Germline Variants Research Articles

Pathogenic and likely pathogenic germline variation in patients with myeloid malignancies and their unrelated HLA-matched hematopoietic stem cell donors

Aims: The revised 2022 World Health Organization classification recognizes myeloid neoplasms with associated germline predisposition as a defined subcategory, underscoring the clinical significance of likely pathogenic (LPV) and pathogenic (PV) germline variation in these diseases. To better understand the role of LPV/PV in blood or marrow transplants (BMT), a curative therapy for myeloid neoplasms, we measure their frequency and association with mortality in two cohorts of donor-recipient pairs. Methods: LPV/PV frequencies in 665 cancer-related genes were measured using exomechip genotyping data in 1990 acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients and their unrelated donors, registered with the Center for International Blood and Marrow Transplant Research. Cox proportional hazard models were used to test variant association with recipient mortality one-year post-transplant. Results: Thirteen autosomal dominant (AD) LPV/PV in eight genes were found in 2.8% of patients and 2.2% of donors; those linked to autosomal recessive conditions appeared in 11.1% of patients and 11% of donors. The most common AD LPV/PV mutations in recipients were found in DDX41 (n = 18). For donors, the most frequent AD PVs occurred in CHEK2 (n = 21) and Fanconi Anemia (FA) genes (n = 7). DDX41 and CHEK2 variation did not correlate with patient survival, but patients with donors with an LPV/PVs in an FA gene had lower survival (HR = 2.38, 95%CI: 1.06-5.31, P = 0.035) than patients whose donors did not have an FA LPV/PV. Conclusion: We identified LPVs/PVs in cancer genes in donors and recipients and are the first to show an association of donor FA PVs with mortality after BMT.

Challenges and approaches to calibrating patient phenotype as evidence for cancer gene variant classification under ACMG/AMP guidelines.

Since first publication of the American College of Medical Genetics and Genomics/Association for Medical Pathology (ACMG/AMP) variant classification guidelines, additional recommendations for application of certain criteria have been released (https://clinicalgenome.org/docs/), to improve their application in the diagnostic setting. However, none have addressed use of the PS4 and PP4 criteria, capturing patient presentation as evidence towards pathogenicity. Application of PS4 can be done through traditional case-control studies, or "proband counting" within or across clinical testing cohorts. Review of the existing PS4 and PP4 specifications for Hereditary Cancer Gene Variant Curation Expert Panels revealed substantial differences in the approach to defining specifications. Using BRCA1, BRCA2 and TP53 as exemplar genes, we calibrated different methods proposed for applying the "PS4 proband counting" criterion. For each approach, we considered limitations, non-independence with other ACMG/AMP criteria, broader applicability, and variability in results for different datasets. Our findings highlight inherent overlap of proband-counting methods with ACMG/AMP frequency codes, and the importance of calibration to derive dataset-specific code weights that can account for potential between-dataset differences in ascertainment and other factors. Our work emphasizes the advantages and generalizability of logistic regression analysis over simple proband-counting approaches to empirically determine the relative predictive capacity and weight of various personal clinical features in the context of multigene panel testing, for improved variant interpretation. We also provide a general protocol, including instructions for data formatting and a web-server for analysis of personal history parameters, to facilitate dataset-specific calibration analyses required to use such data for germline variant classification.

Genotype-phenotype correlation study of structural abnormalities in a fetal brain caused by a novel KDM4B variant.

Fetal ventriculomegaly (VM), a common brain structure malformation detected during prenatal ultrasound diagnosis, is associated with an increased risk of neurodevelopmental disorders (NDDs) after birth. KDM4B encodes a lysine-specific demethylase that interacts with histone H3K23me3. Variations in KDM4B are reportedly associated with human NDDs; however, only 11 such patients have been reported. Herein, we report a fetus with VM and agenesis of the corpus callosum (ACC), which suggests that KDM4B plays an important role in fetal brain development. Fetal skin tissue and parental peripheral venous blood samples were collected. Whole-exome and Sanger sequencing were performed to analyze fetal germline variants. Human 293T cells transfected with wild-type or mutant KDM4B were used for western blotting (WB) to analyze protein expression levels. An insertion variant of KDM4B, NM_015015.3: c.2889_2890insGAGAGCATCACGGTGAGCTGTGGGGTGGGGCAGGGGGCGGGGGGAGGCTGGGAGCACAGTGACAACCTGTACCCC, was identified in the fetal tissue; however, the parents carried the wild-type gene. The WB results indicated significantly reduced expression of the mutant protein, likely owing to decreased stability. The structural abnormalities in the brain of the studied fetus may be attributed to an insertion variant of KDM4B. This study highlights the importance of screening for KDM4B variants and considering potential copy number variations when observing VM or ACC in prenatal ultrasound imaging.

