17p Deletion Research Articles

Lfng-expressing centroacinar cell is a unique cell-of-origin for p53 deficient pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies with limited understanding of etiology. Studies in mice showed that both acinar and ductal cells of the pancreas can be targeted by combination of oncogenic Kras and p53 mutations to form PDAC. How the transforming capacities of pancreatic cells are constrained, and whether a subset of cells could serve as a prime target for oncogenic transformation, remain obscure. Here we report that expression of a Notch modulator, Lunatic Fringe (Lfng), is restricted to a limited number of cells with centroacinar location and morphology in the adult pancreas. Lfng-expressing cells are preferentially targeted by oncogenic Kras along with p53 deletion to form PDAC, and deletion of Lfng blocks tumor initiation from these cells. Notch3 is a functional Notch receptor for PDAC initiation and progression in this context. Lfng is upregulated in acinar- and ductal-derived PDAC and its deletion suppresses these tumors. Finally, high LFNG expression is associated with high grade and poor survival in human patients. Taken together, Lfng marks a centroacinar subpopulation that is uniquely susceptible to oncogenic transformation when p53 is lost, and Lfng functions as an oncogene in all three lineages of the exocrine pancreas.

SURG-02. ANAPLASTIC PLEOMORPHIC XANTHOASTROCYTOMA WITH LEPTOMENINGEAL DISSEMINATION PRESENTING WITH CRANIAL NEUROPATHY IN AN ADULT PATIENT: ILLUSTRATIVE CASE AND REVIEW OF THE LITERATURE

Abstract INTRODUCTION Anaplastic pleomorphic xanthoastrocytomas (APXA) are very rare, grade III malignant astrocytic glial neoplasms first described as a distinct entity in the 2016 World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS). They are generally seen in pediatric and young adult patients as supratentorial lesions with both solid and cystic components and have a high propensity for recurrence despite local treatment. APXAs occasionally demonstrate leptomeningeal dissemination (LMD) but extremely seldom at the time of diagnosis. They are typically treated via surgical resection with adjuvant chemoradiation, although there is no standard of care for adjuvant therapy. Case Presentation: The authors describe the case of a 37-year-old male with a history of seizures since age 11 who presented with four months of worsening headache, increasingly frequent seizures, and diplopia with right cranial nerve III palsy. Imaging at the time of diagnosis of his seizure disorder as a child demonstrated a small left temporal lesion, which remained stable on imaging for over 20 years and was never biopsied, however MRI at current presentation showed significant interval enlargement with intralesional hemorrhage and leptomeningeal enhancement involving the left temporal and parietal lobes, left internal auditory canal, and right oculomotor nerve. He underwent surgical resection with gross total resection achieved and pathology revealed WHO Grade III pleomorphic xanthoastrocytoma with ATG7::RAF1 fusion, 9p21 deletion, and TERT promoter mutation on next generation sequencing. This was followed by adjuvant whole brain radiation with boost and treatment with MEK inhibitor cobimetinib. His postoperative course was remarkable for intermittent speech difficulty and improving right third nerve palsy. CONCLUSION We describe the unusual presentation of an already exceedingly rare primary CNS tumor, namely APXA in an adult patient with LMD and cranial neuropathy at the time of diagnosis, and detail tailored adjuvant therapy based on genomic profiling.

TMET-32. THE ROLE OF HOXC10 IN DRIVING GLIOBLASTOMA AGGRESSIVENESS

Abstract BACKGROUND Glioblastoma (GBM) is an aggressive malignancy, with a tumor doubling time of just 49.6 days. Despite maximal safe surgical resection, radiation, and temozolomide, median survival is only 14.6 months. Homeobox gene, homeobox C10 (HOXC10), a transcription factor of the HOX10 family, is pivotal in neuronal development, upregulated in several cancers, including glioma, and correlates with poor survival. METHODS RNA sequencing analysis was done on our mouse glioma syngeneic cell lines. HOXC10 expression analysis was done on human and mouse GBM cell lines and tissues by immunoblotting and immunohistochemistry, respectively. HOXC10 and p16-/-silencing were done using 4 unique 29mer shRNA constructs in the GFP vector, respectively. Gene Ontology predicted HOXC10 functions. HOXC10 and pyrroline-5-carboxylic acid reductase 1 (PYCR 1), a proline biosynthetic enzyme co-expression was studied using immunofluorescence analysis. RESULTS HOXC10 is highly expressed in human and mouse GBM tissues. HOXC10 was upregulated only in the high-grade/aggressive cell line [EGFRvIII; p16-/- & GFAP Cre] and demonstrated increased expression with p16 deletion in the mouse glioma cell line. Compellingly, TCGA analysis of GBM correlated the negatively prognostic p16 homozygous deletion (HD) with HOXC10 upregulation. Gene Ontology supports the role of HOXC10 for proline biosynthesis and metabolism. Immunofluorescence on mouse GBM sections revealed co-expression of HOXC10 and PYCR1. HOXC10 silencing significantly decreased GBM cell line proliferation, induced apoptosis, and decreased PYCR1 expression in vitro. CONCLUSIONS HOXC10 expression is increased in GBM and with p16 HD. HOXC10 silencing significantly decreased GBM cell line proliferation and decreased PYCR1 expression. HOXC10-mediated proline biosynthesis may present a novel target to improve GBM survival.

