Microsatellite instability in sporadic endometrial carcinoma

Microsatellite Instability Occurs in a Subset of Follicular Thyroid Cancers

BACKGROUND

Inactivation of DNA mismatch repair (MMR) and the resulting microsatellite instability (MSI) are frequently observed in endometrial, stomach, and colorectal cancers, as well as more rarely in other solid tumor types. The prevalence of MSI in thyroid cancer has not been explored in depth, although recent studies utilizing data from large cancer sequencing efforts such as The Cancer Genome Atlas indicate that MSI is absent or at least very rare in the most common and most well studied histologic subtype, papillary thyroid carcinoma. This study aimed to determine the prevalence of MSI in thyroid cancer by using a large series comprising all major histological subtypes.

METHODS

A total of 485 thyroid cancer patients were screened for MSI/MMR deficiency, including all major histologic subtypes (195 papillary thyroid carcinoma, 156 follicular thyroid carcinoma [FTC], 50 anaplastic thyroid carcinoma, 65 medullary thyroid carcinoma, and 17 poorly differentiated thyroid carcinomas) by using a combination of polymerase chain reaction-based detection, immunohistochemistry, and next-generation sequencing.

RESULTS

A total of four tumors were MSI-high and had loss of MMR protein expression, all of which were from FTC patients. Whole-exome sequencing was performed on two MSI-high FTCs and revealed a hemizygous loss of function mutation in MSH2 in one tumor.

CONCLUSIONS

Based on these data, it is estimated that the overall prevalence of MSI in FTC is 2.5%, and MSI is either entirely absent or rare in other histology subtypes of thyroid carcinoma. These findings highlight the importance of testing for MSI in FTC.

Gynecologic Cancers: Molecular Updates 2018

Ovarian carcinoma continues to be a concern for woman and maintains significant morbidity and mortality. Emerging molecular markers are providing additional opportunities for effective diagnosis and prognosis of disease. An integrated clinicopathologic and molecular classification of gynecologic malignancies has the potential to refine the clinical risk prediction of patients with cancer and to provide more tailored treatment recommendations.

PD-L1 and CD8 are associated with deficient mismatch repair status in triple-negative and HER2-positive breast cancers

Triple-negative and HER2-positive breast cancers (BCs) are more aggressive than hormone receptor-positive/HER2-negative BCs and show higher levels of tumor-infiltrating lymphocytes (TILs) and PD-L1 expression. Recently, US Food and Drug Administration approved anti-PD-L1 immunotherapy for solid tumors with deficient mismatch repair (MMR). In this study, we aimed to examine the prevalence of deficient MMR and its association with checkpoint immune markers in BCs. Immunohistochemistries (IHCs) with anti-MMR proteins (MLH1, PMS2, MSH2 and MSH6) and multiplex IHCs with anti-PD-L1, anti-CD8 or anti-CD163 were performed on tissue microarrays (TMAs) with 101 triple-negative BCs (TNBC) and 197 HER2-positive BCs. Additional IHCs for MMR proteins were also performed on whole-tissue sections from selected cases. Thirteen cases (4.4%) showed complete loss of MMR protein on TMAs, including 7 TNBCs (6.9%) and 6 HER2-positive BCs. On whole-tissue sections, only one of 13 cases showed complete loss of MMR proteins, while the other 12 cases showed partial loss. PD-L1 expression was identified in 37% of cases and was significantly higher in TNBCs than in HER2-positive BCs (71% versus 19%). Furthermore, BCs with complete/partial loss of MMR demonstrated significantly more PD-L1 and CD8 expressions than BCs with preserved MMR proteins. Although complete loss of MMR proteins exists in an extremely low frequency, partial loss is not uncommon in BCs. The association of partial loss of MMR proteins with increased PD-L1 and CD8 expression suggests a potential use of MMR testing as a screening method for anti-PD-L1 immunotherapy in BCs.

Molecular Genetics of Hereditary Non-Polyposis Colorectal Cancer (HNPCC)

The story of the molecular genetics of HNPCC is one of astonishingly rapid achievements. In just 16 months, from May 1993 to September 1994, four different genes, namely hMSH2, hMLH1, hPMS1 and hPMS2 have been identified and demonstrated to be associated with the disease. Their cloning was facilitated by the finding that tumor cells in HNPCC patients display a hypermutability of DNA short tandem repeats (microsatellite instability). In fact, HNPCC associated genes are the human counterparts of genetic elements known to control the fidelity of DNA replication in lower organisms. So far, more than 50 germline mutations of hMSH2 and hMLH1 genes have been reported in HNPCC kindreds. In addition, somatic mutations have been documented in hereditary as well as sporadic cancers. Unfortunately, the molecular diagnosis of HNPCC is hampered by the lack of mutational “hot spots” and of clearly defined genotype-phenotype correlations and different screening methods are to be employed for the analysis of affected and at-risk individuals.

KRAS Mutation in Gastric Cancer and Prognostication Associated with Microsatellite Instability Status

Microsatellite instability (MSI) is one of the subgroups based on the new molecular classification of gastric cancer (GC). In this study, we analyzed the role of KRAS status in MSI GC and the impact of MSI status on KRAS mutation. We performed analysis on 595 GC patients. Polymerase chain reaction (PCR) was used for the screening of KRAS mutation (exon 2) and 5 quasi-monomorphic mononucleotide repeats, namely, BAT-26, BAT-25, NR -24, NR-21, and NR-27 were used to determine the MSI status. The KRAS and MSI status were then compared with clinicopathologic data of the GC patients. MSI GC was found in 20.3% of all cases. KRAS mutation was seen in 24 patients; 18 were MSI (75%) and 6 were microsatellite stable (MSS) (25%). MSI GC patients with KRAS mutation were older and mostly female, but MSS presented more advanced T and N stage of the disease, more cardia tumors, and adjuvant treatment. Five-year survival was 72.2% for KRAS mutation patients with MSI and 0% for MSS (p < 0.001). Although KRAS mutations in GC are linked with MSI in the majority of cases, KRAS mutations with MSS status presented with a poor prognosis and a worse outcome. In multivariate analysis, MSI was associated with better survival (p < 0.001) but KRAS was with worse survival (p = 0.304). Our study suggests that KRAS mutations are based on MSI status rather than different codon subtypes of mutation, and such a division could be used to determine the GC patient outcome.

