A Model for Predicting DNA Mismatch Repair-deficient Colorectal Cancer.

BACKGROUND/AIM: Identifying patients with DNA mismatch repair-deficient (dMMR) colorectal cancer (CRC) is vital to improve treatment and identify patients with Lynch syndrome (LS). We developed a prediction model for dMMR CRC using clinicopathologic features. PATIENTS AND METHODS: We reviewed the medical records of 1,147 patients who underwent resection of stage I-IV CRC in whom universal screening for LS using immunohistochemistry for MMR proteins had performed. Univariate and multivariate logistic regression analyses were used to build a prediction model of dMMR CRC. RESULTS: The prevalence of dMMR CRC was 5.2%. Age (≥75 years), tumor location (right-sided colon), main histologic features (poor differentiation), maximum tumor size (≥65 mm), and stage (I/II) were independent significant variables related to dMMR. We created a formula for predicting the likelihood of dMMR, and the probability ranged from 0.2% to 83%. CONCLUSION: dMMR CRC can be identified efficiently using clinicopathologic features obtained in daily clinical practice.

High homogeneity of MMR deficiency in ovarian cancer.

OBJECTIVE: Mismatch repair (MMR) deficiency and Bethesda panel microsatellite instability (MSI) are increasingly analyzed to identify tumors that might benefit from immune checkpoint inhibitors, but tumor heterogeneity is a potential obstacle for such analyses. In ovarian cancer, data on intratumoral heterogeneity of MMR deficiency/MSI are lacking. METHODS: N = 582 ovarian cancers were screened for MMR deficiency by immunohistochemistry (IHC) on a tissue microarray. 10 cases suspect for MMR deficiency were identified among 478 interpretable cancers and repeated IHC on large sections combined with polymerase chain reaction (PCR)-based MSI analysis validated MMR deficiency/MSI in 9 of these tumors. RESULTS: MMR deficiency/MSI was predominantly seen in endmetrioid cancers (8 of 35, 23%) and also in 1 of 358 serous carcinomas (0.3%), but was absent in 34 mucinous carcinomas, 23 clear cell carcinomas, 17 malignant mixed Mullerian tumors (carcinosarcomas), and 11 mixed carcinomas. MMR deficiency involed protein loss of PMS2/MLH1 in 6 cases and of MSH2 and/or MSH6 in 3 cases. 7 MMR deficient cancers were MSI-high (all endometrioid), one was MSI-low (endometrioid) and one cancer with unequivocal MMR protein loss exhibited microsatellite stability (serous). MLH1 promotor methylation was observed in 4 of 5 endometrioid cancers with MLH1 protein loss. Immunostaining of all available cancer-containing tissue blocks (n = 114) of tumors with confirmed MMR deficiency/MSI revealed uniform MMR status throughout the entire tumor mass. CONCLUSIONS: Our data show that MSI is present in a substantial proportion of endometrioid ovarian cancers but can also occur in other tumor subtypes. MMR deficiency/MSI typically involves the entire tumor mass, suggesting that MMR inactivation occurs early in tumorigenesis in a subset of ovarian cancers.

Loss of mismatch repair signaling impairs the WNT-bone morphogenetic protein crosstalk and the colonic homeostasis.

The fine balance between proliferation, differentiation, and apoptosis in the colonic epithelium is tightly controlled by the interplay between WNT, Notch, and bone morphogenetic protein (BMP) signaling. How these complex networks coordinate the colonic homeostasis, especially if cancer predisposing mutations such as mutations in the DNA mismatch repair (MMR) are present, is unclear. Inactivation of the MMR system has long been linked to colorectal cancer; however, little is known about its role in the regulation of the colonic homeostasis. It has been shown that loss of MMR promotes the proliferation of colon epithelial cells that renders them highly susceptible to transformation. The mechanism through which MMR mediates this effect, yet, remains to be determined. Using an MMR-deficient mouse model, we show that increased methylation of Dickkopf1 impacts its expression, and consequently, the ability to negatively regulate WNT signaling. As a result, excessive levels of active ß-catenin promote strong crypt progenitor-like phenotype and abnormal proliferation. Under these settings, the development and function of the goblet cells are affected. MMR-deficient mice have fewer goblet cells with enlarged mucin-loaded vesicles. We further show that MMR inactivation impacts the WNT-BMP signaling crosstalk.

