as well as screening for gene-
tic problems not conventionally asso-
ciated with invasive prenatal diagnos-
tic techniques.
There are some disadvantages of PGD
compared to conventional prenatal
diagnostic methods. Even if the co-
uple is fertile, In Vitro Fertilization
(IVF) is required to conceive when
PGD is the choice. In Vitro Fertiliza-
tion (IVF) is an expensive, exhausting
and time consuming procedure and
has some risks, such as ovarian hy-
perstimulation syndrome and multip-
le pregnancies. In addition, fetal
structural anomalies not associated
with cytogenetic or single gene disor-
ders are not detected by PGD, but
can often be identified by sonog-
raphy performed in conjunction with
conventional prenatal diagnostic
methods.
Indications for Preimplantation
Genetic Diagnosis
Potential indications for PGD include
avoidance of pregnancy termination
with an affected child, preselection of
HLA type to permit treatment of a
sibling by cord blood transfusion or
bone marrow transplantation, sex se-
lection, improvement of ongoing
pregnancy rates and detection of
structural chromosomal abnormali-
ties and single gene disorders. The
expanding identification of genes and
proteins associated with particular di-
seases, syndromes, conditions, and
phenotypes are pushing the current
barriers and limitations of PGD. The
technique has already been used to
screen for mutations associated with
certain heritable cancers and for pre-
disposition to early-onset Alzheimer
disease (3,4), uncommon indications
for conventional prenatal testing.
Preimplantation genetic diagnosis invol-
ving IVF and embryo biopsy was de-
veloped to prevent pregnancies affec-
ted with serious life-threatening gene-
tic diseases. It has been used for high
penetrance recessive disorders like
cystic fibrosis and β-thalassaemia,
dominant disorders like Huntington’s
disease and myotonic dystrophy and
X-linked disorders like Fragile X and
Duchenne muscular dystrophy which
occur early in life and for high penet-
rance cancer syndromes like familial
adenomatous polyposis coli and mul-
tiple endocrine neoplasia that occur
later in life (5).
Recently there has been a debate about
extending the use of PGD to include
lower penetrance, late onset cancer
susceptibility syndromes such as he-
reditary breast and ovarian cancer
(HBOC) (6). Genetic counseling and
testing for breast and ovarian cancers
are mainly concerning the oncologic
care, but some important questions
regarding cancer risk for themselves
and their siblings particularly daugh-
ters, the benefits of genetic testing,
and the efficacy of management op-
tions for those at increased risk re-
main unanswered. A critical issue is
determining which patients’ daugh-
ters are most likely to harbor gene
mutations that can be identified by
genetic testing. In May 2006, the UK
Human Fertilization and Embryology
Authority (HFEA) decided that in
principle it was appropriate for PGD
to be available for HBOC. A family
history of breast or ovarian cancer,
particularly before the age of 50 years
in a first order relative, and Ashkena-
zi Jewish ancestry are risk factors for
BRCA1 or BRCA2 mutations.
Hereditary Breast and Ovarian
Cancer
Hereditary breast and ovarian cancer
syndrome is an inherited cancer-
susceptibility syndrome. The hall-
marks of this syndrome are multiple
family members with breast cancer or
ovarian cancer or both, the presence
of both breast cancer and ovarian
cancer in a single individual and on-
set of breast cancer at early ages.
One of the most important risk factors
for breast and ovarian cancers is fa-
mily history. A positive family history
significantly increases a woman's risk
for breast cancer. 20-30% of women
with breast cancer have at least one
relative with the disease (7,8).
However, the majority of women
with a positive family history do not
have "hereditary" breast cancer. Most
hereditary breast cancers arise from
mutations in the genes BRCA1 and
BRCA2, which are inherited in an au-
tosomal dominant fashion and tho-
ught to function as tumor suppressor
genes ().
Just like breast cancer, inherited genetic
mutations are thought to be associa-
ted with 10% of women with ovarian
cancer. The hereditary ovarian cancer
as well as breast cancer is mainly due
to BRCA1 and BRCA2 gene mutati-
ons. Germline mutations in BRCA1
and BRCA2 account for the vast ma-
jority of families with hereditary bre-
ast and ovarian cancer syndrome.
Approximately 10% of cases of ova-
rian cancer and 3-5% of cases of bre-
ast cancer are due to mutations in
BRCA1 and BRCA2 (9,10). Carriers
were predicted to have at least 15-
fold age-specific risk of ovarian can-
cer compared with non-carriers (11).
The estimated risk was 2% by the age
of 50 years and 16% by the age of 70
years compared with the non-carrier
risk of 0.4% by 50 years and 1.6% by
70 years (12).
