Search

Constitutional mismatch repair deficiency (CMMRD) is a rare syndrome characterized by an increased incidence of cancer. It is caused by biallelic germline mutations in one of the four mismatch repair genes (MMR) genes: MLH1, MSH2, MSH6, or PMS2. Accurate diagnosis accompanied by a proper molecular genetic examination plays a crucial role in cancer management and also has implications for other family members. In this report, we share the impact of the diagnosis and challenges during the clinical management of two brothers with CMMRD from a non-consanguineous family harbouring compound heterozygous variants in the PMS2 gene. Both brothers presented with different phenotypic manifestations and cancer spectrum. Treatment involving immune checkpoint inhibitors significantly contributed to prolonged survival in both patients affected by lethal gliomas. The uniform hypermutation also allowed immune-directed treatment using nivolumab for the B-cell lymphoma, thereby limiting the intensive chemotherapy exposure in this young patient who remains at risk for subsequent malignancies., (© 2024. The Author(s).)

Background: Constitutional mismatch repair deficiency (CMMRD) is a rare and extraordinarily penetrant childhood-onset cancer predisposition syndrome. Genetic diagnosis is often hampered by the identification of mismatch repair (MMR) variants of unknown significance and difficulties in PMS2 analysis, the most frequently mutated gene in CMMRD. We present the validation of a robust functional tool for CMMRD diagnosis and the characterization of microsatellite instability (MSI) patterns in blood and tumors., Methods: The highly sensitive assessment of MSI (hs-MSI) was tested on a blinded cohort of 66 blood samples and 24 CMMRD tumor samples. Hs-MSI scores were compared with low-pass genomic instability scores (LOGIC/MMRDness). The correlation of hs-MSI scores in blood with age of cancer onset and the distribution of insertion-deletion (indel) variants in microsatellites were analyzed in a series of 169 individuals (n = 68 CMMRD, n = 124 non-CMMRD)., Results: Hs-MSI achieved high accuracy in the identification of CMMRD in blood (sensitivity 98.5% and specificity 100%) and detected MSI in CMMRD-associated tumors. Hs-MSI had a strong positive correlation with whole low-pass genomic instability LOGIC scores (r = 0.89, P = 2.2e-15 in blood and r = 0.82, P = 7e-3 in tumors). Indel distribution identified PMS2 pathogenic variant (PV) carriers from other biallelic MMR gene PV carriers with an accuracy of 0.997. Higher hs-MSI scores correlated with younger age at diagnosis of the first tumor (r = -0.43, P = 0.011)., Conclusions: Our study confirms the accuracy of the hs-MSI assay as ancillary testing for CMMRD diagnosis, which can also characterize MSI patterns in CMMRD-associated cancers. Hs-MSI is a powerful tool to pinpoint PMS2 as the affected germline gene and thus potentially personalize cancer risk., (© Association for Diagnostics & Laboratory Medicine 2024.)

