Clinical and pathologic significance of microsatellite instability in endometrial cancer

Clinicopathologic Significance of Mismatch Repair Defects in Endometrial Cancer: An NRG Oncology/Gynecologic Oncology Group Study

PURPOSE

The clinicopathologic significance of mismatch repair (MMR) defects in endometrioid endometrial cancer (EEC) has not been definitively established. We undertook tumor typing to classify MMR defects to determine if MMR status is prognostic or predictive.

METHODS

Primary EECs from NRG/GOG0210 patients were assessed for microsatellite instability (MSI), MLH1 methylation, and MMR protein expression. Each tumor was assigned to one of four MMR classes: normal, epigenetic defect, probable mutation (MMR defect not attributable to MLH1 methylation), or MSI-low. The relationships between MMR classes and clinicopathologic variables were assessed using contingency table tests and Cox proportional hazard models.

RESULTS

A total of 1,024 tumors were assigned to MMR classes. Epigenetic and probable mutations in MMR were significantly associated with higher grade and more frequent lymphovascular space invasion. Epigenetic defects were more common in patients with higher International Federation of Gynecology and Obstetrics stage. Overall, there were no differences in outcomes. Progression-free survival was, however, worse for women whose tumors had epigenetic MMR defects compared with the MMR normal group (hazard ratio, 1.37; P < .05; 95% CI, 1.00 to 1.86). An exploratory analysis of interaction between MMR status and adjuvant therapy showed a trend toward improved progression-free survival for probable MMR mutation cases.

CONCLUSION

MMR defects in EECs are associated with a number of well-established poor prognostic indicators. Women with tumors that had MMR defects were likely to have higher-grade cancers and more frequent lymphovascular space invasion. Surprisingly, outcomes in these patients were similar to patients with MMR normal tumors, suggesting that MMR defects may counteract the effects of negative prognostic factors. Altered immune surveillance of MMR-deficient tumors, and other host/tumor interactions, is likely to determine outcomes for patients with MMR-deficient tumors.

Frequent mutations in the RPL22 gene and its clinical and functional implications

OBJECTIVE

To determine the frequency and spectrum of mutations in RPL22 a gene identified by The Cancer Genome Atlas (TCGA) as mutated in endometrioid endometrial cancer, and determine the relationship between RPL22 defects and clinicopathologic features.

METHODS

Direct sequencing of the entire coding region of the RPL22 cDNA and exons 2/4 was performed in tumors with/without microsatellite instability (MSI). RPL22 expression was assessed by immunofluorescence microscopy in the KLE, RL952 and AN3CA cell lines, wildtype, heterozygous and homozygous mutants, respectively. Relationships between RPL22 mutation and clinicopathological features were assessed using Chi-squared analysis and Student's t test. Progression-free survival (PFS) was calculated from the date of diagnosis to the date of recurrence.

RESULTS

A single nucleotide deletion in an A8 coding repeat was identified in exon 2 of the RPL22 gene in 116/226 (52%) of MSI-high tumors. No mutations were identified in MSI-stable tumors. Only 2% of the tumors expressed a homozygous A deletion. RPL22 mutation was not associated with stage, grade, race and lymphovascular space invasion. Women whose tumors harbored RPL22 mutations were significantly older (67 vs. 63years, p=0.005). There was no difference in PFS between patients with the wildtype and mutant genotypes.

CONCLUSIONS

RPL22 is frequently mutated in MSI-high endometrioid endometrial cancers. The A8 mutation identified was not reported in the whole exome sequences analyzed by the TCGA. The demonstration of frequent mutation in RPL22 may point to a limitation of the exome capture and next generation sequencing analysis methods for some mononucleotide string mutations. Functional assessment of the RPL22 knockdown may be warranted.

Biomarkers and microsatellite instability analysis of curettings can predict the behavior of FIGO stage I endometrial endometrioid adenocarcinoma