BRCA1 and BRCA2 Mutations
BRCA1 is located on the long arm of
chromosome 17q, and BRCA2 is lo-
cated on chromosome 13q12. More
than 2500 different mutations have

Journal Of Ankara University Faculty of Medicine 2016, 69 (2)
Yavuz Emre Șükür, Batuhan Özmen, Murat Sönmezer, Cem Somer Atabekoğlu
135
been reported for BRCA1 and
BRCA2. BRCA1 and BRCA2 are
tumor suppressor genes that encode
proteins that function in the DNA
repair process. Although individuals
with hereditary breast and ovarian
cancer syndrome inherit one defecti-
ve allele in BRCA1 or BRCA2 from
their father or mother, they have a
second, functional allele. If the se-
cond allele becomes nonfunctional,
cancer can develop through the ac-
cumulation of additional mutations.
This situation is called as the “two-hit
hypothesis” (13).
In general population, the incidence of
BRCA mutations is between 1/300
and 1/800 (14). For a woman with a
BRCA1 mutation, the risk of ovarian
cancer is 39-46%. For a woman with
a BRCA2 mutation, the risk of ova-
rian cancer is 12-20%. The estimated
lifetime risk of breast cancer with a
BRCA1 or BRCA2 mutation is 65-
74% (15,16). For women with breast
cancer, the 10-year risk of developing
ovarian cancer is 12.7% for BRCA1
mutation carriers and 6.8% for
BRCA2 mutation carriers (17). Ova-
rian cancer associated with BRCA1
and BRCA2 mutations has a distinct
histological phenotype; predomi-
nantly of high grade serous or endo-
metrioid histology (18). Primary fal-
lopian tube and primary peritoneal
cancer also are part of the spectrum
of disease associated with BRCA1
and BRCA2 mutations (19).
PGD for BRCA Gene Mutations
BRCA mutation carriers have a 50%
chance for the inheritance of cancer
predisposition mutation. There are
some choices for healthy relatives of
cancer patients and young breast can-
cer survivors to prevent this inheri-
tance: avoid having children, ovum
donation (or sperm donation in case
of male carriers), prenatal diagnosis,
or PGD. In two different studies atti-
tudes or decisions of BRCA mutation
carriers were researched. In the first
study, 75% of 52 patients with BRCA
mutation found PGD acceptable (5).
However, in the second study 13% of
213 patients with BRCA mutation
stated PGD was considerable (20).
In clinical practice, there are only a few
reports on PGD for BRCA mutati-
ons. Jasper et al. (21) performed
PGD for a 31 year-old BRCA1 muta-
tion carrier who was already infertile
for 3 years. Recently, Sagi et al. (22)
reported their data on PGD for
BRCA mutations. 10 BRCA1/2 mu-
tation carriers, that 8 of them were al-
ready infertile, applied for PGD co-
unseling. 6 patients accepted PGD
and 5 of them underwent PGD for
BRCA mutations and 3 patients were
conceived each in the first attempt
(22). In the total of these two reports
IVF was required due to coexisting
infertility for 9 of 11 patients. Fertile
couples would be more reluctant to
enter into an IVF procedure, especi-
ally having learned about the limited
success rate, the potential risks invol-
ved in ovulation induction, and the
high cost. The balance between ad-
vantages and disadvantages of PGD
obviously differs between fertile and
infertile couples. However, some fer-
tile women/couples might seriously
consider this option depending on
other factors, such as a very strong
family history of cancer, and survi-
ving breast cancer that occurred at a
very young age (22).
On the other hand, prenatal diagnosis for
BRCA mutation in an ongoing preg-
nancy and termination of the preg-
nancy for a BRCA mutation carrier
fetus brings some ethical and psycho-
logical questions together. Although
it is not acceptable to terminate the
pregnancy for a BRCA mutation car-
rier fetus, it may be favorable to per-
form PGD for patients with BRCA
mutations. Eventually, PGD may be
recommended at least to the infertile
patients with BRCA mutation who
should already undergo IVF.
REFERENCES
1. Verlinsky Y, Rechitsky S, Verlinsky O, et
al. Preimplantation diagnosis for sonic
hedgehog mutation causing familial ho-
loprosencephaly. N Engl J Med. 2003;
348: 1449-1454.
2. Harper JC, Bui TH. Pre-implantation
genetic diagnosis. Best Pract Res Clin
Obstet Gynaecol 2002; 16: 659-670.
3. Verlinsky Y, Rechitsky S, Verlinsky O, et
al. Preimplantation diagnosis for early-
onset Alzheimer disease caused by V717L
mutation. JAMA. 2002; 287: 1018-1021.