Molecular Pathology: Predictive, Prognostic, and Diagnostic Markers in Uterine Tumors

This article focuses on the diagnostic, prognostic, and predictive molecular biomarkers in uterine malignancies, in the context of morphologic diagnoses. The histologic classification of endometrial carcinomas is reviewed first, followed by the description and molecular classification of endometrial epithelial malignancies in the context of histologic classification. Taken together, the molecular and histologic classifications help clinicians to approach troublesome areas encountered in clinical practice and evaluate the utility of molecular alterations in the diagnosis and subclassification of endometrial carcinomas. Putative prognostic markers are reviewed. The use of molecular alterations and surrogate immunohistochemistry as prognostic and predictive markers is also discussed.

Immunohistochemical Detection of Hematopoietic Cell-specific Protein-Tyrosine Phosphatase (Tyrosine Phosphatase SHP-1) in a Series of Endometrioid and Serous Endometrial Carcinoma

In this study, we evaluated the expression of SHP-1 (PTPN6) in endometrioid (Ec) and serous (Sc) subtypes of endometrial carcinoma by immunohistochemical analysis. In total, 114 patients with Ec carcinoma and 48 patients with Sc carcinoma were enrolled in this study. The correlation between the type of histology, the grade of tumor, the stage of development, and immunoreactivity to SHP-1 was evaluated. Kaplan-Meier and multivariate survival analyses, using a Cox regression model, were performed to establish whether this marker has prognostic value in these malignancies, on the basis of follow-up and stratification of the patients according to their SHP-1 immunoreactivity. A significantly higher SHP-1 expression was observed in the Ec group compared with the Sc group (P=0.0005, Fisher exact test). In the Ec group, SHP-1 immunoreactivity was correlated with grading, demonstrating that more differentiated lesions expressed SHP-1 more frequently than less differentiated neoplasms (G1 vs. G2, P=0.0243, statistically significant value, Fisher exact test; G1 vs. G3, P=0.0088, extremely significant value, Fisher exact test). Instead, in the Sc group, SHP-1 expression was not correlated with grading, as Sc is now defined as a high-grade carcinoma. SHP-1 expression did not change with neoplastic progression in Ec and Sc groups. From both univariate and multivariate analysis in the Ec group, expression of SHP-1 remained a positive prognostic factor (P=0.004, log-rank test) [HR=0.32 (0.11 to 0.94), P=0.039]. In contrast, in the Sc group, no correlation between SHP-1 expression and survival was noted (P=0.77, log-rank test). In this study, we observed that the absence of SHP-1 in immunohistochemical analysis might serve as a marker of poor prognosis for a subset of high-grade endometrial cancer.

Bokhman Redux: Endometrial cancer "types" in the 21st century

In 1983 Jan V. Bokhman, M.D. published a landmark paper entitled "Two Pathogenetic Types of Endometrial Carcinoma" in which an enduring dualistic view of endometrial cancer was first proposed. "Type I" cancers are thought to represent estrogen driven mostly low grade endometrioid tumors strongly associated with obesity and other components of the metabolic syndrome. "Type II" cancers represent higher grade non-endometrioid tumors for which the latter associations are less significant. Basic tenets of this dichotomy including significant prognostic differences have been abundantly confirmed by later literature. The construct has in turn contributed a useful framework for decades of teaching and scientific advancement across disciplines. However, recent large epidemiologic studies indicate a more complex web of risk factors with obesity and hormones likely playing an important role across the entire endometrial cancer histologic and clinical spectrum. Moreover, high quality molecular data and refinements in pathologic classification challenge any simplistic classification of endometrial cancer. For example, the Cancer Genome Atlas (TCGA) recently defined four clinically distinct endometrial cancer types based on their overall mutational burden, specific p53, POLE and PTEN mutations, microsatellite instability and histology. Additionally, new histologic categories with clear prognostic implications have been accepted and it is becoming evident from an epidemiologic point of view that metabolic factors may play an important role in endometrial cancer overall. While Bokhman's intuitive dualistic model remains relevant when working with large registries and databases lacking granular information; most other efforts should integrate clinical, pathological and molecular specifics into more nuanced classifications.

The Significance of Mismatch Repair Deficiency in Young Patients With Endometrial Cancer

The objective of this study was to identify the tumor characteristics associated with mismatch repair deficiency in young patients with endometrial carcinoma. Young patients (45 yr old or younger) with endometrial carcinoma treated by hysterectomy in our institution between July 2001 and June 2009 were identified. The clinical and pathologic data were obtained by review of clinical records. Among the 122 cases identified, paraffin sections were available in 67 cases for immunohistochemical staining and frozen tissue available in 62 cases for microsatellite instability (MSI) analysis. Both paraffin sections and frozen tissue were available in 36 cases. Among the 67 cases with immunohistochemical staining, 22 (32.8%) showed loss of expression of at least 1 mismatch repair protein. Defective MLH1 or MSH2 expression was associated with poor prognostic factors, including a higher incidence of pelvic lymph nodes metastasis (P=0.018) and higher stage (P=0.022) for MLH1, and an increased risk of lymphovascular permeation (P=0.015) for MSH2. On the contrary, defective MSH6 protein expression was associated with a lower incidence of high-grade tumors (P=0.04). Among the 62 cases with MSI analysis, 12 (19.4%) tumors were classified as microsatellite-high (MSI-H), whereas 2 (3.2%) were classified as microsatellite-low (MSI-L). There was no difference in the pathologic characteristics between MSI-stable and MSI-H tumor. We concluded that defective mismatch repair expression is important in young patients with endometrial carcinoma, with MSH6 protein being most commonly affected. The phenotype resulting from defective MSH6 expression was different from that caused by MLH1 or MSH2 loss.

Defective DNA Mismatch Repair Influences Expression of Endometrial Carcinoma Biomarkers

Endometrial endometrioid carcinomas are related to estrogen excess and express estrogen and progesterone receptors. However, hormone receptor expression can be variable from tumor to tumor, and this variability is not always explained by differences in tumor grade. Variable expression of other biomarkers that may be used in the diagnostic work-up of endometrial cancer has also been noted. We hypothesized that mismatch repair (MMR) defects may contribute to this variability. A total of 411 unselected endometrial carcinomas were evaluated for immunohistochemical expression of DNA MMR proteins and MLH1 methylation. Loss of immunohistochemical expression of MLH1, MSH2, MSH6, or PMS2 was defined as MMR deficient; positive expression was defined as MMR intact. A case-control cohort of 80 Grade 2 endometrioid carcinomas was selected from this set (40 MMR deficient, 40 MMR intact). Cases were matched for histotype, grade, and age. Estrogen receptor, progesterone receptor, CK7(+), CK20, and Pax-8 immunohistochemistry was evaluated. The median percentage of CK7 tumor cells was significantly lower in the MMR deficient group compared with the MMR intact group. The mean percentage of tumor cells exhibiting estrogen receptor expression was similar in both the MMR-deficient and MMR intact groups. However, there was greater variability in the MMR-deficient group. Our study shows that MMR defects influence the expression of clinically important biomarkers for endometrioid-type endometrial carcinoma as decreased cytokeratin 7 expression is more commonly associated with MMR deficiency.

