POLE Gene Research Articles

Characterizing POLE Mutation-Associated Colorectal Carcinoma: Clinical and Pathologic Insight

Abstract Introduction/Objective Colorectal carcinoma (CRC) is one of the most common cancers and a leading cause of cancer-related death in the United States. Pathogenically, colorectal carcinoma is a heterogeneous disease that develops via stepwise accumulation of well-characterized genetic and epigenetic alteration. Identification of DNA polymerase mutation leads to the characterization of a new molecular pathway of carcinogenesis named the POLE pathway. Methods/Case Report Utilizing the cBioportal platform and Cancer Genome Atlas (TCGA) Firehouse Legacy data, we identified 118 cases of CRC with mutations in the POLE gene. We evaluated the various clinical and pathologic features of POLE mutation-associated CRC. Results (if a Case Study enter NA) Within the cohort of 118 cases linked to mutations in the POLE gene, gender distribution reveals that 63 individuals, comprising 53.8% of the sample, are male, while 42 individuals, accounting for 35.9%, are female. Ethnicity breakdown showcases a predominantly White population, with 92 cases (78.6%), followed by 8 cases (6.8%) attributed to Asian-Far East/Indian Subcontinent descent, 5 cases (4.3%) categorized as Asian, and 4 cases (3.4%) each identified as Black and Black or African American. Additionally, one case (0.9%) has an unknown ethnicity, while 4 cases (3.4%) have unspecified racial backgrounds. The average age at diagnosis is recorded at 48.5 years, with ages ranging from 25 to 85, signifying a broad age spectrum within the affected population. Delving into cancer subtypes, the majority of cases, constituting 64 instances (54.2%), manifest as colon adenocarcinoma, while 38 cases (32.2%) present as rectal adenocarcinoma. Moreover, 9 cases (7.6%) are characterized as colorectal adenocarcinoma, 6 cases (5.1%) are classified as mucinous adenocarcinoma of the colon and rectum, and one case (0.8%) manifests as medullary adenocarcinoma of the colon. This detailed elucidation provides a comprehensive understanding of the demographics and clinical presentation within the cohort affected by POLE gene mutations. Conclusion In summary, our research has meticulously examined 118 instances of colorectal carcinoma (CRC) intricately linked to mutations in the POLE gene. Within this cohort, a predominant demographic emerges, with a notable prevalence among individuals of White ethnicity. Delving deeper into the pathological spectrum, colon adenocarcinoma emerges as the prevailing subtype, exemplifying the intricate interplay between genetic aberrations and cancer manifestation.

8145 Type 2 Diabetes In A Patient With IMAGe Syndrome

Abstract Disclosure: N. Mulpuri: None. S. Mirfakhraee: None. J. Abramowitz: None. Background: Individuals with mutations that lead to deficiency of POLE1 (a catalytic subunit of polymerase epsilon) may have clinical features of IMAGe syndrome (intrauterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia congenital, and genitourinary anomalies) in addition to distinctive facial features and variable immunodeficiency. Of 15 reported cases in the literature, none were previously characterized with type 2 diabetes mellitus (T2DM). Clinical case: This is a 25-year-old woman with a history of IMAGe syndrome (confirmed mutation in the POLE gene). With regards to IMAGe syndrome history, during the prenatal period, she had growth restriction in the third trimester with delivery at 38 weeks. At 4 years-old, she presented with adrenal crisis and was started on glucocorticoid and mineralocorticoid therapy, now taking hydrocortisone 2.5mg three times daily (8.6 mg/m2/day) and fludrocortisone 0.05mg daily. Initial labs in the adult endocrine clinic were notable for serum glucose 339 mg/dL (65-99 mg/dL), undetectable estradiol (< 15 pg/ml) with FSH 6.8 mIU[JA1] /mL and LH 2.0 mIU/mL, TSH 1.25 mIU/L (0.40-4.50 mIU/dL), FT4 0.7 ng/dL (0.8-1.8 ng/dL). The patient denied any history of T2DM. She also denied polyuria, polydipsia, or weight loss. There was no stigmata of peripheral insulin resistance on exam. Subsequent labs included HbA1c 8.9%, fructosamine 417 mcmol/L (200-285 mcmol/L), insulin 18.4 mcIU/mL (2.6-24.9 mcIU/mL), and C-peptide 3.9 ng/dL (1.1-4.4 ng/dL) with serum glucose 164 mg/dL. Islet cell, insulin, and GAD-65 antibodies were undetectable. CT abdomen/pelvis did not show any pancreatic mass or anomalies. Initially, prandial insulin (lispro 3 units prior to each meal) was initiated given post-prandial hyperglycemia noted on continuous glucose monitoring. Low-dose levothyroxine, 25 mcg daily, was initiated given concern for secondary hypothyroidism, with subsequent normalization of serum thyroxine. HbA1c improved to 7.4% six months later. Ultimately, she transitioned to sitagliptin 25 mg daily and her latest HbA1c was 6.2% three years after initial diagnosis of T2DM. Conclusion: Of the 15 cases of IMAGe syndrome with mutations in POLE described in Logan et al, none were noted to have diabetes. The patient described above was diagnosed with new-onset diabetes at age 21, presumably T2DM in the context of undetectable antibodies and high-normal C-peptide. Interestingly, she did not have any typical stigmata of peripheral insulin resistance. Glucocorticoids used for the treatment of adrenal insufficiency in patients with IMAGe syndrome can contribute to development of T2DM. Patients with IMAGe syndrome on chronic glucocorticoids should be monitored for hyperglycemia and diabetes. Additionally, glucocorticoid doses should be optimized to balance mitigating side effects such as hyperglycemia and osteoporosis while preventing adrenal crisis. Presentation: 6/3/2024