PATH-04. THE PROGNOSTIC IMPACT OF CDKN2A/B HETEROZYGOUS DELETIONS IN MENINGIOMA- INSIGHTS OF A MULTICENTER ANALYSIS

Abstract BACKGROUND Meningiomas are one of the most common primary brain tumors. Homozygous deletions of CDKN2A/B have reliably been shown to confer an increased risk of progression. However, the role of heterozygous CDKN2A/B deletions remains less clear. MATERIAL AND METHODS DNA methylation data, copy-number information and mutation data were generated on a multicenter cohort of meningiomas for a total of 970 samples. The CDKN2A/B locus was determined manually for each individual case in relation to whole chromosomal or larger segmental losses and gains in the chromosomal profile. Survival probabilities were assessed using the Kaplan–Meier method. RESULTS A total of 970 meningioma cases were identified with 30 homozygous and 114 heterozygous CDKN2A/B deletion cases, 826 cases had balanced CDKN2A/B. Heterozygous CDKN2A/B deletions in general did not confer an increased risk of progression compared to CDKN2A/B balanced cases (p= 0.074). However, segmental heterozygous losses of 9p, encompassing CDKN2A/B, yielded a significantly worse prognosis when compared to meningiomas CDKN2A/B-balanced (p= 0.002) and in contrast to focal heterozygous deletions (p= 0.523). Segmental heterozygous 9p deletions encompassing CDKN2A/B were significantly more frequently associated with a higher amount of copy number variations (CNVs) than focal losses. CONCLUSION Segmental heterozygous CDKN2A/B deletions do confer an increased risk of progression, but focal heterozygous CDKN2A/B deletions do not. The signal for segmental deletions may not be locus-specific but just one representation of the generally instable genome of aggressive meningiomas.

Mosaic chromosomal alterations (mCAs) in individuals with monoclonal B-cell lymphocytosis (MBL)

MBL is a precursor condition to chronic lymphocytic leukemia (CLL), characterized by monoclonal B-cells in blood. Mosaic chromosomal alterations (mCAs) are a form of clonal hematopoiesis that include gains, losses, and copy-neutral loss-of-heterozygosity of large DNA segments. Both MBL and mCAs have been found to increase the risk of CLL and lymphoid malignancies, and the aim of our study was to investigate how mCAs relate to MBL, which is currently unknown. We analyzed genetic, flow cytometric, and hematologic data from 4632 individuals from the Mayo Clinic Biobank and CLL Database. MBL was detected using flow cytometry and classified as high-count (HC) or low-count (LC) MBL based on clone size. mCAs were detected primarily from whole blood DNA using sensitive SNP-array-based analyses. mCAs commonly altered in CLL (deletion of 6q, 11q, 13q, 17p, and trisomy 12) were specific (>99%) to individuals with MBL and CLL. HC-MBL and LC-MBL individuals were 881-fold and 8-fold, respectively, more likely to harbor CLL-associated mCAs than those without MBL. The cell fraction bearing these mCAs typically exceeded the B-cell fraction, suggesting their origin prior to the B-cell lineage. Integrating genetic and blood count data enabled detecting HC-MBL with high specificity in a biobank sample. These results quantify the contribution of mCAs to MBL and could enable large studies of HC-MBL without the need for flow cytometric screening.

Treatment selection and influencing factors for chronic lymphocytic leukemia: a physician survey in Japan.

Chronic lymphocytic leukemia (CLL) is a rare form of lymphoma in Japan. This study aimed to explore hematologists' motivations and considerations in making treatment decisions for CLL. Responses from hematologists treating CLL, obtained through an online survey, were descriptively analyzed. Subgroup analyses by preferred first-line (1L) treatment, years of clinical experience, and level of interest in CLL were conducted. Out of 107 hematologists surveyed, 82.2% identified Bruton tyrosine kinase inhibitors (BTKi) as their primary choice for 1L treatment; the reasons included established clinical evidence (61.4%) and oral administration convenience (56.8%). Key factors influencing 1L treatment selection among those favoring BTKi included the presence of 17p deletion, TP53 mutation, and patient's fitness status. BTKi was favored by 92.6% of hematologists with < 10 years of clinical experience and by 78.8% with more experience. The main reasons for choosing BTKi included safety (50.0%) and tolerance (46.7%) among hematologists who stated they had a specific interest in CLL and the oral administration route (62.1%) among hematologists with lower interest. When BTKi was used as 1L therapy, venetoclax-based regimens were preferred for second-line treatment. The most common concern about BTKi was substantial out-of-pocket costs. Although many Japanese hematologists select their treatment based on clinical evidence, variations exist in treatment strategies, possibly associated with hematologists' experience and interest in CLL. These findings underscore the importance of further promoting evidence-based treatments to ensure that all physicians can make informed decisions. Future research should explore additional factors that influence CLL treatment decisions.