Quantifying Microsatellite Mutation Rates from Intestinal Stem Cell Dynamics in Msh2-Deficient Murine Epithelium.

Microsatellite sequences have an enhanced susceptibility to mutation, and can act as sentinels indicating elevated mutation rates and increased risk of cancer. The probability of mutant fixation within the intestinal epithelium is dictated by a combination of stem cell dynamics and mutation rate. Here, we exploit this relationship to infer microsatellite mutation rates. First a sensitive, multiplexed, and quantitative method for detecting somatic changes in microsatellite length was developed that allowed the parallel detection of mutant [CA]n sequences from hundreds of low-input tissue samples at up to 14 loci. The method was applied to colonic crypts in Mus musculus, and enabled detection of mutant subclones down to 20% of the cellularity of the crypt (∼50 of 250 cells). By quantifying age-related increases in clone frequencies for multiple loci, microsatellite mutation rates in wild-type and Msh2-deficient epithelium were established. An average 388-fold increase in mutation per mitosis rate was observed in Msh2-deficient epithelium (2.4 × 10-2) compared to wild-type epithelium (6.2 × 10-5).

A lentivirus-based system for Cas9/gRNA expression and subsequent removal by Cre-mediated recombination.

A major concern of CRISPR and related genome engineering technologies is off-target mutagenesis from prolonged exposure to Cas9 and related editing enzymes. To help mitigate this concern we added a loxP site to the 3'-LTR of an HIV-based lentiviral vector capable of expressing Cas9/gRNA complexes in a wide variety of mammalian cell types. Transduction of susceptible target cells yields an integrated provirus that expresses the desired Cas9/gRNA complex. The reverse transcription process also results in duplication of the 3'-LTR such that the integrated provirus becomes flanked by loxP sites (floxed). Subsequent expression of Cre recombinase results in loxP-to-loxP site-specific recombination that deletes the Cas9/gRNA payload and effectively prevents additional Cas9-mediated mutations. This construct also expresses a gRNA with a single transcription termination sequence, which results in higher expression levels and more efficient genome engineering as evidenced by disruption of the SAMHD1 gene. This hit-and-run CRISPR approach was validated by recreating a natural APOBEC3B deletion and by disrupting the mismatch repair gene MSH2. This hit-and-run strategy may have broad utility in many areas and especially those where cell types are difficult to engineer by transient delivery of ribonucleoprotein complexes.

Patients with hMLH1 or/and hMSH2-deficient Metastatic Colorectal Cancer Are Associated with Reduced Levels of Vascular Endothelial Growth Factor-1 Expression and Higher Response Rate to Irinotecan-based Regimen.

BACKGROUND/AIM: The benefit of IFL (irinotecan, fluorouracil and leucovorin) regimen for metastatic colorectal cancer patients (mCRCs) with high levels of microsatellite instability (MSI-H) or loss of mismatch repair (dMMR) protein expression, is uncertain. This study investigated the association of tumour MMR-status and VEGF-1 expression with response to first-line IFL regimen in mCRCs. PATIENTS AND METHODS: This prospective study analyzed patients diagnosed with mCRC between August 1st, 1998, and August 30th, 2003, at the Turku University Hospital, Finland. All patients received postoperative IFL regimen. Tumour expression of the MMR proteins, hMLH1 and hMSH2, and VEGF-1 expression were assessed by immunohistochemistry (IHC). Tumours with dMMR were those demonstrating loss of MMR protein expression, and tumours with high VEGF-1 expression were those showing moderate or strong cytoplasmic staining. The primary endpoint was the association between tumour hMLH1 or/and hMSH2-deficient and VEGF-1 expression; the relation between tumour MMR-status and IFL response rate was the secondary endpoint. RESULTS: Of the 67 mCRCs patients, 29 (43%) were hMLH1 or/and hMSH2-deficient and 15 (22%) were pMMR mCRCs. At diagnosis, patients with hMLH1 or/and hMSH2-deficient tumours expressed lower levels of VEGF-1 compared to pMMR tumour patients (p=0.01). More than half (n=17, 59%) of those with dMMR were chemosensitive to first-line IFL regimen, while just one-fifth (n=3, 20%) of those with pMMR were chemosensitive to the IFL regimen (p=0.045). CONCLUSION: Association between MMR-status and VEGF-1 expression predicts clinical outcome in mCRC patients.