S2663 Metastatic Pancreatic Adenocarcinoma: A Rare Case of Successful Checkpoint Inhibitor Monotherapy in High Tumor Mutational Burden With POLE Gene

S2663 Metastatic Pancreatic Adenocarcinoma: A Rare Case of Successful Checkpoint Inhibitor Monotherapy in High Tumor Mutational Burden With POLE Gene

Rare Germline Variants in DNA Repair Genes Detected in BRCA-Negative Finnish Patients with Early-Onset Breast Cancer.

Breast cancer is the most common malignancy, with a mean age of onset of approximately 60 years. Only a minority of breast cancer patients present with an early onset at or before 40 years of age. An exceptionally young age at diagnosis hints at a possible genetic etiology. Currently, known pathogenic genetic variants only partially explain the disease burden of younger patients. Thus, new knowledge is warranted regarding additional risk variants. In this study, we analyzed DNA repair genes to identify additional variants to shed light on the etiology of early-onset breast cancer. Germline whole-exome sequencing was conducted in a cohort of 63 patients diagnosed with breast cancer at or before 40 years of age (median 33, mean 33.02, range 23-40 years) with no known pathogenic variants in BRCA genes. After filtering, all detected rare variants were sorted by pathogenicity prediction scores (CADD score and REVEL) to identify the most damaging genetic changes. The remaining variants were then validated by comparison to a validation cohort of 121 breast cancer patients with no preselected age at cancer diagnosis (mean 51.4 years, range 28-80 years). Analysis of novel exonic variants was based on protein structure modeling. Five novel, deleterious variants in the genes WRN, RNF8, TOP3A, ERCC2, and TREX2 were found in addition to a splice acceptor variant in RNF4 and two frameshift variants in EXO1 and POLE genes, respectively. There were also multiple previously reported putative risk variants in other DNA repair genes. Taken together, whole-exome sequencing yielded 72 deleterious variants, including 8 novel variants that may play a pivotal role in the development of early-onset breast cancer. Although more studies are warranted, we demonstrate that young breast cancer patients tend to carry multiple deleterious variants in one or more DNA repair genes.

Endometrial carcinoma: molecular classification in routine pathology

The molecular classification of endometrial carcinoma defines four main groups: polymerase‑ɛ(PolE) gene mutated, microsatellite unstable (MSI), p53 abnormal tumors and tumors with no specific molecular profile (NSMP). This classification provides significant insights into the prognosis and therapeutic decisions. Each group exhibits unique genetic profiles identified through immunohistochemistry and molecular diagnostics, enabling personalized treatment. The identification of these molecular signatures necessitates precise analytical methods, selected based on the local circumstances at each site. The approach to molecular classification highlights the critical role of pathology in the diagnosis and emphasizes the necessity of collaboration between the clinic and pathology.

Abstract 3854: Revealing mismatch repair deficiency in Egyptian colorectal cancer patients using next generation sequencing a predictive biomarker for immunotherapy efficacy