Genetic Profiling in Chronic Lymphocytic Leukemia: The Role of TP53 Mutations and IGHV Status in Treatment Decision-Making – A Case Report

Introduction. The TP53 gene encodes the p53 protein, crucial for DNA damage response, apoptosis, and cell cycle regulation. In chronic lymphocytic leukemia (CLL), TP53 loss due to 17p deletion or mutation leads to poor chemoimmunotherapy response and shorter survival. Patients with unmutated immunoglobulin heavy chain variable (IGHV) status exhibit a more aggressive disease course, poorer outcomes, and reduced response to standard chemoimmunotherapy. These genetic variations significantly affect disease progression, treatment choice, and response to therapy. Case Report. In November 2023, a 61-year-old man presented to our clinic with complaints of generalized weakness and rapid fatigue since October 2023. CLL was diagnosed in 2018 through pathohistological and immunohistochemical analysis of the bone marrow. The patient received no therapy until 2023 due to the absence of active disease signs. From March 28, 2023, to July 25, 2023, the patient received chemoimmunotherapy with the bendamustine and rituximab (BR) regimen. Five courses of therapy were administered; however, further treatment was discontinued due to side effects that occurred during the fifth course of bendamustine administration. A subsequent diagnostic evaluation aimed at assessing treatment efficacy, prognosis, and genetic profiling included a cytomorphological analysis, which revealed that lymphocytes comprised 80% of the cellular composition. Immunocytological analysis confirmed the presence of monoclonal atypical lymphocytes, accounting for 70% of the cell population. Next-generation sequencing identified a pathogenic TP53 mutation, and fragment analysis confirmed an unmutated IGHV status. The presence of the TP53 mutation and unmutated IGHV status categorizes the patient as being in the very high-risk group, for which the use of Bruton’s tyrosine kinase inhibitors (BTKIs) and/or B-cell lymphoma-2 (BCL-2) inhibitors is recommended. Conclusions. This case highlights the significance of comprehensive genetic profiling in CLL patients using techniques such as fluorescence in situ hybridization, polymerase chain reaction, and next-generation sequencing. Such profiling detects molecular genetic alterations, facilitating personalized and effective treatment.

Event-free survival in neuroblastoma with MYCN amplification and deletion of 1p or 11q may be associated with altered immune status

BackgroundNeuroblastoma exhibits substantial heterogeneity, which is intricately linked to various genetic alterations. We aimed to explore immune status in the peripheral blood and prognosis of patients with neuroblastoma with different genetic characteristics.MethodsWe enrolled 31 patients with neuroblastoma and collected samples to detect three genetic characteristics. Peripheral blood samples were tested for immune cells and cytokines by fluorescent microspheres conjugated with antibodies and flow cytometry. Event-free survival (EFS) was analyzed using the Kaplan‒Meier method.ResultsTwenty-two patients had genetic aberrations, including MYCN amplification in 6 patients, chromosome 1p deletion in 9 patients, and chromosome 11q deletion in 14 patients. Two genetic alterations were present in seven patients. The EFS was worse in patients with MYCN amplification or 1p deletion than in the corresponding group, whereas 11q deletion was a prognostic factor only in patients with unamplified MYCN. Changes in immune status revealed a decrease in the proportion of T cells in blood, and an increase in regulatory T cells and immunosuppression-related cytokines such as interleukin (IL)-10. The EFS of the IL-10 high-level group was lower than that of the low-level group. Patients with concomitant genetic alterations and a high level of IL-10 had worse EFS than other patients.ConclusionsPatients with neuroblastoma characterized by these genetic characteristics often have suppressed T cell response and an overabundance of immunosuppressive cells and cytokines in the peripheral blood. This imbalance is significantly associated with poor EFS. Moreover, if these patients show an elevated levels of immunosuppressive cytokines such as IL-10, the prognosis will be worse.