4. Spits C, De Rycke M, Van Ranst N, et al.
Preimplantation genetic diagnosis for
cancer predisposition syndromes. Prenat
Diagn 2007; 27: 447-456.
5. Menon U, Harper J, Sharma A, et al.
Views of BRCA gene mutation carriers
on preimplantation genetic diagnosis as a
reproductive option for hereditary breast
and ovarian cancer. Hum Reprod 2007;
22: 1573-1577.
6. Robertson JA. Extending preimplantation
genetic diagnosis: the ethical debate. Et-
hical issues in new uses of preimplanta-
tion genetic diagnosis. Hum Reprod
2003; 18: 465-471.
7. Slattery ML, Kerber RA. A comprehensi-
ve evaluation of family history and breast
cancer risk. JAMA 1993; 270: 1563-1568.
8. Claus EB, Risch NJ, Thompson WD.
Age at onset as an indicator of familial
risk of breast cancer. Am J Epidemiol
1990; 131: 961-972.
9. Risch HA, McLaughlin JR, Cole DE, et
al. Population BRCA1 and BRCA2 muta-
tion frequencies and cancer penetrances:
a kin-cohort study in Ontario, Canada. J
Natl Cancer Inst. 2006; 98: 1694-1706.
10. Rubin SC, Blackwood MA, Bandera C, et
al. BRCA1, BRCA2, and hereditary non-
polyposis colorectal cancer gene mutati-
ons in an unselected ovarian cancer po-
pulation: relationship to family history
and implications for genetic testing. Am J
Obstet Gynecol 1998; 178: 670-677.
11. Copeland LJ. Epithelial Ovarian Cancer.
In: Disaia PJ, Creasman WT. Clinical Gy-
necologic Oncology. Philadelphia, Mosby
Elsevier Press, 2007; 313-367.
12. Struewing JP, Hartge P, Wacholder S, et
al. The risk of cancer associated with spe-

Ankara Üniversitesi Tıp Fakültesi Mecmuası 2016, 69 (2)
Preimplantation Genetic Diagnosis for Brca1 and Brca2 Mutations
136
cific mutations of BRCA1 and BRCA2
among Ashkenazi Jews. N Engl J
Med. 1997; 336: 1401-1408.
13. Knudson AG Jr. Mutation and cancer:
statistical study of retinoblastoma. Proc
Natl Acad Sci USA 1971; 68: 820-823.
14. Whittemore AS, Gong G, Itnyre J. Preva-
lence and contribution of BRCA1 muta-
tions in breast cancer and ovarian cancer:
results from three U.S. population-based
casecontrol studies of ovarian cancer. Am
J Hum Genet 1997; 60: 496-504.
15. Antoniou A, Pharoah PD, Narod S, et al.
Average risks of breast and ovarian can-
cer associated with BRCA1 or BRCA2
mutations detected in case series unselec-
ted for family history: a combined analy-
sis of 22 studies.Am J Hum Genet 2003;
72: 1117-1130.
16. King MC, Marks JH, Mandell JB. Breast
and ovarian cancer risks due to inherited
mutations in BRCA1 and BRCA2. New
York Breast Cancer Study Group. Science
2003; 302: 643-646.
17. Metcalfe KA, Lynch HT, Ghadirian P, et
al. The risk of ovarian cancer after breast
cancer in BRCA1 and BRCA2 carriers.
Gynecol Oncol 2005; 96: 222-226.
18. Lakhani SR, Manek S, Penault-Llorca F,
et al. Pathology of ovarian cancers in
BRCA1 and BRCA2 carriers. Clin Cancer
Res 2004; 10: 2473-2481.
19. Levine DA, Argenta PA, Yee CJ, et al.
Fallopian tube and primary peritoneal
carcinomas associated with BRCA muta-
tions. J Clin Oncol 2003; 21: 4222-4227.
20. Staton AD, Kurian AW, Cobb K, et al.
Cancer risk reduction and reproductive
concerns in female BRCA1/2 mutation
carriers. Fam Cancer 2008; 7: 179-186.
21. Jasper MJ, Liebelt J, Hussey ND. Preimp-
lantation genetic diagnosis for BRCA1
exon 13 duplication mutation using lin-
ked polymorphic markers resulting in a
live birth. Prenat Diagn 2008; 28: 292-
298.
22. Sagi M, Weinberg N, Eilat A, et al. Pre-
implantation genetic diagnosis for
BRCA1/2-a novel clinical experience.
Prenat Diagn 2009; 29: 508-513.