Abstract Background: The mismatch repair (MMR) deficiency is a potential predictive biomarker for immunotherapy efficacy, particularly in colorectal cancer (CRC), where alterations in various DNA polymerases and MMR genes are prevalent. The accumulation of these genetic aberrations may cause a subsequent neoantigen formation. study aimed to identify the mutational profile of DNA polymerases and MMR genes in Egyptian CRC patients', providing insights into colorectal carcinogenesis and potential implications for immunotherapy. Material and Methods: Thirty-nine blood samples from Egyptian patients with CRC and twenty-four blood samples from healthy controls were collected. The libraries were prepared by Qiaseq UMI-based targeted panel and sequenced via an Ion proton sequencer. The detected genetic variants with an average coverage of 500x were annotated against Cosmic, dbSNP, and ClinVar databases using Ingenuity Variant analysis (IVA). Results: Our results revealed that the POLD1andPOLE genes (DNA polymerases) in the CRC patients, when compared with healthy controls, harbored 10 and 13 pathogenic variants (PVs), respectively. These PVs cause a loss of their functionality. The most frequently detected PVs and likely to be novel in the POLD1gene werec.44delC(31%)andc.3008delG(31%), while c.3510delA(18%)andc.2793delT(15%) were detected in the POLE gene. As per MMR genes, our study showed that the MLH1, MLH3, MSH2, MSH3, MSH6, PMS1,and PMS2 harbored 8, 13, 23, 19, 22, 23, and 7 PVs, respectively. The highly frequent PV in the MLH1wasc.469delT (26%), while the novel most frequently detected PV in the MLH3 wasc.1467delA (23%). Moreover, the PVs found highly frequent are c.2647delA (36%) in MSH2,c.1148delA (41%)in the MSH3, and c.2079delA (44%) in the MSH6. RegardingPMS1/2, the most frequently detected PV and likely to be novel was c.1647delA (44%) in PMS1, while c.869delT (13%) was the most prevalent PV in PMS2. Conclusion: Our results revealed the MMR mechanism deficiency in Egyptian CRC patients offering crucial insights into colorectal carcinogenesis and neoantigen formation. These insights are pivotal for developing ethnic-based personalized immunotherapy strategies in Egyptian CRC patients, shedding light on their role in CRC. Interestingly, we have identified novel variants in the DNA repair enzymes. However, further investigations and validations are required to corroborate these findings and explore their clinical significance in the personalized medicine. Citation Format: Amira Salah El-Din Youssef, Mohamed Ragab, Heba Aly Ateya, Mostafa Elberry, Nasra Fathy, Asmaa Elleithy, Abdel Rahman Zekri, Ola Sayed Ahmed, Auhood Nassar. Revealing mismatch repair deficiency in Egyptian colorectal cancer patients using next generation sequencing a predictive biomarker for immunotherapy efficacy [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 3854.

The Clinical and Pathological Characteristics of POLE-Mutated Endometrial Cancer: A Comprehensive Review.

Endometrial cancer shows high histological and molecular heterogeneity. The POLE mutation is a significant molecular alteration in endometrial cancer, leading to the identification of a specific subtype known as POLE-mutated endometrial cancer. This subtype exhibits a high tumor mutation burden, abundant lymphocyte infiltration, and a favorable prognosis, making it a promising candidate for immune checkpoint inhibitor therapy. This paper presents a comprehensive review of the clinical and pathological characteristics, outcomes, treatment advancements, pathogenic POLE gene detection, and alternative testing methods for POLE-mutated endometrial cancer.

Evaluation of mismatch-repair and microsatellite-instability status in a Chinese colorectal cancer Cohort

BackgroundImmunohistochemistry (IHC) and traditional polymerase chain reaction (PCR) are the methods of choice in clinical practice to identify the mismatch repair (MMR) and microsatellite instability (MSI) status in colorectal cancer (CRC). In some previous researches, the concordance rate between two methods was different and discordance existed in about 1 %–9.7 %. MethodsWe retrospectively reviewed 406 patients received surgical CRC resections and tests of both MMR IHC and MSI PCR from January 2019 to April 2022 in Shanghai Changzheng Hospital. The incidence of deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H) CRCs, the concordance rate between two methods, and the reasons for discordant results were evaluated with clinicopathological data, immunochemical staining, whole-exome sequencing, and MLH1 methylation analysis. ResultsAmong 406 patients, the incidence of MSI-H CRCs was 7.88 %. Nearly a quarter of the cases under reexamination of IHC was initial misinterpreted. Besides, the concordance rate between MMR IHC and MSI PCR was 99.26 % (401 of 404) and the Kappa value was 0.945 (p < 0.001). Finally, some somatic variants of MMR and POLE genes which may explain the discordance were identified. ConclusionThe incidence rate of MSI-H in Chinese patients with CRC might be relatively low owing to tumor location. Although MSI and IHC analyses are highly concordant, both MMR IHC and MSI PCR tests should be simultaneously performed and MMR IHC should be interpreted by experienced pathologists. In the future, further studies on discordant results should be carried out to improve the personalized management of CRC.

Value of Molecular Typing Combined with Integrated Positron Emission Tomography/Magnetic Resonance Imaging in Risk Stratification of Endometrial Cancer.