Mismatch tolerance during homologous recombination in mammalian cells.

We investigated the homology dependency of recombination in thymidine kinase (tk)-deficient mouse fibroblasts. Cells were transfected with DNA constructs harboring a herpes tk gene (the "recipient") rendered non-functional by an oligonucleotide containing the recognition site for endonuclease I-SceI. Constructs also contained a "donor" tk sequence that could restore function to the recipient gene through spontaneous gene conversion or via repair of a double-strand break (DSB) at the I-SceI site. Recombination events were recoverable by selection for tk-positive clones. Three different donors were used containing 16, 25, or 33 mismatches relative to the recipient. The mismatches were clustered, forming an interval of "homeology" relative to the recipient sequences. We show that when homeologous sequences were surrounded by high homology, mismatches were frequently included in gene conversion events. Notably, conversion tracts from spontaneous recombination included either all or none of the mismatches, suggesting that recombination must begin and end in high homology. This requirement was relaxed for events that occurred near an induced DSB, as a significant number of these latter conversion tracts had one end positioned within homeology. Knock-down of mismatch repair showed that incorporation of mismatches into gene conversion tracts can involve repair of mismatched heteroduplex intermediates, indicating that mismatch repair does not necessarily impede homeologous genetic exchange. Our results illustrate (1) genetic exchange between homeologous sequences in a mammalian genome is enabled by nearby homology, (2) proximity to a DSB impacts the homology requirements for where genetic exchange may begin and end, and (3) mismatch correction and previously documented anti-recombination activity are separable functions of the mismatch repair machinery in mammalian cells.

Frequency of Defective Mismatch Repair System in a Series of Consecutive Cases of Colorectal Cancer in a National Cancer Center.

BACKGROUND: The frequency of colorectal cancer (CRC) with defective mismatch repair (dMMR) is estimated between 5 and 15%. In our population, the frequency of dMMR is unknown. Our objective was to show the frequency of dMMR. METHODS: Determination of dMMR with immunohistochemistry was performed prospectively for 202 patients who presented consecutively with CRC for the first time at our institution. RESULTS: The median age was 59 years (IQR 47 to 68), 119 (58.9%) were women, and 43 (21.3%) cases showed dMMR. The only clinicopathological characteristics associated with dMMR were the location in the right colon and the presence of a family history of cancer. In the multivariate analysis, only the presence of the tumor in the right colon was associated with dMMR (OR = 5.823, 95%-C.I. = 2.653-12.784, p < .001). CONCLUSION: The 21.3% of the cases demonstrated a dMMR and the only clinical-pathological characteristic associated with dMMR was location in the right colon.

Analysis of Sebaceous Neoplasms for DNA Mismatch Repair Proteins in Muir-Torre Syndrome.

Muir-Torre syndrome is a rare genodermatosis inherited most frequently in an autosomal dominant fashion. Current criteria for its diagnosis include at least one sebaceous tumor and an underlying visceral malignancy. Muir-Torre syndrome is strongly associated with a germline mutation in DNA mismatch repair genes. We report two patients with a history of colorectal carcinoma who presented with sebaceous neoplasms on the face and trunk. Immunohistochemical staining of the sebaceous neoplasms demonstrated absence of mismatch repair proteins MSH2 and MSH6. Genetic studies confirmed deletions in the MSH2 gene, and a diagnosis of Lynch syndrome was made. Immunohistochemical staining for mismatch repair genes MLH1, MSH2, MSH6 and PMS2 may aid in the diagnosis of Muir-Torre syndrome in cases where there is high suspicion. Genetic testing is an important final step in the confirmation of Muir-Torre syndrome.

Mismatch repair deficient hematopoietic stem cells are preleukemic stem cells.

