MSI-high Patients Research Articles

MITO END-3: efficacy of avelumab immunotherapy according to molecular profiling in first-line endometrial cancer therapy

Immunotherapy combined with chemotherapy significantly improves progression-free survival (PFS) compared to first-line chemotherapy alone in advanced endometrial cancer (EC), with a much larger effect size in microsatellite instability-high (MSI-H) cases. New biomarkers might help to select patients who may have benefit among those with a microsatellite-stable (MSS) tumor. In a pre-planned translational analysis of the MITO END-3 trial, we assessed the significance of genomic abnormalities in patients randomized to standard carboplatin/paclitaxel without or with avelumab. Out of 125 randomized patients, 109 had samples eligible for next-generation sequencing analysis, and 102 had MSI tested. According to The Cancer Genome Atlas (TCGA), there were 29 cases with MSI-H, 26 with MSS TP53 wild type (wt), 47 with MSS TP53 mutated (mut), and 1 case with POLE mutation. Four mutated genes were present in >30% of cases: TP53, PIK3CA, ARID1A, and PTEN. Eleven patients (10%) had a BRCA1/2 mutation (five in MSI-H and six in MSS). High tumor mutational burden (≥10 muts/Mb) was observed in all MSI-H patients, in 4 out of 47 MSS/TP53 mut, and no case in the MSS/TP53 wt category. The effect of avelumab on PFS significantly varied according to TCGA categories, being favorable in MSI-H and worst in MSS/TP53 mut (P interaction= 0.003); a similar non-significant trend was seen in survival analysis. ARID1A and PTEN also showed a statistically significant interaction with treatment effect, which was better in the presence of the mutation (ARID1A P interaction= 0.01; PTEN P interaction= 0.002). The MITO END-3 trial results suggest that TP53 mutation is associated with a poor effect of avelumab, while mutations of PTEN and ARID1A are related to a positive effect of the drug in patients with advanced EC.

The Expression Patterns of Immune Checkpoint Molecules in Colorectal Cancer: An Analysis Based on Microsatellite Status.

Recently, immunotherapy has arisen as a novel treatment approach for patients with colorectal cancer (CRC), but the effectiveness of immunotherapy varies in these patients. We hypothesized that immune checkpoint molecules (ICMs), which are the targets of immunotherapy, are often exhibited concomitantly. Our objective was to investigate the patterns of ICM expression in patients with CRC and the differences in ICM expression based on microsatellite instability status. The immunohistochemical expression of programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), and lymphocyte-activation gene 3 (LAG-3) in the tumor center and periphery was assessed in patients with non-metastatic colorectal cancer. We enrolled 83 patients with CRC: a total of 40 microsatellite-stable (MSS) and 43 microsatellite-instability-high (MSI-H) cancer patients. PD-L1 was more frequently expressed in the tumor center in the MSI-H patients with than that in the MSS patients (18 [41.9%] vs. 3 [7.5%], respectively; p < 0.001), and the same trend was observed for TIM-3 expression (30 [69.8%] vs. 19 [47.5%], respectively; p = 0.047). The concomitant expression of two or more ICMs was more frequently observed than no expression or the expression of a single molecule in both the MSS and MSI-H groups; a total of 34 (79.7%) patients with MSI-H cancer and 23 (57.5%) with MSS cancer showed ICM expression at the tumor center, whereas 34 (79.7%) patients with MSI-H cancer and 22 (55%) with MSS cancer showed expression at the tumor periphery. Patients with the genetic characteristics of MSI-H cancer showed higher expression levels of ICMs than those in patients with MSS cancer, and predominantly, two or more ICMs were concurrently expressed. Our findings highlight the potential efficacy of the dual-blockade approach in immunotherapy, particularly in patients with MSI-H CRC.

Abstract 7602: Discovery of GH1581, a potent and selective WRN inhibitor as a cancer therapy

Abstract Defects in DNA mismatch repair (MMR) proteins could induce damage of genome, resulting microsatellite instability (MSI). MSI is highly correlated with the occurrence of several types of cancers, mainly in colon, gastric, endometrial, and ovarian cancers. Despite advances in the treatment of MSI-high cancers, tumor evolution and drug resistance remain the leading causes of treatment failure and death in cancer patients. About 50% MSI cancers have no response to immune checkpoint inhibitors. There is still unmet needs to be fulfilled for MSI-high patients. WRN is a RecQ family helicase involves in genome stability maintenance, DNA repair, replication, transcription, and telomere maintenance. Recent studies have identified WRN as a synthetic lethal target of MSI-high cancers. Employing structure-based drug design strategy, we have discovered a potent and selective WRN inhibitor, GH1581. In vitro, GH1581 displayed specific &amp;lt; 10 nM potency in ADP-Glo assay and &amp;lt; 10 nM potency in cell proliferation assay using MSI cancer cell lines. In vivo, GH1581 demonstrated favorable pharmacokinetic properties in different species. In SW48 xenograft model, it inhibited the tumor growth with 100% TGI at QD dosing of 10 mg/kg without severe adverse effect on body weight. In summary, we discovered GH1581 as a novel inhibitor of WRN with high in vitro and in vivo efficacy. Citation Format: Jiapeng Li, Guiping Zhang, Jie Jack Li. Discovery of GH1581, a potent and selective WRN inhibitor as a cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7602.

