Sporadic Endometrial Cancer Research Articles

P16INK4A alterations are accompanied by aberrant protein immunostaining in endometrial carcinomas.

To date, the significance of p16INK4A tumor suppressor gene inactivation in sporadic endometrial cancer (EC) has only rarely been described. In this study, we examined the alteration type and frequency of gene alterations [point mutations, aberrant promoter methylation and loss of heterozygosity (LOH)] in 50 sporadic ECs, and correlated the genetic findings with the immunohistochemical expression of the p16INK4A protein and the classical clinicopathological features. Gene mutations were detected by PCR-SSCP-sequencing analysis, promoter hypermethylation by methylation-specific PCR (MSP), and LOH by PCR of the STS-marker c5.1. In total, p16INK4A alterations were found in 14 of 50 (28%) sporadic ECs. In six (12%) cases, two alterations occurred simultaneously. Partial p16INK4A deletions were found in four of 50 (8%) samples. There was one missense mutation (codon 70; CCC-->GCC) and one frameshift mutation (1-bp deletion in exon 2). Only 2 of 47 (4.2%) tumors exhibited aberrant promoter methylation. An allelic loss was detected in 12 of 50 (24%) carcinomas with a higher incidence in advanced endometrial carcinomas than in early-stage uterine tumors. p16INK4A alterations were generally accompanied by gene silencing, confirmed by aberrant protein immunostaining ( r=-0.442; P=0.001). There was a significant difference in the frequency of p16INK4A alterations between early (stage I; 18%) and advanced (stages II-IV; 58%) ECs ( P=0.022). One case showed complete protein loss, but absence of genetic alterations. Our data indicate that p16INK4A inactivation plays a role in the tumorigenesis of the subset of sporadic ECs, particularly in cases exhibiting an aggressive clinical behavior. We demonstrate that p16INK4A methylation can act efficiently and similarly to other genetic alterations as one of the two necessary hits according to the Knudson two-hit hypothesis of tumor suppressor gene inactivation.

BAT-26 microsatellite instability does not correlate with the loss of hMLH1 and hMSH2 protein expression in sporadic endometrial cancers

Microsatellite instability (MSI) is detected in about 20-25% of endometrial cancers (ECs). Incidence of this alteration correlates with lack of expression of certain mismatch repair genes such as hMLH1 and hMSH2. Although assessment of several markers has been proposed for identification of microsatellite unstable tumours, BAT-26, a mononucleotide microsatellite repeat, has been shown to be highly efficient when used as a single marker. The aim of the study was to evaluate instability within BAT-26 and expression of hMLH1 and hMSH2 proteins in sporadic endometrial cancer as well as to correlate these findings with histopathologic and clinical characteristics of tumours. Samples of 88 (74 endometrioid and 14 non-endometrioid) ECs were investigated for instability within BAT-26 by means of PCR and expression of hMLH1 and hMSH2 proteins using immunohistochemistry. BAT-26 MIS was discovered in 23.9% of endometrial cancers. Incidence of MSI did not correlated with grade, stage or depth of invasion. BAT-26 MSI was more frequent in non-endometrioid compared to endometrioid tumours (35.7% vs. 21.6%, respectively), but the difference was not statistically significant. Lack of hMLH1 and hMSH2 protein expression was detected in 21.6 and 15.9% of ECs, respectively, and did not correlate with clinicopathologic features of tumours. Loss of both hMLH1 and hMSH2 protein expression was similar in BAT-26 stable and unstable cancers. All cases of non-endometrioid tumours with BAT-26 MSI were positive for hMLH1. We can conclude that BAT-26 used alone may not be a reliable marker for identification of sporadic ECs with microsatellite instability induced by deficient expression of hMLH1 and hMSH2.

Prevalence of defective DNA mismatch repair and MSH6 mutation in an unselected series of endometrial cancers.

