Global expression changes of constitutive and hormonally regulated genes during endometrial neoplastic transformation

OBJECTIVE

Endometrioid endometrial carcinoma is caused by a combination of mutational events and hormonal factors. We used large-scale messenger RNA expression analysis to discover genes that distinguish neoplastic transformation and examine the patterns of tumor expression of those genes which are normally regulated during the menstrual cycle.

METHODS

Expression of approximately 6000 unique genes was quantified in 4 normal (2 proliferative, 2 secretory) and 10 malignant endometria using Affymetrix Hu6800 GeneChip probe arrays. Expression differences between normal and malignant tissue groups were measured by a test of statistical significance comparing the individual t statistic for each gene to the distribution of maximum t statistics among all genes following 1001 permutations of the tissue group assignments (Permax test). Hormonally responsive genes, selected by comparison of proliferative and secretory subsets of normal endometria using a combination of filters applied to the group means and t test rankings, were then examined in the tumors.

RESULTS

Fifty genes with a Permax <0.50 provided excellent discrimination between normal and malignant groups and were predominantly characterized by diminished expression levels in the cancers. We found that 100 genes which are hormonally regulated in normal tissues are expressed in a disordered and heterogeneous fashion in cancers, with tumors resembling proliferative more than secretory endometrium.

CONCLUSION

Neoplastic transformation is accompanied by predominant loss of activity of many genes constitutively expressed in normal source tissues and absence of expression profiles which characterize the antitumorigenic progestin response.

Loss of heterozygosity at the RB-1 locus and pRB immunostaining in epithelial ovarian tumors: a molecular, immunohistochemical, and clinicopathologic study

Alterations in the retinoblastoma gene (RB-1) are common in human neoplasia. The frequency of loss of heterozygosity (LOH) at the RB-1 locus on chromosome 13q14 was studied in a series of 51 epithelial ovarian tumors (10 benign, 7 borderline, and 34 malignant). LOH was scored by the absence or reduction of the signal to < 50% of one of the alleles in tumor DNA compared with normal DNA. LOH results were correlated with retinoblastoma protein (pRB) immunostaining. LOH at the RB-1 locus was observed in 9 tumors (17.6%), specifically in 1 of 7 borderline tumors and 8 of 34 ovarian carcinomas (23.5%). Among the malignant tumors, LOH occurred more frequently in carcinomas with serous differentiation (7/23; 30%). A heterogeneous (10% to 70% cells) or diffuse (> 70% cells) pRB immunostaining was less frequent in benign (1/10; 10%) and borderline (2/7; 28%) tumors than in ovarian carcinomas (15/34; 44%), an observation that correlated with the higher proliferative index in carcinomas than in benign and borderline tumors. However, lack or only focal (< 10% cells) pRB immunostaining occurred in the vast majority of tumors with LOH at the RB-1 locus (7/9; 77%), a finding that may suggest a tumor suppressor role for RB-1 in these tumors. The results suggest that RB-1 may play a role in a subset of ovarian carcinomas, particularly those exhibiting serous differentiation.

BARX2 induces cadherin 6 expression and is a functional suppressor of ovarian cancer progression

The human homeobox BARX2 is located at 11q24-q25, within a minimal region associated with frequent loss of heterozygosity and adverse survival in epithelial ovarian cancer. BARX2 is a transcription factor that regulates transcription of specific cell adhesion molecules in the mouse. We show that BARX2 and cadherin 6 are expressed in normal human ovarian surface epithelium. BARX2 and cadherin 6 both have significantly lower expression in a clinical sample of endometrioid and clear cell ovarian cancers, as compared with serous or mixed mesodermal tumors. In a series of ovarian cancer cell lines, BARX2 expression showed a significant direct correlation with cadherin 6 expression. In OAW42, an ovarian cancer cell line that does not endogenously express BARX2, in vitro transfection of human BARX2 cDNA induced cadherin 6 expression. Transfection of BARX2 into OAW42 inhibited Matrigel invasion, haptotactic cellular migration to a collagen IV signal, and adhesion to collagen IV-coated plates. Our data demonstrate that BARX2 is expressed in the ovarian surface epithelium and has functional suppressor properties in ovarian cancer cells.