Modal variety of microsatellite instability in human endometrial carcinomas

PURPOSE

Microsatellite instability (MSI) in human endometrial cancer (EC) was analysed using a unique fluorescent technique. MSI is associated with various human neoplasms. However, the reported frequency of MSI differs widely in each malignancy. Methodological difficulties have in fact been pointed out in its assay techniques.

METHODS

We previously established a sensitive fluorescent technique in which the major methodological problems are overcome. Application of this technique has revealed two distinct modes of microsatellite alterations, i.e. Type A and Type B. In the present study, we have applied this technique to 94 ECs.

RESULTS

Significant microsatellite alterations were observed in 38 (40.4%) tumours of the panel. The two modes, Type A and Type B, were indeed observed in this malignancy. More importantly, we found that the modes more closely correlated with the molecular and clinicopathological backgrounds of the tumours than the established and widely used MSI grades, MSI-H and MSI-L. Type B MSI widely correlated with family history of hereditary non-polyposis colorectal cancer-associated cancers, whereas MSI-H only did with that of colorectal cancer. Furthermore, mutation in the KRAS oncogene, which has been regarded as generally infrequent in microsatellite-unstable tumours, was clearly associated with Type A MSI.

CONCLUSIONS

Our observations may suggest a biological relevance and a potential utility of the modal classification of MSI and, furthermore, added complexities to genomic instability underlying tumourigenesis in human endometrium.

High frequency strand slippage mutations in CTCF in MSI-positive endometrial cancers

Tumors with defective mismatch repair acquire large numbers of strand slippage mutations including frameshifts in coding sequence repeats. We identified a mutational hotspot, p.T204fs, in the insulator-binding protein (CTCF) in MSI-positive endometrial cancers. Although CTCF was described as a significantly mutated gene by the endometrial cancer TCGA, the A₇ track variants leading to T204 frameshifts were not reported. Reanalysis of TCGA data using Pindel revealed frequent T204fs mutations, confirming CTCF is an MSI target gene and revealed the same frameshifts in tumors with intact mismatch repair. We show that T204fs transcripts are subject to nonsense-mediated decay and as such, T204fs mutations are unlikely to act as dominant negatives. The spectrum and pattern of mutations observed is consistent with CTCF acting as a haploinsufficient tumor suppressor.

The landscape of microsatellite instability in colorectal and endometrial cancer genomes

Microsatellites-simple tandem repeats present at millions of sites in the human genome-can shorten or lengthen due to a defect in DNA mismatch repair. We present here a comprehensive genome-wide analysis of the prevalence, mutational spectrum, and functional consequences of microsatellite instability (MSI) in cancer genomes. We analyzed MSI in 277 colorectal and endometrial cancer genomes (including 57 microsatellite-unstable ones) using exome and whole-genome sequencing data. Recurrent MSI events in coding sequences showed tumor type specificity, elevated frameshift-to-inframe ratios, and lower transcript levels than wild-type alleles. Moreover, genome-wide analysis revealed differences in the distribution of MSI versus point mutations, including overrepresentation of MSI in euchromatic and intronic regions compared to heterochromatic and intergenic regions, respectively, and depletion of MSI at nucleosome-occupied sequences. Our results provide a panoramic view of MSI in cancer genomes, highlighting their tumor type specificity, impact on gene expression, and the role of chromatin organization.

Gynecologic cancers: molecular updates

This article reviews the molecular features and pathogenesis of gynecologic malignancies. Understanding the molecular basis of endometrial carcinoma helps to provide an explanation for the prognosis of these tumors and opens up avenues for research into novel therapies that may prove beneficial.

Histological features associated with occult lymph node metastasis in FIGO clinical stage I, grade I endometrioid carcinoma

AIMS

Lymph node involvement affects prognosis/treatment in endometrial carcinoma patients. We assessed various histological features associated with nodal metastasis in patients with grade I, stage I endometrial endometrioid carcinoma (EEC).

METHODS AND RESULTS

Eighteen stage I EECs with occult positive lymph nodes and 36 controls were assessed for depth of myoinvasion; microcystic, elongated and fragmented (MELF) pattern of myometrial invasion; lymphovascular invasion (LVI); and epithelial metaplasia. Nodal metastases were subclassified as isolated tumour cells (ITCs; ≤0.2 mm), micrometastasis (>0.2 mm and <2 mm), or macrometastasis (≥2 mm). Node-positive cases had significantly higher rates of LVI (P < 0.001) and MELF invasion (P = 0.003) on univariate analysis. Only LVI was associated significantly with nodal metastasis on multivariate analysis (P = 0.002). Tumours with MELF invasion demonstrated reduced E-cadherin expression. Macrometastases were identified in seven cases (39%) with or without micrometastasis/ITCs. Eight (44%) contained only ITCs. Eleven (61%) had histiocyte-like nodal metastases. Biopsy material from four of six (67%) and five of 17 (29%) cases with and without nodal metastasis showed detached eosinophilic tumour cell buds. Of the former, three were associated with histiocyte-like nodal metastases - a feature absent in biopsies without tumour budding.

CONCLUSIONS

Lymph nodes from grade I EEC exhibiting cellular budding or LVI should be examined for occult metastases, especially in the form of histiocyte-like cells.

FGFR signalling in women's cancers

FGFs, in a complex with their receptors (FGFRs) and heparan sulfate (HS), are responsible for a range of cellular functions, from embryogenesis to metabolism. Both germ line and somatic FGFR mutations are known to play a role in a range of diseases, most notably craniosynestosis dysplasias, dwarfism and cancer. Because of the ability of FGFR signalling to induce cell proliferation, migration and survival, FGFRs are readily co-opted by cancer cells. Mutations in, and amplifications of, these receptors are found in a range of cancers with some of the most striking clinical findings relating to their contribution to pathogenesis and progression of female cancers. Here, we outline the molecular mechanisms of FGFR signalling and discuss the role of this pathway in women's cancers, focusing on breast, endometrial, ovarian and cervical carcinomas, and their associated preclinical and clinical data. We also address the rationale for therapeutic intervention and the need for FGFR-targeted therapy to selectively target cancer cells in view of the fundamental roles of FGF signalling in normal physiology.