Endometrial cancer is the most common gynecologic malignancy in the United States and the most frequent extracolonic tumor in hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC patients have inherited defects in DNA mismatch repair and the microsatellite instability (MSI) tumor phenotype. Sporadic endometrial cancers also exhibit MSI, usually associated with methylation of the MLH1 promoter. Germ-line MSH6 mutations, which are rare in HNPCC, have been reported in several families with multiple members affected with endometrial carcinoma. We reasoned that MSH6 mutation might account for loss of mismatch repair in MSI-positive endometrial cancers in which the cause of MSI is unknown. We therefore investigated MSI and MLH1 promoter methylation in 441 endometrial cancer patients unselected for age or personal and family history of cancers. MSI and MLH1 promoter methylation status were associated with age of onset and tumor histology. One hundred cases (23% of the entire series) were evaluated for MSH6 defects. Inactivating germ-line MSH6 mutations were identified in seven women with MSI-positive, MLH1 promoter unmethylated cancers. Most of the MSI in these cases was seen with mononucleotide repeat markers. The MSH6 mutation carriers were significantly younger than the rest of the population (mean age 54.8 versus 64.6, P = 0.04). Somatic mutations were seen in 17 tumors, all of which had MSI. Our data suggest that inherited defects in MSH6 in women with endometrial cancer are relatively common. The minimum estimate of the prevalence of inherited MSH6 mutation in endometrial cancer is 1.6% (7 of 441), comparable with the predicted prevalence for patients with colorectal cancer.

Expression of the cell-cycle regulatory proteins (pRb, cyclin D1, p16INK4A and cdk4) in human endometrial cancer: correlation with clinicopathological features.

Derailments of the control mechanisms in the G1/S phase of the cell cycle play a fundamental role in the initiation and progression of cancer. However, only a few reports have addressed the issue of simultaneously occurring abnormalities of Rb-pathway components in malignant endometrial tumors. Currently, we assessed the expression of cell-cycle regulatory proteins (pRb, cyclin D1, p16(INK4A) and cdk4) in 48 sporadic endometrial cancers, and investigated these tumors for a possible relationship between aberrant protein staining and clinicopathological variables of cancer and RB-LOH. There was abnormal pRb, cyclin D1, p16(INK4A) and cdk4 immunoreactivity in 2%, 50%, 6% and 25% of cases, respectively. Altogether, 33 of 48 (69%) endometrial malignant tumors showed abnormal expression of at least one Rb-pathway protein immunohistochemically. However, there was significant correlation neither between the cell-cycle regulators nor between the frequency of pRb, p16(INK4A) and cyclin D1 abnormalities and clinicopathological variables of cancer, but a significant correlation did exist between cdk4 staining and the clinical stage of disease ( P<0.05, Fisher's exact test). Moreover, an inverse relationship was also demonstrated between cdk4 expression and patient age ( r=-0.367; P=0.01). However, none of the cell-cycle regulatory proteins, except for pRb, was related to loss of heterozygosity at locus 13q14. As a conclusion, derailments of the Rb-pathway components, cyclin D1 and cdk4 in particular, seems to participate in the endometrial cancer development in humans. Overexpression of cdk4 was related to the progression of neoplastic disease and corresponds with age of onset, suggesting a major role of altered cdk4 immunoreactivity in the progression of endometrial cancer.

Chromosomal abnormalities and microsatellite instability in sporadic endometrial cancer

Defective DNA mismatch repair and nonfunctional mechanisms controlling the proper progression of the cell cycle have been proposed as being responsible for the genomic instability and accumulation of karyotypic alterations in endometrial cancer (EC). To assess whether numerical chromosomal anomalies (aneuploidy) and microsatellite instability (MSI) might be representative of distinctive tumour behaviour, paraffin-embedded tissue samples from 86 patients with sporadic EC were evaluated by both fluorescence in situ hybridisation (FISH) and microsatellite analysis, using free nuclei and genomic DNAs (respectively). Approximately one-third of the tumours analysed (24/74; 32%) exhibited MSI, whereas 38/86 (44%) of the EC samples displayed aneuploidy. The majority of the unstable cases (15/24; 63%) were from advanced-stage patients. Conversely, 23 (61%) out of the 38 tumours with aneuploidy were from early-stage patients. No apparent correlation was found between MSI and aneuploidy, whereas the immunohistochemical (IHC) analysis revealed that inactivation of the MLH1 mismatch repair gene may be involved in the majority of the MSI+ sporadic ECs. No genetic or cytogenetic alteration analysed here seems to add any significant predictive value to the stage of disease.