B-220 Clinical Application of the “Clg-Fish” Technique for the Diagnosis of Multiple Myeloma

Abstract Background The international standard system [R2-ISS] for Multiple Myeloma (MM) includes genetic characteristics of malignant cells by fluorescent in situ hybridization -t(4;14), del(17p) and t(14;16) at diagnosis; We included interphase fluorescent in situ hybridization (cIg-FISH) of purified CD138 cells in this evaluation. The aim of this study is to evaluate the implementation of cIg-FISH in MM for disease diagnosis and stratification. Methods oBone marrow [BM] from patients with MM diagnosed by the European Myeloma Network (REM) criteria were evaluated. BM mononuclear cells obtained by density gradient centrifugation for 30 minutes, with Ficoll-Hypaque density medium; followed by immunoassay with anti-Kappa/anti-Lambda antibodies labeled with FISH probes. We detected the following abnormalities: t(4;14), t(14;16) and deletion of 17p13. The t(11;14) and the amplification/deletion of 1q21-q22 (CKS1B)/1p32.3 (CDKN2C). We used the probes: TP53, IGH::FGFR3, IGH::CCND1, IGH:MAF and CKS1B/CDKN2C, one hundred cells per probe. Signals exceeding the cutoff recommended by REM were considered abnormal. The viability of the method was tested on samples 24, 48 and 72 hours after collection. Results Genetic aberrations seen in 24 and 48 hs plasma cells, a specific rearrangement of 14q32.33 t(4;14) in the 48 hs sample; Samples processed for 72 hours resulted in cells that were unviable for analysis. Genetic aberrations were detected by cIg-FISH in cells from 40% of patients. We detected the following abnormalities t(4;14) (Fig.1A), del(17p) (Fig. 1B); deletion of 1p32.3 amplification (CDKN2C) 1q21 (Fig. 1 C-D). The cIg-FISH study detected genetic aberrations in MM as those recommended by the European Myelomat Network - t(4;14), t(14;16) and del(17p), by FISH analysis for risk stratification for MM. Conclusions The inclusion of cIg-FISH in risk stratification systems has clinical relevance because cIg-FISH is a standard tool for detecting genetic abnormalities and prognosing the disease.

Real-World Outcomes of Upfront Autologous Hematopoietic Stem Cell Transplantation in Patients With Newly Diagnosed Multiple Myeloma With Deletion 17p

Despite tremendous advancements in multiple myeloma (MM) therapeutics, outcomes remain heterogeneous, heavily influenced by clinical and cytogenetic factors. Among these, deletion of the short arm of chromosome 17 (del(17p)) is a strong predictor of poor prognosis. The aim of this study was to evaluate real-world outcomes in patients with newly diagnosed MM (NDMM) with del(17p) undergoing upfront autologous hematopoietic stem cell transplantation (auto-HCT). We conducted a single-center retrospective analysis of patients with NDMM who underwent upfront auto-HCT at MD Anderson Cancer Center between 2008 and 2018. Primary endpoints were progression-free survival (PFS) and overall survival (OS), with secondary endpoints being hematological response and measurable residual disease (MRD) status postauto-HCT. MRD status in the bone marrow biopsy was evaluated using 8-color next-generation flow cytometry with a sensitivity of 1/10-5 cells. One hundred and fifteen patients were included (55% male). Median age at auto-HCT was 62 years (range 34 to 83). The median del(17p) clone size was 20%, with 51 (53%) patients having clone sizes >20% and 15 (15%) patients having clone sizes >55%. Additional high-risk cytogenetic abnormalities included t(4;14) in 15 (13%) patients, t(14;16) in 8 (7%) patients, and 1q21+ in 25 (22%) patients. After induction, 10% of patients achieved ≥ CR, and 50% achieved ≥ VGPR, with 25% having MRD-negative ≥ VGPR. Post-transplant, 42% achieved ≥ CR, and 83% achieved ≥ VGPR as best response, with 55% (48/87) having MRD-negative ≥ VGPR. With a median follow-up of 31.4 months (range 3.1 to 199.1), median PFS and OS for the entire cohort were 19.9 and 71.5 months, respectively, and 5-year OS was 53%. Concurrent del(17p) and t(4;14) were associated with significantly worse outcomes, with median PFS and OS of 11.5 and 22.4 months, respectively. In multivariable analysis (MVA), female sex was associated with worse PFS (HR [95% CI] 2.87 [1.75 to 4.72], P < .001), while MRD negative CR post-transplant (0.35 [0.18 to 0.68], P = .002) and maintenance therapy (0.46 [0.27 to 0.77], P = 0.003) were associated with better PFS. In MVA for OS, female sex (2.22 [1.18 to 4.17], P = 0.013) and the presence of t(4;14) (2.55 [1.09 to 5.95], P = 0.030) were associated with worse OS, whereas Karnofsky Performance Status of ≥90 (0.47 [0.23 to 0.94], P = 0.034) was associated with better OS. This study affirms del(17p) as a high-risk abnormality with unfavorable outcomes despite modern therapies. The co-occurrence of del(17p) and t(4;14) was associated with particularly poor outcomes. Novel approaches are needed for this high-risk subgroup.