Background: Constitutional mismatch repair deficiency (CMMRD) syndrome is a rare and aggressive cancer predisposition syndrome. Because a scarcity of data on this condition contributes to management challenges and poor outcomes, we aimed to describe the clinical spectrum, cancer biology, and impact of genetics on patient survival in CMMRD., Methods: In this cohort study, we collected cross-sectional and longitudinal data on all patients with CMMRD, with no age limits, registered with the International Replication Repair Deficiency Consortium (IRRDC) across more than 50 countries. Clinical data were extracted from the IRRDC database, medical records, and physician-completed case record forms. The primary objective was to describe the clinical features, cancer spectrum, and biology of the condition. Secondary objectives included estimations of cancer incidence and of the impact of the specific mismatch-repair gene and genotype on cancer onset and survival, including after cancer surveillance and immunotherapy interventions., Findings: We analysed data from 201 patients (103 males, 98 females) enrolled between June 5, 2007 and Sept 9, 2022. Median age at diagnosis of CMMRD or a related cancer was 8·9 years (IQR 5·9-12·6), and median follow-up from diagnosis was 7·2 years (3·6-14·8). Endogamy among minorities and closed communities contributed to high homozygosity within countries with low consanguinity. Frequent dermatological manifestations (117 [93%] of 126 patients with complete data) led to a clinical overlap with neurofibromatosis type 1 (35 [28%] of 126). 339 cancers were reported in 194 (97%) of 201 patients. The cumulative cancer incidence by age 18 years was 90% (95% CI 80-99). Median time between cancer diagnoses for patients with more than one cancer was 1·9 years (IQR 0·8-3·9). Neoplasms developed in 15 organs and included early-onset adult cancers. CNS tumours were the most frequent (173 [51%] cancers), followed by gastrointestinal (75 [22%]), haematological (61 [18%]), and other cancer types (30 [9%]). Patients with CNS tumours had the poorest overall survival rates (39% [95% CI 30-52] at 10 years from diagnosis; log-rank p<0·0001 across four cancer types), followed by those with haematological cancers (67% [55-82]), gastrointestinal cancers (89% [81-97]), and other solid tumours (96% [88-100]). All cancers showed high mutation and microsatellite indel burdens, and pathognomonic mutational signatures. MLH1 or MSH2 variants caused earlier cancer onset than PMS2 or MSH6 variants, and inferior survival (overall survival at age 15 years 63% [95% CI 55-73] for PMS2, 49% [35-68] for MSH6, 19% [6-66] for MLH1, and 0% for MSH2; p<0·0001). Frameshift or truncating variants within the same gene caused earlier cancers and inferior outcomes compared with missense variants (p<0·0001). The greater deleterious effects of MLH1 and MSH2 variants as compared with PMS2 and MSH6 variants persisted despite overall improvements in survival after surveillance or immune checkpoint inhibitor interventions., Interpretation: The very high cancer burden and unique genomic landscape of CMMRD highlight the benefit of comprehensive assays in timely diagnosis and precision approaches toward surveillance and immunotherapy. These data will guide the clinical management of children and patients who survive into adulthood with CMMRD., Funding: The Canadian Institutes for Health Research, Stand Up to Cancer, Children's Oncology Group National Cancer Institute Community Oncology Research Program, Canadian Cancer Society, Brain Canada, The V Foundation for Cancer Research, BioCanRx, Harry and Agnieszka Hall, Meagan's Walk, BRAINchild Canada, The LivWise Foundation, St Baldrick Foundation, Hold'em for Life, and Garron Family Cancer Center., Competing Interests: Declaration of interests ALa reports payment from Alexion, support from Servier and stock from Gilead, outside of the submitted work. AV is co-lead role of the Consortium for Childhood Cancer Predisposition, outside of the submitted work. BH reports payment and stock from Invitae, outside of the submitted work. BC reports participation as data safety and monitoring board member in ReRad Study, participation in the chapter advisory board for Make a Wish Canada Nova Scotia, and participation in the medical advisory committee for Make a Wish Canada, outside of the submitted work. CCP reports grants from St Baldrick's Foundation, outside of the submitted work. DSZ reports consulting fees for Bayer, AstraZeneca, Accendatech, Novartis, Day One, FivePhusion, Alexion, Amgen, and Norgine, outside of the submitted work. DTB reports grants from MSD and Novocure, consulting fees from Nanocarry Therapeutics and Servier, and payment from Servier, outside of the submitted work. EO reports payment and support from Alexion for educational event, outside of the submitted work. EB reports grants from Roche and board participation for Novartis, Alexion and Gilead, outside of the submitted work. FC reports grants from Hall Hunter Foundation (UK), outside of the submitted work. HBF reports payments from Illumina and Sanofi Genzyme, support from Illumina, participation as scientific advisory committee for Sanofi Genzyme, International Gaucher Alliance and Igentify, stock from Igentify, and receipt of materials from Illumina, outside of the submitted work. IW reports grants from Chimerix and payment from COG Partners, outside of the submitted work. IS reports grants from Fondation Saint-Luc and FNRS-CDR, outside of the submitted work. JK reports other financial interests at Servier and PRA Health Sciences, outside of the submitted work. JRG-S reports participation on the board of the Philippine Society of Pediatric Oncology and Philippine Board of Pediatric Oncology, and stock in Macrogenics, Moderna, Mirati Therapeutics, CRISPR Therapeutics, Repligen, Quidelortho, and Shockwave Medical, outside of the submitted work. KJB reports consulting fees from US WorldMeds, Springworks Therapeutics, Alexion, and YmAbs, and payment from Alexion, outside of the submitted work. MS reports grants and support from the Swedish Childhood Cancer Fund, participation as a data safety and monitoring board member for clinical trial NCT05230758, and participation in the Swedish Pediatric CNS tumour group, outside of the submitted work. MAC reports financial support from SUNY Upstate Department of Pediatrics and board participation for Paige's Butterfly Run, outside of the submitted work. MO reports payment from Aptitude Health and participation on a data safety monitoring board or advisory board for Ultragenyx and Abeona, outside of the submitted works. MZ reports payment and support from and board participation for AstraZeneca. NW reports grants from CANSEARCH Foundation, Childhood Cancer Research Switzerland, and the Foundation for Children and Adolescents with Cancer; payment, support, and advisory board participation for Swedish Orphan Biovitrum; and board participation for Childhood Cancer Switzerland, outside of the submitted work. NH reports grants from the National Institutes of Health (NIH) and board participation for Incyte and Pfizer, outside of the submitted work. PCN reports grants from the Canadian Institutes for Health Research (CIHR) Foundation, US Department of Defense, and Garron Family Cancer Centre, outside of the submitted work. RP reports participation in the Collaborative Group of the Americas on Inherited Gastrointestinal Cancer, outside of the submitted work. RT reports consulting fees from Fennec Pharmaceuticals and Day One Biopharmaceuticals and payment from Fennec Pharmaceuticals, outside of the submitted work. SS reports payments from Sanofi Pharmaceuticals and Mylan Pharmaceutical, and board participation for Sanofi Pharmaceuticals, outside of the submitted work. SB reports consulting fees from Hoffmann-La Roche, YmAbs, MAP Biopharma and SERB SAS, and payment from Zschimmer & Schwarz Mohsdorf, outside of the submitted work. UI reports board participation in Pakistan Society of Pediatric Oncology, outside of the submitted work., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Immune checkpoint inhibition (ICI) is effective for replication-repair-deficient, high-grade gliomas (RRD-HGG). The clinical/biological impact of immune-directed approaches after failing ICI monotherapy is unknown. We performed an international study on 75 patients treated with anti-PD-1; 20 are progression free (median follow-up, 3.7 years). After second progression/recurrence (n = 55), continuing ICI-based salvage prolonged survival to 11.6 months (n = 38; P < 0.001), particularly for those with extreme mutation burden (P = 0.03). Delayed, sustained responses were observed, associated with changes in mutational spectra and the immune microenvironment. Response to reirradiation was explained by an absence of deleterious postradiation indel signatures (ID8). CTLA4 expression increased over time, and subsequent CTLA4 inhibition resulted in response/stable disease in 75%. RAS-MAPK-pathway inhibition led to the reinvigoration of peripheral immune and radiologic responses. Local (flare) and systemic immune adverse events were frequent (biallelic mismatch-repair deficiency > Lynch syndrome). We provide a mechanistic rationale for the sustained benefit in RRD-HGG from immune-directed/synergistic salvage therapies. Future approaches need to be tailored to patient and tumor biology., Significance: Hypermutant RRD-HGG are susceptible to checkpoint inhibitors beyond initial progression, leading to improved survival when reirradiation and synergistic immune/targeted agents are added. This is driven by their unique biological and immune properties, which evolve over time. Future research should focus on combinatorial regimens that increase patient survival while limiting immune toxicity. This article is featured in Selected Articles from This Issue, p. 201., (©2023 American Association for Cancer Research.)