PTEN Mutational Spectra, Expression Levels, and Subcellular Localization in Microsatellite Stable and Unstable Colorectal Cancers

PTEN on 10q23.3 encodes a dual-specificity phosphatase that negatively regulates the phosphoinositol-3-kinase/Akt pathway and mediates cell-cycle arrest and apoptosis. Germline PTEN mutations cause Cowden syndrome and a range of several different hamartoma-tumor syndromes. Hereditary nonpolyposis colon cancer (HNPCC) syndrome is characterized by germline mutations in the mismatch repair (MMR) genes and by microsatellite instability (MSI) in component tumors. Although both colorectal carcinoma and endometrial carcinoma are the most frequent component cancers in HNPCC, only endometrial cancer has been shown to be a minor component of Cowden syndrome. We have demonstrated that somatic inactivation of PTEN is involved in both sporadic endometrial cancers and HNPCC-related endometrial cancers but with different mutational spectra and different relationships to MSI. In the current study, we sought to determine the relationship of PTEN mutation, 10q23 loss of heterozygosity, PTEN expression, and MSI status in colorectal cancers (CRCs). Among 11 HNPCC CRCs, 32 MSI+ sporadic cancers, and 39 MSI- tumors, loss of heterozygosity at 10q23.3 was found in 0%, 8%, and 19%, respectively. Somatic mutations were found in 18% (2 of 11) of the HNPCC CRCs and 13% (4 of 32) of the MSI+ sporadic tumors, but not in MSI- cancers (P = 0.015). All somatic mutations occurred in the two 6(A) coding mononucleotide tracts in PTEN, suggestive of the etiological role of the deficient MMR. Immunohistochemical analysis revealed 31% (14 of 45) of the HNPCC CRCs and 41% (9 of 22) of the MSI+ sporadic tumors with absent or depressed PTEN expression. Approximately 17% (4 of 23) of the MSI- CRCs had decreased PTEN expression, and no MSI- tumor had complete loss of PTEN expression. Among the five HNPCC or MSI+ sporadic CRCs carrying frameshift somatic mutations with immunohistochemistry data, three had lost all PTEN expression, one showed weak PTEN expression levels, and one had mixed tumor cell populations with weak and moderate expression levels. These results suggest that PTEN frameshift mutations in HNPCC and sporadic MSI+ tumors are a consequence of mismatch repair deficiency. Further, hemizygous deletions in MSI- CRCs lead to loss or reduction of PTEN protein levels and contribute to tumor progression. Finally, our data also suggest that epigenetic inactivation of PTEN, including differential subcellular compartmentalization, occurs in CRCs.

Genetic progression in sporadic endometrial and gastrointestinal cancers with high microsatellite instability.

This study selected a series of 136 MSI-H (microsatellite instability at high frequency) gastric, colorectal, and endometrial carcinomas combining immunohistochemical analysis for hMLH1 or hMSH2 gene products and microsatellite study. The clinico-pathological profile of all tumours was correlated with the overall instability rates at coding and non-coding repeats, in order to clarify the role and the mutation timing of seven target genes (TGFbetaRII, IGFIIR, BAX, hMSH3, hMSH6, CHK1, and BRCA2) in the progression of an MSI-H neoplasm. Regardless of the primary site, the results confirm a model of oncogenesis in which inactivation of hMLH1, or less frequently hMSH2, may initiate a pathway culminating in a progressive accumulation of frameshifts in coding region (CDR) microsatellites. Comparing gastrointestinal and endometrial tumours, significantly lower levels of microsatellite instability at both coding and non-coding repeats were observed. Among gastric and colorectal tumours, the detection of small shortening within Bat-26 and Bat-25 markers defines a subgroup of MSI-H gastrointestinal tumours invariably characterized by early stage at diagnosis. In these tumours, mutations of TGFbetaRII or BAX genes precede frameshifts in the other tested genes. The analysis of correlations between the mutational and clinico-pathological profiles of advanced gastrointestinal tumours revealed that the higher levels of microsatellite instability at both coding and non-coding repeats were not associated with a more advanced clinico-pathological stage or a less favourable outcome. A significant association was observed between a low number of CDR frameshifts and the presence of lymph-node metastasis in advanced gastrointestinal tumours. The existence of advanced MSI-H tumours with more aggressive behaviour and a 'mild mutator phenotype' could be explained by hypothesizing an overlapping of different mechanisms of tumourigenesis, including both the mutator and the suppressor pathways; this should be tested by further studies.