Low platelet counts and low CD4/CD8 ratios at apheresis increase the risk of CAR T-cell manufacturing failure in myeloma

AbstractChimeric antigen receptor (CAR) T-cell (CAR-T) therapy has significantly improved management of relapsed or refractory multiple myeloma. However, manufacturing failure due to poor cell growth necessitates revision of treatment strategies that negatively impact patients. To identify risk factors for CAR-T manufacturing failure in patients with myeloma, a nationwide cohort study was performed, analyzing patients who underwent apheresis for idecabtagene vicleucel in Japan. Of 154 patients analyzed, 13 cases (8.4%) experienced manufacturing failure. We compared clinical factors between patients with manufacturing failure (failed group) and those who met specifications (successful group). Patients in the failed group had a higher prevalence of deletion 17p at diagnosis (38.5% vs 14.9%), were more likely to have been treated with alkylating agents within 6 months before apheresis (53.8% vs 23.4%), and had undergone more chemotherapy lines before apheresis (median, 6 vs 5). Additionally, patients with manufacturing failure exhibited significantly lower hemoglobin levels (8.6 vs 10.0 g/dL), platelet counts (5.9 × 104/μL vs 13.8 × 104/μL), and CD4/CD8 ratios (0.169 vs 0.474) than patient with successful manufacturing. Multivariate analysis revealed that low platelet counts (odds ratio [OR], 0.130 for every increase of 105/μL; P = .041), or low CD4/CD8 ratios (OR, 0.100 for each doubling; P = .003) at apheresis increased the risk of manufacturing failure. Alkylating agents within 6 months before apheresis were associated with decreased platelet counts and CD4/CD8 ratios. Manufacturing failure remains an obstacle to CAR-T therapy for patients with myeloma. Avoiding risk factors, such as alkylating agents, and adopting risk-adapted strategies may optimize CAR-T therapy for patients with myeloma.

Biallelic Loss of 7q34 (TRB) and 9p21.3 (CDKN2A/2B) in Adult Ph-Negative Acute T-Lymphoblastic Leukemia

Tumor cells of acute lymphoblastic leukemia (ALL) may have various genetic abnormalities. Some of them lead to a complete loss of certain genes. Our aim was to reveal biallelic deletions of genes in Ph–negative T-ALL. Chromosomal microarray analysis (CMA) was performed for 47 patients with de novo Ph–negative T-ALL, who received treatment according to RALL-2016m clinical protocol at the National Medical Research Center for Hematology (Moscow, Russia) from 2017 to 2023. Out of forty-seven patients, only three had normal molecular karyotype. The other 44 patients had multiple gains, losses, and copy neutral losses of heterozygosity. Biallelic losses were found in 14 patients (30%). In ten patients (21%), a biallelic deletion of 9p21.3 involved a different number of genes, however CDKN2A gene loss was noted in all ten cases. For seven patients (15%), a biallelic deletion of 7q34 was found, including two genes—PRSS1, PRSS2 located within the T-cell receptor beta (TRB) locus. A clonal rearrangement of the TRB gene was revealed in 6 out of 7 cases with 7q34 biallelic loss. Both biallelic deletions can be considered favorable prognostic factors, with an association with 9p21 being statistically significant (p = 0.01) and a trend for 7q34 (p = 0.12) being observed.

The Prevalence of Cytogenetic Abnormalities Detected by Interphase FISH Method in Chronic Lymphocytic Leukemia

Abstract Background Chronic lymphocytic leukemia (CLL) is the most prevalent adult leukemia. Identification of genomic aberration provides prognostic/predictive information that is helpful in the precision medicine management of these patients. The aim of this study was to determine prevalence of the most common cytogenetic abnormalities of CLL patients in the southwest region (Shiraz) of Iran and correlate with clinical prognostic parameters to clarify their prognostic value. Materials and Methods In this cross-sectional study, 100 patients with CLL were recruited from April 2019 to October 2021. Four milliliters of anticoagulated peripheral blood was collected from each participant. The sample was used for complete blood count (CBC) test and fluorescence in situ hybridization (FISH) test. Interphase FISH (I-FISH) was performed for most common cytogenetic abnormalities, including trisomy 12, 13q14 deletion, 11q deletion, and 17p deletion on interphasic cell nuclei. Results Among 100 patients with CLL, 33 (33%) were females and 67 (67%) were males. The mean age (mean ± standard error [SE]) of the patients was 59.00 ± 1.14 years, with a ranged of 25 to 79 years. Our analysis demonstrated that 86 (86%) patients had at least one chromosomal aberration. The most commonly detected abnormality was 13q deletion (61, 61%), followed by 17q deletion (50 cases, 50%). Trisomy 12 was detected in 14 (14%) cases and 10 cases (10%) had 11q deletion. Conclusion The higher frequency of 13q14 and 17p anomalies in our study may be attributed to delayed medical consultations, leading to the emergence of secondary abnormalities. More studies are recommended for verifying the results.