In this study, we investigated the value of molecular typing combined with integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) semi-quantitative indices in endometrial cancer risk stratification. A retrospective study was conducted on 86 patients who were pathologically diagnosed with endometrial cancer and underwent surgical treatment after curettage at the Department of Obstetrics and Gynecology, Xuanwu Hospital, Capital Medical University between January 2017 and March 2023. Prior to surgery, each patient underwent integrated PET/MRI examination. The postoperative samples were subjected to pathological diagnosis, immunohistochemistry, and POLE gene sequencing. The differences in clinicopathological features between the four molecular subtypes and the differences in integrated PET/MRI semi-quantitative indexes (SUV max, ADC min) between the four molecular subtypes were analyzed. The cutoff value of molecular typing combined with integrated PET/MRI semi-quantitative indices for endometrial cancer risk stratification was determined. There were statistically significant differences in pathological types and tumor grades among the four molecular subtypes of endometrial cancer. The values of the four integrated PET/MRI semi-quantitative indices (SUV max and ADC min) of the molecular subtypes were statistically different. The SUV max was greater in the p53abn mutation group than in the POLE mutation group (P < 0.05). The ADC minimum of the POLE mutation group and the MMR-d group was lower than the NSMP group (P <0.05). Molecular typing combined with the integrated PET/MRI semi-quantitative SUV max index can predict the low/medium risk group of endometrial cancer and the medium-high/high risk group, and the cut-off value of SUV max for predicting the risk of early endometrial cancer was 14.72 (sensitivity 66.7%, specificity 68.7%). Molecular typing combined with integrated PET/MRI semi-quantitative indicators is useful to achieve risk stratification in patients diagnosed with endometrial cancer and guide individualized treatment.

Novel Pathogenic Variants in Hereditary Cancer Syndromes in a Highly Heterogeneous Cohort of Patients: Insights from Multigene Analysis.

Cancer is a major global public health challenge, affecting both quality of life and mortality. Recent advances in genetic research have uncovered hereditary cancer syndromes (HCS) that predispose individuals to malignant neoplasms. While traditional single-gene testing has focused on high-penetrance genes, the past decade has seen a shift toward multigene panels, which facilitate the analysis of multiple genes associated with specific HCS. This approach reveals variants in less-studied gene regions and improves our understanding of cancer predisposition. In a study composed of Russian patients with clinical signs of HCS, we used a multigene hereditary cancer panel and revealed 21.6% individuals with pathogenic or likely pathogenic genetic variants. BRCA1/BRCA2 mutations predominated, followed by the CHEK2 and ATM variants. Of note, 16 previously undescribed variants were identified in the MUTYH, GALNT12, MSH2, MLH1, MLH3, EPCAM, and POLE genes. The implications of the study extend to personalized cancer prevention and treatment strategies, especially in populations lacking extensive epidemiological data, such as Russia. Overall, our research provides valuable genetic insights that give the way for further investigation and advances in the understanding and management of hereditary cancer syndromes.

Exploring the basis of heterogeneity of cancer aggressiveness among the mutated POLE variants.

Germline pathogenic variants in the exonuclease domain of the replicative DNA polymerase Pol ε encoded by the POLE gene, predispose essentially to colorectal and endometrial tumors by inducing an ultramutator phenotype. It is still unclear whether all the POLE alterations influence similar strength tumorigenesis, immune microenvironment, and treatment response. In this review, we summarize the current understanding of the mechanisms and consequences of POLE mutations in human malignancies; we highlight the heterogeneity of mutation rate and cancer aggressiveness among POLE variants, propose some mechanistic basis underlining such heterogeneity, and discuss novel considerations for the choice and efficacy of therapies of POLE tumors.

Comprehensive assessment of mismatch repair and microsatellite instability status in molecular classification of endometrial carcinoma