Oncogenic potential of c-erbB-2 and its association with c-K-ras in premalignant and malignant lesions of the human uterine endometrium

The aim of this study was to detect activated c-K-ras by gene point mutation and to find c-erbB-2 gene amplification with p185 expression in association with the c-K-ras gene product p21 in the human endometrium. Specimens obtained from 25 normal, 31 hyperplastic and 72 malignant samples of the human endometrium were examined for point mutation in codons 12, 13 and 61 of the c-K-ras by direct sequencing and c-erbB-2 gene amplification with p185 and p21 expression by differential polymerase chain reaction (DPCR) and immunohistochemistry. Neither the normal endometrium nor endometrial hyperplasias were found to have mutations in the c-K-ras gene, although a double mutation of codons 12 and 13 as a single-point mutation was observed in one case of endometrioid carcinoma (2.8%). In each of two other cases of endometrioid carcinoma (2/72), two single-point mutations of codon 13 (5.6%) were shown. Using DPCR, we found c-erbB-2 to be amplified in 15 premalignant (48%) and 45 malignant (63%) samples. We noticed that nonamplification of the c-erbB-2 gene was associated with the absence of immunoreactivity. Our data indicate that, while c-erbB-2 plays a role in the early development of endometrioid carcinomas, c-K-ras gene activation by point mutation does not.

Detection of numerical aberration in chromosome 17 and c-erbB2 gene amplification in epithelial ovarian cancer using recently established dual color FISH

This paper presents a new dual color FISH technique that will allow the use of cell specimens isolated from formaldehyde-fixed and paraffin-embedded (F-P) tissues. The new FISH method was used to examine numerical aberration in chromosome 17 and c-erbB2 gene amplification in 26 F-P epithelial ovarian cancer tissues. Numerical aberration of chromosome 17 appears frequently in clear cell adenocarcinoma. The frequency of amplification of the c-erbB2 gene in stage III and IV cases was significantly higher than in stage I cases. The FISH technique as established here may serve as a molecular tool for examination of clinico-pathological significance in F-P tissues.

Prognostic aspects on endometrial hyperplasia and neoplasia

There are various forms of endometrial hyperplasia which, in terms of prognosis and therapy, can be subdivided into those having cytological atypia and those lacking this feature. The former may progress into invasive endometrial malignancy through a transitional non-invasive stage. This is a continuous process and, as a result, the distinction between an atypical hyperplasia and an intraepithelial adenocarcinoma (IEA) or an adenocarcinoma with stromal invasion is not histologically reproducible. The concept of endometrioid neoplasia, which includes the entire spectrum of the aforementioned proliferating endometrial lesions, was introduced. Adenocarcinomas arising from an atypical hyperplasia are invariably of the endometrioid cell type, whereas those developing from an atrophic endometrium may be either of the endometrioid or of the non-endometrioid cell type. Endometrioid adenocarcinomas arising through the hyperplasia-neoplasia sequence are oestrogen induced and tend to be well differentiated and less invasive of the myometrium, lack lymphatic and metastatic involvement and have an excellent prognosis. Oestrogen-induced adenocarcinomas are also endometrioid, arising from an atrophic or a rather weakly proliferating endometrium, but these neoplasms are frequently of higher histological grade and have a somewhat less favourable prognosis. Finally, endometrial carcinomas of the non-endometrioid cell type, mainly serous papillary and clear cell carcinomas, are non-oestrogen induced, non-hyperplasia associated and show adverse aggressive histological features and an extremely poor prognosis. The antigenic characteristics and the molecular events associated with the development of these forms of endometrial malignancy are distinct and allow the description of, at least, two pathogenetic types of endometrial carcinoma.

Thrombospondin-1 and -2 messenger RNA expression in epithelial ovarian tumor

BACKGROUND

The role of thrombospondin (TSP) in tumor progression remains controversial. The association of TSP with clinicopathological features regarding prognostic significance was examined in patients with epithelial ovarian tumor.