Microsatellite Instability Is Insufficiently Used as a Biomarker for Lynch Syndrome Testing in Clinical Practice.

The pan-cancer presence of microsatellite instability (MSI)-positive tumors demonstrates its clinical utility as an agnostic biomarker for identifying immunotherapy-eligible patients. Additionally, MSI is a hallmark of Lynch syndrome (LS), the most prevalent cancer susceptibility syndrome among patients with colorectal and endometrial cancer. Therefore, MSI-high results should inform germline genetic testing for cancer-predisposing genes. However, in clinical practice, such analysis is frequently disregarded. A next-generation sequencing (NGS)-based technique was used for MSI analysis in 4,553 patients with various tumor types. Upon request, somatic BRAF gene analysis was conducted. In addition, hereditary testing of cancer-associated genes was performed in MSI-high cases using a capture-based NGS protocol. MLH1 promoter methylation analysis was conducted retrospectively in patients with colorectal and endometrial cancer to further investigate the origin of MSI at the tumor level. The MSI positivity rate for the entire cohort was 5.27%. Endometrial, gastric, colorectal, urinary tract, and prostate cancers showed the highest proportion of MSI-high cases (15.69%, 8.54%, 7.40%, 4.55%, and 3.19%, respectively). A minority of 45 patients (22.73%) among the MSI-high cases underwent germline testing to determine whether the mismatch repair pathway deficiency was inherited. 24.44% of those who performed the genetic test carried a pathogenic variant in an LS-associated gene. Three MSI-high individuals had non-LS gene alterations, including BRCA1, BRCA2, and CDKN2A pathogenic variants, indicating the presence of non-LS-associated gene alterations among MSI-high patients. Although MSI analysis is routinely performed in clinical practice, as many as 77% of MSI-high patients do not undergo LS genetic testing, despite international guidelines strongly recommending it. BRAF and MLH1 methylation analysis could shed light on the somatic origin of MSI in 42.50% of the MSI-high patients; however, MLH1 analysis is barely ever requested in clinical practice.

ImmuneMirror: A machine learning-based integrative pipeline and web server for neoantigen prediction.

Neoantigens are derived from somatic mutations in the tumors but are absent in normal tissues. Emerging evidence suggests that neoantigens can stimulate tumor-specific T-cell-mediated antitumor immune responses, and therefore are potential immunotherapeutic targets. We developed ImmuneMirror as a stand-alone open-source pipeline and a web server incorporating a balanced random forest model for neoantigen prediction and prioritization. The prediction model was trained and tested using known immunogenic neopeptides collected from 19 published studies. The area under the curve of our trained model was 0.87 based on the testing data. We applied ImmuneMirror to the whole-exome sequencing and RNA sequencing data obtained from gastrointestinal tract cancers including 805 tumors from colorectal cancer (CRC), esophageal squamous cell carcinoma (ESCC) and hepatocellular carcinoma patients. We discovered a subgroup of microsatellite instability-high (MSI-H) CRC patients with a low neoantigen load but a high tumor mutation burden (> 10 mutations per Mbp). Although the efficacy of PD-1 blockade has been demonstrated in advanced MSI-H patients, almost half of such patients do not respond well. Our study identified a subset of MSI-H patients who may not benefit from this treatment with lower neoantigen load for major histocompatibility complex I (P < 0.0001) and II (P = 0.0008) molecules, respectively. Additionally, the neopeptide YMCNSSCMGV-TP53G245V, derived from a hotspot mutation restricted by HLA-A02, was identified as a potential actionable target in ESCC. This is so far the largest study to comprehensively evaluate neoantigen prediction models using experimentally validated neopeptides. Our results demonstrate the reliability and effectiveness of ImmuneMirror for neoantigen prediction.

Exploring the connection between microsatellite instability and inflammatory indicators in cancers.