A semiautomated test for microsatellite instability and its significance for the prognosis of sporadic endometrial cancer in northern Norway.

Archival histologic material from 105 women (median age 62 years) treated for endometrial cancer was investigated for the replication error phenotype indicated by the observation of widespread microsatellite instability (MSI). Polymerase chain reaction (PCR) of DNA isolated from paraffin-embedded tissue was analyzed for MSI using six microsatellite loci with a fluorescent-based detection system. Flow cytometry and morphometric investigation were performed in the same material for each of the patients. Twenty percent (21 of 105) of screened endometrial cancers were found to have high MSI at two or more of the loci tested. The mean detection frequency per marker was highest in the dinucleotide repeat sequence, D2S123, and the mononucleotide repeat sequences amplified by Bat 25 and Bat 26. Death from endometrial cancer was not related to the occurrence of MSI (p=0.6). There was no significant association between MSI and FIGO stage (p=0.5), myometrial invasion depth (p=0.8), histological grade (p=0.3), or vessel invasion (p=0.5). There were, however, more MSI cases among the group of diploid cases compared with the aneuploid and tetraploid group. MSI is not a valuable prognosticator for survival of sporadic endometrial cancer, and diploid cases are significantly more often MSI positive than aneuploid and tetraploid cases.

Assessment of microsatellite instability and genetic analysis of mismatch repair genes in sporadic endometrial cancer: identification of different subsets of patients and a MLH1 founder mutation in Sardinia

Assessment of microsatellite instability and genetic analysis of mismatch repair genes in sporadic endometrial cancer: identification of different subsets of patients and a MLH1 founder mutation in Sardinia

MLH1 and MSH2 protein expression as a pre-screening marker in hereditary and non-hereditary endometrial hyperplasia and cancer.

The predictive value of MLH1 or MSH2 protein expression for the presence of truncating germline mutations was examined in benign and (pre)malignant endometrial samples from 3 patient groups: (I) 10 endometrial cancer patients from hereditary non-polyposis colorectal cancer (HNPCC) families with (n = 6) or without (n = 4) a known germline mutation; (II) 15 women from HNPCC families with (n = 7) or without (n = 8) a known germline mutation, who underwent endometrial sampling for non-malignant reasons; (III) 38 endometrial cancer patients <50 years of age, without HNPCC family history. Immunostaining for MLH1 and MSH2 was performed on paraffin-embedded sections. In group III, tumor DNA was examined for microsatellite instability (MSI) and MLH1, MSH2 and MSH6 mutation analysis was carried out. In 6/6 MLH1/MSH2 mutation carriers with endometrial cancer (group I), concordance was found between protein loss in the tumor and the corresponding mutation. In 3 MLH1 mutation carriers, MLH1 protein loss was also observed in concurrent endometrial hyperplasia. In group II, no protein loss was detected in normal endometrial tissue samples; in 3/4 patients with endometrial hyperplasia, MLH1/MSH2 protein loss was observed. In group III, protein loss was detected in 12/38 patients (9 MLH1, 3 MSH2), while in 3/11 patients with concurrent endometrial hyperplasia protein loss was also observed in the hyperplasia. MSI analysis in group III revealed 26 MSI-low and 12 MSI-high tumors. Mutation analysis in 28/38 patients showed only 1 missense MSH6 and no MLH1 or MSH2 germline mutations. In group III, loss of MLH1/MSH2 protein expression was not related to the presence of MSI or MLH1/MSH2 germline mutations. In conclusion, MLH1 or MSH2 protein loss in HNPCC-related endometrial neoplasia is strongly related to corresponding germline mutations. This relation was not clearly present in young sporadic endometrial cancer patients. Immunohistochemical pre-screening of the MLH1 and MSH2 proteins in endometrial hyperplasia or cancer can thus be helpful in HNPCC families. Frequent loss of MLH1 or MSH2 protein in endometrial hyperplasia indicates that this loss is an early event in endometrial carcinogenesis.