Objective: To explore the concordance and causes of different mismatch repair (MMR) and microsatellite instability (MSI) detection results in endometrial carcinoma (EC) molecular typing. Methods: A total of 214 EC patients diagnosed from January 2021 to April 2023 were selected at the Department of Pathology, Peking University Third Hospital. The immunohistochemistry (IHC) results of MMR protein were reviewed. Tumor specific somatic mutations, MMR germline mutations, microsatellite scores and tumor mutation burden (TMB) were detected by next-generation sequencing (NGS) with multi-gene panel. Methylation-specific PCR was used to detect the methylation status of MLH1 gene promoter in cases with deficient MLH1 protein expression. In cases with discrepant results between MMR-IHC and MSI-NGS, the MSI status was detected again by PCR (MSI-PCR), and the molecular typing was determined by combining the results of TMB and MLH1 gene promoter methylation. Results: (1) In this study, there were 22 cases of POLE gene mutation subtype, 55 cases of mismatch repair deficient (MMR-d) subtype, 29 cases of p53 abnormal subtype, and 108 cases of no specific molecular profile (NSMP). The median age at diagnosis of MMR-d subtype (54 years old) and the proportion of aggressive histological types (40.0%, 22/55) were higher than those of NSMP subtype [50 years old and 12.0% (13/108) respectively; all P<0.05]. (2) Among 214 patients, MMR-IHC test showed that 153 patients were mismatch repair proficient (MMR-p), 49 patients were MMR-d, and 12 patients were difficult to evaluate directly. MSI-NGS showed that 164 patients were microsatellite stable (MSS; equal to MMR-p), 48 patients were high microsatellite instability (MSI-H; equal to MMR-d), and 2 patients had no MSI-NGS results because the effective sequencing depth did not meet the quality control. The overall concordance between MMR-IHC and MSI-NGS was 94.3% (200/212). All the 12 discrepant cases were MMR-d or subclonal loss of MMR protein by IHC, but MSS by NGS. Among them, 10 cases were loss or subclonal loss of MLH1 and (or) PMS2 protein. Three discrepant cases were classified as POLE gene mutation subtype. In the remaining 9 cases, 5 cases and 3 cases were confirmed as MSI-H and low microsatellite instability (MSI-L) respectively by MSI-PCR, 6 cases were detected as MLH1 gene promoter methylation and 7 cases demonstrated high TMB (>10 mutations/Mb). These 9 cases were classified as MMR-d EC. (3) Lynch syndrome was diagnosed in 27.3% (15/55) of all 55 MMR-d EC cases, and the TMB of EC with MSH2 and (or) MSH6 protein loss or associated with Lynch syndrome [(71.0±26.2) and (71.5±20.1) mutations/Mb respectively] were significantly higher than those of EC with MLH1 and (or) PMS2 loss or sporadic MMR-d EC [(38.2±19.1) and (41.9±24.3) mutations/Mb respectively, all P<0.01]. The top 10 most frequently mutated genes in MMR-d EC were PTEN (85.5%, 47/55), ARID1A (80.0%, 44/55), PIK3CA (69.1%, 38/55), KMT2B (60.0%, 33/55), CTCF (45.5%, 25/55), RNF43 (40.0%, 22/55), KRAS (36.4%, 20/55), CREBBP (34.5%, 19/55), LRP1B (32.7%, 18/55) and BRCA2 (32.7%, 18/55). Concurrent PTEN, ARID1A and PIK3CA gene mutations were found in 50.9% (28/55) of MMR-d EC patients. Conclusions: The concordance of MMR-IHC and MSI-NGS in EC is relatively high.The discordance in a few MMR-d EC are mostly found in cases with MLH1 and (or) PMS2 protein loss or MMR protein subclonal staining caused by MLH1 gene promoter hypermethylation. In order to provide accurate molecular typing for EC patients, MLH1 gene methylation, MSI-PCR, MMR gene germline mutation and TMB should be combined to comprehensively evaluate MMR and MSI status.

Relationship among DDR gene mutations, TMB and PD-L1 in solid tumour genomes identified using clinically actionable biomarker assays

The DNA damage response (DDR) pathway regulates DNA repair and cell survival, and inactivating mutations in DDR genes can increase tumour mutational burden (TMB), a predictive biomarker of treatment benefit from anti-PD-1/PD-L1 immunotherapies. However, a better understanding of the relationship among specific DDR mutations, TMB and PD-L1 expression is needed to improve translational strategies. Here, we determined genomic alteration frequencies in selected DDR genes that are clinically actionable biomarkers and investigated their association with TMB and PD-L1 in bladder, colorectal, non-small cell lung, ovarian and prostate cancers using the FoundationInsights® web portal. Our results not only confirm known associations, such as mismatch repair and POLE gene mutations with high TMB, but also identify significant associations between mutations in the SWI/SNF chromatin remodelling genes ARID1A and SMARCA4 and high TMB in multiple tumour types. Mutations in the ATR gene were associated with high TMB in colorectal and prostate cancers; however, associations between individual DDR mutations and high PD-L1 expression were uncommon and tumour-type specific. Finally, we found that high TMB and high PD-L1 expression were poorly associated, emphasising their independence as predictive biomarkers for immune checkpoint inhibitor use.

Proximity Proteomics Revealed Aberrant mRNA Splicing Elicited by ALS-Linked Profilin-1 Mutants.