DOP58 Human Leukocyte Antigen drives methylation signatures in primary sclerosing cholangitis but not in IgG4-related sclerosing cholangitis

Abstract Background Primary sclerosing cholangitis (PSC) and IgG4-related sclerosing cholangitis (IgG4-SC) are fibro-inflammatory hepatobiliary conditions, with genetic, environmental, and immunologic risk factors, in which epigenetic alterations may provide insights into pathophysiology and novel biomarkers. Methods Whole blood DNA methylation profiling and genotyping was performed in 70 PSC (57 with PSC and ulcerative colitis (PSC-UC)), 56 IgG4-SC, 66 UC, and 88 healthy controls (HC), with MethylationEPIC and Global Screening arrays (Illumina). UC patients were selected to match the clinical characteristics of UC in the PSC-UC cohort. Methylation data was processed with Minfi and limma, genotyping analysed with Plink, and meQTLs with linear models. Results There were 31, 13 and 8 Holm-significant methylation differences between PSC and controls, IgG4-SC and controls, and UC and controls respectively (8 probes shared). Inflammatory genes (including CEP97, IFNAR1, TXK, and SMAD2) and methylation loci associated with mitochondrial DNA copy number (C5orf36, PYY, and MTRNR2L1) were predominant. Sub-analyses of PSC-UC and PSC without IBD detected 25 and 4 differences with HC respectively (p<0.05). DNA methylation age acceleration was observed in IgG4-SC, but not on PSC, PSC-IBD or UC. MeQTL analyses to identify genetic determinants of methylation revealed a strong HLA signal in PSC but not IgG4-SC, with 19/40 significant findings in 5 clusters (HLA-DRB1, HLA-DPB1, BTNL2, CSNK2B, and SFTA2). There was no overlap with the 36 meQTLs found in IgG4-SC. Using multivariate adaptive shrinkage for meQTLs in PSC, IgG4-SC, and UC yielded 5505 meQTLs with local false discovery rate <0.05 in at least one condition, with 1230 unique to PSC, and 1043 to IgG4-SC. Conclusion We identify characteristic epigenetic alterations in PSC and IgG4-related disease, providing insights into disease pathogenesis; and highlight the potential interaction with germ-line variation.

Expansion of the complex genotypic and phenotypic spectrum of FGFR2-associated neurocutaneous syndromes

The fibroblast growth factor receptors comprise a family of related but individually distinct tyrosine kinase receptors. Within this family, FGFR2 is a key regulator in many biological processes, e.g., cell proliferation, tumorigenesis, metastasis, and angiogenesis. Heterozygous activating non-mosaic germline variants in FGFR2 have been linked to numerous autosomal dominantly inherited disorders including several craniosynostoses and skeletal dysplasia syndromes. We report on a girl with cutaneous nevi, ocular malformations, macrocephaly, mild developmental delay, and the initial clinical diagnosis of Schimmelpenning–Feuerstein–Mims syndrome, a very rare mosaic neurocutaneous disorder caused by postzygotic missense variants in HRAS, KRAS, and NRAS. Exome sequencing of blood and affected skin tissue identified the mosaic variant c.1647=/T > G p.(Asn549=/Lys) in FGFR2, upstream of the RAS signaling pathway. The variant is located in the tyrosine kinase domain of FGFR2 in a region that regulates the activity of the receptor and structural mapping and functional characterization revealed that it results in constitutive receptor activation. Overall, our findings indicate FGFR2-associated neurocutaneous syndrome as the accurate clinical-molecular diagnosis for the reported individual, and thereby expand the complex genotypic and phenotypic spectrum of FGFR-associated disorders. We conclude that molecular analysis of FGFR2 should be considered in the genetic workup of individuals with the clinical suspicion of a mosaic neurocutaneous condition, as the knowledge of the molecular cause might have relevant implications for genetic counseling, prognosis, tumor surveillance and potential treatment options.

Development and evaluation of INT2GRATE: a platform for comprehensive assessment of the role of germline variants informed by tumor signature profile in Lynch syndrome.

The presence of variants of uncertain significance (VUS) in DNA mismatch repair (MMR) genes leads to uncertainty in the clinical management of patients being evaluated for Lynch syndrome (LS). Currently, there is no platform to systematically use tumor-derived evidence alongside germline data for the assessment of VUS in relation to LS. We developed INT2GRATE (INTegrated INTerpretation of GeRmline And Tumor gEnomes) to leverage information from the tumor genome to inform the potential role of constitutional VUS in MMR genes. INT2GRATE platform has two components: a comprehensive evidence-based decision tree that integrates well-established clinico-genomic data from both the tumor and constitutional genomes to help inform the potential relevance of germline VUS in LS; and a web-based user interface (UI). With the INT2GRATE decision tree operating in the backend, INT2GRATE UI enables the front-end collection of comprehensive clinical genetics and tumor-derived evidence for each VUS to facilitate INT2GRATE assessment and data sharing in the publicly accessible ClinVar database. The performance of the INT2GRATE decision tree was assessed by qualitative retrospective analysis of genomic data from 5057 cancer patients with MMR alterations which included 52 positive control cases. Of 52 positive control cases with LS and pathogenic MMR alterations, 23 had all the testing parameters for the evaluation by INT2GRATE. All these variants were correctly categorized as INT2GRATE POSITIVE. The stringent INT2GRATE decision tree flagged 29 of positive cases by identifying the absence or unusual presentation of specific evidence, highlighting the conservative INT2GRATE logic in favor of a higher degree of confidence in the results. The remaining 99% of cases were correctly categorized as INCONCLUSIVE due to the absence of LS criteria and ≥1 tumor parameters. INT2GRATE is an effective platform for clinical and genetics professionals to collect and assess clinical genetics and complimentary tumor-derived information for each germline VUS in suspected LS patients. Furthermore, INT2GRATE enables the collation of integrated tumor-derived evidence relevant to germline VUS in LS, and sharing them with a large community, a practice that is needed in precision oncology.