Whereas transformation events in hematopoietic malignancies may occur at different developmental stages, the initial mutation originates in hematopoietic stem cells (HSCs), creating a preleukemic stem cell (PLSC). Subsequent mutations at either stem cell or progenitor cell levels transform the PLSC into lymphoma/leukemia initiating cells (LIC). Thymic lymphomas have been thought to develop from developing thymocytes. T cell progenitors are generated from HSCs in the bone marrow (BM), but maturation and proliferation of T cells as well as T-lymphomagenesis depends on both regulatory mechanisms and microenvironment within the thymus. We studied PLSC linked to thymic lymphomas. In this study, we use MSH2-/- mice as a model to investigate the existence of PLSC and the evolution of PLSC to LIC. Following BM transplantation, we found that MSH2-/- BM cells from young mice are able to fully reconstitute multiple hematopoietic lineages of lethally irradiated wild-type recipients. However, all recipients developed thymic lymphomas within three and four months post transplantation. Transplantation of different fractions of BM cells or thymocytes from young health MSH2-/- mice showed that an HSC enriched fraction always reconstituted hematopoiesis followed by lymphoma development. In addition, lymphomas did not occur in thymectomized recipients of MSH2-/- BM. These results suggest that HSCs with DNA repair defects such as MSH2-/- are PLSCs because they retain hematopoietic function, but also carry an obligate lymphomagenic potential within their T-cell progeny that is dependent on the thymic microenvironment.

Elucidating the molecular basis of MSH2-deficient tumors by combined germline and somatic analysis.

In a proportion of patients presenting mismatch repair (MMR)-deficient tumors, no germline MMR mutations are identified, the so-called Lynch-like syndrome (LLS). Recently, MMR-deficient tumors have been associated with germline mutations in POLE and MUTYH or double somatic MMR events. Our aim was to elucidate the molecular basis of MSH2-deficient LS-suspected cases using a comprehensive analysis of colorectal cancer (CRC)-associated genes at germline and somatic level. Fifty-eight probands harboring MSH2-deficient tumors were included. Germline mutational analysis of MSH2 (including EPCAM deletions) and MSH6 was performed. Pathogenicity of MSH2 variants was assessed by RNA analysis and multifactorial likelihood calculations. MSH2 cDNA and methylation of MSH2 and MSH6 promoters were studied. Matched blood and tumor DNA were analyzed using a customized next generation sequencing panel. Thirty-five individuals were carriers of pathogenic or probably pathogenic variants in MSH2 and EPCAM. Five patients harbored 4 different MSH2 variants of unknown significance (VUS) and one had 2 novel MSH6 promoter VUS. Pathogenicity assessment allowed the reclassification of the 4 MSH2 VUS and 6 probably pathogenic variants as pathogenic mutations, enabling a total of 40 LS diagnostics. Predicted pathogenic germline variants in BUB1, SETD2, FAN1 and MUTYH were identified in 5 cases. Three patients had double somatic hits in MSH2 or MSH6, and another 2 had somatic alterations in other MMR genes and/or proofreading polymerases. In conclusion, our comprehensive strategy combining germline and somatic mutational status of CRC-associated genes by means of a subexome panel allows the elucidation of up to 86% of MSH2-deficient suspected LS tumors.

Clinical Management and Tumor Surveillance Recommendations of Inherited Mismatch Repair Deficiency in Childhood.

Replication proofreading is crucial to avoid mutation accumulation in dividing cells. In humans, proofreading and replication repair is maintained by the exonuclease domains of DNA polymerases and the mismatch repair system. Individuals harboring germline mutations in genes involved in this process are at increased risk of early cancers from multiple organs. Biallelic mutations in any of the four mismatch repair genes MSH2, MSH6, MLH1, and PMS2 result in one of the most aggressive childhood cancer predisposition syndromes, termed constitutional mismatch repair deficiency or constitutional mismatch repair deficiency syndrome (CMMRD). Data gathered in the last decade allow us to better define the clinical manifestations, tumor spectrum, and diagnostic algorithms for CMMRD. In this article, we summarize this information and present a comprehensive consensus surveillance protocol for these individuals. Ongoing research will allow for further definition of replication repair-deficient cancer syndromes, assessing the cost-effectiveness of such surveillance protocols and potential therapeutic interventions for these children and families. Clin Cancer Res; 23(11); e32-e37. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Comparison between mononucleotide and dinucleotide marker panels in gastric cancer with loss of hMLH1 or hMSH2 expression.