Abstract A028: MTAP deficiency is frequent and mostly homogeneous in ductal adenocarcinomas of the pancreas

Abstract Complete expression loss of S-methyl-5′-thioadenosine phosphorylase (MTAP) is caused by homozygous 9p21 deletion and results in a critical vulnerability of cancer cells towards drugs targeting multiple different pathways. MTAP deficiency is common in ductal adenocarcinoma of the pancreas, but data on its intratumoral heterogeneity - a potential obstacle for targeted therapies - are lacking. To learn more on the role and potential heterogeneity of MTAP deficiency in pancreatic adenocarcinoma, 236 primary tumors were analyzed in a tissue microarray (TMA) format by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) for MTAP expression and 9p21 deletions. The cohort included 236 cancers from which 6 samples were taken from as many as possible different tumor containing primary tumor blocks and 3 samples were added from as many as possible lymph node metastases to construct a “heterogeneity TMA”. All available tumor containing blocks (average 4) from 6 selected cancers were also analyzed by IHC and FISH on whole sections. Complete absence of MTAP staining was seen in 350 (38.6%) of 907 interpretable TMA samples. 284 (98.6%) of 288 samples with a complete MTAP expression loss and FISH data had a homozygous 9p21 deletion while there were only two tumor spots with homozygous deletions within 557 samples with retained MTAP expression (99.6% concordance). On a patient level, an MTAP deficiency was found in 64 (41.0%) of 156 tumors for which at least 3 different samples were interpretable on the TMAs. 62 (96.9%) of these patients showed an MTAP loss in all interpretable samples (homogeneous MTAP deficiency). The TMA data were confirmed on whole sections in 5 of 6 patients. In the discrepant case a focal MTAP loss was identified in a tumor considered MTAP wild type based on the TMA results. It is concluded that MTAP expression loss is frequent and highly homogeneous in ductal adenocarcinomas of the pancreas. Given the high concordance rate between homozygous deletion and MTAP expression loss homozygous deletion may represent the only mechanism for MTAP deficiency in pancreatic cancer. MTAP IHC is an excellent tool for identification of MTPA deficient cases. MTAP IHC may also have considerable diagnostic value as even low-grade cancer glands can be easily identified in small biopsies from MTAP deficient cases. Considering also their aggressive clinical behavior, pancreatic adenocarcinomas may represent an ideal cancer type for studying new drugs targeting MTAP deficient cancer cells in clinical trials. Citation Format: Natalia Gorbokon, Katharina Teljuk, Frank Jacobsen, Till Krech, Till Clauditz, Stefan Steurer, Ronald Simon, Guido Sauter, Sarah Minner, Lukas Bubendorf, Thilo Hackert, Nina Schraps, Faik G Uzunoglu, Martina Kluth. MTAP deficiency is frequent and mostly homogeneous in ductal adenocarcinomas of the pancreas [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A028.

Abstract B084: Comparative functional analysis of TP53 alleles in pancreatic ductal adenocarcinoma in vivo

Abstract TP53 is the second most mutated gene in pancreatic ductal adenocarcinoma (PDAC), bearing both truncal loss-of-function and missense point mutations. TP53 encodes a stress-induced transcription factor (p53) capable of activating tumor suppressive pathways mediating cell cycle arrest, apoptosis, senescence, and metabolic reprogramming. Despite high mutational frequency, how TP53 mutants function to suppress pancreatic tumorigenesis in vivo remains unclear. Previous studies indicate that the most frequent point mutations observed in human PDAC (TP53 R175H and R273H; mouse homologues Trp53 R172H and R270H) exhibit both dominant-negative (e.g., response to radiation in leukemia cells) and gain-of-function (e.g., increased liver metastasis in advanced PDAC models) roles compared to p53 null cells in various contexts. To rigorously explore the differential functions of p53 point and deletion mutants in PDAC progression, we performed an isogenic comparative analysis of Trp53 alleles in vivo using Mosaic Analysis with Double Markers (MADM) in mice. MADM uses stochastic mitotic recombination to induce two genotypically distinct daughter cells – created at 1-to-1 ratios – expressing different Trp53 variants dependent on the genotype of the mouse (+/+ vs. -/-, R172H/R172H vs. +/+, R172H/R172H vs. -/-, R270H/R270H vs. +/+, R270H/R270H vs. -/-) and simultaneously label them with unique genetically encoded fluorescent markers (TdTomato vs. GFP). We integrated MADM into a faithful Kras-driven model of pancreatic tumorigenesis (KC: Kras LSL-G12D/+ ; Pdx1-Cre) and used fluorescence microscopy to trace subclonal populations with various Trp53 alleles within the same mouse. By analyzing the ratio of TdTomato+ to GFP+ cells, we studied the functional differences between alleles in driving tumor initiation and expansion at various stages of progression. Strikingly, we found that Trp53 -/- cells exhibited greater expansion in preinvasive pancreatic intraepithelial neoplasias (PanINs) compared to not only Trp53 +/+ cells but also cells harboring either point mutation (Trp53 R172H/R172H or Trp53 R270H/R270H ). While Trp53 R270H/R270H cells predominated over Trp53 +/+ in PanINs, Trp53 R172H/R172H cells were surprisingly indistinguishable from Trp53 +/+ cells, suggesting that p53R172H retains tumor suppressive properties in early PDAC progression. Conversely, both Trp53 R172H/R172H and Trp53 R270H/R270H cells progressed to advanced PDAC with comparable PDAC incidence and survival as Trp53 -/- , arguing that Trp53 R172H is a separation-of-function mutant concordant with a distinct transcriptional profile relative to Trp53 -/- tumor cells. Together, these studies offer the strongest evidence to date for stage-specific functional differences between TP53 mutant variants in cancer progression in vivo and provide a faithful MADM-based PDAC model to define molecular mechanisms (through ongoing transcriptomic, epigenomic, and metabolomic studies) that govern functional differences amongst these diverse alleles. Citation Format: Sherry S. Agabiti, Andy Tang, Timothy Nottoli, Mandar D. Muzumdar. Comparative functional analysis of TP53 alleles in pancreatic ductal adenocarcinoma in vivo [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B084.

