Oncogene (1998) 17, 1185 ± 1188
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SHORT REPORT
Frequent loss of heterozygosity and three critical regions on the short arm
of chromosome 8 in ovarian adenocarcinomas
K Wright1, PJ Wilson1, J Kerr1, K Do1, T Hurst2, S-K Khoo2, B Ward2 and G Chenevix-Trench1
1
Queensland Cancer Research Unit, The Queensland Institute of Medical Research, Herston, Brisbane, QLD 4029; 2Department of
Obstetrics and Gynaecology, The University of Queensland, Royal Brisbane Hospital, Herston, Brisbane, QLD 4029, Australia
Many chromosomal regions undergo loss of heterozygosity (LOH) in ovarian adenocarcinomas but few of
the target regions have been ®nely mapped. One of the
chromosome arms likely to harbour one or more tumour
suppressor genes inactivated in ovarian cancer is the
short arm of chromosome 8 which is frequently deleted in
many other solid tumours. We have examined a large
panel of microsatellite markers on 8p for LOH in 53
ovarian adenocarcinomas. LOH was observed in 27
tumours (51%), with a signi®cant trend towards a higher
frequency of LOH in more advanced tumours. Detailed
examination of nine tumours with partial deletions
de®ned three regions of overlap, two in 8p23 and one
in 8p22, which suggests that there might be as many as
three tumour or metastasis suppressor genes on 8p which
are inactivated during ovarian tumorigenesis. LOH on 8p
was signi®cantly associated with 9p LOH which suggests
that inactivation of target genes on these chromosomes
may be cooperative events.
Keywords: loss of heterozygosity; ovarian adenocarcinomas; tumour suppressor gene
Ovarian carcinomas are the leading cause of death
from gynaecological malignancies worldwide (Parkin et
al., 1993). The majority of ovarian neoplasms, the
adenocarcinomas, arise from the surface epithelium of
the ovary and benign, low malignant potential and
malignant forms exist. The majority of malignant
adenocarcinomas present at an advanced stage when
metastatic spread is already evident. When this occurs,
patients have a very poor prognosis with a ®ve year
survival rate of 13% and 4% for FIGO stages III and
IV respectively.
The molecular events leading to the development of
ovarian adenocarcinomas are poorly understood
although it is generally accepted that, as for other
neoplasms, both activation of oncogenes and inactivation of tumour suppressor genes are involved in disease
etiology. However point mutations have rarely been
described in ovarian tumours except in the K-ras
oncogene and the TP53 tumour suppressor gene
(Teneriello et al., 1993). The search for relevant
suppressor genes has involved the analysis of tumours
for loss of genetic material using LOH and comparative genomic hybridization techniques. These ap-
Correspondence: G Chenevix-Trench
Received 29 December 1997; revised 2 April 1998; accepted 2 April
1998
proaches have shown that many chromosomal
regions are lost during the development of ovarian
tumours (Shelling et al., 1995) but the identity of the
target genes and the signi®cance of most of these
deletions remains unknown.
One region that frequently undergoes LOH in solid
tumours is the short arm of chromosome 8. Previous
small studies have found that 26 ± 40% of ovarian
adenocarcinomas undergo LOH in this region but ®ne
mapping of the region of deletion has not been possible
because very few polymorphic markers have been used
(Yang-Feng et al., 1993; Cliby et al., 1993; Osbourne
and Leech, 1994; Iwabuchi et al., 1994). However,
comparative genomic hydridization analysis suggests
that the target of deletions in ovarian adenocarcinomas
is in the 8p21-23 region (Iwabuchi et al., 1994).
In contrast, there have been many large studies
showing moderate-high (25 ± 85%) rates of LOH on
8p, particularly in the advanced stages, in cancers of
the lung, head and neck, breast, prostate, bladder,
colon and liver (Ohata et al., 1993; Field et al., 1995;
Yaremko et al., 1996; Vocke et al., 1996; Tackle and
Knowles, 1996; Gustafson et al., 1996; Becker et al.,
1996). These analyses have also de®ned several critical
regions within the short arm of chromosome 8,
particularly at 8p21-22, suggesting that more than
one suppressor gene might be located there, and that
they might act at di€erent points in the neoplastic
pathway to suppress tumorigenicity or metastasis.
This is supported by functional evidence because
transfer of chromosome 8 into a colorectal cancer cell
line has been shown to suppress tumorigenicity
(Gustafson et al., 1996) while transfer into a prostate
cancer cell line suppresses metastasis (Ichikawa et al.,
1994).
Our aim was to evaluate a large panel of malignant
ovarian adenocarcinomas, using many microsatellite
markers from the short arm of chromosome 8, in order
to determine the frequency of LOH and to de®ne the
smallest region of overlap of the deletions. Fifty-three
ovarian adenocarcinomas were obtained from patients
undergoing surgery. The series comprised 28 serous,
®ve endometrioid, ®ve clear cell, four undi€erentiated,
and three mucinous tumours as well as eight of mixed
or unknown histology. All patients were staged at
laparotomy in accordance with the recommendations
of the International Federation of Gynaecology and
Obstetrics (FIGO). Germline DNA was obtained from
peripheral blood. Tumour tissue was prepared, DNA
extracted and microsatellite markers genotyped as
described previously (Chenevix-Trench et al., 1992,
1994). LOH was scored conservatively as a substantial
reduction in the intensity of one allele but in a few
LOH on the short arm of chromosome 8 in ovarian adenocarcinomas
K Wright et al
1186
cases scoring was impossible because of the proximity
of the two alleles and the presence of shadow bands so
in these cases no score was given with respect to LOH.