MATERIALS AND METHODS

Gene expression of TSP-1 and TSP-2 was assessed by reverse transcriptase-polymerase chain reaction in 6 borderline and 29 malignant epithelial ovarian tumors.

RESULTS

TSP-1 mRNA expression was detected in 14 out of the 29 malignant epithelial ovarian tumors (48.3%), whereas TSP-2 mRNA expression was detected in 7 malignant epithelial ovarian tumors (24.1%). In contrast, no specimen from the borderline epithelial ovarian tumors expressed TSP mRNA. TSP-1 expression was significantly higher in tumors with advanced stage, massive ascites, positive peritoneal cytology and high grade. TSP-2 expression was significantly higher in tumors with massive ascites. Patients exhibiting TSP-1 and -2 mRNA expression demonstrated a markedly poorer prognosis than those lacking TSP-1 and -2 mRNA expression.

CONCLUSION

These findings provide evidence that TSP expression may be associated with an aggressive phenotype in this class of neoplasm.

Early uterine serous carcinoma: clonal origin of extrauterine disease

Uterine serous carcinoma (USC) is an uncommon but aggressive type of endometrial carcinoma that is frequently associated with extrauterine disease despite minimal or no myometrial invasion. The origin of the extrauterine tumors in this setting remains controversial. The majority of USCs (90%) and endometrial intraepithelial carcinomas (78%), the putative precursor of USC, have p53 mutations, suggesting that p53 alterations occur early in the pathogenesis of USC. To determine if the extrauterine tumors associated with minimally invasive USC and endometrial intraepithelial carcinoma (EIC) represent metastases or multifocal primary tumors, we examined the mutational pattern of the p53 gene in 3 cases of minimally invasive USC and 1 case of EIC and in the corresponding extrauterine tumors associated with each of the cases. In all 4 cases, the primary tumors and the associated extrauterine tumor foci had identical p53 mutations. Our results support the premise that extrauterine serous tumors found in association with EIC or minimally invasive USC represent a unifocal process and thus are early metastases.

beta-Catenin expression pattern, beta-catenin gene mutations, and microsatellite instability in endometrioid ovarian carcinomas and synchronous endometrial carcinomas

beta-Catenin gene mutations and microsatellite instability (MI) have been reported in endometrioid ovarian carcinomas. In colon but not endometrial cancer, beta-catenin gene mutations are associated with a replication error phenotype and MI. In this study the authors investigate whether beta-catenin mutations and MI are two independent oncogenic pathways in endometrioid ovarian carcinomas. They also evaluate the usefulness of these molecular markers in determining the primary origin of simultaneous tumors in the ovary and endometrium. This study was performed on 26 patients diagnosed with primary endometrioid ovarian carcinoma, five of whom also had pathologically diagnosed primary synchronous endometrioid endometrial carcinoma. Immunohistochemical and molecular analyses indicated that there were 25 primary ovarian tumors with four primary synchronous endometrial cancers and one ovarian metastasis of a primary endometrial carcinoma. All studies were performed on formalin-fixed, paraffin-embedded tissue samples. The beta-catenin expression pattern (nuclear vs. membranous) was analyzed immunohistochemically. Mutations in exon 3 of the beta-catenin gene were studied by polymerase chain reaction, single-strand conformational polymorphism, and direct sequencing. MI status was established by studying BAT-26 and BAT-25 mononucleotide repeats. In the group with 21 single ovarian tumors, 18 (85%) had beta-catenin nuclear expression, eight (38%) had beta-catenin gene mutations (always associated with beta-catenin nuclear expression), and four (19%) had MI. Only one case (5%) had both beta-catenin gene mutations and MI. The mutations affected one of the serine/threonine residues targeted for phosphorylation by glycogen synthase kinase-3beta or adjacent residues. At codon 32, a GAC-to-TAC (D32Y) change was found; at codon 33, two TCT-to-TGT (S33C) changes were found; at codon 37, three TCT-to-TTT (S37F) changes and one TCT-to-TGT (S37C) change were found; and, lastly, one ACC-to-GCC change at codon 41 (T41A) was detected. Four of the 25 endometrioid ovarian carcinomas (16%) had an associated synchronous endometrial carcinoma. There was a higher percentage of beta-catenin mutations (n = 3, 75%) in synchronous ovarian carcinomas than in single ones, although with a similar percentage of MI (n = 1, 25%). beta-catenin mutations were S37C in two cases and D32G in one. One of the four endometrial carcinomas showed an S33C beta-catenin mutation, and two carcinomas had MI. None of the four tumors had both beta-catenin gene mutation and MI. beta-catenin gene mutations were always associated with a nuclear beta-catenin expression pattern, whereas MI was associated with a membranous pattern. In one patient both the ovarian and the endometrial carcinomas had beta-catenin gene mutations, in another patient both tumors showed MI, whereas in the remaining two patients the ovarian carcinomas showed beta-catenin gene mutations and the endometrial carcinomas showed MI. To summarize, the results of this study suggest that beta-catenin mutations and MI could represent two independent pathways in endometrioid ovarian carcinomas because they occur simultaneously very infrequently (in 5% of these cases). beta-catenin mutations are always associated with a nuclear beta-catenin expression pattern, whereas cases with a replication error -plus phenotype showed no abnormal beta-catenin subcellular localization. The study of the beta-catenin expression pattern, beta-catenin mutations, and MI, together with conventional clinicopathologic findings, could aid in distinguishing between the metastatic or independent origin of simultaneous endometrioid ovarian and endometrial carcinomas. Tumors with identical immunohistochemical and molecular features should therefore be considered to have a common origin.