Chronic intermittent hypoxia triggers cardiac fibrosis: Role of epididymal white adipose tissue senescent remodeling?

Obstructive sleep apnea (OSA) is a growing health problem affecting nearly 1 billion people worldwide. The landmark feature of OSA is chronic intermittent hypoxia (CIH), accounting for multiple organ damage, including heart disease. CIH profoundly alters both visceral white adipose tissue (WAT) and heart structure and function, but little is known regarding inter-organ interaction in the context of CIH. We recently showed that visceral WAT senescence drives myocardial alterations in aged mice without CIH. Here, we aimed at investigating whether CIH induces a premature visceral WAT senescent phenotype, triggering subsequent cardiac remodeling. In a first experiment, 10-week-old C57bl6J male mice (n = 10/group) were exposed to 14 days of CIH (8 h daily, 5%-21% cyclic inspired oxygen fraction, 60 s per cycle). In a second series, mice were submitted to either epididymal WAT surgical lipectomy or sham surgery before CIH exposure. Finally, we used p53 deficient mice or Wild-type (WT) littermates, also exposed to the same CIH protocol. Epididymal WAT was assessed for fibrosis, DNA damages, oxidative stress, markers of senescence (p16, p21, and p53), and inflammation by RT-qPCR and histology, and myocardium was assessed for fibrosis and cardiomyocyte hypertrophy. CIH-induced epididymal WAT remodeling characterized by increased fibrosis, oxidative stress, DNA damage response, inflammation, and increased expression of senescent markers. CIH-induced epididymal WAT remodeling was associated with subtle and early myocardial interstitial fibrosis. Both epididymal WAT surgical lipectomy and p53 deletion prevented CIH-induced myocardial fibrosis. Short-term exposure to CIH induces epididymal WAT senescent remodeling and cardiac interstitial fibrosis, the latter being prevented by lipectomy. This finding strongly suggests visceral WAT senescence as a new target to mitigate OSA-related cardiac disorders.

17p13 (TP53) Deletions Are Associated With an Aggressive Phenotype but Unrelated to Patient Prognosis in Urothelial Bladder Carcinomas.

17p13 deletions including TP53 and other genes represent a common cause for reduced/lost p53 function in tumor cells. In this study, we analyzed the impact of 17p13 (TP53) deletions and p53 expression on tumor aggressiveness and patient prognosis in urothelial carcinoma. The 17p13 copy number status was analyzed by fluorescence in situ hybridization (FISH) on more than 2700 urothelial bladder carcinomas in a tissue microarray format. 17p13 deletion data were compared to p53 expression data measured by immunohistochemistry (IHC) in a previous study. Different types of p53 alterations were compared with tumor phenotype and clinical outcome data. Deletions of 17p13 occurred in 23% of 2185 analyzable carcinomas. The fraction of tumors with 17p13 deletions increased from pTa G2 low (9%) to pTa G3 (24%, p < 0.0001). In muscle-invasive carcinomas, 17p13 deletions were associated with advanced pT stage (p = 0.0246), but unrelated to patient prognosis (p > 0.5). 17p13 deletions were significantly related to p53 immunostaining (p = 0.0375). 17p13 deletions were most common in tumors with complete lack of p53 staining (31%), which supports the concept that many of these tumors have a complete loss of p53 function (p53 null phenotype). 17p13 deletions were also increased in tumors with high p53 staining (25%). In conclusion, 17p13 deletions were most commonly seen in p53 negative cancers, supporting their role as a cause for the p53 null phenotype in urothelial cancer. The association of 17p13 deletions with high grade and advanced pT stage may reflect increasing genomic instability going along with stage and grade progression.