Relationship between PTEN, DNA mismatch repair, and tumor histotype in endometrial carcinoma: retained positive expression of PTEN preferentially identifies sporadic non-endometrioid carcinomas

Loss of PTEN (phosphatase and tensin homolog) expression and microsatellite instability are two of the more common molecular alterations in endometrial carcinoma. From the published literature, it is controversial as to whether there is a relationship between these different molecular mechanisms. Therefore, a cohort of 187 pure endometrioid and non-endometrioid endometrial carcinomas, carefully characterized as to clinical and pathological features, was examined for PTEN sequence abnormalities and the immunohistochemical expression of PTEN and the DNA mismatch repair proteins MLH1, MSH2, MSH6, and PMS2. MLH1 methylation analysis was performed when tumors had loss of MLH1 protein. Mismatch repair protein loss was more frequent in endometrioid carcinomas compared with non-endometrioid carcinomas, a difference primarily attributable to the presence of MLH1 methylation in a greater proportion of endometrioid tumors. Among the non-endometrioid group, mixed endometrioid/non-endometrioid carcinomas were the histotype that most commonly had loss of a mismatch repair protein. In endometrioid tumors, the frequency of PTEN loss measured by immunohistochemistry and mutation did not differ significantly between the mismatch repair protein intact or mismatch repair protein loss groups, suggesting that PTEN loss is independent of mismatch protein repair status in this group. However, in non-endometrioid carcinomas, both intact positive PTEN immunohistochemical expression and PTEN wild type were highly associated with retained positive expression of mismatch repair proteins in the tumor. Relevant to screening endometrial cancers for Lynch Syndrome, an initial PTEN immunohistochemistry determination may be able to replace the use of four mismatch repair immunohistochemical markers in 63% of patients with non-endometrioid endometrial carcinoma. Therefore, PTEN immunohistochemistry, in combination with tumor histotype, is a useful adjunct in the clinical evaluation of endometrial carcinomas for Lynch Syndrome.

Anthropometric measures and the risk of endometrial cancer, overall and by tumor microsatellite status and histological subtype

Obesity is an established risk factor for endometrial cancer, but this association is not well understood for subtypes of endometrial cancer. We evaluated the association of recent and adult-life obesity with subtypes of endometrial cancer based on microsatellite status (microsatellite-stable (MSS) vs. microsatellite-instable (MSI)) and histology (type I vs. type II). Analyses were based on a population-based case-control study (524 cases and 1,032 controls) conducted in Alberta, Canada (2002-2006) and included the following groupings of subtypes: MSS = 337 and MSI = 130; type I = 458 and type II = 66. Logistic and polytomous logistic regression were used to estimate odds ratios and 95% confidence intervals for overall endometrial cancer and subtypes of endometrial cancer, respectively. The risks of all subtypes of endometrial cancer, except type II, increased with an increase in all of the anthropometric characteristics examined. The risks for MSI tumors were suggestively stronger than those for MSS tumors; the risk with high (≥30) body mass index (weight (kg)/height (m)(2)) was significantly stronger for MSI tumors (odds ratio = 4.96, 95% confidence interval: 2.76, 8.91) than for MSS tumors (odds ratio = 2.33, 95% confidence interval: 1.66, 3.28) (P-heterogeneity = 0.02). Obesity is associated with most subtypes of endometrial cancer, and further studies are warranted to elucidate the biological mechanisms underlying the stronger risk for the MSI subtype with a high body mass index.

Molecular pathology of endometrial carcinoma

This review paper discusses the main molecular alterations of endometrial carcinoma, the most common cancer of the female genital tract. Two clinicopathological variants are recognized: the oestrogen-related (type I, endometrioid carcinoma) and the non-oestrogen-related (type II, non-endometrioid carcinoma). Whereas type I shows microsatellite instability and mutations in PTEN, PIK3CA, K-RAS and CTNNB1 (beta-catenin), type II exhibits TP53 mutations and chromosomal instability. Recent investigations regarding the role of non-coding RNA have provided important information regarding tumour progression. Understanding pathogenesis at the molecular level is essential for identifying biomarkers of potential use in targeted therapies.

Sequencing of candidate chromosome instability genes in endometrial cancers reveals somatic mutations in ESCO1, CHTF18, and MRE11A

Most endometrial cancers can be classified histologically as endometrioid, serous, or clear cell. Non-endometrioid endometrial cancers (NEECs; serous and clear cell) are the most clinically aggressive of the three major histotypes and are characterized by aneuploidy, a feature of chromosome instability. The genetic alterations that underlie chromosome instability in endometrial cancer are poorly understood. In the present study, we used Sanger sequencing to search for nucleotide variants in the coding exons and splice junctions of 21 candidate chromosome instability genes, including 19 genes implicated in sister chromatid cohesion, from 24 primary, microsatellite-stable NEECs. Somatic mutations were verified by sequencing matched normal DNAs. We subsequently resequenced mutated genes from 41 additional NEECs as well as 42 endometrioid ECs (EECs). We uncovered nonsynonymous somatic mutations in ESCO1, CHTF18, and MRE11A in, respectively, 3.7% (4 of 107), 1.9% (2 of 107), and 1.9% (2 of 107) of endometrial tumors. Overall, 7.7% (5 of 65) of NEECs and 2.4% (1 of 42) of EECs had somatically mutated one or more of the three genes. A subset of mutations are predicted to impact protein function. The co-occurrence of somatic mutations in ESCO1 and CHTF18 was statistically significant (P = 0.0011, two-tailed Fisher's exact test). This is the first report of somatic mutations within ESCO1 and CHTF18 in endometrial tumors and of MRE11A mutations in microsatellite-stable endometrial tumors. Our findings warrant future studies to determine whether these mutations are driver events that contribute to the pathogenesis of endometrial cancer.

Hormonal and reproductive risk factors for sporadic microsatellite stable and unstable endometrial tumors

Hormonal and reproductive factors modulate bioavailable estrogen to influence endometrial cancer risk. Estrogen affects the microsatellite status of tumors, but the relation between these estrogen-related factors and microsatellite instability (MSI) status of endometrial tumors is not known. We evaluated associations between hormonal and reproductive factors and risks of microsatellite stable (MSS) and MSI endometrial cancer among postmenopausal women (MSS cases = 258, MSI cases = 103, and controls = 742) in a population-based case-control study in Alberta, Canada (2002-2006). Polytomous logistic regression was used to estimate ORs and 95% confidence intervals (95% CI). We observed a significant trend in risk reduction for MSI (Ptrend = 0.005) but not MSS (Ptrend = 0.23) cancer with oral contraceptive use; with 5-year use or more, the risk reduction was stronger for MSI (OR = 0.42; 95% CI, 0.23-0.77) than for MSS cancer (OR = 0.80; 95% CI, 0.54-1.17; Pheterogeneity = 0.05). For more recent use (<30 years), the risk reduction was stronger for MSI (OR = 0.36; 95% CI, 0.19-0.69) than for MSS cancer (OR = 0.77; 95% CI, 0.51-1.15; Pheterogeneity = 0.032). No differential risk associations were observed for menopausal hormone use, parity and age at menarche, menopause or first pregnancy. We found limited evidence for statistical heterogeneity of associations of endometrial cancer risk with hormonal and reproductive factors by MSI status, except with oral contraceptive use. This finding suggests a potential role for the MMR system in the reduction of endometrial cancer risk associated with oral contraceptive use, although the exact mechanism is unclear. This study shows for the first time that oral contraceptive use is associated with a reduced risk for MSI but not for MSS endometrial cancer.