Ovarian carcinoma recurring as carcinosarcoma

Malignant mixed mesodermal tumor is a rare tumor of the ovary and its histogenesis is controversial. We report the case of an ovarian tumor that seemed to be a pure carcinoma and recurred as a carcinosarcoma, and suggest a possible histogenesis for this kind of tumor. The patient was a 62-year-old Japanese woman. The primary tumor was confined to the right ovary and was a histologically poorly differentiated endometrioid adenocarcinoma with focal squamous differentiation. The tumor recurred as peritoneal dissemination 9 months later showing a histological appearance of carcinosarcoma of heterologous type. The recurrent tumor also contained intermingled foci of similar histology as the primary tumor. The carcinomatous component of the recurrent tumor showed more obvious differentiation to adenocarcinoma with increased expression of epithelial markers compared to the primary tumor. Epithelial membrane antigen was positive also in a few cells of the sarcomatous component, which implies that this tumor had features of metaplastic carcinoma. The DNA ploidy pattern of the primary ovarian tumor was diploid, while an additional aneuploid subpopulation appeared in the recurrent tumor. These findings suggest the possible histogenesis of carcinosarcoma of the ovary as progression and clonal evolution of endometrioid adenocarcinoma.

Beta- and gamma-catenin expression in endometrial carcinoma. Relationship with clinicopathological features and microsatellite instability

The activation of the adenomatous polyposis coli (APC)/beta-catenin/T-cell factor (Tcf) pathway due to beta-catenin gene mutation has been recently implicated in the development of some endometrial carcinomas. beta- and gamma-catenin are structurally and functionally related molecules that participate in cell adhesion and signal transduction. Nuclear accumulation of beta- and gamma-catenin have been related to the activation of the APC/beta-catenin/Tcf pathway. In this study, we investigate the immunohistochemical expression pattern (nuclear vs membranous) of beta- and gamma-catenin in 40 endometrial carcinomas and their correlation with clinicopathological features and microsatellite instability (MI) status. MI was detected at three or more loci in 12 tumors: 11 were endometrioid and one was non-endometrioid. Nuclear catenin expression was found in 13 carcinomas: ten carcinomas had nuclear beta-catenin expression and three carcinomas had nuclear gamma-catenin expression. The nuclear catenin expression pattern significantly correlated with the histological type, International Federation of Gynecology and Obstetrics (FIGO) grade, and the presence of a second neoplasm. Nuclear catenin expression was always observed in low-grade endometrioid carcinomas; it was also more frequently associated with a second carcinoma. No correlation was observed between the catenin expression pattern and the level of myometrial infiltration, stage, associated endometrial hyperplasia, the existence of a source of estrogenic stimulation, and MI. However, four of 13 endometrioid carcinomas in this series had both catenin nuclear expression and MI. These data suggest that at least two different neoplastic pathways can lead to endometrial carcinomas with an endometrioid phenotype. In one, MI would be a key event, while in the other, the APC/beta-catenin/Tcf signaling pathways could be activated. Probably, in some cases, both pathways could simultaneously occur.