Clinical Impact of Comprehensive Molecular Profiling in Adolescents and Young Adults with Sarcoma.

Sarcomas are a heterogenous group of tumours that commonly carry poor prognosis with limited therapeutic options. Adolescents and young adults (AYAs) with sarcoma are a unique and understudied patient population that have only achieved modest survival gains compared to other groups. We present our institutional experience of AYAs with sarcoma who underwent comprehensive molecular profiling (CMP) via either large-panel targeted DNA sequencing or whole genome and transcriptome sequencing and evaluated the feasibility and clinical impact of this approach. Genomic variants detected were determined to be clinically relevant and actionable following evaluation by the Molecular Tumour Board. Clinicians provided feedback regarding the utility of testing three months after reporting. Twenty-five patients who were recruited for CMP are included in this analysis. The median time from consent to final molecular report was 45 days (interquartile range: 37-57). Potentially actionable variants were detected for 14 patients (56%), and new treatment recommendations were identified for 12 patients (48%). Pathogenic germline variants were identified in three patients (12%), and one patient had a change in diagnosis. The implementation of CMP for AYAs with sarcoma is clinically valuable, feasible, and should be increasingly integrated into routine clinical practice as technologies and turnaround times continue to improve.

Germline USP36 Mutation Confers Resistance to EGFR-TKIs by Upregulating MLLT3 Expression in Patients with Non-Small Cell Lung Cancer.

Although somatic mutations were explored in depth, limited biomarkers were found to predict the resistance of EGFR tyrosine kinase inhibitors (EGFR-TKI). Previous studies reported N6-methyladenosine (m6A) levels regulated response of EGFR-TKIs; whether the germline variants located in m6A sites affected resistance of EGFR-TKIs is still unknown. Patients with non-small cell lung cancer (NSCLC) with EGFR-activating mutation were enrolled to investigate predictors for response of EGFR-TKIs using a genome-wide-variant-m6A analysis. Bioinformatics analysis and series of molecular biology assays were used to uncover the underlying mechanism. We identified the germline mutation USP36 rs3744797 (C > A, K814N) was associated with survival of patients with NSCLC treated with gefitinib [median progression-free survival (PFS): CC vs. CA, 16.30 vs. 10.50 months, P < 0.0001, HR = 2.45] and erlotinib (median PFS: CC vs. CA, 14.13 vs. 9.47 months, P = 0.041, HR = 2.63). Functionally, the C > A change significantly upregulated USP36 expression by reducing its m6A level. Meanwhile, rs3744797_A (USP36 MUT) was found to facilitate proliferation, migration, and resistance to EGFR-TKIs via upregulating MLLT3 expression in vitro and in vivo. More importantly, MLLT3 and USP36 levels are tightly correlated in patients with NSCLC, which were associated with prognosis of patients. Mechanistically, USP36 MUT stabilized MLLT3 by deubiquitinating MLLT3 in nucleoli and consequently activating its downstream signaling (HIF1α and Snai). Furthermore, inhibition of MLLT3 alleviated USP36 variant-induced EGFR-TKIs resistance in EGFR-mutant NSCLC. These findings characterized rs3744797 as an oncogenic variant in mediating EGFR-TKI resistance and tumor aggressiveness through deubiquitinating MLLT3, highlighting the variant as a predictive biomarker for EGFR-TKI response in NSCLC.

A phase II study of maintenance rucaparib in patients with platinum sensitive, advanced pancreatic cancer and a pathogenic germline or somatic variant in BRCA1, BRCA2 or PALB2: A four year survival update.