BACKGROUND: DNA mismatch repair deficiency is an important molecular mechanism of genetic instability in gastric cancer, and a high instability at microsatellites is associated with favorable prognosis. We compared mononucleotide and dinucleotide microsatellite instability (MSI) marker panels in 56 paired gastric tumor and normal samples. METHODS: The mononucleotide marker panel (mono panel) consisted of 8 markers: BAT25, BAT26, BAT40, BAT-RII, NR21, NR22, NR24 and NR27. The dinucleotide marker panel (di panel) contained D2S123, D5S346, D17S250, D17S261, D17S520, D18S34 and D18S58. The NCI panel was used as reference panel. RESULTS: Among 13 gastric tumors showing no hMLH1 or hMSH2 expression, 8 MSI-H (high) and 5 MSI-L (low) were identified. The analytical sensitivities of the NCI, mono and di panels to detect unstable MSI were 61.5% (8/13), 76.9% (10/13) and 84.6% (11/13), respectively. The size change of allele shift was statistically greater in the mono panel than in the di panel (p = 0.02 by Mann-Whitney U-test). The BAT40 (69.2%, 9/13) and D18S34 (76.9%, 10/13) markers showed high sensitivity for determination of MSI status. CONCLUSIONS: To improve the detection rate of MSI in gastric cancer with loss of hMLH1 or hMSH2 expression, the kind of MSI marker may need to be considered more, instead of the repetitive type of marker. Thus, an MSI panel designed with a combination of both BAT40 and D18S34 is suggested for providing more accurate and sensitive MSI analysis in gastric cancer.

Msh2 deficiency leads to dysmyelination of the corpus callosum, impaired locomotion, and altered sensory function in mice.

A feature in patients with constitutional DNA-mismatch repair deficiency is agenesis of the corpus callosum, the cause of which has not been established. Here we report a previously unrecognized consequence of deficiency in MSH2, a protein known primarily for its function in correcting nucleotide mismatches or insertions and deletions in duplex DNA caused by errors in DNA replication or recombination. We documented that Msh2 deficiency causes dysmyelination of the axonal projections in the corpus callosum. Evoked action potentials in the myelinated corpus callosum projections of Msh2-null mice were smaller than wild-type mice, whereas unmyelinated axons showed no difference. Msh2-null mice were also impaired in locomotive activity and had an abnormal response to heat. These findings reveal a novel pathogenic consequence of MSH2 deficiency, providing a new mechanistic hint to previously recognized neurological disorders in patients with inherited DNA-mismatch repair deficiency.

Mismatch repair enhances convergent transcription-induced cell death at trinucleotide repeats by activating ATR.

Trinucleotide repeat (TNR) expansion beyond a certain threshold results in some 20 incurable neurodegenerative disorders where disease anticipation positively correlates with repeat length. Long TNRs typically display a bias toward further expansion during germinal transmission from parents to offspring, and then are highly unstable in somatic tissues of affected individuals. Understanding mechanisms of TNR instability will provide insights into disease pathogenesis. Previously, we showed that enhanced convergent transcription at long CAG repeat tracks induces TNR instability and cell death via ATR activation. Components of TC-NER (transcription-coupled nucleotide excision repair) and RNaseH enzymes that resolve RNA/DNA hybrids oppose cell death, whereas the MSH2 component of MMR (mismatch repair) enhances cell death. The exact role of the MMR pathway during convergent transcription-induced cell death at CAG repeats is not well understood. In this study, we show that siRNA knockdowns of MMR components-MSH2, MSH3, MLHI, PMS2, and PCNA-reduce DNA toxicity. Furthermore, knockdown of MSH2, MLH1, and PMS2 significantly reduces the frequency of ATR foci formation. These observations suggest that MMR proteins activate DNA toxicity by modulating ATR foci formation during convergent transcription.

The transcription-coupled repair protein ERCC6/CSB also protects against repeat expansion in a mouse model of the fragile X premutation.

The fragile X-related disorders (FXDs) are members of the group of diseases known as the repeat expansion diseases. The FXDs result from expansion of an unstable CGG/CCG repeat tract in the 5' UTR of the FMR1 gene. Contractions are also seen, albeit at lower frequency. We have previously shown that ERCC6/CSB plays an auxiliary role in promoting germ line and somatic expansions in a mouse model of the FXDs. However, work in model systems of other repeat expansion diseases has suggested that CSB may protect against expansions by promoting contractions. Since FXD mice normally have such a high expansion frequency, it is possible that such a protective effect would have been masked. We thus examined the effect of the loss of CSB in an Msh2(+/-) background where the germ line expansion frequency is reduced and in an Msh2(-/-) background where expansions do not occur, but contractions do. Our data show that in addition to promoting repeat expansion, CSB does in fact protect the genome from germ line expansions in the FXD mouse model. However, it likely does so not by promoting contractions but by promoting an error-free process that preserves the parental allele.