Microsatellite instability and hMLH1/hMSH2 expression in young endometrial carcinoma patients: associations with family history and histopathology.

Endometrial cancer is the second most common malignancy in patients with hereditary nonpolyposis colorectal cancer (HNPCC). The age at diagnosis of HNPCC-associated endometrial cancer is approximately 15 years younger than for sporadic endometrial cancer. Our current study was undertaken to determine the frequency of microsatellite instability (MSI) and absence of hMLH1 or hMSH2 protein expression in young patients with endometrial carcinoma and to correlate these findings with histopathologic and clinical features. Endometrial carcinoma from 62 women (23-52 years, median age 46) were assessed for MSI. Twenty-one of the 62 (34%) tumors demonstrated MSI. Of the 21 tumors demonstrating MSI, 12 showed an absence of hMLH1 expression, 4 showed an absence of hMSH2 expression, and 5 demonstrated normal expression of both proteins. All 41 tumors without MSI demonstrated normal hMLH1 and hMSH2 expression. Two patients with MSI tumors fulfilled the Amsterdam criteria for HNPCC, while 2 had histories suggestive of HNPCC. None of the patients with tumors without MSI had a personal or family cancer history suggestive of HNPCC. The MSI phenotype was associated (p < 0.05) with high FIGO stage and grade, cribriform growth pattern, mucinous differentiation and necrosis. Our findings suggest that the frequency of HNPCC in young endometrial cancer patients is relatively low when compared with the frequency of HNPCC in young colorectal cancer patients. Defects of the MMR proteins hMSH2 or hMLH1 account for MSI in most but not all endometrial cancers from young patients.

The expansion of the CAG repeat in exon 1 of the human androgen receptor gene is associated with uterine endometrial carcinoma

Uterine endometrial carcinoma is common among women. Several reports indicated that this cancer is influenced by androgens mediated through their receptors. The human androgen receptor gene contains a polymorphic CAG repeat in the coding region of exon 1. Other studies suggested a possible association between the CAG repeat of this gene and the development of several cancers. DNA samples isolated from 29 patients with sporadic endometrial cancer were analyzed for allelic changes in 12 highly polymorphic microsatellite loci on nine chromosomes, containing CAG repeat in the exon 1 of the androgen receptor gene. A significantly high rate of allelic change in the CAG repeat was observed (51.7%) in these patients, although the frequencies of additional loci were similar to those reported by others (0-22.2%). The changed alleles of the tumor tissue were always longer than that of normal tissue except in only one case. Since only one allele on the X chromosome is commonly active in female cells, a differential methylation assay was carried out by using genomic DNA cut with HpaII. In 14 of 15 cases, we found that the activated allele was longer in these samples from tumor tissues than those from normal tissue; in the remaining case, the length of this repeat was unchanged. The expression assays were done by using poly(A+) RNA from tumor and normal uterine tissues, revealing that an activated allele in these tumor tissues was longer than that in the normal tissues in all the cases examined. These findings suggest that expansions of the CAG repeat in the androgen receptor gene may play an important role in the carcinogenesis of uterine endometrial cells.