Profilin 1 (PFN1) is a cytoskeleton protein that modulates actin dynamics through binding to monomeric actin and polyproline-containing proteins. Mutations in PFN1 have been linked to the pathogenesis of familial amyotrophic lateral sclerosis (ALS). Here, we employed an unbiased proximity labeling strategy in combination with proteomic analysis for proteome-wide profiling of proteins that differentially interact with mutant and wild-type (WT) PFN1 proteins in human cells. We uncovered 11 mRNA splicing proteins that are preferentially enriched in the proximity proteomes of the two ALS-linked PFN1 variants, C71G and M114T, over that of wild-type PFN1. We validated the preferential interactions of the ALS-linked PFN1 variants with two mRNA splicing factors, hnRNPC and U2AF2, by immunoprecipitation, followed with immunoblotting. We also found that the two ALS-linked PFN1 variants promoted the exonization of Alu elements in the mRNAs of MTO1, TCFL5, WRN and POLE genes in human cells. Together, we showed that the two ALS-linked PFN1 variants interacted preferentially with mRNA splicing proteins, which elicited aberrant exonization of the Alu elements in mRNAs. Thus, our work provided pivotal insights into the perturbations of ALS-linked PFN1 variants in RNA biology and their potential contributions to ALS pathology.

Analysis of germline variants in pediatric patients diagnosed with desmoid tumors and nuchal-type fibromas.

Desmoid tumor (DT) is a fibroblastic proliferation arising in soft tissue characterized by localized infiltrative growth with an inability to metastasize but with a tendency to recurrence. Nuchal-type fibromas are benign soft tissue lesions that are usually developed in the posterior neck. The development of these neoplasms can be associated with a hereditary cancer predisposition syndrome, mainly familial adenomatous polyposis (FAP) syndrome caused by APC germline mutations. Gardner syndrome is a variant of FAP characterized by the presence of extracolonic manifestations including soft tissue tumors as DTs and nuchal-type fibromas. However, the development of these tumors could be associated with germline alterations in other genes related to colorectal cancer development. The objective of this study was to analyze germline variants in APC, MUTYH, POLD1 and POLE genes in five pediatric patients diagnosed with DTs or nuchal-type fibromas. We identified two pathogenic variants in the APC gene in two different patients diagnosed with nuchal-type fibroma and DTs and two variants of uncertain significance in POLD1 in two patients diagnosed with nuchal-type fibroma. Two patients had family history of colorectal cancer, however, only one of them showed an APC germline pathogenic variant. The analysis of germline variants and genetic counseling is essential for pediatric patients diagnosed with DTs or nuchal-type fibromas and their relatives.

Molecular testing of endometrial carcinoma in real-world clinical practice.

Molecular classification has brought significant changes in the management of endometrial cancer (EC). In this article, we aim to analyze our first experience with an implementation of molecular testing into daily clinical practice. In all newly diagnosed EC, the status of mismatch repair (MMR) and p53 proteins has been evaluated immunohistochemically as a part of the routine histopathological examination since May 2021. In tumors that do not meet clinical criteria for a low risk and those with MMR deficiency or p53 mutation, the molecular genetic testing of the POLE gene is performed as well. Recommendations for adjuvant treatment or follow-up are subsequently made based on the risk of recurrence. Genetic counselling is proposed to all patients with MMR-deficient tumors or family history of cancer. A total of 85 patients with newly diagnosed EC between May 2021 and May 2022 were enrolled in the analysis. The median age was 66 years. The results of molecular testing were as follows: 22 (26%) MMR-deficient, 8 (9%) p53-mutated and none POLE-ultramutated of those 40 tumors with performed POLE sequencing. A total of 46 (51%) patient had a low risk, 2 (2%) intermediate, 14 (16%) high-intermediate and 20 (24%) patients had a high risk of recurrence. Advanced or metastatic diseases were diagnosed in 6 (7%) patients. The median time between surgery and multidisciplinary tumor board decision was 21 days (8-36). A total of 76 (90%) patients underwent the whole treatment plan according to the recurrence risk. At the time of analysis, the results of genetic testing were available in 18 patients and revealed 4 (22%) carriers of a pathogenic variant in any of the genes associated with Lynch syndrome. Molecular testing combining immunohistochemical analyses of MMR and p53 proteins in all newly diagnosed EC patients with sequencing analysis of POLE in those with non-low-risk disease is feasible and does not prolong the time needed for treatment decision.

Molecular and immune profiling of TP53-mutated ovarian cancers with non-BRCA1/2 homologous recombination gene alterations.

