Assessment of Immune Status in Patients with Mismatch Repair Deficiency Endometrial Cancer

Objective

This study introduced a novel subtype classification method for endometrial cancer (EC) with mismatch repair deficiency (MMRd) by employing immune status and prognosis as the foundational criteria. The goal was to enhance treatment guidance through precise subtype delineation.

Methods

Study Cohort: This study encompassed a cohort of 119 patients diagnosed with MMRd-EC between 2015 and 2022. Analyses using t-tests and Mann-Whitney U-tests were performed to assess prognostic markers and peripheral blood immune cell profiles in patients with MutS deficiency (MutS-d) versus those with MutL deficiency (MutL-d). Logistic regression analysis was used to identify independent risk factors. Bioinformatics Analysis: An online database was used to assess the prognostic implications, immune cell infiltration, and immune checkpoint involvement associated with the deficiency of MutS versus MutL in EC.

Results

Patients with MutL-d exhibited heightened risk factors, including elevated cancer grade and increased myometrial invasion, leading to poorer prognosis and shorter overall survival and progression-free survival. Regarding systemic immune status, patients with MutL-d demonstrated decreased peripheral blood lymphocyte percentage, lymphocyte count, and CD8+ T cell percentage. For local immunity, the infiltration of natural killer cells, CD8+ T cells, and cytotoxic T lymphocytes in the tumor tissue was reduced in patients with MutL-d. Additionally, patients with MutL-d exhibited lower expression of immune checkpoint markers. The composition of immune subtypes and survival outcomes also indicate that patients with MutL-d have a poorer immune status and prognosis than the patients with MutS-d.

Conclusion

Patients with MMRd-EC can be subclassified according to MutS or MutL deficiency. Patients with MutS-d exhibited better immune status, prognosis, and immunotherapy benefits than those with MutL-d. These results can help guide patients to a more precise treatment.

Molecular and Clinicopathologic Characterization of Mismatch Repair-Deficient Endometrial Carcinoma Not Related to MLH1 Promoter Hypermethylation

Universal tumor screening in endometrial carcinoma (EC) is increasingly adopted to identify individuals at risk of Lynch syndrome (LS). These cases involve mismatch repair-deficient (MMRd) EC without MLH1 promoter hypermethylation (PHM). LS is confirmed through the identification of germline MMR pathogenic variants (PV). In cases where these are not detected, emerging evidence highlights the significance of double-somatic MMR gene alterations as a sporadic cause of MMRd, alongside POLE/POLD1 exonuclease domain (EDM) PV leading to secondary MMR PV. Our understanding of the incidence of different MMRd EC origins not related to MLH1-PHM, their associations with clinicopathologic characteristics, and the prognostic implications remains limited. In a combined analysis of the PORTEC-1, -2, and -3 trials (n = 1254), 84 MMRd EC not related to MLH1-PHM were identified that successfully underwent paired tumor-normal tissue next-generation sequencing of the MMR and POLE/POLD1 genes. Among these, 37% were LS associated (LS-MMRd EC), 38% were due to double-somatic hits (DS-MMRd EC), and 25% remained unexplained. LS-MMRd EC exhibited higher rates of MSH6 (52% vs 19%) or PMS2 loss (29% vs 3%) than DS-MMRd EC, and exclusively showed MMR-deficient gland foci. DS-MMRd EC had higher rates of combined MSH2/MSH6 loss (47% vs 16%), loss of >2 MMR proteins (16% vs 3%), and somatic POLE-EDM PV (25% vs 3%) than LS-MMRd EC. Clinicopathologic characteristics, including age at tumor onset and prognosis, did not differ among the various groups. Our study validates the use of paired tumor-normal next-generation sequencing to identify definitive sporadic causes in MMRd EC unrelated to MLH1-PHM. MMR immunohistochemistry and POLE-EDM mutation status can aid in the differentiation between LS-MMRd EC and DS-MMRd EC. These findings emphasize the need for integrating tumor sequencing into LS diagnostics, along with clear interpretation guidelines, to improve clinical management. Although not impacting prognosis, confirmation of DS-MMRd EC may release patients and relatives from burdensome LS surveillance.

A tale of two pathways: Review of immune checkpoint inhibitors in DNA mismatch repair-deficient and microsatellite instability-high endometrial cancers