Is Uterine Serous Papillary Carcinoma a BRCA1-Related Disease? Case Report and Review of the Literature

Objectives. Type II endometrial carcinomas are estrogen-independent and have adverse histologic features and a substantially poorer prognosis. No risk factors have been identified. Interestingly, there is a striking clinical and histopathological similarity between serous papillary carcinomas of the ovary (OSPC), endometrium, and peritoneal cavity, suggesting a common oncogenic mechanism. Several common molecular alterations were found using molecular comparative analysis of OSPC and uterine serous papillary carcinoma (USPC). Germline mutations in the BRCA1 tumor suppressor gene predispose to breast and ovarian cancer but no association with sporadic endometrial cancer has been found. A family of Ashkenazi Jewish origin, in which one sister was first diagnosed with USPC and the second diagnosed with OSPC, led to the hypothesis that a BRCA mutation may contribute to USPC.Methods. Genomic DNA from both patients as well as two unaffected siblings was analyzed for the three mutations common in Ashkenazi Jews. Loss of heterozygosity (LOH) analysis was performed on DNA extracted from USPC tumor tissue.Results. Both affected sisters tested positive for BRCA1 5382insC germline mutation. LOH analysis confirmed the results.Conclusions. We present a breast–ovarian cancer family including two sisters with advanced serous papillary carcinomas of endometrial and ovarian origins, carrying the same BRCA1 mutation (5382insC). LOH analysis on USPC tumor DNA showed loss of the wild-type allele, suggesting a causal relationship between the germline BRCA1 mutation and USPC. We believe a study examining BRCA1 mutations in a large cohort of women with this high-risk endometrial carcinoma is warranted. A positive finding may have implications for surveillance and prophylactic surgery in carriers of BRCA1 mutations.

Mutational Analysis of the PMS2 Gene in Sporadic Endometrial Cancers with Microsatellite Instability

Objective. Approximately 20% of endometrial tumors have a defect in DNA mismatch repair and exhibit microsatellite instability (MSI). We assessed the role of the PMS2 DNA mismatch repair gene in MSI-positive sporadic endometrial tumors.Methods. We examined 40 sporadic endometrial tumor specimens with MSI. All 15 exons of the PMS2 gene were investigated for sequence alterations by single-strand conformational variant analysis.Results. Twelve polymorphisms were identified, 8 of which were in the coding sequence. Four specimens revealed mutations in intronic sequences that are not predicted to affect the PMS2 mRNA. No mutations were detected within the coding region of the PMS2 gene.Conclusion. We conclude that structural mutations in the PMS2 gene are not responsible for defective DNA mismatch repair in sporadic endometrial cancers with MSI. The identification of single nucleotide polymorphisms in the PMS2 locus may aid in the mapping and characterization of genetic diseases.

MLH1 promoter methylation and gene silencing is the primary cause of microsatellite instability in sporadic endometrial cancers.

Defective DNA mismatch repair in human tumors leads to genome-wide instability of microsatellite repeats and a molecular phenotype referred to as microsatellite instability (MSI). MSI has been reported in a variety of cancers and is a consistent feature of tumors from patients with hereditary non-polyposis colorectal cancer. Approximately 20% of cancers of the uterine endometrium, the fifth most common cancer of women world-wide, exhibit MSI. Although the frequency of MSI is higher in endometrial cancers than in any other common malignancy, the genetic basis of MSI in these tumors has remained elusive. We investigated the role that methylation of the MLH1 DNA mismatch repair gene plays in the genesis of MSI in a large series of sporadic endometrial cancers. The MLH1 promoter was methylated in 41 of 53 (77%) MSI-positive cancers investigated. In MSI-negative tumors on the other hand, there was evidence for limited methylation in only one of 11 tumors studied. Immunohistochemical investigation of a subset of the tumors revealed that methylation of the MLH1 promoter in MSI-positive tumors was associated with loss of MLH1 expression. Immunohistochemistry proved that two MSI-positive tumors lacking MLH1 methylation failed to express the MSH2 mismatch repair gene. Both of these cancers came from women who had family and medical histories suggestive of inherited cancer susceptibility. These observations suggest that epigenetic changes in the MLH1 locus account for MSI in most cases of sporadic endometrial cancers and provide additional evidence that the MSH2 gene may contribute substantially to inherited forms of endometrial cancer.