Purpose: Checkpoint inhibitors have limited efficacy for children with unselected solid and brain tumors. We report the first prospective pediatric trial (NCT02992964) using nivolumab exclusively for refractory nonhematologic cancers harboring tumor mutation burden (TMB) ≥5 mutations/megabase (mut/Mb) and/or mismatch repair deficiency (MMRD)., Patients and Methods: Twenty patients were screened, and 10 were ultimately included in the response cohort of whom nine had TMB >10 mut/Mb (three initially eligible based on MMRD) and one patient had TMB between 5 and 10 mut/Mb., Results: Delayed immune responses contributed to best overall response of 50%, improving on initial objective responses (20%) and leading to 2-year overall survival (OS) of 50% [95% confidence interval (CI), 27-93]. Four children, including three with refractory malignant gliomas are in complete remission at a median follow-up of 37 months (range, 32.4-60), culminating in 2-year OS of 43% (95% CI, 18.2-100). Biomarker analyses confirmed benefit in children with germline MMRD, microsatellite instability, higher activated and lower regulatory circulating T cells. Stochastic mutation accumulation driven by underlying germline MMRD impacted the tumor microenvironment, contributing to delayed responses. No benefit was observed in the single patient with an MMR-proficient tumor and TMB 7.4 mut/Mb., Conclusions: Nivolumab resulted in durable responses and prolonged survival for the first time in a pediatric trial of refractory hypermutated cancers including malignant gliomas. Novel biomarkers identified here need to be translated rapidly to clinical care to identify children who can benefit from checkpoint inhibitors, including upfront management of cancer. See related commentary by Mardis, p. 4701., (©2023 The Authors; Published by the American Association for Cancer Research.)