661 Background: We previously reported the results of a single arm, phase II study of maintenance rucaparib in patients with advanced, platinum-sensitive pancreatic cancer and pathogenic germline or somatic BRCA1, BRCA2 or PALB2 variants (Reiss et al, JCO, 2021). We now report the five year follow-up of this trial. Methods: Patients with advanced PC and a pathogenic germline or somatic variant in BRCA1, BRCA2 or PALB2 were enrolled in this single arm phase II study performed at the Abramson Cancer Center. Patients were required to have received ≥16 weeks of platinum-based treatment without evidence of platinum resistance, which was defined as growing lesions, new lesions or steadily rising tumor markers. Chemotherapy was discontinued and patients received rucaparib 600mg PO BID until progression or unacceptable toxicity. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall response rate (ORR), disease control rate (DCR) and overall survival (OS). Results: Of 42 evaluable patients, seven (16.7%) remain progression-free for over four years (5 gBRCA2, 1 sBRCA2, 1 gPALB2) of whom four (9.5%) have been progression-free for five years. Two of these four patients discontinued rucaparib due to adverse events after three and four years of therapy, respectively, without signs or symptoms of progression to date. At the cutoff date, we observe an mPFS 12.9 months, mOS 24.3 months, ORR 41.6% (9 PRs, 6 CRs), noting that three patients converted from partial to complete response since our prior publication. Two patients with ongoing responses succumbed to treatment-related MDS/AML following 2.1 and 4.8 years on study, respectively. Prior to receiving rucaparib, these individuals had received 13 and 10 months of cytotoxic chemotherapy for pancreatic cancer, respectively. Conclusions: Here we report the four year progression-free survival rate of maintenance rucaparib in patients with BRCA or PALB2 related pancreatic cancer. Our data suggest that a select portion of this patient population achieves highly durable clinical remissions. This finding is further highlighted by two patients who have discontinued rucaparib for adverse events one and two years ago, respectively, and have not had biochemical or imaging evidence of progression to date. Given the cost and risk of treatment-related leukemia associated with PARP inhibition, this data highlights the need to better understand the highly variable biology of patients with PC and BRCA or PALB2 variants, and raises the possibility of whether a very small, select group may be cured by PARP inhibitors. Clinical trial information: NCT03140670 .

Survival of patients with microsatellite instability-high and Lynch syndrome-associated pancreatic ductal adenocarcinomas.

640 Background: Pancreatic ductal adenocarcinoma (PDAC) remains a challenging disease due to its aggressive nature, late-stage diagnosis, and limited treatment options. There is an increased interest in cancers which harbor microsatellite instability (MSI) due to their susceptibility to immune checkpoint inhibitors. MSI in PDAC is rare, and little is known about survival in this subtype of pancreas cancers. Our aim was to assess overall survival in surgically resected high microsatellite instability (MSI-H), mismatch repair deficient (MMRd), and Lynch Syndrome (LS) associated PDACs treated in our center. Methods: Patients with surgically resected PDACs from 1990 to 2023 were identified. A total of 936 cases were sequenced utilizing MSK-IMPACT, a targeted next generation sequencing platform. Patients with germline or sporadic pathogenic variants or likely pathogenic variants in one of the DNA MMR genes MLH1, MSH2, MSH6, PMS2, or 3’ end of EpCAM were identified. MSI-H, MMRd, and LS-associated cases were matched to patients with microsatellite stable or MMR proficient, non-LS-associated PDAC in a 1:2 ratio with a direct match on age (±5 years), gender, and year of surgery (±3 years). Kaplan-Meier curves were used to visualize the data. A generalized estimating equation (GEE) cox model with robust sandwich estimator was used to compare matched cohorts. Results: 17 patients with MSI-H, MMRd or LS-associated surgically resected PDACs were identified. Five patients were classified as MSI-H, 3 patients were MSI-indeterminate, and 9 patients were microsatellite stable. Eight patients were found to have pathogenic germline variants in LS-associated genes. The remaining nine patients had sporadic pathogenic DNA MMR gene variants ( MLH1 n=3, MSH6 n=6). Median age at surgery was 66 (interquartile range (IQR) 60-77), 41% of the patients were female, and median year of surgery was 2014. MSI-H, MMRd or LS-associated PDACs were matched to 34 control patients. The median survival time of the cases was 12 years vs. 1.9 years in the control group. Five-year survival rate was 81% (IQR 60-100%) and 18% (7.4%-43%), respectively. LS-associated, MSI-H or MMRd status in resectable PDAC was a strong predictor of good prognosis (hazard ratio 0.17, 95% CI 0.07-0.38, p value &lt;0.001). Conclusions: MSI-H, MMRd or LS-associated PDACs displayed significantly better survival compared to their MSI-stable, MMR proficient, non-LS-associated counterparts, in the era before routine use of immunotherapy. It is expected that survival will be increased further with more frequent availability of immunotherapy.

A review of comprehensive genomic profiling testing in a Japanese single institution.