DNA mismatch repair deficiency accelerates lung neoplasm development in K-ras(LA1/+) mice: a brief report.

Inherited as well as acquired deficiencies in specific DNA mismatch repair (MMR) components are associated with the development of a wide range of benign and malignant neoplasms. Loss of key members such as MSH2 and MLH1 severely cripples the ability of the cell to recognize and correct such lesions as base:base mismatches and replicative DNA polymerase errors such as slippages at repetitive sequences. Genomic instability resulting from MMR deficiency not only predisposes cells to malignant transformation but may also promote tumor progression. To test the latter, we interbred Msh2(-/-) mice with the K-ras(LA1/+) transgenic line that spontaneously develops a range of premalignant and malignant lung lesions. Compared to K-ras(LA1/+) mice, K-ras(LA1/+); Msh2(-/-) mice developed lung adenomas and adenocarcinomas at an increased frequency and also demonstrated evidence of accelerated adenocarcinoma growth. Since MMR defects have been identified in some human lung cancers, the mutant mice may not only be of preclinical utility but they will also be useful in identifying gene alterations able to act in concert with Kras mutants to promote tumor progression.

DNA mismatch repair-related protein loss as a prognostic factor in endometrial cancers.

OBJECTIVE: Recent investigations have revealed DNA mismatch repair (MMR) gene mutations are closely related with carcinogenesis of endometrial cancer; however the impact of MMR protein expression on prognosis is not determined. Correlations between MMR-related protein expression and clinicopathological factors of endometrial cancers are analyzed in the present study. METHODS: A total of 191 endometrial cancer tissues treated between 1990 and 2007 in our hospital were enrolled. Immunoreactions for MSH2, MLH1, MSH6, and PMS2 on tissue microarray specimens and clinicopathological features were analyzed retrospectively. RESULTS: Seventy-six cases (40%) had at least one immunohistochemical alteration in MMR proteins (MMR-deficient group). There were statistically significant differences of histology, International Federation of Gynecology and Obstetrics (FIGO) stage, and histological grade between MMR-deficient group and the other cases (MMR-retained group). Response rate of first-line chemotherapy in evaluable cases was slightly higher in MMR-deficient cases (67% vs. 44%, p=0.34). MMR-deficient cases had significantly better progression-free and overall survival (OS) compared with MMR-retained cases. Multivariate analysis revealed MMR status was an independent prognostic factor for OS in endometrial cancers. CONCLUSION: MMR-related proteins expression was identified as an independent prognostic factor for OS, suggesting that MMR was a key biomarker for further investigations of endometrial cancers.

DNA mismatch repair-related protein loss as a prognostic factor in endometrial cancers / 부인종양

OBJECTIVE: Recent investigations have revealed DNA mismatch repair (MMR) gene mutations are closely related with carcinogenesis of endometrial cancer; however the impact of MMR protein expression on prognosis is not determined. Correlations between MMR-related protein expression and clinicopathological factors of endometrial cancers are analyzed in the present study. METHODS: A total of 191 endometrial cancer tissues treated between 1990 and 2007 in our hospital were enrolled. Immunoreactions for MSH2, MLH1, MSH6, and PMS2 on tissue microarray specimens and clinicopathological features were analyzed retrospectively. RESULTS: Seventy-six cases (40%) had at least one immunohistochemical alteration in MMR proteins (MMR-deficient group). There were statistically significant differences of histology, International Federation of Gynecology and Obstetrics (FIGO) stage, and histological grade between MMR-deficient group and the other cases (MMR-retained group). Response rate of first-line chemotherapy in evaluable cases was slightly higher in MMR-deficient cases (67% vs. 44%, p=0.34). MMR-deficient cases had significantly better progression-free and overall survival (OS) compared with MMR-retained cases. Multivariate analysis revealed MMR status was an independent prognostic factor for OS in endometrial cancers. CONCLUSION: MMR-related proteins expression was identified as an independent prognostic factor for OS, suggesting that MMR was a key biomarker for further investigations of endometrial cancers.