Constitutional mismatch repair deficiency (CMMRD) is an aggressive and highly penetrant cancer predisposition syndrome. Because of its variable clinical presentation and phenotypical overlap with neurofibromatosis, timely diagnosis remains challenging, especially in countries with limited resources. Since current tests are either difficult to implement or interpret or both we used a novel and relatively inexpensive functional genomic assay (LOGIC) which has been recently reported to have high sensitivity and specificity in diagnosing CMMRD. Here we report the clinical and molecular characteristics of nine patients diagnosed with cancer and suspected to have CMMRD and highlight the challenges with variant interpretation and immunohistochemical analysis that led to an uncertain interpretation of genetic findings in 6 of the 9 patients. Using LOGIC, we were able to confirm the diagnosis of CMMRD in 7 and likely exclude it in 2 patients, resolving ambiguous result interpretation. LOGIC also enabled predictive testing of asymptomatic siblings for early diagnosis and implementation of surveillance. This study highlights the varied manifestations and practical limitations of current diagnostic criteria for CMMRD, and the importance of international collaboration for implementing robust and low-cost functional assays for resolving diagnostic challenges., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The neuroendocrine peptide somatostatin (SST) has long been thought of as influencing the deposition of the amyloid β peptide (Aβ) in Alzheimer's disease (AD). Missing have been in vivo data in a relevant Aβ amyloidosis model. Here we crossed App NL-F/NL-F mice with Sst-deficient mice to assess if and how the presence of Sst influences pathological hallmarks of Aβ amyloidosis. We found that Sst had no influence on whole brain neprilysin transcript, protein or activity levels, an observation that cannot be accounted for by a compensatory upregulation of the Sst paralog, cortistatin (Cort), that we observed in 15-month-old Sst-deficient mice. Sst-deficiency led to a subtle but significant increase in the density of cortical Aβ amyloid plaques. Follow-on western blot analyses of whole brain extracts indicated that Sst interferes with early steps of Aβ assembly that manifest in the appearance of SDS-stable smears of 55-150 kDa in Sst null brain samples. As expected, no effect of Sst on tau steady-state levels or its phosphorylation were observed. Results from this study are easier reconciled with an emerging body of data that point toward Sst affecting Aβ amyloid plaque formation through direct interference with Aβ aggregation rather than through its effects on neprilysin expression., (© 2023. The Author(s).)

Purpose: Diagnosis of Mismatch Repair Deficiency (MMRD) is crucial for tumor management and early detection in patients with the cancer predisposition syndrome constitutional mismatch repair deficiency (CMMRD). Current diagnostic tools are cumbersome and inconsistent both in childhood cancers and in determining germline MMRD., Patients and Methods: We developed and analyzed a functional Low-pass Genomic Instability Characterization (LOGIC) assay to detect MMRD. The diagnostic performance of LOGIC was compared with that of current established assays including tumor mutational burden, immunohistochemistry, and the microsatellite instability panel. LOGIC was then applied to various normal tissues of patients with CMMRD with comprehensive clinical data including age of cancer presentation., Results: Overall, LOGIC was 100% sensitive and specific in detecting MMRD in childhood cancers (N = 376). It was more sensitive than the microsatellite instability panel (14%, P = 4.3 × 10 -12 ), immunohistochemistry (86%, P = 4.6 × 10 -3 ), or tumor mutational burden (80%, P = 9.1 × 10 -4 ). LOGIC was able to distinguish CMMRD from other cancer predisposition syndromes using blood and saliva DNA ( P < .0001, n = 277). In normal cells, MMRDness scores differed between tissues (GI > blood > brain), increased over time in the same individual, and revealed genotype-phenotype associations within the mismatch repair genes. Importantly, increased MMRDness score was associated with younger age of first cancer presentation in individuals with CMMRD ( P = 2.2 × 10 -5 )., Conclusion: LOGIC was a robust tool for the diagnosis of MMRD in multiple cancer types and in normal tissues. LOGIC may inform therapeutic cancer decisions, provide rapid diagnosis of germline MMRD, and support tailored surveillance for individuals with CMMRD.

Competing Interests: Daniel A. MorgensternHonoraria: Ology Medical Education, WebMD, PlatformQ HealthConsulting or Advisory Role: Clarity Pharmaceuticals, EUSA Pharma, Ymabs Therapeutics IncSpeakers' Bureau: Ymabs Therapeutics IncResearch Funding: Bristol Myers Squibb (Inst), AbbVie (Inst), Lilly (Inst), Bayer (Inst), Cellectar (Inst), Roche (Inst)Travel, Accommodations, Expenses: Lilly Sumedha SudhamanEmployment: Strand Life Sciences David E. KramConsulting or Advisory Role: Foundation Medicine Cynthia HawkinsConsulting or Advisory Role: BayerPatents, Royalties, Other Intellectual Property: IP for low-grade glioma and sarcoma fusion panels as well as medulloblastoma subgrouping panel Eric BouffetConsulting or Advisory Role: NovartisResearch Funding: Roche (Inst), Bristol Myers Squibb (Inst) Yoon-Jae ChoExpert Testimony: Barr and MudfordNo other potential conflicts of interest were reported.

Competing Interests: Sumedha SudhamanEmployment: Strand Life Sciences Cynthia HawkinsConsulting or Advisory Role: BayerPatents, Royalties, Other Intellectual Property: IP for low-grade glioma and sarcoma fusion panels and medulloblastoma subgrouping panel Eric BouffetConsulting or Advisory Role: NovartisResearch Funding: Roche, Bristol Myers SquibbNo other potential conflicts of interest were reported.