Aim: This study aimed to investigate the association between microsatellite instability (MSI) status and inflammatory indicators in patients with cancer. Patients & methods: A total of 204 patients with various cancer diagnoses, including 102 with MSI-high (MSI-H) and 102 with microsatellite stabletumors, were enrolled. Neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), C-reactive protein (CRP)-to-albumin ratio and systemic immune-inflammation indexwere evaluated. Results: In microsatellite stable patients, NLR, LMR, PLR and systemic immune-inflammation index were significantly linked to worse survival in univariate analysis, and having aLMR ≤2.6 negatively affected survival in multivariate analysis, although these indicators did notaffect the survival of MSI-H patients. Conclusion: The impact of chronic inflammationon survival varies with MSI status. Further research is needed for targeted therapies in different tumors.

Genomic profile and clinical features of MSI-H and TMB-high pancreatic cancers: real-world data from C-CAT database.

Microsatellite instability high (MSI-H) and tumor mutational burden high (TMB-high) pancreatic cancer are rare, and information is lacking. Based on the C-CAT database, we analyzed the clinical and genomic characteristics of patients with these subtypes. We retrospectively reviewed data on 2206 patients with unresectable pancreatic adenocarcinoma enrolled in C-CAT between July 2019 and January 2022. The clinical features, proportion of genomic variants classified as oncogenic/pathogenic in C-CAT, overall response rate (ORR), disease control rate (DCR), and time to treatment failure (TTF) of chemotherapy as first-line treatment were evaluated. Numbers of patients with MSI-H and TMB-high were 7 (0.3%) and 39 (1.8%), respectively. All MSI-H patients were TMB-high. MSI-H and TMB-high patients harbored more mismatch repair genes, such as MSH2, homologous recombination-related genes, such as ATR and BRCA2, and other genes including BRAF, KMT2D, and SMARCA4. None of the 6 MSI-H patients who received chemotherapy achieved a clinical response, including 4 patients treated with gemcitabine plus nab-paclitaxel (GnP) therapy, whose DCR was significantly lower than that of microsatellite stable (MSS) patients (0 vs. 67.0%, respectively, p = 0.01). Among the TMB-high and TMB-low groups, no significant differences were shown in ORR, DCR (17.1 vs. 23.1% and 57.1 vs. 63.1%, respectively), or median TTF (25.9 vs. 28.0weeks, respectively) of overall first-line chemotherapy. MSI-H and TMB-high pancreatic cancers showed some distinct genomic and clinical features from our real-world data. These results suggest the importance of adapting optimal treatment strategies according to the genomic alterations.

Molecular Subtypes and Outcomes in a Multi-Institutional Review of Rectal Cancer Patients

Colorectal cancer (CRC) is a heterogeneous malignancy associated with a variety of genetic mutations. More recent data indicates that CRC can be broken down into unique biologically distinct consensus molecular subtypes (CMS) based on different pathological and genetic signatures. The purpose of this study is to evaluate the outcomes of rectal cancer patients in a multi-institutional network based on tumor mutational assessment and CMS group. Patient exome and transcriptome sequencing data and clinical outcomes were collected under the Total Cancer Care Protocol and Avatar® project within the Oncology Research Information Exchange Network (ORIEN). A total of 101 patients with demographic and outcomes information had data for microsatellite instability (MSI), tumor mutation burden (TMB), transcriptome, and whole exome sequencing (WES). Molecular subclasses (CMS1, CMS2, CMS3, CMS4, CMS-Mixed) were assigned based on transcriptional signatures by the R package "CMS Caller." Survival analysis was performed with the R packages "Survival" and "Survminer." A total of 101 rectal cancer patients, with a median age of 56.8, had a median follow up of 3.5 years (range 0.26-23.5). 78 patients were treated with curative intent for clinically localized disease and 35% of these patients developed metastatic disease. The remaining 23 patients had synchronous metastatic disease at presentation. There were 5 (5%) CMS1, 29 (29%) CMS2, 13 (13%) CMS 3, 49 (49%) CMS 4, and 5 (5%) CMS-Mixed patients in our cohort respectively. The cohort included 5 (5%) BRAF, 51 (50%) KRAS, and 63 (62%) TP53 mutated patients and 5 (5%) MSI high patients. Median survival was 18.8, 117.2, 125.7 and 119 months for CMS1, CMS2, CMS3, and CMS4 patients respectively, with insufficient events in CMS-mixed for calculation (p = 0.15). CMS1 patients had a significantly shorter survival compared to the other cohorts (p = 0.02), with 2 of 5 of these patients having received immunotherapy. 40% (2,0) CMS1, 52% (7,8) of CMS2, 15% (1,1) of CMS3, 59% (13,15) of CMS4, and 40% (1,1) of CMS-Mixed presented with or developed metastatic disease respectively. When divided into mutation groups, median survival was 43 versus 119, 119 versus 117, and 126 versus 119 months for BRAF, KRAS, and TP53 mutated and wild type patients respectively (p = 0.18, p = 0.48, p = 0.93). Evaluation of TMB and MSI status did not reveal significant differences in outcomes (p = 0.54, p = 0.7), with median survival of 126 months versus 117 in TMB high versus low patients and unreached versus 119 months in MSI versus MSS patients respectively. Of note, 3 of the 5 MSI patients were also CMS1, with the other two coming from CMS4 and CMS-mixed cohorts. CMS classification and tumor mutation status are associated with differential outcomes for rectal cancer patients, with some groups having a large likelihood of developing metastatic disease. Further work on optimizing and personalizing treatments for these high-risk populations is necessary.