Primary squamous cell carcinoma of the endometrium unrelated to human papilloma virus: a molecular study

In this paper we report a molecular study of a case of Primary Endometrial Squamous Carcinoma (PESC), in which a Human Papilloma Virus (HPV) infection had been previously excluded by Polymerase Chain Reaction (PCR). The studies performed in an effort to explain the carcinogenesis included immunohistochemical over-expression of p53 and p16 proteins as previously observed in our own papers, plus microsatellite analysis of D10S1765 at 10q23.3 (PTEN) and TP53 at 17p13.1 (P53) as well as the methylation status of the of BRCA1 and p16 promoters using specific PCRs. In this rare malignancy, we found allelic imbalance (AI) at 17p13.1 (P53). Instead, AI at D10S1765 (PTEN) gene was absent. The genetic alteration of p53, with hyper-expression of p53 protein and an absence of abnormalities in the PTEN gene are consistent with the similarities between Uterine Serous Carcinoma (USC) and our case of PESC. The aberrant methylation of both p16 and BCAR1 promoters was not detected in our case. This finding too could imply that ESC is more similar to Uterine Serous Carcinoma than Uterine Endometrioid Carcinoma (UEC). Moreover, the lack of aberrant methylation of p16, which is in accordance with over-expression of p16 immunoreactivity, in the absence of HPV infection may be related to other unknown genetic alterations. In our opinion, it is hard to reach any definite conclusion concerning the carcinogenesis of PESC, because of its rarity and the very few molecular studies reported in the literature. Further studies with more numerous cases and larger molecular analyses are mandatory for this malignancy, to confirm whether it is more closely related to papillary endometrial cancer than to endometrioid carcinoma.

Molecular targets and targeted therapeutics in endometrial cancer

PURPOSE OF REVIEW

Endometrial cancer is the most common gynaecological malignancy in the western world. Two clinicopathological subtypes are recognized: type I (endometrioid) and type II (nonendometrioid) carcinomas. This review describes the molecular alterations in endometrial cancer and how this knowledge is leading to the development of novel treatments in this area.

RECENT FINDINGS

Molecularly targeted agents have entered clinical trials in endometrial cancer. So far, mechanistic target of rapamycin (mTOR) inhibitors and antiangiogenic agents appear promising and are being pursued further in addition to other targeted approaches.

SUMMARY

The clinicopathological and molecular heterogeneity of endometrial cancer needs to be taken into account in the design of future clinical trials as well as the incorporation of robust biomarkers for the success of therapeutic strategies in endometrial cancer.

Endometrial carcinoma: molecular alterations involved in tumor development and progression

In the western world, endometrial carcinoma (EC) is the most common cancer of the female genital tract. The annual incidence has been estimated at 10-20 per 100,000 women. Two clinicopathological variants are recognized: the estrogen related (type I, endometrioid) and the non-estrogen related (type II, non-endometrioid).The clinicopathological differences are paralleled by specific genetic alterations, with type I showing microsatellite instability and mutations in phosphatase and tensin homologue deleted on chromosome 10, PIK3CA, K-RAS and CTNNB1 (β-catenin), and type II exhibiting TP53 mutations and chromosomal instability. Some non-endometrioid carcinomas probably arise from pre-existing endometrioid carcinomas as a result of tumor progression and, not surprisingly, some tumors exhibit combined or mixed features at the clinical, pathological and molecular levels. In EC, apoptosis resistance may have a role in tumor progression. Understanding pathogenesis at the molecular level is essential in identifying biomarkers for successful targeted therapies. In this review, the genetic changes of endometrial carcinogenesis are discussed in the light of the morphological features of the tumors and their precursors.

The genomics and genetics of endometrial cancer

Most sporadic endometrial cancers (ECs) can be histologically classified as endometrioid, serous, or clear cell. Each histotype has a distinct natural history, clinical behavior, and genetic etiology. Endometrioid ECs have an overall favorable prognosis. They are typified by high frequency genomic alterations affecting PIK3CA, PIK3R1, PTEN, KRAS, FGFR2, ARID1A (BAF250a), and CTNNB1 (β-catenin), as well as epigenetic silencing of MLH1 resulting in microsatellite instability. Serous and clear cell ECs are clinically aggressive tumors that are rare at presentation but account for a disproportionate fraction of all endometrial cancer deaths. Serous ECs tend to be aneuploid and are typified by frequent genomic alterations affecting TP53 (p53), PPP2R1A, HER-2/ERBB2, PIK3CA, and PTEN; additionally, they display dysregulation of E-cadherin, p16, cyclin E, and BAF250a. The genetic etiology of clear cell ECs resembles that of serous ECs, but it remains relatively poorly defined. A detailed discussion of the characteristic patterns of genomic alterations that distinguish the three major histotypes of endometrial cancer is reviewed herein.

DNA methylation in endometrial cancer

Endometrial cancer is the most commonly diagnosed gynecological cancer, and it has been shown to be a complex disease driven by abnormal genetic, and epigenetic alterations, as well as environmental factors. Epigenetic changes resulting in aberrant gene expression are dynamic and modifiable features of many cancer types. A significant epigenetic change is aberrant DNA methylation. In this review, we review evidence on the role of aberrant DNA methylation, examining changes in relation to endometrial carcinogenesis, and report on recent advances in the understanding of the contribution of aberrant DNA methylation to endometrial cancer with the emphasis on the role of dietary/ lifestyle and environmental factors, as well as opportunities and challenges of DNA methylation in endometrial cancer management and prevention.