Loss of heterozygosity of BRCA1, TP53 and TCRD markers analysed in sporadic endometrial cancer

Genetic alterations of tumour suppressor genes, for which loss of heterozygosity (LOH) is one mechanism of gene inactivation, are important steps in the development of endometrial cancer. To investigate the clinical relevance of LOH of BRCA1 (17q21), TP53 (17p13) and TCRD (14q11) in endometrial cancer, polymerase chain reaction (PCR)-based fluorescent DNA technology for the detection of microsatellite polymorphisms was applied. One hundred and thirteen archival endometrial cancer samples with matched normal tissues were examined. Allele loss at three loci were correlated with age, tumour size, lymph node status, metastases, stage, histological types, grade, expression of oestrogen receptor (ER) and progesterone receptor (PgR), family history of cancer, previous history of cancer or precursor lesions, and previous history of hormone replacement therapy (HRT). LOH for BRCA1 was detected in 18.1%, of TP53 in 26.9%, and of TCRD in 26.3% of informative cases. LOH of BRCA1 correlated with medium grade, positive ER status, and family history of cancer; LOH of TP53 correlated with younger age, high grade, positive PgR status, and with tumours from patients without HRT; LOH of TCRD correlated only with family history of cancer. LOH at all three loci correlated only with grade and positive family history. Allele loss of one of the three tumour suppressor loci did not correlate with disease-free survival (DFS), but LOH of BRCA1 correlated significantly with decreased overall survival (OS). The latter, together with the correlation of LOH of BRCA1 locus with steroid hormone receptor expression, might give a hint to the potential involvement of the co-localised 17β-hydroxysteroid dehydrogenase (HSD) gene in the development of endometrial cancer.

Association of replication error positive phenotype with lymphocyte infiltration in endometrial cancers.

Microsatellite instability (MI) has been detected in certain sporadic cancers as well as in hereditary non‐polyposis colorectal cancer (HNPCC). In order to determine the precise clinicopathological characteristics of MI in endometrial cancer, we examined 90 sporadic endometrial cancers (83 endometrioid adenocarcinomas, 3 adenosquamous carcinomas, 3 papillary serous carcinomas, and 1 clear cell carcinoma) and eight lesions of endometrial hyperplasia for replication error (RER) using polymerase chain reaction amplification of CA repeated microsatellite sequences at 15 loci. RER was observed in 23 (28%) of the 83 endometrioid adenocarcinomas at at least one locus and in 19 (23%) at two or more loci (RER+ phenotype) in the seven most commonly observed loci, but not in carcinomas of other histological types or in endometrial hyperplasia. Lymphocyte infiltration around carcinoma cells, which is one of the histological features seen in tumors from HNPCC, was severer in RER+ phenotype tumors (79%, 11/14) than in the RER– tumors (25%, 11/44) (marked/moderate infiltration versus slight, P<0.001, χ2 test), when 58 tumors with muscular invasion were examined. The RER+ phenotype was associated with a higher parity and gravidity (P<0.05, Wilcoxon test). However, RER+ phenotype was not associated with tumor stage, histological grade, muscular invasion, lymph node metastasis or patient survival. In conclusion, MI occurs in a subset of endometrial cancers, which often show marked infiltration of lymphocytes around the tumor.

Analysis of MSH3 in endometrial cancers with defective DNA mismatch repair.

To clarify the origin of defective mismatch repair (MMR) in sporadic endometrial cancers with microsatellite instability (MSI), a thorough mutation analysis was performed on the human mismatch repair gene MSH3. Twenty-eight MSI-positive endometrial cancers were investigated for mutations in the human mismatch repair gene MSH3 using single-strand conformation variant (SSCV) analysis of all 24 exons. All variants were sequenced. Loss of heterozygosity was investigated at all MSH3 polymorphisms discovered. A subset of tumors were investigated for methylation of the 5' promoter region of MSH3 using Southern blot hybridization. An identical single-base deletion (delta A) predicted to result in a truncated proteins was discovered in six tumors (21.4%). This deletion occurs in a string of eight consecutive adenosine residues (A8). Because simple repeat sequences are unstable in cells with defective MMR, the observed mutation may be an effect, rather than a cause, of MSI. Evidence of inactivation of the second MSH3 allele in tumors with the delta A mutation would strongly support a causal role for these MSH3 mutations. However, there was no evidence of a second mutation, loss of sequences, or methylation of the promoter region in any of the tumors with the delta A mutation. Although the delta A mutation is a frequent event in sporadic MSI-positive endometrial cancers, it may not be causally associated with defective DNA MMR.