The prognostic value of molecular biomarkers, microsatellite instability, DNA ploidy and morphometric mean shortest nuclear axis in endometrial cancer is conflicting, possibly due to the fact that different studies have used mixtures of histotypes, FIGO stages and different non-standardized non-automated methods. We have evaluated the prognostic value of classical prognostic factors, molecular biomarkers, microsatellite instability, DNA ploidy and morphometric mean shortest nuclear axis in a population-based cohort of FIGO stage I endometrial endometrioid adenocarcinomas. Curettings of 224 FIGO stage I endometrial endometrioid adenocarcinoma patients were reviewed. Clinical information, including follow-up, was obtained from the patients' charts. Microsatellite instability and morphometric mean shortest nuclear axis were obtained in whole tissue sections and molecular biomarkers using tissue microarrays. DNA ploidy was analyzed by image cytometry. Univariate (Kaplan-Meier method) and multivariate (Cox model) survival analysis was performed. With median follow-up of 66 months (1-209), 14 (6%) patients developed metastases. Age, microsatellite instability, molecular biomarkers (p16, p21, p27, p53 and survivin) and morphometric mean shortest nuclear axis had prognostic value. With multivariate analysis, combined survivin, p21 and microsatellite instability overshadowed all other variables. Patients in which any of these features had favorable values had an excellent prognosis, in contrast to those with either high survivin or low p21 (97 vs 78% survival, P<0.0001, hazard ratio=7.8). Combined high survivin and low p21 values and microsatellite instability high identified a small subgroup with an especially poor prognosis (survival rate 57%, P=0.01, hazard ratio=5.6). We conclude that low p21 and high survivin expression are poor prognosis indicators in FIGO stage I endometrial endometrioid adenocarcinoma, especially when high microsatellite instability occurs.

Microsatellite instability in endometrial polyps

OBJECTIVE(S)

To investigate the prevalence of microsatellite instability (MSI) in endometrial polyps and to evaluate whether there are clinical and histopathological parameters associated with this kind of instability.

STUDY DESIGN

Between September 2008 and April 2009, endometrial polyps were collected from 109 patients. MSI was evaluated using the NCI recommended markers BAT25, BAT26, D2S123, D5S346 and D17S250. Histopathological analysis was performed, and clinical information was obtained from patients' records.

RESULT(S)

MSI low was detected in 6.4% of the validated samples (7/109). Of the seven MSI that were detected, six were positive for instability at D17S250 and one at D5S346. There were no significant differences between polyps with or without MSI with regard to age, BMI, menarche, parity, miscarriage or menopause; however, MSI was more frequent in polyps with simple hyperplasia without atypia (3/20; 15%). Furthermore, patients with multiple polyps had a marginally but statistically insignificant increase in the frequency of MSI (p<0.07).

CONCLUSION(S)

This is the first prospective study of MSI in endometrial polyps using hysteroscopically obtained samples. In a population of 109 patients, MSI was infrequent in endometrial polyps. Although MSI appears to be more frequent in multiple polyps and polyps with simple hyperplasia without atypia, this was not statistically significant.

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 cancer associated with defective DNA mismatch repair

Defective DNA mismatch repair is one of the most common and best-characterized genetic defects detected in endometrial cancer. Defective DNA mismatch repair in endometrial cancer can be either inherited or acquired (sporadic). This article describes the clinical and pathologic significance of acquired and inherited defective DNA mismatch repair in endometrial cancer.

Microsatellite Instability and Epigenetic Inactivation of MLH1 and Outcome of Patients With Endometrial Carcinomas of the Endometrioid Type

Purpose

Most studies of microsatellite instability (MSI) and outcomes in endometrial cancer patients have included varied histologic subtypes. Nonetheless, MSI occurs almost exclusively in endometrioid tumors. The impact of MSI on outcomes in patients with endometrial cancer is controversial. We sought to determine whether MSI and MLH1 methylation are associated with clinicopathologic variables and survival outcomes in a large series of patients with endometrial carcinomas of the endometrioid type.

Patients and Methods

Tumor samples, blood, and clinicopathologic data were prospectively collected and analyzed for 446 patients with endometrioid carcinomas. MSI was determined using five National Cancer Institute (NCI) consensus panel markers, and the methylation status of the MLH1 promoter was determined by combined bisulfite restriction analysis (COBRA). Associations with clinicopathologic variables and survival outcomes were evaluated.

Results

MSI was identified in 147 cases (33%). MSI was associated with higher International Federation of Gynecology and Obstetrics (FIGO) grade (P < .0001). MSI+ tumors without MLH1 methylation were associated with younger age (P < .001). MSI was not associated with overall survival (OS; hazard ratio [HR], 1.011; 95% CI, 0.688 to 1.484; P = .96) or disease-free survival (DFS; HR 0.951; 95% CI, 0.554 to 1.635; P = .86). The combined MSI/MLH1 methylation status (treating MSI− as the reference) did not predict OS (MSI+/MLH1-U: HR, 0.62; 95% CI, 0.27 to 1.44; P = .26; MSI+/MLH1-M: HR, 0.95; 95% CI, 0.62 to 1.46; P = .82) or DFS (MSI+/MLH1-U: HR, 0.51; 95% CI, 0.22 to 1.19; P = .12; MSI+/MLH1-M: HR, 0.93; 95% CI, 0.62 to 1.40; P = .72).

Conclusion

MSI is not associated with survival in patients with endometrioid endometrial cancer.

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.

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.

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.