Evaluation of the tyrosine kinase domain of the Met proto-oncogene in sporadic ovarian carcinomas*

Most of the ovarian cancers originate from the ovarian surface epithelium derived from the coelomic mesothelium. The Met proto-oncogene encodes a transmembrane tyrosine kinase receptor (Met) that has the capacity to regulate cell proliferation and differentation and it is activated by hepatocyte growth factor. Trisomy of chromosome 7 and Met protein overexpression have been were observed in ovarian carcinomas, the papillary renal cancers and other solid tumors. Frequent mutations of Met proto-oncogene have been found in hereditary papillary renal cancer (HPRC) and most of the mutations are located in the tyrosine kinase domain. The aim of this study to perform a mutation analysis of exons 17 19 of Met proto-oncogene in epithelial ovarian tumors (EOTs). We have examined 24 tumor samples from patients, operated with EOTs. Mutation was detected in exon 18 in only one sample of 24 EOTs. Our results indicate that mutations located in the Met proto-oncogene is not a common event in EOT. It is not clear whether the mutation plays a role in the tumorigenesis or progression of EOT or not.

Favorable survival associated with microsatellite instability in endometrioid endometrial cancers

OBJECTIVE

To determine whether microsatellite instability in endometrioid endometrial cancer is associated with favorable survival.

METHODS

Microsatellite instability analysis was performed in 131 patients with endometrioid endometrial cancer using three polymorphic markers in paired cancer and normal DNA. Logistic regression and multivariable analyses calculated the relation between microsatellite instability, clinical features, and survival.

RESULTS

Microsatellite instability was detected in 29 of 131 (22%) endometrioid endometrial cancers. There was no correlation between microsatellite instability and age, race, grade, stage, or depth of myometrial invasion. Microsatellite instability was associated with better survival in univariate and multivariable analyses after controlling for confounding influences (P =.03). The 5-year survival rate of those with microsatellite instability was 77% (95% confidence interval 55%, 90%) compared with only 48% (95% confidence interval 39%, 57%) in other cases. Microsatellite instability was associated with other molecular features that predict favorable outcome including PTEN mutation (P =.002) and the absence of p53 overexpression (P =.01).

CONCLUSION

Microsatellite instability is a molecular alteration associated with favorable outcome in endometrioid endometrial cancers, even when accounting for other prognostic factors. This association might be explained by the finding that the pathway of molecular carcinogenesis characterized by loss of DNA mismatch repair favors alteration of genes that result in a less virulent clinical phenotype.

Expression and mutation of p53 in tumor effusion cells of patients with ovarian carcinoma: response to cisplatin-based chemotherapy