Molecular pathogenesis of endometrial and ovarian cancer

Pregnancy, breastfeeding, and oral contraceptive pill use interrupt menstrual cycles and reduce endometrial and ovarian cancer risk. This suggests the importance of turnover within Mullerian tissues, where the accumulation of mutations in p53 and PTEN has been correlated with number of cycles. The most common type of endometrial cancer (Type I) is endometrioid and molecular abnormalities include mutations in PTEN, KRAS and β-catenin. The Type I precursor is Endometrial Intraepithelial Neoplasia which displays PTEN defects. Type II endometrial cancer (whose precursors are less clear) includes serous and clear cell tumors and the most common alteration is p53 mutation. For ovarian cancer, histopathologic types parallel endometrial cancer and include serous, mucinous, endometrioid, and clear cell; some molecular features are also shared. The most frequent type of ovarian cancer is high grade serous that often displays p53 mutation and its precursor lesions may originate from normal-appearing fallopian tube epithelium that contains a p53 "signature". Mutations in KRAS, BRAF and PTEN are described in mucinous, endometrioid and low grade serous cancers and these may originate from ovarian cortical inclusion cysts. A consideration of molecular and other pathogenetic features, like epidemiology and histopathology, may provide a better understanding of endometrial and ovarian cancer.

Precursors of endometrial and ovarian carcinoma

This review discusses precursor lesions of endometrial and ovarian carcinoma with an emphasis on the unique molecular alterations that have led to the development of binary classification schemes for tumors of both the endometrium and ovary. While such a system is well established for endometrial carcinoma, only recently has a binary classification scheme been proposed for ovarian carcinoma. For both, the morphologic and molecular genetic-defining characteristics of their respective precursor lesions are described in detail. Furthermore, similarities and differences of the precursor lesions of specific tumors of these two genital tract organs are also addressed with a brief discussion of the clinical implications of their diagnosis.

DNA mismatch repair deficiency in endometrial carcinoma

Microsatellite instability (MSI) is the hallmark of a molecular pathway to carcinogenesis due to sporadic or inherited abnormalities of DNA mismatch repair genes. Inherited mutations are seen in hereditary nonpolyposis colorectal cancer syndrome. Endometrial carcinoma shows as high an incidence of MSI as does colorectal carcinoma. This review provides a framework for the gynecologic pathologist to understand the complexities of MSI in endometrial carcinoma, by discussing the basic mechanisms of mismatch repair and carcinogenesis, testing, the morphologic features of MSI endometrial cancer and the contradictory data regarding prognosis.

Endometrial hyperplasia and the risk of progression to carcinoma

The primary presenting symptom of endometrial neoplasia is abnormal uterine bleeding, which typically prompts an endometrial biopsy to rule out carcinoma. Approximately 70% of women with abnormal uterine bleeding are diagnosed with benign findings and 15% are diagnosed with carcinoma. The remaining 15% receive a diagnosis of endometrial hyperplasia (EH), which includes a broad range of lesions, from mild, reversible proliferations to the immediate precursors of carcinoma. The widely used World Health Organization (WHO) system classifies EH according to four combinations of glandular crowding and nuclear atypia: simple (SH), complex (CH), simple atypical (SAH), or complex atypical hyperplasia (CAH), although the two forms of atypical hyperplasia (AH) are often collapsed into one category. Diagnoses of EH raise three issues. First, the low interobserver reproducibility-less than 50% in almost all studies-hinders the ability of WHO-based classification to effectively guide clinical management. Second, approximately 50% of women diagnosed with AH have concurrent carcinoma. Not surprisingly, most women with AH undergo hysterectomy as primary treatment, but non-surgical management can be effective. Third, data on progression risks for women with EH who retain their uterus are extremely limited. Emerging data indicate the long-term risk among women with SH or CH is less than 5%, but the risk among women with AH is approximately 30%. These data highlight priority areas for future research, such as increasing the diagnostic reproducibility of EH, improving the discrimination between AH and carcinoma, and identifying biomarkers to stratify risks or serve as indicators of response to clinical treatment.

Microsatellite instability at a tetranucleotide repeat in type I endometrial carcinoma

BACKGROUND

Microsatellite instability (MSI) at tri- or tetranucleotide repeat markers (elevated microsatellite alterations at selected tetranucleotide repeat, EMAST) has been recently described. But, the underlying genetic mechanism of EMAST is unclear. This study was to investigate the prevalence of EMAST, in type I endometrial carcinoma, and to determine the correlation between the MSI status and mismatch repair genes (MMR) or p53.

METHODS

We examined the 3 mono-, 3 di-, and 6 tetranucleotide repeat markers by PCR in 39 cases of type I endometrial carcinoma and performed the immunohistochemistry of hMSH2, hMLH1, and p53 protein.

RESULTS

More than two MSI at mono- and dinucleotide repeat markers was noted in 8 cases (MSI-H, 20.5%). MSI, at a tetranucleotide repeat, was detected in 15 cases (EMAST, 38.5%). In remaining 16 cases, any MSI was not observed. (MSS, 42.1%), MSI status was not associated with FIGO stage, grade or depth of invasion. The absence of expression of either one of both hMSH2 or hMLH1 was noted in seven (87.5%) of eight MSI-H tumors, one (6.3%) of 16 MSS tumors, and five (33.3%) of 15 EMAST tumors. (p = 0.010) The expression of p53 protein was found in one (12.5%) of eight MSI-H tumors, five (31.3%) of 16 MSS tumors, and seven of 15 EMAST tumors. (p = 0.247)

CONCLUSION

Our results showed that about 38.5% of type I endometrial carcinomas exhibited EMAST, and that EMAST was rarely associated with alteration of hMSH2 or hMLH1.

Current issues in the management of endometrial cancer

Endometrial cancer (EC) remains the most common gynecologic malignancy in the United States. It is expected to become more common as the prevalence of obesity, one of the most common risk factors for EC, increases worldwide. The 2 main histologic subcategories of EC, endometrioid and nonendometrioid EC, show unique molecular aberrations and are responsible for markedly disparate clinical behaviors. The primary treatment of EC is surgery, ie, hysterectomy, removal of the adnexa, and pelvic and para-aortic lymphadenectomy, either via laparotomy or endoscopic techniques. Adjuvant therapy is necessary for patients at high risk of recurrence and consists of vaginal brachytherapy, teletherapy, systemic chemotherapy, or some combination thereof. Multi-institutional trials are in progress in this country and in Europe to better define optimal adjuvant treatment for subsets of patients, as well as the role of surgical staging in reducing both overuse and underuse of radiation therapy. Hormonal therapy is an option for some young women with EC who wish to preserve fertility. This review summarizes the diagnosis and management of EC and discusses current controversies and upcoming investigations pertaining to EC staging and adjuvant treatment.