Neoadjuvant chemoradiation therapy combined with immunotherapy for microsatellite stable ultra-low rectal cancer (CHOICE II): study protocol of a multicentre prospective randomised clinical trial

IntroductionNeoadjuvant chemoradiotherapy (nCRT) could bring tumour shrinking and downstaging and increase the probability of organ preservation for patients with low rectal cancer. But for ultra-low rectal cancer, there is little...

Pattern of mismatch repair proteins in colorectal cancer patients in tertiary cancer center.

40 Background: Prevalence of MSI high in colorectal cancer patients in India has been debated in previous literature. Microsatellite instability pathway is one of the major pathways in carcinogenesis of colorectal carcinoma. MSI status has paramount significance in therapeutic and prognostic aspects of colorectal cancer management. MSI status can be evaluated by presence or absence of mismatch repair proteins. Aims &amp; objectives: we aimed to determine the prevalence of MSI high in colorectal carcinoma and pattern of mismatch repair proteins. Methods: This was retrospective study which included consecutively operated colorectal carcinoma patients from 01 may 2022 to 31 December 2022 in our institute. Immunohistochemistry with four mismatch repair (MMR) proteins; MLH1, MSH2, MSH6, and PMS2 was performed. Correlation with various clinical and histopathological features was done. Results: total 296 colorectal carcinoma patients were included in our study. Fourty one (13.85%) patients were MSI high. Most common pattern of MMR protein expression loss was dual loss of MLH1 and PMS2 (n=18). Most common single protein loss was PMS2 (n=22). Most common location of tumor in MSI high patients was the right colon. (n=20). Out of 153 carcinoma rectum patients only five patients were MSI high. Conclusions: The study shows that prevalence of MSI high is more common in right colon cancer. Prevalence of MSI high is very low in carcinoma rectum. We discuss and compare our results with previous studies.

Relationship Between ABO Blood Group and Microsatellite Instability in Colorectal Cancer: A Retrospective Single-Center Study.

Colorectal cancer (CRC) is the second most common cancer in both women and men. Microsatellite instability-high (MSI-H) CRC is a molecular subgroup and has distinct clinical and pathologic features from microsatellite stable (MSS) CRC. Studies have suggested an association between hereditary antigens in ABO blood group system and the risk of developing various cancers but the relationship between blood groups and MSI-H CRC has not been investigated. This study aimed to investigate this relationship and its possible effect on clinicopathological features in patients with CRC. This is a retrospective cross-sectional single-center study including pathology-confirmed CRC patients. Demographic and clinicopathological features, blood groups, and microsatellite status were examined among two groups. Microsatellite instability was examined by immunohistochemistry (IHC) in pathology specimen. A total of 144 patients, 72 patients with MSI-H CRC and 72 patients with MSS CRC, were included in the study. Among all patients, median age was 61.7 ± 12.9 (range 27-89) and 57.6% were male. MSI-H and MSS groups were similar in terms of age, gender distribution, and comorbidities. Patients with MSI-H CRC had significantly common O-blood group than control group (44.4% vs 18.1%, p: 0.001). In multivariate analysis, O-blood group was 4.2 times more common in the MSI-H patient group (95% CI: 1.514-11.819, p: 0.006). Also patients with MSI-H CRC were found to have significantly more right-sided, high-grade tumors and early-stage disease. MSI-H CRC is an important subgroup in colon cancer with different molecular and clinicopathological features. It was observed that O-blood group was 4.2 times more common in MSI-H CRC. We believe that clarifying the relationship between microsatellite instability and O-blood group and its possible genetic and epigenetic mechanismsin larger studies will enable us to better understand tumor behavior and prognosis, also affect our treatment choices of these patient groups.