p53 alterations are considered as one of the most important factors responsible for drug resistance in ovarian carcinomas, although the relationship between p53 gene status and response to cisplatin-based chemotherapy in ovarian cancer patients remains unclear. The aim of the study was to evaluate the relationship between p53 protein accumulation, p53 gene mutation and response to cisplatin-based chemotherapy in patients with ovarian carcinoma considering conventional clinicopathological parameters. Tissue sections and corresponding cyst and/or ascitic fluid cells from 79 patients with epithelial ovarian cancer were analyzed immunohistochemically for p53 expression. The PCR-SSCP analysis was performed in 25 cases and the results were compared with immunohistochemical data. It was demonstrated that p53 expression reaching approximately 50% of positive cells in immunostaining was usually associated with PCR-amplified exons showing abnormal migration and suspected for mutation. p53 gene changes were not correlated with histological structure, grade of differentiation or residual tumor after cytoreductive surgery, despite being detected more frequently in III/IV than in II FIGO stages and in patients with residual disease above 2 cm. A significant correlation between p53 accumulation and p53 gene alteration and poor response to cisplatin-based chemotherapy was shown. The overall survival time of patients decreased with an increase in p53 protein expression. A strong p53 expression especially accompanied by p53 changes detectable by PCR-SSCP analysis appears to be a good indicator of the resistance to cisplatin-based chemotherapy. The association between strong p53 overexpression and shorter overall survival time was also revealed.

Risk of endometrial carcinoma associated with BRCA mutation

OBJECTIVE

Inherited mutations in the BRCA1 or BRCA2 genes are associated with a greatly increased lifetime risk of breast and ovarian cancers and a modestly increased risk of several other cancer types. Several case reports of endometrial carcinoma in women with a BRCA mutation have led to speculation regarding the effect of these genes on the risk of endometrial cancer. The purpose of this study was to test the hypothesis that germline mutation of a BRCA gene is associated with an increased risk of endometrial carcinoma.

METHODS

A retrospective cohort of 199 consecutive Ashkenazi Jewish patients with endometrial carcinoma was identified from a 12-year period at this institution. All were genotyped for the three BRCA founder mutations (185delAG and 5382insC in BRCA1 and 6174delT in BRCA2) that exist in this population, and the case frequency was compared to the known population frequency of these mutations. Additionally, endometrial carcinomas occurring in patients with BRCA mutations were assessed for somatic loss of the wild-type BRCA allele.

RESULTS

Germline BRCA mutations were identified in 3 (1 in BRCA1 and two in BRCA2) of 199 (1.5%) patients, compared to a frequency of 2.0% in this population generally. A relative risk of endometrial carcinoma associated with BRCA mutation, as estimated by the odds ratio, was calculated as 0.75 (95% CI = 0.24--2.34; P = 0.6). Loss of the wild-type BRCA allele was observed in two of three tumors associated with a BRCA mutation.

CONCLUSIONS

For individuals with a germline BRCA mutation, the lifetime risk of endometrial carcinoma is not increased.

Common genetic changes between endometriosis and ovarian cancer

We analyzed 81 ovarian cancers for loss of heterozygosity (LOH) on 10q23 and for mutations in PTEN. LOH was common among the endometrioid (43%) and serous (28%) cancers, but was infrequent among the other histological subtypes. Somatic PTEN mutations were detected in seven (21%) endometrioid cancers and the mutation in all informative cases was accompanied by loss of the wild-type allele. One mucinous cancer without 10q23 LOH was shown to harbor two somatic PTEN mutations. Frequent LOH was observed on chromosome 6q (60.0%) and chromosome 10q (40.0%) in ovarian atypical endometriosis, but no PTEN mutations were observed. These findings support the hypothesis that endometrioid and clear cell ovarian carcinomas may arise through malignant transformation of endometriotic lesions.

Molecular genetic defects in endometriosis

In a series of studies, we have hypothesised that endometriotic proliferation is, in part, precipitated by mutations in oncogenes or deletions in tumor suppressor genes that have been shown to be important steps in the transformation from a benign to a malignant epithelium. We reported previously that we could find no mutations in the TP53 and RASK genes in cases of endometriosis. However, having shown that endometriotic deposits were monoclonal, we showed loss of heterozygosity on chromosomes 9p (18%), 11q (18%), and 22q (15%) - in total 28% of endometriotic lesions showed loss of heterozygosity at one or more sites [1]. We could not demonstrate any loss of heterozygosity in normal endometrium. We examined adjacent endometriosis, atypical endometriosis, and endometrioid carcinoma of the ovary and showed common genetic alterations that are consistent with a common lineage. These common alterations were not seen in lesions that were distant from each other [2]. In endometrioid tumors, we reported an increased frequency of mutations in the PTEN/MMAC tumor suppressor genes that was not seen in clear cell or serous carcinoma, suggesting distinct developmental pathways for these tumors [3].