Hormonal heterogeneity of endometrial cancer

Endometrial cancer is the most common malignant tumor of the female genital tract in the developed world. Increasing evidence suggests that the majority of cases can be divided into two different types ofendometrial cancer based on clinico-pathological and molecular characteristics. Type I is associated with an endocrine milieu of estrogen predominance. These tumors are ofendometroid histology and develop from endometrial hyperplasia. They have good prognosis and are sensitive to endocrine treatment. Type II endometrial cancers are not associated with a history of unopposed estrogens and develop from the atrophic endometrium of elderly women. Mainly, they are of serous papillary or clear cell morphology, have a poor prognosis and do not react to endocrine treatment. Both types of endometrial cancer probably differ markedly with regard to the molecular mechanisms of transformation. The transition from normal endometrium to a malignant tumor is thought to involve a stepwise accumulation of alterations in cellular mechanisms leading to dysfunctional cell growth. This chapter reviews the current knowledge of the molecular mechanisms commonly associated with development of type I and type II endometrial cancer.

Routinely assessed morphological features correlate with microsatellite instability status in endometrial cancer

Microsatellite instability (MSI) has been shown to be important in the molecular pathogenesis of both sporadic and inherited endometrial carcinomas of endometrioid type. It is likely prognostically significant as well. The aim of this study was to determine whether MSI phenotype in endometrial carcinoma was associated with specific morphologic patterns and therefore predictable by tumor morphology. The study subjects consisted of 102 patients with nearly equal representation of MSI high (MSI-H; n = 52) and non-MSI-H (n = 50) endometrial tumors. Microsatellite instability was determined by the standard polymerase chain reaction method using the National Cancer Institute-recommended set of 5 markers. The MSI-H and non-MSI-H groups were matched for patient age, race, histologic type (all endometrioid), International Federation of Gynecology and Obstetrics grade, and disease stage. Assessed morphological features included host inflammatory response (tumor infiltrating lymphocytes [TILs], peritumoral lymphocytes, peritumoral lymphoid follicles, and neutrophilic infiltration), tumor characteristics (cytologic grade, growth pattern, tumor heterogeneity, invasion pattern, metaplastic changes, necrosis, and lymphovascular invasion), and background endometrium (hyperplasia, atrophy, and polyp). Of all the features examined, TIL counts and peritumoral lymphocytes correlated significantly with MSI-H status. Their statistical relationship was strengthened in the presence of a nonpapillary growth pattern and endometrial hyperplasia. On multivariate analysis, TIL counts and peritumoral lymphocytes remained independent predictors for MSI-H status. At a cutoff point of 40 TILs/10 high power fields, TIL counts had a sensitivity of 85% in predicting MSI status in endometrioid endometrial carcinoma, with a specificity of 46%. This specificity increased as higher cutoff points were selected, but sensitivity decreased. Given that analogous features have been encountered in MSI-H colorectal cancers, our findings suggest a similar relationship between tumor phenotype and DNA mismatch repair abnormalities in both endometrial and colorectal tumors. Therefore, morphological patterns encountered in endometrial carcinoma may prove useful in screening tumors under consideration for MSI testing and identifying appropriate patients for referral to a genetic counseling service.

Endometrial carcinoma: pathology and genetics

In the Western world, endometrial carcinoma is the most common malignant tumour of the female genital tract and the fourth most common cancer in women after carcinomas of breast, colorectum, and lung. The annual incidence has been estimated at 10-20 per 100 000 women. In the United States, endometrial carcinoma accounts for approximately 6000 deaths per year. Two different clinicopathological subtypes are recognised: the oestrogen-related (type I, endometrioid) and the non-oestrogen related (type II, non-endometrioid). The clinicopathological differences are parallelled by specific genetic alterations, with type I showing microsatellite instability and mutations in PTEN, PIK3CA, K-Ras, and CTNNB1 (beta-catenin), and type II exhibiting p53 mutations and chromosomal instability. This article reviews the genetic changes of endometrial carcinogenesis in the light of morphological features of the tumours and their precursors.

Loss of hMLH1 expression is associated with less aggressive clinicopathological features in sporadic endometrioid endometrial adenocarcinoma

AIM

To assess the incidence and clinicopathological significance of microsatellite instability (MSI) and the protein expression of hMLH1 and hMSH2 in sporadic endometrioid endometrial adenocarcinoma (SEEA).

METHODS

A total of 50 patients with pure endometrioid sporadic endometrial adenocarcinoma were enrolled in the study. MSI analysis was done using five polymorphic markers (BAT26, D5S346, BAT25, D17S250, D2S123) and the protein expression of the hMLH1 and hMSH2 genes was determined by immunohistochemical staining. MSI was detected in 24% (12/50) of SEEA cases.

RESULTS

There was a significant correlation between MSI status and loss of hMLH1, hMSH2 expression, respectively. No significant association was found between MSI status and clinicopathological parameters, including age, grade, stage, depth of myometrial invasion, lymph-vascular space invasion (LVI), lymph node involvement or peritoneal cytology. However, significant correlations were found between loss of hMLH1 and a lower histological grade and the absence of LVI in patients with SEEA.

CONCLUSIONS

According to these results, MSI and a loss of protein expression of hMLH1 and hMSH2 may be associated with the pathogenesis of SEEA. In addition, hMLH1 immunostaining might have a role as a prognostic parameter. Further research using a large number of cases is needed to confirm our observations.

Molecular and Pathologic Aspects of Endometrial Carcinogenesis

Endometrial cancer is the most common gynecological malignancy, with 41,000 new cases projected in the United States for 2006. Two different clinicopathologic subtypes are recognized: the estrogen-related (type I, endometrioid) and the non–estrogen-related types (type II, nonendometrioid such as papillary serous and clear cell). The morphologic differences in these cancers are mirrored in their molecular genetic profile with type I showing defects in DNA-mismatch repair and mutations in PTEN, K-ras, and beta-catenin, and type II showing aneuploidy and p53 mutations. This article reviews the genetic aspects of endometrial carcinogenesis and progression. We will define the precursor lesion of type I endometrioid cancer and the role of genetics and estrogen in its progression.

Birt-Hogg-Dubé gene mutations in human endometrial carcinomas with microsatellite instability

Birt-Hogg-Dubé (BHD) syndrome is a rare form of autosomal dominantly inherited genodermatosis characterized by benign hamartomatous skin lesions named fibrofolliculomas, and an increased risk for developing pulmonary cyst/pneumothorax and various forms of renal cell carcinoma. Many of the patients harbour insertion/deletion mutations in the hypermutable poly(C)8 tract in exon 11 of the BHD gene. This mutational hot spot is also reported to be a target of mutation in microsatellite instability (MSI) sporadic colorectal cancer. To test the hypothesis that the BHD gene is also a mutational target in sporadic endometrial carcinoma with microsatellite instability, 139 cases of sporadic endometrial carcinoma were screened for MSI status, and mutations of the poly(C)8 tract in exon 11 as well as other coding exons of the BHD gene. The poly(G)8 tract of the BAX gene, the poly(C)8 tract of MSH6, and methylation status of hMLH1 were also assessed. Thirty-nine of 139 cases (28%) showed MSI. Mutations in the poly(C)8 tract of BHD were detected in five of the 39 MSI cases (12.8%). Of these, one showed additional mutation in exon 4, possibly satisfying the two-hit hypothesis of tumour suppressor genes. BAX gene mutation was detected in ten of the 39 MSI cases (25.6%). Four tumours showed both BAX and BHD mutations, and a significant positive association was found between mutations of the two genes. No association was found between BHD status and MSH6 mutation or hMLH1 methylation. When multiple foci were microdissected and individually screened for mutation, BHD mutations were shown to have been acquired during tumour progression, after mutation of the BAX gene, in three of five cases. Taken together, these findings show that the BHD gene is a target gene in MSI endometrial carcinoma. However, its mutational frequency is lower than that of BAX, and BHD mutation tends to occur during neoplastic progression after the acquisition of mutations in another MSI target gene, BAX.