Survival impact of microsatellite instability in stage II gastric cancer patients who received S-1 adjuvant monotherapy after curative resection

Adjuvant S-1 monotherapy is the standard of care for stage II gastric cancer (GC) after curative resection in Japan, but its efficacy for microsatellite instability–high (MSI-H) tumors has remained unknown. Among a multi-institutional cohort of patients with stage II GC who underwent R0 resection followed by S-1 adjuvant chemotherapy between February 2008 and December 2018, we assessed MSI status with an MSI-IVD Kit (Falco). MSI status was assessable for 184 (88.5%) of the 208 enrolled patients, with MSI-H being identified in 24 (13.0%) individuals. Although neither relapse-free survival (RFS) (hazard ratio [HR] = 1.00, p = 0.997) nor overall survival (OS) (HR = 0.66, p = 0.488) differed between MSI-H versus microsatellite-stable (MSS) patients, MSI-H patients showed a nonsignificant but better RFS (HR = 0.34, p = 0.064) and OS (HR = 0.22, p = 0.057) than did MSS patients after adjustment for background characteristics by propensity score (PS) analysis. Gene expression analysis in the PS-matched cohort suggested that recurrence was associated with the immunosuppressive microenvironment in MSI-H tumors but with expression of cancer/testis antigen genes in MSS tumors. Our data reveal a better adjusted survival for MSI-H versus MSS stage II GC treated with S-1 adjuvant therapy, and they suggest that mechanisms of recurrence differ between MSI-H and MSS tumors.

Genomic characterization of MSI-H and TMB in gastrointestinal cancer.

e15524 Background: Microsatellite instability (MSI) is a molecular marker of a deficient in mismatch repair (MMR) system. It is one of the main hallmarks in colorectal cancer (CRC) and gastric cancer (GC), occurring in 15% and 18% of CRC and GC respectively. Mutations occur in MMR system genes will impair DNA mismatch recognition and cause accumulation of mutations in DNA microsatellite regions. As a result, microsatellite instability-high (MSI-H) patients often possess an abnormally high number of somatic mutations and would lead to high tumour mutation burden (TMB), which is a prevalent biomarker in cancer immunotherapy. Here we analysed the genomic landscape of 974 gastrointestinal cancer patients to provide new insights on the relationship between MSI, TMB and other genetic mutation characteristics. Methods: Panel sequencing targeting 680 cancer-related genes were performed on patients with colonrectal cancer (n = 569), gastric cancer (n = 375), intestinal cancer (n = 25) and oesophagal cancer (n = 5) on either fresh tumour tissue or formalin-fixed paraffin embedded tumor DNA. Genomic alterations including single nucleotide variations, short insertions and deletions, copy number variations, tumour mutation burden and micro-satellite instability were analysed. Results: Among the 974 patients, 86 patients (8.83%) were classified as MSI-H based on evaluation of 117 MMR-related loci, while rest of the patients (n = 888, 91.2%) were classified as microsatelite stable (MSS). In MSI-H cohort, 68.6% of the patients were classified as TMB-H with a TMB level higher than 10 Muts/Mb, while in MSS cohort, only 3.71% of the patients were classified as TMB-H. The TMB value of MSI-H cohort is also significantly higher than the MSS cohort (p &lt; 0.0001, two-tailed T-test). Meanwhile, we discovered that proportion of patients with mutated lysine methyltransferase family gene KMT2D (54.65% vs 7.17%, p &lt; 0.0001), KMT2B (48.84% vs 3.25%, p &lt; 0.0001) and KMT2C (44.19% vs 7.17%, p &lt; 0.0001) showed significant difference between MSI-H and MSS cohorts (Two-sided Fisher’s exact test). Conclusions: This study demonstrated that MSI-H is highly correlated with TMB-H, providing a new insight of evaluating gastrointestinal cancer treatment on MSI-H patients. The study also revealed novel MSI-H genetic mutation landscape for KMT gene family. Concurrent with recent researches, this study further boosts the potential of KMT genes to be used as a biomarker in both diagnosis and immunotherapy treatment.

A pan-cancer statistical study of microsatellite instability and Lynch syndrome–associated mismatch repair genes germline mutations.