740 Background: In Japan, comprehensive genomic profiling (CGP) testing, including OncoGuide and FoundationOne CDx (F-1), were approved in June 2019 for patients with advanced solid tumors. Here, we report the landscape of CGP testing in our hospital. Methods: This study was conducted with a retrospective design to evaluate the clinico-genomic characteristics of patients who underwent CGP testing. OncoGuide is a panel using matched tumor tissue and blood sample, containing 124 genes, developed by the National Cancer Center. F1 is a tumor-only panel, containing 324 genes, developed by Foundation Medicine Industry. Results: Of the 460 patients enrolled in this study, 376 and 84 underwent F-1 and OncoGuide, respectively. The most common primary tumor was colorectal cancer (93 pts), followed by malignant melanoma (33 pts) and pancreatic cancer (33 pts). Actionable gene alteration was detected in 304 patients (66.1%). The detected actionable genes were TP53 (55.9%), APC (27.8%), KRAS (22.6%), and BRAF (8.5%) in colorectal cancer, BRAF (10.1%), CDKN2A (30.2%), CDKN2B (9.4%), and TERT (33.3%) in malignant melanoma, and KRAS (18.8%), TP53 (54.3%), and CDKN2A (21.8%) in pancreatic cancer. The mean time from sample shipment to result receipt was 42.5 days. As a result of CGP testing, candidate anticancer drugs were found in 304 patients: however, 108 patients were not treated due to poor general condition, complications, or age, which limited access to clinical trials. In germline findings, a pathogenic germline variant of BRCA2 was detected in one patient in OncoGuide, and presumed germline pathogenic variants of MLH1, BRCA2, and PTEN were detected in 1, 13, 26 patients in F-1. Conclusions: In Japan, CGP testing found candidate anticancer drugs, however it requires a significant amount of time to receive treatment because of limiting access to ongoing clinical trials and being typically performed after standard chemotherapy. Therefore, improving access to clinical trials, including determining the timing of testing and selecting appropriate cases, was critical.

Predicting recurrence using a tumor-uninformed ctDNA assay detecting MRD in patients with resected stage II or III colorectal cancer: Subset analysis from the GALAXY study in CIRCULATE-Japan.

21 Background: The presence of circulating tumor DNA (ctDNA) after curative-intent surgery can identify patients with minimal residual disease (MRD) who are at risk of recurrence and aid with postsurgical risk stratification. ~80% of stage II and only 50% of stage III colorectal cancer (CRC) patients are cured by surgery alone. A tumor-uninformed plasma-only approach for MRD assessment accelerates the turnaround time, enabling rapid adjuvant chemotherapy (ACT) treatment decision making, optimizing the impact on patient outcomes. Methods: A subset of samples from GALAXY, an observational arm of the CIRCULATE-Japan study (UMIN000039205), were analyzed for postsurgical ctDNA detection at a landmark time point (LMT) defined as 4 weeks after curative surgery in pathological stage II or III CRC patients. In a prospective lead-in to clinical validation, 80 patients meeting pre-specified eligibility criteria were randomly selected with enrichment for recurrence to 50% while maintaining the stage II:III recurrent (R)/nonrecurrent (NR) ratio to that observed in GALAXY. Residual plasma samples were analyzed with the Tempus xM assay (xM), a tumor-uninformed ctDNA MRD assay that integrates methylation and genomic variant MRD classifiers to deliver a binary MRD call. All calls were blinded to clinical outcomes. The methylation-based classifier detects fragments with CRC methylation signatures in differentially methylated regions trained by sequencing CRC and presumed-healthy samples on a 6Mbp panel. The variant-based MRD classifier detects highly prevalent CRC variants. Artifacts, CHIP, and germline variant filtering algorithms were also applied. Results: Of the 80 patients (pts), 70 [Stage II n= 29 (41%), Stage III n= 41 (59%)] were evaluable (36 R and 34 NR). At the LMT and with at least 1-year follow-up, 18/36 R pts had detectable ctDNA (xM MRD+) and 30/34 NR pts had undetectable ctDNA (xM MRD-), providing a sensitivity of 50% and specificity of 88%. Additionally, xM MRD+/- status strongly correlated with disease-free survival (DFS) with a hazard ratio (HR) of 5.09, adjusted to account for a 24% recurrence rate in GALAXY. In an updated, ongoing longitudinal analysis of the 4 false positive pts, 2 were Stage III, MRD+ from both the methylation and genomic classifiers, received ACT, and have likely cleared their ctDNA without any sign of clinical recurrence. An adjusted sensitivity and specificity analysis resulted in xM clinical performance of 53% (20/38 R) and 94% (30/32 NR), respectively. Conclusions: xM is a novel tumor-uninformed assay that demonstrated remarkable performance to detect clinical recurrence at a LMT, and a clinically meaningful correlation with DFS. A larger clinical validation study including longitudinal analysis, correlation with ACT, and outcomes from the GALAXY study is currently underway.

One of these is not like the others: A descriptive study of the attenuated phenotype of PMS2.

76 Background: Data from Lynch syndrome (LS) registries reveal that patients (pts) with PMS2 pathogenic germline variants (PGVs) have the lowest cancer risk. This retrospective study of pts undergoing germline genetic testing (GGT) for any indication compared the phenotypes of PMS2 carriers to other LS pts. We hypothesized that PMS2 pts were more likely to have no cancer or non–LS associated cancers than other LS pts. Methods: All Pts with a single PGV in any LS gene were identified from a commercial laboratory database. Demographics and personal and family cancer history data were clinician-reported on the test requisition form. Data from PMS2 pts were compared to MSH6 and MLH1/MSH2/EPCAM pts using descriptive statistics, unpaired two-samples t tests, Chi-square tests, and multivariate logistic regression analyses that also included patients with no PGVs, with p&lt;0.05 defining significance. Results: 17,711 pts met inclusion criteria (5,189 PMS2, 5,182 MSH6, and 7,340 MLH1/MSH2/EPCAM). PMS2 pts were significantly older at testing (mean 55.1±16.0y) than MLH1/MSH2/EPCAM (48.7±15.7y) and had significantly less family cancer history (84.9%) than both MSH6 (86.8%) and MLH1/MSH2/EPCAM (86.6%) pts. PMS2 pts had lower odds of any colorectal and uterine cancers than the MSH6 and MLH1/MSH2/EPCAM cohorts (Table). All LS-related PGVs were significantly associated with lower odds of breast, pancreatic, and prostate cancer. Conclusions: Pts with PMS2 PGVs were older at the time of testing and had lower odds of any and LS-related cancers than other LS pts. These data are consistent with prior registry studies and can aid in counseling and management of PMS2 pts. [Table: see text]

Idiopathic erythrocytosis: a germline disease?