Clinicopathologic Significance of Defective DNA Mismatch Repair in Endometrial Carcinoma

Purpose

Defective DNA mismatch repair is commonly present in sporadic manifestations of gastrointestinal, endometrial, and other cancers. The pathognomonic molecular manifestation of this repair defect is microsatellite instability (MSI). Here, we test the hypothesis that MSI predicts the clinicopathologic features of endometrial carcinoma.

Patients and Methods

A retrospective cohort of 473 patients treated for endometrial carcinoma at this institution was identified. All cases were reviewed by a gynecologic pathologist, and clinical information was abstracted from medical records. Using consensus criteria, DNA samples from nontumor and tumor tissue pairs were genotyped for MSI. Associations between MSI status and pathologic and clinical variables were assessed.

Results

Ninety-three (20%) of 473 tumors were MSI+. In the MSI+ tumor group compared with the MSI− tumor group, the proportion of advanced compared with early-stage tumors was higher (92% v 81%; P = .01), as was the proportion of tumors of endometrioid compared with nonendometrioid histologic subtype (94% v 23%; P = .001), and the proportion of tumors with myometrial invasion compared with those with none (92% v 78%; P = .01). By multivariate analyses, disease-free survival (hazard ratio, 0.3; 95% CI, 0.2 to 0.7) and disease-specific survival (hazard ratio, 0.3; 95% CI, 0.1 to 0.8) were significantly improved in patients with MSI+ tumors.

Conclusion

In endometrial carcinoma, the presence of MSI was independently associated with a more favorable clinical outcome.

Cell cycle regulators and apoptosis-associated proteins in relation to proliferative activity and degree of apoptosis in HNPCC versus sporadic endometrial carcinoma

AIMS

Mismatch repair gene malfunction occurs early in the carcinogenesis of hereditary non-polyposis colorectal cancers (HNPCCs), leading to an accelerated accumulation of mutations and possibly to change in expression of cell cycle proteins. There is strong evidence that tumorigenesis in HNPCCs differs from sporadic ones. HNPCC-related endometrial cancers are less well studied. Our aim was to compare expression of cell cycle and apoptosis-related proteins in relation to proliferation and apoptosis in HNPCC-related and sporadic endometrial cancers to identify differences in their carcinogenetic pathways.

METHODS AND RESULTS

Eighteen HNPCC-related endometrial cancers, each matched by tumour type, stage and grade with two sporadic endometrial cancers, were examined for proliferation, apoptosis and the expression of oestrogen and progesterone receptors, cyclin B1, D3 and E, p21, p27, bcl-2, bax, p53 and COX-2. No differences in proliferation or apoptotic indices were detected between HNPCC-related and sporadic endometrial cancers. Cyclin B1 expression was significantly higher in HNPCC-related cancers than in sporadic endometrial cancers. More HNPCC-related endometrial cancers had total loss of bax expression.

CONCLUSIONS

Apart from differences in cyclin B1 and bax expression, HNPCC-related and sporadic endometrial cancers are comparable. The subtle differences detected are consistent with the minor clinical diversity between HNPCC-related and sporadic endometrial cancers.

RASSF1A hypermethylation and its inverse correlation withBRAF and/orKRAS mutations in MSI-associated endometrial carcinoma

Both hypermethylation of the tumor suppressor gene RASSF1A and activating mutations of the KRAS and/or BRAF gene have been reported in a variety of human cancers. To investigate these epigenetic and genetic alterations in endometrial carcinoma (EC), we examined their frequency in 4 uterine EC cell lines and in 75 sporadic primary ECs. Using methylation specific PCR, we found RASSF1A methylation in 25 of 75 (33.3%) ECs. RASSF1A methylation was significantly associated with microsatellite instability (MSI, p < 0.001) and also with hMLH1 methylation (p < 0.001). KRAS mutations were detected in 14 of 75 (18.7%) ECs. BRAF mutations were identified in only 3 of 75 (4.0%) ECs and were not found in ECs with KRAS mutations or RASSF1A methylation. RASSF1A methylation was more frequent in KRAS mutation-negative ECs than in KRAS mutation-positive ECs (37.7% vs 14.3%), but this inverse correlation is not statistically significant (p = 0.122). However, we observed that RASSF1A methylation was inversely correlated with KRAS and/or BRAF mutations (p = 0.028) in MSI-negative ECs, while this inverse correlation disappeared in MSI-positive ECs. Furthermore, in MSI-positive ECs, 2 cases of concomitant RASSF1A methylation and KRAS mutation were found. Taken together, these results provide strong evidence that, in EC tumorigenesis, RASSF1A promoter hypermethylation is as important as KRAS mutations in activating the RAS pathway.

Two Japanese kindreds occurring endometrial cancer meeting new clinical criteria for hereditary non-polyposis colorectal cancer (HNPCC), Amsterdam Criteria II

Hereditary non-polyposis colorectal cancer (HNPCC), also called Lynch syndrome, is an autosomal dominantly inherited disorder of cancer susceptibility. Patients with HNPCC exhibit an increased risk for HNPCC-associated extracolonic tumors such as cancer of the endometrium. HNPCC is associated with germline mutations in DNA mismatch repair (MMR) genes: hMLH1, hMSH2 and hMSH6. Here, we describe two Japanese kindreds (0.5%) who met the new clinical criteria for HNPCC, Amsterdam criteria II, from among 375 endometrial cancer patients treated at Keio University Hospital from 1990 to 2002. From these results, it was found that female HNPCC patients comprised approximately 0.5% of all endometrial cancer patients. Decreased expression of two MMR gene protein products (hMLH1 and hMSH6) was confirmed immunohistochemically in these two endometrial tumors in HNPCC kindreds. This case report provides important information on Japanese HNPCC patients occurring endometrial cancer.