Loss of heterozygosity at 7q22 and mutation analysis of the CDP gene in human epithelial ovarian tumors

Many tumor types including that of the ovary show loss of heterozygosity (LOH) on chromosome arm 7q, which suggests the existence of at least one tumor suppressor gene (TSG) on this chromosome arm. We have studied the region surrounding the putative tumor suppressor gene CUTL1 at 7q22 in 127 epithelial ovarian tumors. LOH was found across 7q22 in 31% of malignant and 14% of benign ovarian tumors. In 16% of the tumors the LOH appeared to be centered on the CUTL1 gene. This gene has been implicated previously as a TSG in both uterine leiomyomas and breast carcinoma. However, mutation analysis of the CUTL1 gene in 47 tumors with 7q22 LOH failed to identify any somatic alterations in the coding regions. This finding suggests that CUTL1 may not be the target of the 7q22 LOH in ovarian cancers.

Increased expression of protease M in ovarian tumors

Proteases are known to play important roles in tumor invasion and metastasis. Protease M, which was originally identified by Anisowicz and colleagues in 1996, is a new member of the serine protease family. We also identified the protease M transcript in a differential PCR screen of ovarian tumors and have investigated its expression in 44 ovarian tumors (12 low malignant potential tumors, 32 carcinomas) and 10 normal ovaries using quantitative PCR. The PCR product was labeled with (32)P and a phosphoimager was used to determine the relative expression of the protease M gene compared to internal control beta-tubulin. mRNA expression levels of protease M were significantly elevated in 9 of 12 low malignant potential tumors and 30 of 32 carcinomas. Northern blot hybridization showed that the 1.7-kb protease M transcript was abundant in carcinoma but not detected in normal ovary. Immunohistochemical staining of normal ovary and ovarian tumor tissue sections with antibodies generated to protease M derived peptides corroborated the semi-quantitative PCR and Northern analysis data. Our results suggest that protease M is frequently overexpressed in ovarian tumors and may therefore contribute to the invasive nature or growth capacity of ovarian carcinomas.

Polymorphisms at the glutathione S-transferase GSTM1, GSTT1 and GSTP1 loci: risk of ovarian cancer by histological subtype

The phase II glutathione S-transferases (GSTs) GSTT1, GSTM1 and GSTP1 catalyse glutathione-mediated reduction of exogenous and endogenous electrophiles. These GSTs have broad and overlapping substrate specificities and it has been hypothesized that allelic variants associated with less effective detoxification of potential carcinogens may confer an increased susceptibility to cancer. To assess the role of GST gene variants in ovarian cancer development, we screened 285 epithelial ovarian cancer cases and 299 unaffected controls for the GSTT1 deletion (null) variant, the GSTM1 deletion (null) variant and the GSTP1 codon 104 A-->G Ile-->Val amino acid substitution variant. The frequencies of the GSTT1, GSTM1 and GSTP1 polymorphic variants did not vary with tumour behaviour (low malignant potential or invasive) or p53 immunohistochemical status. There was a suggestion that ovarian cancers of the endometrioid or clear cell histological subtype had a higher frequency of the GSTT1 and GSTM1 deletion genotype than other histological subgroups. The GSTT1, GSTM1 and GSTP1 genotype distributions did not differ significantly between unaffected controls and ovarian cancer cases (overall or invasive cancers only). However, the GSTM1 null genotype was associated with increased risk of endometrioid/clear cell invasive cancer [age-adjusted OR (95% CI) = 2.04 (1.01-4.09), P = 0.05], suggesting that deletion of GSTM1 may increase the risk of ovarian cancer of these histological subtypes specifically. This marginally significant finding will require verification by independent studies.