Polycythemia Vera (PV) is typically caused by V617F or exon 12 JAK2 mutations. Little is known about Polycythemia cases where no JAK2 variants can be detected, and no other causes identified. This condition is defined as idiopathic erythrocytosis (IE). We evaluated clinical-laboratory parameters of a cohort of 56 IE patients and we determined their molecular profile at diagnosis with paired blood/buccal-DNA exome-sequencing coupled with a high-depth targeted OncoPanel to identify a possible underling germline or somatic cause. We demonstrated that most of our cohort (40/56: 71.4%) showed no evidence of clonal hematopoiesis, suggesting that IE is, in large part, a germline disorder. We identified 20 low mutation burden somatic variants (Variant allelic fraction, VAF, < 10%) in only 14 (25%) patients, principally involving DNMT3A and TET2. Only 2 patients presented high mutation burden somatic variants, involving DNMT3A, TET2, ASXL1 and WT1. We identified recurrent germline variants in 42 (75%) patients occurring mainly in JAK/STAT, Hypoxia and Iron metabolism pathways, among them: JAK3-V722I and HIF1A-P582S; a high fraction of patients (48.2%) resulted also mutated in homeostatic iron regulatory gene HFE-H63D or C282Y. By generating cellular models, we showed that JAK3-V722I causes activation of the JAK-STAT5 axis and upregulation of EPAS1/HIF2A, while HIF1A-P582S causes suppression of hepcidin mRNA synthesis, suggesting a major role for these variants in the onset of IE.Graphical abstract

NSABP C-14/Exact Sciences 16-002: CORRECT-MRD II—Second colorectal cancer clinical validation study to predict recurrence using a circulating tumor DNA assay to detect minimal residual disease.

TPS241 Background: Detectable circulating tumor DNA (ctDNA) after resection of early-stage solid tumors has been associated with very high risk of recurrence, suggesting ctDNA is evidence of minimal residual disease (MRD). Several studies are ongoing to investigate the role of ctDNA in the optimal management of patients (pts) with colorectal cancer using different assay technologies. Methods: This is a prospective, observational, multicenter study in the United States and Canada of 750 pts who have undergone complete surgical resection for stage II or III colorectal cancer, who have FFPE tissue available from the primary resection sufficient for a novel bespoke MRD assay and are willing to provide serial whole blood specimens for ctDNA analysis. Participants are asked to provide study specimens after definitive surgical resection, pre-recurrence follow-up, and clinical recurrence (if applicable). Recently amended eligibility criteria include inclusion of rectal cancer pts who have completed neo-adjuvant therapy and surgical resection, as well as enrollment of all stage II and III pts regardless of microsatellite stability status. The Oncotype Colon Recurrence Score® will be assessed on all pts from their surgical specimen, if criteria are met for this testing. ctDNA will be analyzed with an NGS-based tumor-informed MRD assay that identifies somatic genomic alterations from DNA derived from the patient’s tumor tissue, subtracts germline variants, and detects a selected subset of tumor-specific (bespoke) ctDNA in their blood. All primary tumor specimens will undergo full exome and transcriptome sequencing using the Onco ExTra assay. If there is evidence of disease recurrence, the metastatic tissue will also undergo Onco ExTra testing and results will be shared with participants. The primary objective is to validate the association of post-definitive therapy and pre-recurrence follow-up ctDNA positivity with recurrence-free interval (RFI). Further objectives are to assess the: sensitivity and specificity of ctDNA positivity for subsequent clinical recurrence; contribution of post-surgery baseline, post-adjuvant therapy, and pre-recurrence follow-up ctDNA results on RFI; time from positive ctDNA to clinical recurrence in participants who had a positive ctDNA result; and to compare the Oncotype Colon Recurrence Score estimate of 3-year recurrence risk with the observed 3-year recurrence rate. The primary analysis will use a Cox proportional hazards regression applied to the RFI with ctDNA result (positive or negative) measured after surgery, or end of adjuvant therapy if received, and serially after that as a single, time-dependent covariate. Enrollment has currently surpassed the 50% target. Protocol#: NSABP C-14 / Exact Sciences 16-002 NCT#: 05210283. Support: NSABP Foundation, ExactSciences. Clinical trial information: NCT05210283.

Germline testing in patients with early-onset pancreatic cancer (EOPC).