Eight microsatellite markers, distributed over the
short arm of chromosome 8, were used initially. All 53
cases were informative for at least one marker and
27/53 (51%) showed LOH at one or more informative
loci. The LOH rates were 7/29 (24.0%) at ANK1,
12/31 (38.7%) at D8S87, 13/36 (36.1%) at D8S136,
13/28 (46.4%) at LPL, 13/30 (43.3%) at D8S254, 18/33
(54.6%) at D8S1827, 13/30 (43.3%) at D8S550 and
14/28 (50.0%) at D8S264. The highest rates were
therefore at D8S264, D8S550 and D8S1827 which are
located at 8p22-23, while the lowest were at D8S87 and
ANK1 at 8p11-12.
In 16/27 (59.3%) of the tumours with LOH, all the
informative loci showed LOH indicating that the whole
chromosome arm had probably been lost. The
remaining 11 tumours showed LOH at some but not
all informative markers. In nine of the tumours for
which sucient DNA was available, a further eight
markers located at 8p22-23 (D8S439, D8S1759,
D8S1130, D8S511, D8S549, AFM333TH1, D8S1754
and D8S261) were used to de®ne three smallest regions
of overlap of the deletions (Figures 1 and 2). This
analysis indicated that there might be as many as three
target regions harbouring suppressor genes on 8p ±
distal to D8S1759 at 8p23, around D8S549 at 8p23 and
around LPL at 8p22.
LOH on 8p was observed in no (0/7) stage I
tumours but in 33% (2/6), 61% (20/33) and 71% (5/7)
tumours of stage II, III and IV respectively. This trend
of increased rates of LOH with advancing stage was
signi®cant (P=0.014; Mantel ± Haentzel test for trend).
In contrast there was no association with grade
(P=0.11; Mantel ± Haentzel test) or histological subtype of the tumour (P=0.47; Fisher's Exact test). 8p
LOH was observed in 15/28 serous, 3/5 endometrioid,
2/5 clear cell, 0/3 mucinous, and 7/12 tumours of
undi€erentiated, mixed or unknown histology. Since
LOH analysis has been performed at many other loci
in these tumours (Chenevix-Trench et al., 1997) we also
analysed the data for associations between LOH on 8p
and other chromosomal arms. LOH on 8p was
signi®cantly associated with LOH on 9p (P=0.0005;
Fisher's Exact test) and on chromosome 18 (P=0.001)
even when the Bonferroni correction was used
(P50.003). When the associations were strati®ed for
stage, only the relationship between 8p and 9p
remained signi®cant (P=0.026; Mantel ± Haentzel
Figure 1 Loss of heterozygosity at 16 loci on the short arm of chromosome 8 in nine tumours with partial deletions. The three
smallest regions of overlap, which include the loci D8S550-D8S264, D8S549 and LPL, are indicated. Black box ± LOH; Clear box ±
no LOH; Grey box ± not informative
LOH on the short arm of chromosome 8 in ovarian adenocarcinomas
K Wright et al
Figure 2 Loss of heterozygosity analyses in selected tumours
which de®ne the smallest regions of overlap. Deleted alleles are
noted with an arrowhead. G ± germline, T ± tumour
test) which indicates that this association is independent of tumour progression. Survival analysis was also
carried out for the 51 patients for whom follow up
data was available. Using the Cox Proportional
Hazard Model there was no signi®cant e€ect on
survival for patients having LOH on 8p only, on 9p
only or on both 8p and 9p, but survival was related to
stage (P=0.009).
In summary, LOH on the short arm of chromosome
8 is a frequent event in ovarian adenocarcinomas,
occurring in our series more often than on any other
chromosomal arm except 1p, 5q, 6q, 9p, 17p, 17q or
18q (Chenevix-Trench et al., 1997). LOH on 8p is
signi®cantly associated with LOH on 9p suggesting
that inactivation of the target genes on these
chromosomes may be cooperative events. Fine deletion mapping suggests that there might be as many as
three suppressor genes in 8p22-23 inactivated in
ovarian cancer. However these data should be
interpreted with caution until independently confirmed
since the regions are de®ned by LOH in only a few
tumours which had partial deletions and some of these
may represent random events.
Regions of 8p22-23 have been implicated by LOH
analysis as harbouring suppressor genes relevant to the
progression of many other tumour types (Suzuki et al.,
1995; Yaremko et al., 1995; Bova et al., 1996). Whether
these are all independent targets, or whether there are
common targets inactivated in a wide variety of
tumours will not be known until the relevant genes
have been cloned. There is already some functional
evidence from monochromosome transfer experiments
to suggest that both tumour and metastasis suppressor
genes exist on the short arm of chromosome 8. LOH
on 8p occurs more frequently in ovarian tumours of
advanced stage which might indicate that a metastasis
suppressor gene is involved. However this might not be
the case. The same trend with advanced stage is found
in colorectal tumours but transfer of chromosome 8
into the SW620 cell line still suppresses tumorigenicity
in athymic mice (Gustafson et al., 1996). Despite some
extensive research aimed at identifying these putative
suppressor genes which has been particularly aimed at
characterizing a region homozygously deleted in a
metastatic prostate cancer (Bova et al., 1996), the
identity of these genes is currently unknown.
Acknowledgements
This work was supported by the National Health and
Medical Research Council of Australia and the Queensland
Cancer Fund.
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