Loss of heterozygosity on 10q23.3 and mutation of the tumor suppressor gene PTEN in benign endometrial cyst of the ovary: possible sequence progression from benign endometrial cyst to endometrioid carcinoma and clear cell carcinoma of the ovary

Loss of heterozygosity (LOH) at locus 10q23.3 and mutation of the PTEN tumor suppressor gene occur frequently in both endometrial carcinoma and ovarian endometrioid carcinoma. To investigate the potential role of the PTEN gene in the carcinogenesis of ovarian endometrioid carcinoma and its related subtype, clear cell carcinoma, we examined 20 ovarian endometrioid carcinomas, 24 clear cell carcinomas, and 34 solitary endometrial cysts of the ovary for LOH at 10q23.3 and point mutations within the entire coding region of the PTEN gene. LOH was found in 8 of 19 ovarian endometrioid carcinomas (42.1%), 6 of 22 clear cell carcinomas (27.3%), and 13 of 23 solitary endometrial cysts (56.5%). In 5 endometrioid carcinomas synchronous with endometriosis, 3 cases displayed LOH events common to both the carcinoma and the endometriosis, 1 displayed an LOH event in only the carcinoma, and 1 displayed no LOH events in either lesion. In 7 clear cell carcinomas synchronous with endometriosis, 3 displayed LOH events common to both the carcinoma and the endometriosis, 1 displayed an LOH event in only the carcinoma, and 3 displayed no LOH events in either lesion. In no cases were there LOH events in the endometriosis only. Somatic mutations in the PTEN gene were identified in 4 of 20 ovarian endometrioid carcinomas (20.0%), 2 of 24 clear cell carcinomas (8.3%), and 7 of 34 solitary endometrial cysts (20.6%). These results indicate that inactivation of the PTEN tumor suppressor gene is an early event in the development of ovarian endometrioid carcinoma and clear cell carcinoma of the ovary.

Mutation analysis of the Smad6 and Smad7 gene in human ovarian cancers

The Smad6 and Smad7 genes are members of the Smad family, involved in the transforming growth factor-beta (TGF-beta) signaling pathway. Mutations in TGF-beta receptors and their cytoplasmic elements of transduction signals commonly accompany various cancers. Using PCR-SSCP analysis we searched for the presence of Smad6 and Smad7 gene mutations in 30 human ovarian cancers and 4 ovarian cancer cell lines, and found that 12 cases (35.3%) had a polymorphism in intron 2 of the Smad6 gene and that 8 cases (23.5%) had a polymorphism at codon 208 in the Smad7 gene. Because these polymorphisms were not accompanied by amino acid substitution, the present results show that the mutations in the Smad6 and Smad7 genes are unlikely to be involved in human ovarian cancers.

p21WAF1/CIP1 protein expression in primary ovarian cancer

p21WAF1/CIP1 protein is a cyclin-dependent kinase inhibitor, able to prevent the CDK2/cyclin E induced retinoblastoma protein (pRB) phosphorylation, thus inhibiting cell cycle progression at G1 phase. p21WAF1/CIP1 protein levels were examined in a series of 102 ovarian tissue samples including normal ovary, primary ovarian tumors, omental metastasis, recurrent disease and residual tumor after chemotherapy exposure, by Western blot analysis. The association of p21WAF1/CIP1 status with clinicopathological parameters and clinical outcome was also investigated. p21WAF1/CIP1 protein was detectable in 76 out of 102 (74%) ovarian tissue samples. We observed a significant trend of p21 levels to gradually increase from normal ovarian tissues (median 0 a.u.) through primary ovarian cancers (median 0.19 a.u.), omental metastases (median 0.33 a.u.) and recurrence of disease (median 0.44 a.u.) (p=0.015). In the group of stage III-IV ovarian cancer patients, p21-positive cases showed a more favourable prognosis with respect to p21-negative cases: the 3-year time to progression (TTP) rate was 58% for p21-positive compared with 33% of p21-negative cases (p=0.036). In conclusion, p21WAF1/CIP1 expression levels seem to be correlated with tumor status at the time of diagnosis and can predict TTP in a selected group of patients.