639 Background: EOPC, defined as pancreatic cancer (PC) diagnosed at 60 years of age or younger, is associated with significant life years lost. Approximately 5-10% of average-onset PC have an underlying germline etiology. Currently NCCN &amp; ASCO guidelines recommend germline testing in all pts w PC. However, there is limited data regarding to what extent pts with EOPC pursue recommended germline testing. We examined the findings from genetic evaluation in EOPC. Methods: A retrospective review of EOPC pts at the Levine Cancer Institute who underwent clinical genetic assessment between January 2019 and December 2021 was performed. Data on clinicodemographic, family history, and genetic testing results were obtained and analyzed descriptively. Results: We identified 69 EOPC pts who were evaluated by genetics. Baseline characteristics include median age of 55 years (range 25-60) with 52% male, 48% white, 23% black, and 52% with current or prior tobacco use. At presentation, 41% and 59% had metastatic and non-metastatic disease, respectively. Eight (12%) pts declined germline testing. Among the 61 who underwent germline testing, 30 (49%) pts had negative testing, 21 (34%) had only variants of uncertain significance, and 10 (16%) had pathogenic/likely pathogenic germline variants (PVs). The most frequently seen PVs were ATM (20%), BRCA1 (20%), BRCA2 (10%), MLH1 (10%), NTHL1 (10%), PTCH1 (10%), CFTR (10%) and one (10%) with multiple pathogenic germline findings including RAD51 and BRCA1. Among the 10 pts with PVs, only two reported any first or second-degree family members with cancer. Conclusions: In this cohort of EOPC at a large community multi-site cancer center, 16% of patients had germline PVs, higher than reported in older patients with PC. Only 20% of pts w PVs reported first or second-degree family members with cancer and highlights the importance to recommend germline testing independent of family history even among EOPC cohorts. Further investigation to clarify reasons for refusal of germline testing in EOPC should be evaluated.

Genome-wide association study (GWAS) and novel prognostic markers in metastatic colorectal cancer (mCRC).

174 Background: Few genome-wide investigations have examined germline variants associated with mCRC outcomes following primary treatment. Here, we performed a GWAS meta-analysis to explore the impact of germline genetic variation on progression-free survival (PFS) and overall survival (OS) in four clinical trials of mCRC. Methods: The GWAS comprised 1,324 mCRC patients (pts) enrolled in four randomized Phase II/III trials for first line treatment: FIRE-3 (FOLFIRI-bevacizumab [bev]; FOLFIRI-cetuximab[cet]), MAVERICC (FOLFIRI-bev; FOLFOX6-bev), TRIBE (FOLFIRI-bev; FOLFOXIRI-bev), and TRIBE2 (mFOLFOX6-bev; FOLFOXIRI-bev). DNA isolated from blood was genotyped using the OncoArray and imputed against the Haplotype Reference Consortium panel. In each trial arm, associations between SNPs and PFS and OS were assessed using an additive coding in a Cox proportional hazard framework, adjusting for trial specific patient characteristics and principal components. Meta-analysis was carried out using an inverse-variance weighted fixed effect model. All reported GWAS p-values were adjusted for genomic inflation. To further investigate significant hits, we evaluated associations between gene expression measured from FFPE tumor samples and PFS and OS in 433 pts enrolled in an independent randomized first-line Phase III trial, CALGB/SWOG 80405. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated in multivariable Cox models for expression levels in the top (Q4, high) vs the bottom quartile (Q1, low). Results: Two SNPs in the MLPH intronic region and one SNP in the TYR intronic region surpassed the GWAS significance threshold for PFS and OS, respectively. The top ranked SNPs associated with PFS and OS, rs13409241 (A&gt;G, PFS HR: 1.35, 95% CI [1.21, 1.51], P=4.34E-8) and rs10765199 (T&gt;A, OS HR: 1.45, 95%CI [1.27, 1.65], P=4.69E-8), showed similar effects across all eight treatment arms ( I2 = 0% and 38.5%, respectively). No significant heterogeneity variant was found. In the CALGB/SWOG 80405 cohort, pts with MLPH-low tumors (N=109) showed significantly longer PFS (median 14.8 vs 7.6 months, low vs. high (as reference) adjusted HR 0.53, 95% CI [0.38, 0.74], P=2.1E-4) and OS (median 35.8 vs. 18.2 months, adjusted HR 0.65, 95% CI [0.46, 0.92], P=0.015) compared to MLPH-high (N=107). No significant associations for TYR expression and outcomes were found. MLPH and TYR are involved in melanosome transport and melanogenesis. Melanin has been shown to reduce vitamin D levels, which can affect CRC prognosis. MLPH has also been reported to accelerate epithelial-mesenchymal transition and metastasis in lung and prostate cancers. Conclusions: These results suggest that germline genetic variation in MLPH and TYR may affect mCRC prognosis via a mechanism that involves melanin and possibly the epithelial-mesenchymal transition. Note: Authors Millstein and Lenz contributed equally to this work.