The DNA mismatch repair (MMR) pathway is critical for correcting DNA mismatches generated during DNA replication. MMR-deficiency (MMR-D) leads to microsatellite instability (MSI) associated with an increased mutation rate, driving cancer development. This is particularly relevant in endometrial cancer (EC) as 25%-30% of tumors are of MMR-D/MSI-high (MSI-H) phenotype. Comprehensive assessment using immunohistochemistry (IHC) and sequencing-based techniques are necessary to fully evaluate ECs given the importance of molecular subtyping in staging and prognosis. This also influences treatment selection as clinical trials have demonstrated survival benefits for immune checkpoint inhibitors (ICIs) alone and in combination with chemotherapy for MMR-D/MSI-H EC patients in various treatment settings. As a portion of MMR-D/MSI-H ECs are driven by Lynch syndrome, an inherited cancer predisposition syndrome that is also associated with colorectal cancer, this molecular subtype also prompts germline assessment that can affect at-risk family members. Additionally, heterogeneity in the tumor immune microenvironment and tumor mutation burden (TMB) have been described by MMR mechanism, meaning MLH1 promoter hypermethylation versus germline/somatic MMR gene mutation, and this may affect response to ICI therapies. Variations by ancestry in prevalence and mechanism of MMR-D/MSI-H tumors have also been reported and may influence health disparities given observed differences in tumors of Black compared to White patients which may affect ICI eligibility. These observations highlight the need for additional prospective studies to evaluate the nuances regarding MMR-D heterogeneity as well as markers of resistance to inform future trials of combination therapies to further improve outcomes for patients with EC.

Pan-integrin inhibitor GLPG-0187 promotes T-cell killing of mismatch repair-deficient colorectal cancer cells by suppression of SMAD/TGF-β signaling

Colorectal cancer is the third leading cause of cancer-related death and the third most common cause of cancer. As the five-year survival with advanced metastatic colorectal cancer (mCRC) is 14%, new treatment strategies are needed. Immune checkpoint blockade, which takes advantage of an individual's immune system to fight cancer, has an impact in the clinic; however, for CRC, it is only effective and approved for treating mismatch repair (MMR)-deficient cancer. Moreover, long-term outcomes in MMR-deficient mCRC suggest that most patients are not cured and eventually develop therapy resistance. We hypothesized that targeting TGF-β signaling may enhance immune-mediated T-cell killing by MMR-deficient CRC cells. Using GLPG-0187, an inhibitor of multiple integrin receptors and TGF-β, we demonstrate minimal cytotoxicity against MMR-deficient HCT116 or p53null HCT116 human CRC cells. GLPG-0187 promoted significant immune cell killing of the CRC cells by TALL-104 T lymphoblast cells and reduced phosphoSMAD2 in HCT116 p53-null cells either in the absence or presence of exogenous TGF-β. We observed a reduction in CCL20, CXCL5, prolactin, and TRAIL-R3, while GDF-15 was increased in TALL-104 cells treated with a T-cell activating dose of GLPG-0187 (4 µM). Our results suggest that TGF-β signaling inhibition by a general integrin receptor inhibitor may boost T-cell killing of MMR-deficient colorectal cancer cells and suggest that a combination of anti-GDF-15 in combination with TGF-β blockade be further investigated in the treatment of MMR-deficient mCRC. Our results support the development of a novel immune-based therapeutic strategy to treat colorectal cancer by targeting the TGF-β signaling pathway through integrin receptor blockade.

Broad spectrum integrin inhibitor GLPG-0187 bypasses immune evasion in colorectal cancer by TGF-β signaling mediated downregulation of PD-L1

Integrin receptors have long posed as a potentially attractive target for disrupting cancer hallmarks. Promising preliminary findings with integrin inhibition as an adjuvant to chemotherapy have not translated to clinical success. However, the effect of integrin inhibition on tumor-immune cell interactions remains largely unexplored. Further investigation could shed light on a connection between integrin signaling and immune checkpoint expression, opening the path for using integrin inhibitors to sensitize otherwise resistant tumors to immunotherapy. Fluorescently labeled wild-type HCT-116 colorectal cancer cells and TALL-104 T-cells were co-cultured and treated with GLPG-0187, a small molecule integrin inhibitor, at various doses. This assay revealed dose dependent cancer cell killing, indicating that integrin inhibition may be sensitizing cancer cells to immune cells. The hypothesized mechanism involves TGF-β-mediated PD-L1 upregulation in cancer cells. To investigate this mechanism, both WT and p53-/- HCT-116 cells were pre-treated with GLPG-0187 and subsequently with latent-TGF-β. Western blot analysis demonstrated that the addition of latent-TGF-β increased the expression of PD-L1 in cancer cells. Additionally, a low dose of integrin inhibitor rescued these effects, returning PD-L1 expression back to control levels. This indicates that the immunostimulatory effects of integrin inhibition may be due to downregulation of immune checkpoint PD-L1 on cancer cells. It must be noted that the higher dose of the drug did not reduce PD-L1 expression. This could potentially be due to off-target effects conflicting with the proposed pathway; however, these findings are still under active investigation. Ongoing proteomic experiments will include a larger range of both drug and latent-TGF-β doses. Probing for additional downstream markers of TGF-β and up-stream markers of PD-L1 will help to further elucidate this mechanism. Further co-culture experiments will also include anti-PD-L1 and anti-PD-1 therapy to investigate the viability of integrin inhibition as an adjuvant to immune checkpoint blockade.

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.