Postmenopausal HRT – a role for a safe antioestrogen

In his editorial ‘Postmenopausal HRT – a role for tamoxifen?‘ in the July/August issue,1 Dr Graham Jackson raises the important issue of using antioestrogens in postmenopausal HRT. The potential benefits of such an approach are impressive: bone preservation, atherosclerosis prevention and, as Dr Jackson discussed, a decrease in breast and even uterine cancer risk. The possibility of cancer reduction is especially attractive compared to conventional HRT, which is associated with an increase in breast cancer risk.2 Antioestrogens could be used as the sole therapy in women with increased risk for breast cancer, or after about 10 years of conventional HRT, to prevent the late onset increase in breast cancer mortality. Nevertheless, I wish to comment on two very important points. Firstly, tamoxifen is not the only available antioestrogen with selective oestrogen receptor modulatory activity for this indication; a related analogue, toremifene (Fareston), has been approved for marketing in Europe, Japan and the US. Toremifene is equally effective in treating breast cancer; it lowers serum LDL cholesterol and Lp(a) levels comparable with tamoxifen and preserves bone density.3-5 In contrast to tamoxifen, toremifene has been reported to increase serum HDL levels.4 Secondly, a huge population of women without any cancer history would be expected to be the target group of this new antioestrogen indication for a considerable period (10 years or more). Accordingly, the safety aspects of the therapy need to be taken into account. Dr Jackson already points out the potential increase in endometrial cancers with tamoxifen.6 In non-clinical studies, it has been shown to be a strong liver carcinogen in the rat.7 It is activated into highly reactive intermediates which alkylate DNA and lead to mutations (permanent DNA changes)8 and carcinogenesis. Some studies in humans show DNA adduct formation in endometrium and blood leucocytes,9, 10 differing from earlier negative results. In addition, a recent preliminary communication states that tamoxifen-induced endometrial cancers exhibit a high frequency of p53 mutations (91%) compared with sporadic endometrial cancers (19%),11 which supports a genotoxic mechanism in endometrial cancer induction by tamoxifen in women. Thus, I suggest it might be unwise to treat healthy women with a genotoxic carcinogen. Toremifene, which does not seem to be genotoxic or mutagenic in vivo to any significant extent,7, 8 would be preferable. The idea of using antioestrogens as HRT is attractive and warrants further evaluation, ultimately large-scale trials. At this point, however, the drug of choice would be the obviously more safe toremifene, which is now available.

Mutational Analysis of the BRCA1 Tumor Suppressor Gene in Endometrial Carcinoma

Objective.To investigate whether alteration of BRCA1 tumor suppressor gene occurs in sporadic endometrial carcinomas.Methods.Genomic DNAs were prepared from 33 consecutively collected endometrial carcinoma tissues for BRCA1 mutational analysis. To screen for BRCA1 mutation, polymerase chain reaction (PCR) amplification and single strand conformation polymorphism (SSCP) technique were used with 41 overlapping PCR primer pairs for the 23 coding exons of BRCA1. Tumors that demonstrated SSCP variants were further subjected to direct DNA sequencing in the appropriate exons to identify the DNA alteration.Results.In addition to detecting a previously described polymorphism in exon 11, single strand conformation polymorphism analysis of the 33 endometrial cancers identified 3 tumors with mobility shifts. Two tumors shifted in exon 3 and showed the same pattern of band shift. The other tumor shifted in exon 9. DNA sequencing revealed sequence alterations in the 3 tumors; all appeared heterozygous. In the 2 tumors shifted in exon 3, the sequence alteration caused no amino acid change and was consistent with an infrequent silent polymorphism. In the third tumor, a missense alteration at codon 191 was detected and was recognized as germline in origin.Conclusions.Because a normal allele of BRCA1 was retained in the tumor where a germline missense alteration was detected, the heterozygous DNA alteration should not be cancer predisposing in terms of the two-hit model for inactivation of the tumor suppressor gene. We conclude that mutation of BRCA1 may not be involved in the development of sporadic endometrial cancer.