10593 Background: Lynch Syndrome (LS), known as hereditary nonpolyposis colorectal cancer (HNPCC1), is caused by germline mutations in the mismatch repair (MMR) genes ( MLH1, MSH2, PMS2, MSH6), or epigenetic silencing of MSH2 which caused by deletion of 3-prime exons of the EPCAM gene and intergenic regions directly upstream of the MSH2 gene. DNA mismatches commonly occur in regions of repetitive nucleotide sequences called microsatellites, and the status of microsatellite instability (MSI) is the key feature in LS-associated cancers. Although there are sporadic reports of MSI and LS in certain cohorts, the real-world status of MSI in large pan-cancer cohort remains to be analyzed. Methods: We retrospectively reviewed all 18189 solid tumor patients from August 1, 2020 to February 5, 2023 from HaploX Genomic Sequencing Center and analyzed their germline mutations in MMR genes ( MLH1,MSH2,PMS2,MSH6 and EPCAM). MSI status was determined using Sanger sequencing or Next-generation sequencing, with tumor MSI status classified as microsatellite instability-high (MSI-H), or microsatellite-stable (MSS). Results: LS-associated germline mutations were detected in 0.313% (n = 57) of patients, and75.4% (n = 43) of patients were identified as MSI-H, and 24.6% (n = 14) of patients were MSS. The patients were grouped into CRC/EC group (colorectal cancer and endometrial cancer) and non-CRC/EC (lung cancer, central nervous system tumor, gastric cancer, esophageal cancer, hepatological cancer, pancreatic adenocarcinoma, small bowel carcinoma, kidney cancer, etc.). Among MSI-H patients, the CRC/EC group accounted for 90.7% (n = 39) and the non-CRC/EC group accounted for 9.3% (n = 4). In MSS patients, the CRC/EC patients accounted for 35.7% (n = 5), and the non-CRC/EC patients accounted for 60% (n = 9). Among patients with MSI-H, the most frequently mutated gene was MSH6 (n = 9): MSH6 (NM_000179) c.3261dup (p.F1088Lfs*5) mutation was detected in 4 patients, of which 2 patients were paternal and both were diagnosed as colorectal cancer; MSH6 c.718C &gt; T (p.R240*) mutation was detected in 2 patients with available MMR IHC results, and one of them was MSH6 negative in IHC staining. Conclusions: Traditionally, a family history of colorectal cancer or endometrial cancers was the primary clinical feature to diagnose Lynch syndrome. Once it was recognized that Lynch-associated CRCs were microsatellite unstable, tumor testing became an additional tool for identification of Lynch syndrome. Some previous studies also reported Lynch syndrome mutations, primarily MSH6 and PMS2, were present in a few MSS patients. Thus, MSI status or family history as diagnostic factor alone may result in Lynch syndrome under-recognized, and additional NGS test on MMR genes should facilitate more accurate diagnosis.

Immunohistochemical expression of ER and p53 as predictive biomarkers of immunotherapy in endometrial cancer.

e17626 Background: Immune Checkpoint Inhibitors (ICIs), either as monotherapy or in combination with tyrosine kinase inhibitors (TKIs), were recently incorporated into the therapeutic guidelines for recurrent/metastatic endometrial cancer (EC). Microsatellite Instability (MSI) is the only biomarker to guide treatment. We evaluated the predictive significance of Estrogen Receptor (ER) and p53 expression. Methods: Medical charts of EC patients that received ICIs in our institution for advanced/metastatic disease were retrospectively reviewed. TP53 and ER expression were determined by immunohistochemistry. Survival analysis was performed using IBM SPSS statistics v.25. Results: Thirty-two patients were included in our analysis. The median age was 63.1 years (25th-75th percentile: 57.6 – 69.6). 62.5% of the patients had endometrioid histology, 21.9% serous histology and 15.6% of them displayed other histology. 46.9% of the patients had grade 1-2 tumors and 53.1% grade 3 tumors. 21.9% of them were diagnosed with stage 1-2 disease, while 78.1% presented with stage 3 disease. 62.5% received 0-1 prior lines of treatment and 37.5% of them received more than 2 prior lines. Molecular characteristics are presented in the table. All MSI-High patients received anti-PD1 monotherapy with a median PFS of 11.9 months (95% CI:2.3-21.5). Microsatellite Stable (MSS) patients received pembrolizumab-lenvatinib combination with median PFS 7.54 months (95% CI:2.6-11.5). ER positivity was associated with significant PFS benefit in both the ICI monotherapy group (11.9 vs. 0.63 months, p=0.061) and the group that received ICI/TKI combination (11.3 vs. 1.75 months, p=0.001). Analogous benefit was noted in the Overall Survival post start of IO or IO/TKI treatment (9.8 vs 0.6 months in MSI-high patients and 20.6 vs 5.9 months in MSS patients). ER-positivity remained an independent predictive factor favoring PFS in the Multivariate Cox regression analysis when adjusting for immunotherapy type, histology, and previous lines of therapy (HR=0.216, p=0.013). Conclusions: ER expression proved to be an independent prognostic factor regarding PFS in our cohort of patients. Further studies are needed to investigate the role of ER as a predictive biomarker for immunotherapy in EC. [Table: see text]

ENVASARC: A pivotal trial of envafolimab and envafolimab in combination with ipilimumab in patients with advanced or metastatic undifferentiated pleomorphic sarcoma or myxofibrosarcoma who have progressed on prior chemotherapy.