5579 Background: Molecular alterations in homologous recombination (HR) pathway genes lead to HR deficiency (HRD) in ~50% of high grade serous ovarian carcinomas (HGSOC). The immune microenvironment of BRCA1/2-mutated HGSOC has been extensively characterized, in contrast to tumors with mutations in other HR genes. We evaluated a cohort of epithelial ovarian cancers (EOC) enriched for HGSOC and compared molecular and immune signatures of tumors with BRCA1/2 mutations ( BRCAm) to those with non-BRCA1/2 HR gene mutations (NBHRD). Methods: We characterized 173 EOC by comprehensive genomic and immune profiling (CGIP) using panel-based next-generation DNA (523 genes) and RNA sequencing (384 genes), respectively. We enriched for HGSOC by selecting for TP53 mutations and excluding tumors with non-serous histology or any mutation in POLE, MLH1, PMS2, MSH2, MSH6, or nucleotide excision repair genes. Tumors lacking BRCA1/2-mutations were classified as NBHRD if a reportable mutation was present in canonical HR genes. Mutational burden (TMB, mut/Mb) was estimated from detected SNV/indels. We calculated immune-related expression signatures, including tumor immunogenicity score (TIGS), cellular proliferation (CP), and cancer testis antigen burden (CTAB). PD-L1 expression was assessed by tumor proportion score (TPS) following 22C3 immunohistochemistry. Differences in TMB, TIGS, CP, CTAB, PD-L1 and gene expression rank were tested for using Wilcoxon rank-sum test. Results: Of 173 EOC, 84 cases had complete CGIP, including 11 (13%) BRCAm, 7 (8%) NBHRD (Table), and 66 (79%) lacking HR gene alterations. On average, NBHRD tumors harbored lower TMB (4.1±2.3 vs. 6.6±2.3 vs. p=0.03) and elevated TIGS (59.1±16.2 vs. 41.7±16.2 p=0.044) compared to BRCAm tumors. We found no difference in PD-L1 (p=0.21), CP (p=0.26), or CTAB (p=0.48). Expression changes were identified in 32 immune genes, of which 31 (97%) were substantially up-regulated (1.3-3.3 fold) in NBHRD compared to BRCAm tumors. Conclusions: Our findings showed our cohort of NBHRD tumors were more immunogenic but less mutagenic than BRCAm tumors, implying enhanced immunogenicity unrelated to neoantigen load. Given that immune checkpoint inhibitors have shown limited efficacy in ovarian cancer, our data suggest NBHRD tumors may have stronger and possibly distinct immune escape mechanisms compared to BRCAm tumors. [Table: see text]

In-silico analysis of TCGA data showing multiple POLE-like favourable subgroups overlapping with TP53 mutated endometrial cancer: Implications for clinical practice in low and middle-income countries

IntroductionThe Cancer Genome Atlas cohort of endometrial carcinoma (TCGA-UCEC) includes almost 40% TP53-mutants encompassing missense and truncated variants. TCGA revealed ‘POLE’, characterized by POLE gene bearing exonuclease domain mutation (EDM), as the prognostically best molecular profile. The worst profile was characterized by TP53-mutated Type 2 cancer requiring adjuvant therapy having cost implications in low-resource settings. We aimed to find more ‘POLE-like’ favourable subgroups by searching TCGA cohort, especially within TP53 mutated risk group, that could eventually avoid adjuvant treatment in resource-poor settings. MethodOur study was an in-silico survival analysis performed on the TCGA-UCEC dataset using SPSS statistical package. TP53 and POLE mutations, microsatellite instability (MSI), time-to-event and clinicopathological parameters were compared among 512 endometrial cancer cases. Deleterious POLE-mutations were identified by Polyphen2. Progression free survival was studied using Kaplan-Meier plots keeping original ‘POLE’ as comparator. ResultIn presence of wild type (WT)-TP53, other deleterious POLE-mutations behaved like POLE-EDM. Only truncated and not missense TP53 benefitted from POLE/MSI overlap. However, TP53 missense mutation, Y220C, was found to be as favourable as ‘POLE’. Overlapping POLE, MSI and WT-TP53 also performed favourably. Truncated TP53 overlapped with POLE and/or MSI, TP53 Y220C alone and, WT-TP53 overlapped with POLE and MSI both, were named ‘POLE-like’ for prognostically behaving like the comparator ‘POLE’. ConclusionObesity being a lesser frequent event in low and middle-income countries (LMICs), relative proportion of women with lower BMI and Type 2 endometrial cancers may be high. Identification of ‘POLE-like’ groups may facilitate therapeutic de-escalation in some TP53-mutated cases - a novel option. Instead of 5% (POLE-EDM), potential beneficiary would then comprise 10% (POLE-like) of TCGA-UCEC.