PDGF-BB overexpression in p53 null oligodendrocyte progenitors increases H3K27me3 and induces transcriptional changes which favor proliferation

Proneural gliomas are brain tumors characterized by enrichment of oligodendrocyte progenitor cell (OPC) transcripts and genetic alterations. In this study we sought to identify transcriptional and epigenetic differences between OPCs with Trp53 deletion and PDGF-BB overexpression (BB-p53n) and those carrying only p53 deletion (p53n). In culture, the BB-p53n OPCs display growth characteristics more similar to glioma cells than p53n OPCs. When injected in mouse brains, BB-p53n OPC form tumors, while the p53n OPCs do not. Unbiased histone proteomics and transcriptomic analysis on these OPC populations identified higher levels of the histone H3K27me3 mark and lower levels of the histone H4K20me3. The transcriptome of the BB-p53n OPCs was characterized by higher levels of transcripts related to proliferation and cell adhesion compared to p53n OPCs. Pharmacological inhibition of the enzyme responsible for histone H3K27 trimethylation (EZH2i) in BB-p53n OPCs, reduced cell cycle transcripts and increased the expression of differentiation markers, but was not sufficient to restore their growth characteristics. This suggests that PDGF-BB overexpression in p53n OPCs favors the early stages of transformation, by promoting proliferation and halting differentiation in a H3K27me3-dependent pathway, and favoring growth characteristics in a H3K27me3 independent manner

Prognostic impact of cytogenetic abnormalities detected by FISH in AL amyloidosis with daratumumab-based frontline therapy

AbstractWe performed an international retrospective study on 283 patients with light chain (AL) amyloidosis to investigate the prognostic impact of cytogenetic abnormalities by fluorescence in situ hybridization, when treated with frontline daratumumab–based therapy. The cytogenetic subgroups of interest were t(11;14), gain/amp(1q) (hereafter, +1q), hyperdiploidy, deletion(13q), del(17p), and myeloma high-risk (HR) translocations (t[4;14], t[14;16], or t[14;20]). The end points of interest were rate of hematologic complete response (heme-CR), very good partial response (VGPR) or better, and hematologic event-free survival (heme-EFS). The incidence of abnormalities was as follows: t(11;14), 53.4%; deletion (13q), 28.9%; +1q, 22.3%; hyperdiploidy, 19.4%; HR translocations, 6.6%; and deletion(17p), 4.5%. The heme-CR rate by cytogenetic subgroups were as follows: t(11;14) vs no t(11;14), 45.2% vs 41.8% (P=0.597); del(13q) vs no del(13q), 46.8% vs 42.8% (P=0.594); +1q vs no +1q, 30.2% vs 47.9% (P=0.022); hyperdiploidy vs no hyperdiploidy, 39.5% vs 44.9% (P=0.541); HR translocations vs none, 45.5% vs 43.1% (P=0.877); and del(17p) vs no del(17p), 50.0% vs 42.9% (P=0.658), respectively. Similarly, +1q was the only subgroup with a significantly lower VGPR or better rate (64.2% vs 79.0%; P=0.033). At a median follow-up of 19.8 months, the median heme-EFS was 49.6 months (95% CI, 24.7-not reached [NR]), and the 2-year overall survival (OS) was 80.98% (95% CI, 75.6-85.4). The presence of +1q was significantly associated with worse heme-EFS on multivariate analysis (HR 2.06, 95% CI, 1.14-3.71; P=0.017). Notably, there was no adverse prognostic impact of t(11;14) on heme-EFS or OS. In conclusion, +1q is associated with worse outcome in the daratumumab-era. Clinical trials testing novel frontline immunotherapies should be enriched in +1q to further improve outcomes in this subgroup.

CIMPACT-NOW Update 8: Clarifications on molecular risk parameters and recommendations for WHO grading of meningiomas.

Meningiomas are the most frequent primary intracranial tumors. Hence, they constitute a major share of diagnostic specimens in neuropathology practice. The 2021 WHO Classification of Central Nervous System Tumors ("CNS5") has introduced the first molecular grading parameters for meningioma with oncogenic variants in the TERT promoter and homozygous deletion of CDKN2A/B as markers for CNS WHO grade 3. However, after publication of the new classification volume, clarifications were requested, not only on novel but also on long-standing questions in meningioma grading that were beyond the scope of the WHO "blue book". In addition, more recent research into possible new molecular grading parameters could not yet be implemented in the 2021 classification but constitute a compelling body of literature. Hence, the cIMPACT-NOW Steering Committee convened a working group to provide such clarification and assess the evidence of possible novel molecular criteria. As a result, this cIMPACT-NOW update provides guidance for more standardized morphological evaluation and interpretation, most prominently pertaining to brain invasion, identifies scenarios in which advanced molecular testing is recommended, proposes to assign CNS WHO grade 2 for cases with CNS WHO grade 1 morphology but chromosomal arm 1p deletion in combination with 22q deletion and/or NF2 oncogenic variants, and discusses areas in which the current evidence is not yet sufficient to result in new recommendations.