TPS11583 Background: Metastatic undifferentiated pleomorphic sarcoma (UPS) and the genetically related myxofibrosarcoma (MFS) are soft tissue sarcoma (STS) subtypes with poor prognoses. While responses to first-line chemotherapy can approach 20%, efficacy remains limited in the 2nd-line setting and beyond. Pazopanib, the only FDA approved treatment in the refractory setting, has demonstrated an objective response rate (ORR) of 4%. Envafolimab is a single domain PD-L1 antibody administered by rapid subcutaneous (SQ) injection that is approved for the treatment of microsatellite instability-high (MSI-H) cancer in China. The activity of envafolimab appears to be similar to other PD-1 antibodies administered intravenously (i.v.). Envafolimab demonstrated a 32% ORR in MSI-H colorectal cancer patients with progressive disease following three approved chemotherapeutics, similar to the ORR of 28% and 33% with nivolumab and pembrolizumab in these patients, respectively. The rationale for the ENVASARC is based on envafolimab activity in STS in phase 1 trials and previously reported activity of checkpoint inhibition in UPS/MFS: single-agent pembrolizumab demonstrated a 23% ORR, while the combination of nivolumab and ipilimumab demonstrated a 29% ORR in refractory UPS/MFS. Methods: ENVASARC (NCT 04480502) is a pivotal multicenter (at 30 U.S. and U.K. centers) open-label, randomized, non-comparative, parallel cohort study of envafolimab 600 mg every 3 weeks by SQ injection (n = 80) or envafolimab 600 mg every 3 weeks by SQ injection combined with ipilimumab 1 mg/kg every 3 weeks i.v. for four doses (n = 80) in patients with locally advanced, unresectable or metastatic UPS/MFS with disease progression on one or two lines of prior therapy. The primary objective of each of parallel cohort is to demonstrate an ORR with a lower limit of the 95% confidence interval that excludes 5.0% in each cohort. If ≥ 9 responders are observed among the 80 patients enrolled in each cohort, then the lower bound of the 95% confidence interval will exclude 5.0%. Secondary endpoints include duration of response, PFS and OS. Key inclusion criteria: ≤ 2 prior lines of therapy ([neo]adjuvant therapy excluded), ECOG ≤ 1. Clinical trial information: NCT04480502 .

Genomic characteristics and prognosis of lung cancer patients with MSI-H: A cohort study

BackgroundMicrosatellite instability (MSI) is the first pan-cancer biomarker approved to guide immune checkpoint inhibitor therapy for MSI-high (MSI-H) solid tumors. In lung cancer, the MSI-H frequency is very low, and the genetic characteristics and prognosis of lung cancer with MSI-H were rarely reported. MethodsNext-generation sequencing and immunohistochemistry were used detect MSI status, tumor mutation burden (TMB) and PD-L1 expression. ResultsAmong 12,484 lung cancer patients screened, 66 were found with MSI-H, the proportion was as low as 0.5%. Compared with Microsatellite stability (MSS), TMB was higher in MSI-H lung cancer patients, while PD-L1 expression showed no considerable difference between MSI-H and MSS. After propensity score matching, compared with MSS, the most common companion mutations in MSI-H were TP53, BRCA2, TGFBR2, PTEN and KMT2C. In MSI-H lung adenocarcinoma with EGFR mutation, TGFBR2 and ERBB2 had higher mutation frequency than in MSS. ConclusionThe current study reveals the genetic characteristics of MSI-H lung cancer, which advanced our understanding of MSI-H lung cancer.

T cell expressed microRNA-155 promotes antitumor immunity and immune checkpoint blockade responses in colon cancer through repression of Ship1

Abstract Colorectal cancer (CRC) is the 2 nddeadliest cancer globally and has the 3 rdhighest incidence and mortality in the United States. Advanced-stage disease is incurable by current clinical standards. Thus, alternative treatments are being explored, including immune checkpoint blockade (ICB) to prevent T cell inactivation by tumors. ICB induces a robust response in patients with microsatellite instability-high (MSI-H) metastatic CRC. However, most CRC patients are not responsive to ICB. Our analysis revealed MSI-H patients exhibit an immune cell-mediated inflammatory tumor microenvironment (TME) that is associated with the expression of microRNAs (miRs) linked to immune cell regulation. By studying T cell-associated miRs in MSI-H colon cancer patients, and through Crispr-Cas9 based in vivo screening, we identified T cell miR-155 as the miR most highly associated with ICB responsive patients. T cell miR-155 was necessary for ICB responses in multiple colon cancer preclinical models and promoted Th1-helper T cell and cytotoxic T lymphocyte enrichment in the TME, reflecting a robust immune response. T cell miR-155 controls ICB response and cancer immunity by repressing a network of target genes, most notably SHIP1. Loss of T cell miR-155 derepressed SHIP-1 gene expression in our study. Additionally, SHIP-1 was expressed in human tumor-associated T cells, with lower expression correlating to better patient outcomes. In vivo, we demonstrated that SHIP-1 inhibition partially restored tumor immunity in mice specifically lacking T cell miR-155. These findings suggest a dependence on T cell miR-155 and its targets for effective cancer immunity and ICB efficacy in colon cancer, identifying miR-155 as a candidate biomarker and therapeutic. Supported by grants from NIH (F30 CA260977)