Epithelioid angiomyolipoma of the liver in a patient with Li-Fraumeni syndrome: a case report

BackgroundEpithelioid angiomyolipoma (EAML) is a rare variant of angiomyolipoma that predominantly consists of epithelioid cells and belongs to the perivascular epithelioid cell neoplasm (PEComa) family. The majority of EAMLs arise in the kidneys, and primary hepatic EAML appears to be much less common than renal EAML. Most PEComas arise sporadically, but may be associated with tuberous sclerosis complex (TSC), an autosomal dominant genetic disorder characterized by germline mutations in the TSC1 or TSC2 genes. However, PEComas have previously been reported in five patients with Li-Fraumeni syndrome (LFS), which is an inherited cancer susceptibility disorder resulting from germline mutations in the TP53 tumor suppressor gene.Case presentationWe report a 49-year-old female patient with hepatic EAML and pancreatic cancer. Because she had previously been diagnosed with bilateral breast cancer at the age of 30, we performed a comprehensive genetic analysis to identify genetic alterations associated with any cancer predisposition syndrome. Whole-exome sequencing of a blood sample identified a heterozygous germline variant of TP53 (NM_000546.5):c.708C>A, and targeted next-generation sequencing of liver EAML and pancreatic cancer tissue samples demonstrated the same TP53 (NM_000546.5):c.708C>A variant in both. This, plus the patient’s history of early-onset breast cancer, met the 2015 version of the Chompret criteria for diagnosis of LFS.ConclusionsThere have been very few case reports regarding the presence of PEComa in LFS, and to the best of our knowledge, this is the first report of EAML of the liver in a patient with LFS.

Compound heterozygous MSH3 germline variants and associated tumor somatic DNA mismatch repair dysfunction

We describe here an individual from a fourth family with germline compound heterozygous MSH3 germline variants and its observed biological consequences. The patient was initially diagnosed with invasive moderately-differentiated adenocarcinoma of the colon at the age of 43. Germline multigene panel testing revealed a pathogenic variant MSH3 c.2436-1 G > A and a variant of (initial) uncertain significance MSH3 c.3265 A > T (p.Lys1089*). Germline genetic testing of family members confirm the variants are in trans with the c.2436-1 G > A variant of paternal and the c.3265 A > T variant of maternal origin. Tumor DNA exhibits low levels of microsatellite instability and elevated microsatellite alterations at selected tetranucleotide repeats (EMAST). Tissue immunohistochemical staining for MSH3 demonstrated variant MSH3 protein is present in the cytoplasm and cell membrane but not in the nucleus of normal and tumor epithelial cells. Furthermore, variant MSH3 is accompanied by loss of nuclear MSH6 and a reduced level of nuclear MSH2 in some tumor cells, suggesting that the variant MSH3 protein may inhibit binding of MSH6 to MSH2.

Presumed Pathogenic Germ Line and Somatic Variants in African American Thyroid Cancer.

Background: African American (AA) thyroid cancer patients have worse prognoses than European Americans (EA), which has been attributed to both health care disparities and possible genetic differences. We investigated the impact of both germ line and somatic variants on clinical outcome in a cohort of AA nonmedullary thyroid cancer (NMTC) patients who had received therapeutic intervention from cancer centers. Methods: Whole-exome sequencing was performed on DNA from available blood/normal tissues (N = 37) and paired tumor samples (N = 32) collected from 37 and 29 AA NMTC patients, respectively. Variants with Combined Annotation Depletion Dependent (CADD) score of ≥20 and VarSome Clinical classification of likely pathogenic or pathogenic were classified as presumed pathogenic germ line or somatic variants (PPGVs/PPSVs). PPGVs/PPSVs in cancer-related genes and PPGVs in cardiovascular risk genes were further investigated, and PPGVs/PPSVs associated with African (AFR) ancestry were identified. Results: Among 17 PPGVs identified in 16 cancer predisposition or known cancer-related genes, only WRN was previously known to associate with NMTC predisposition. Among PPSVs, BRAFV600E was most the prevalent and detected in 12 of the 29 (41%) tumors. Examining PPGVs/PPSVs among three patients who died from NMTC, one patient who died from papillary thyroid carcinoma/anaplastic thyroid carcinoma (PTC/ATC) led us to speculate that the PPGV ERCC4R799W may have increased the risk of PPSV TP53R273H acquisition. Among PPGVs identified in 18 cardiovascular risk genes, PPGVs in SC5NA, GYG1, CBS, CFTR, and SI are known to have causal and pathogenic implications in cardiovascular disease. Conclusion: In this cohort, most AA-NMTC patients exhibit favorable outcomes after therapeutic intervention given at cancer centers, suggesting that health care disparity is the major contributor for worse prognoses among AA-NMTC patients. Nevertheless, the clinical impact of PPGVs that might facilitate the acquisition of TP53 tumor mutations, and/or PPGVs that predispose individuals to adverse cardiovascular events, which could be exacerbated by therapy-induced cardiotoxicity, needs to be further explored. Integrated analysis of PPGV/PPSV profiles among NMTC patients with different stages of disease may help to identify NMTC patients who require close monitoring or proactive intervention.