QPOLE: A Quick, Simple, and Cheap Alternative for POLE Sequencing in Endometrial Cancer by Multiplex Genotyping Quantitative Polymerase Chain Reaction.

Detection of 11 pathogenic variants in the POLE gene in endometrial cancer (EC) is critically important to identify women with a good prognosis and reduce overtreatment. Currently, POLE status is determined by DNA sequencing, which can be expensive, relatively time-consuming, and unavailable in hospitals without specialized equipment and personnel. This may hamper the implementation of POLE-testing in clinical practice. To overcome this, we developed and validated a rapid, low-cost POLE hotspot test by a quantitative polymerase chain reaction (qPCR) assay, QPOLE. Primer and fluorescence-labeled 5'-nuclease probe sequences of the 11 established pathogenic POLE mutations were designed. Three assays, QPOLE-frequent for the most common mutations and QPOLE-rare-1 and QPOLE-rare-2 for the rare variants, were developed and optimized using DNA extracted from formalin-fixed paraffin-embedded tumor tissues. The simplicity of the design enables POLE status assessment within 4-6 hours after DNA isolation. An interlaboratory external validation study was performed to determine the practical feasibility of this assay. Cutoffs for POLE wild-type, POLE-mutant, equivocal, and failed results were predefined on the basis of a subset of POLE mutants and POLE wild-types for the internal and external validation. For equivocal cases, additional DNA sequencing is recommended. Performance in 282 EC cases, of which 99 were POLE-mutated, demonstrated an overall accuracy of 98.6% (95% CI, 97.2 to 99.9), a sensitivity of 95.2% (95% CI, 90.7 to 99.8), and a specificity of 100%. After DNA sequencing of 8.8% equivocal cases, the final sensitivity and specificity were 96.0% (95% CI, 92.1 to 99.8) and 100%. External validation confirmed feasibility and accuracy. QPOLE is a qPCR assay that is a quick, simple, and reliable alternative for DNA sequencing. QPOLE detects all pathogenic variants in the exonuclease domain of the POLE gene. QPOLE will make low-cost POLE-testing available for all women with EC around the globe.

Abstract 5355: Elraglusib response prediction and mechanistic discovery using iterative machine learning

Abstract Elraglusib is a selective GSK-3 inhibitor that has activity on a broad array of neoplasms as well as their immune microenvironment. However the determinants of tumor response have not been elucidated. Here, we use genomic panels of cancer driver genes to predict patient response to elraglusib therapy as measured by RECIST criteria. Patient response in the Phase I 1801 trial (NCT03678883) was matched to genomic data from patient tumors, with 80 cases used to train Machine Learning models and 26 cases reserved as a test set for model evaluation. When predicting response from mutation status alone our models reached a modest accuracy of 65% in the test set, which we attributed to the sparsity of genomic data. To remedy this, we engineered pathway-based features to provide combinatorial information while ensuring feature stability. To select the optimal combination of features, we designed an iterative design process that first randomized feature combinations and then created refined models from the highest performing pathway features. This resulted in several final models with greater than 88% accuracy. We retained several models of similar accuracy to more comprehensively identify potential biomarkers and combinatorial relationships. These models were then interpreted using SHapley Additive exPlanations (SHAP) where we were able to identify highly predictive features for both the entire pan-cancer cohort and specific histologies. We found the feature constructed from the Reactome pathway “Chromatin Modifying Enzymes” frequently occurred in high performing models with a high-ranking SHAP value. This feature included genes such as SMARCA4, HDAC2, and KDM5A, and was negatively associated with patient response. Another frequently observed high-ranking pathway feature with a negative response association was based on the “Innate Immune System” Reactome pathway. Many of the features highlighted in our models were negatively associated with elraglusib response and thus could be general markers of poor prognosis. To address this, we altered our pipeline to test only positively associated features which substantially reduced our feature pool to only 285 features but still produced models with accuracies of up to 81%. Analysis of key features used by these models identified several positive markers of elraglusib including mutations in the POLE gene, which previously has been linked to DNA-damage response deficiency and anti-tumor immune response. In sum, we forecast elraglusib response for a variety of tumor histologies and simultaneously reveal potential mechanisms of elraglusib sensitivity and biological action. In future work we will investigate the utility of using POLE and other identified biomarker candidates to predict the likelihood of patient response to elraglusib, as well as whether our machine learning models will be an effective tool to guide patient stratification. Citation Format: Joseph McDermott, Taylor Weiskittel, Daniel Billadeau, Benedito Carneiro, Hu Li, Andrew Mazar. Elraglusib response prediction and mechanistic discovery using iterative machine learning. [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 5355.