Abstract 5455: Large-scale cancer genomic analysis reveals significant disparities between microsatellite instability and tumor mutational burden

Abstract Microsatellite instability (MSI) and tumor mutational burden (TMB) are efficacy biomarkers for cancer immunotherapies, with both MSI-high and TMB-high considered hypermutator phenotypes that predict better drug responses. However, the inter-relationship between these biomarkers has not been well-investigated. Herein, we conducted a large-scale cancer genomic analysis to characterize patterns of distribution between MSI-high and TMB-high across 22 human cancer types, and identify mutated genes that may contribute to MSI-high cancers.We analyzed somatic mutation data from the Genomics Evidence Neoplasia Information Exchange (GENIE; n=49,496) to characterize gene mutations and patterns of distribution between MSI and TMB for each cancer. Associations between TMB and MSI were evaluated using multivariable linear regression models adjusted for age at sequencing report, sex, race, sequencing center, and histological subtype. Associations between MSI and gene mutations were evaluated using multivariable logistic regression models adjusted for the above mentioned covariates and TMB.Our analysis revealed that considerable differences in the prevalence of MSI-high and TMB-high by cancer types. The moderate differences were observed in cancers with the top prevalence of MSI-high/TMB-high, such as 31.1%/28.7% in endometrial cancer, 18.4%/17.7% in colorectal cancer, and 17.2%/12.2% in stomach cancer, while most other cancers showed high differences of prevalence (&amp;gt;10%). Notably, MSI-high patients were observed to have a substantial proportion of TMB-low phenotypes ranging from 31% to 89% among these cancer types, likely indicating distinct drug responses compared to TMB-high phenotypes. Association analyses between TMB and MSI for these cancers showed the strongest associations in colorectal cancer (P=4.0 × 10-255) and stomach cancer (P=6.2 × 10-60), while marginal or no associations were observed in several cancers including head and neck cancer (P=0.08) and hepatocellular carcinoma (P=0.15). In addition, we identified several mutated genes associated with MSI-high phenotypes, including known mismatch repair genes (e.g., MSH3, POLD1, MLH1, and MSH6) and novel mutated genes (e.g., RNF43, ARID1A, ARID1B, NOTCH3, SMARCA4, KMT2C, and CREBBP), in endometrial cancer (n=32 genes), in colorectal cancer (n=29 genes) and in stomach cancer (n=18 genes), at a Bonferroni-corrected P &amp;lt; 0.05.Our study revealed large discrepancies in prevalence between MSI-high and TMB-high in many cancer types, highlighting the need to consider distinct or combined biomarkers for immunotherapies. Our study also identified novel mutated genes associated with MSI-high cancers, providing additional insights into MSI-high carcinogenesis and candidate genetic biomarkers to screen patients for potential immunotherapy. Citation Format: Jungyoon Choi, Jung Sun Kim, Kyong Hwa Park, Xingyi Guo, Yeul Hong Kim. Large-scale cancer genomic analysis reveals significant disparities between microsatellite instability and tumor mutational burden. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5455.

Evaluation of Microsatellite Instability Molecular Analysis versus Immuno-Histochemical Interpretation in Malignant Neoplasms with Different Localizations.

MMR gene germline mutations are considered a major genetic disorder in patients with hereditary nonpolyposis colon cancer (HNPCC) or Lynch syndrome; A total of 15% of sporadic colon carcinomas are MSI-High. MSI has also been observed in other cancers, such as endometrial, gastric, and ovarian cancer. The aim of the current study was to correlate and outline the optimal method between the molecular testing of the instability of microsatellite DNA regions (MSI status) and the loss of protein expression by immunehistochemistry (MMR). A total of 242 paraffin-embedded tissues from gastrointestinal, gynecological, genitourinary, lung, breast, and unknown primary cancer patients were analyzed for the expression of MLH1/MSH2/MSH6/PMS2 by immunohistochemistry, as well as for the molecular analysis of MSI status using PCR-based molecular fragment analysis. A total of 29 MSI-High patients were detected molecularly, while 23 patients were detected by immunohistochemistry, with rates that are comparable according to the literature. Based on the agreement coefficient of the two methods, a substantial agreement emerged (Kappa = 0.675 with standard error = 0.081, p &lt; 0.001). Despite the substantial agreement, both methods ought to be established to determine MSI-H/dMMR status in all cancer types as a first-line screening test.