Germline Mutations Research Articles

Genetically Distinct Acute Megakaryoblastic Leukemia following Low Hypodiploid B-Lymphoblastic Leukemia linked by TP53 Mutation.

We report a case of acute myeloid leukemia with megakaryoblastic differentiation (AMKL) that developed after an initial B-lymphoblastic leukemia (B-ALL) with low hypodiploidy. Although the AMKL was initially thought either to be a phenotypic change from the original B-ALL or to have arisen as a result of treatment (acute myeloid leukemia, post cytotoxic therapy, AML-pCT [WHO]; AML, therapy related [ICC]), genetic evaluation of both the AMKL and the B-ALL suggest that neither of these considerations was correct. Rather, the AMKL did not harbor the most common genetic hallmark of AML-pCT-rearrangement of KMT2- and was genetically distinct from the B-ALL. Both the B-ALL and the AMKL, however, showed an identical TP53 mutation by next generation sequencing (NGS), while germline testing was negative for this mutant allele. Hence, either the patient had a tissue restricted constitutional TP53 mutation or had a somatic mutation in a multipotent hematopoietic precursor. This case highlights the necessity for close monitoring of patients with TP53-mutant tumors, as they may develop multiple lesions despite negative germline testing.

Phase II study of niraparib and dostarlimab for the treatment of germline or somatic homologous recombination repair mutated (HRD) metastatic pancreatic cancer.

727 Background: PARP inhibition (PARPi) is a standard maintenance therapy for patients (pts) with germline BRCA1/2 mutations in pancreatic cancer. Combination of PARPi therapy and immunotherapy has potential to increase efficacy and may offer benefit beyond germline BRCA1/2 . Methods: We performed a multisite single-arm phase 2 study using the highly potent PARPi niraparib with anti-PD1 drug dostarlimab in pts with germline or somatic HRD mutations in BRCA1/2, PALB2, RAD51C/D, or BARD1 . Pts were required to have metastasis, progressed on ≥1 regimen, and prior platinum-exposure unless refused/intolerant. Pts were treated with niraparib 200 mg orally once daily continuously. Dostarlimab 500 mg was administered IV every 3 weeks for 4 cycles, then 1000 mg IV every 6 weeks. The primary endpoint was disease control rate (DCR) at 12 weeks (DCR12) using iRECIST criteria. At least 8 pts with DCR12 in the first 19 eligible pts (41%) would be considered promising for further trials. Results: 22 pts were enrolled from Dec 2020 to Oct 2023. Two pts withdrew prior to receiving therapy, and 2 were later found to be ineligible, leaving 18 eligible pts for final analyses. Median age was 63.0 yrs, 39% male, 94% non-Hispanic white, 1 black (6%). 17 pts were platinum exposed, 7 were platinum-refractory, and 5 had previously progressed on PARPi maintenance. Mutation distribution was: BRCA2 13/18 (72%), BRCA1 4/18 (22%), BARD1 2/18 (11%). One pt had both BRCA1 (somatic) and BRCA2 (germline) mutations. Germline mutations were identified in 14/18 (78%). DCR12 was achieved in 5/18 (27.8%), so the primary endpoint (>41%) was not met. Pts received a median 2 cycles (range 1-8) of niraparib + dostarlimab. No clinical factors were significantly associated with improved DCR12 (all p > 0.05) in subgroup analyses, but we did observe the following statistically nonsignificant associations. Pts who were platinum-refractory had a lower DCR12 compared to those not (14.3% vs. 36.4%). Counterintuitively, PARPi exposed/refractory pts had a higher DCR12 than non-exposed/non-refractory (50 vs 17% exposed/nonexposed and 40% vs 23% refractory/nonrefractory). Pts with germline mutations had a higher DCR12 compared to those without (38.5% vs. 0%). Non- BRCA2 mutations had a higher DCR12 than those with BRCA2 mutations (50% vs.17%), with highest DCR12 rates among BRCA1 patients (67%). Tolerability was in line with similar combinations, with 60% non-hematologic Gr3 or higher, including fatigue (15%), AST increase (10%), nausea/vomiting (10%), sepsis (10%). Two grade 5 events were not attributed to treatment. Conclusions: PARPi plus anti-PD1 checkpoint inhibition was not sufficiently active as later line therapy in metastatic pancreatic cancer for the majority of patients with HRD mutations. Additional molecular analyses to elucidate predictive markers of sensitivity/resistance are ongoing. Clinical trial information: NCT04493060 .

Molecular characteristics of early-onset versus average-onset gastroesophageal adenocarcinoma.

496 Background: Incidence of early-onset gastroesophageal adenocarcinoma (eoGEA, ages <50 years) has been increasing in the United States since the 1990s, the etiology of which is still unclear, and limited data exists on molecular drivers. This study evaluates somatic and germline profiles in eoGEA compared to average-onset GEA (aoGEA, ages≥ 50 years). Methods: This is a retrospective, cross-sectional study utilizing data from de-identified records of GEA (esophageal, gastroesophageal junction and gastric adenocarcinomas) patients who underwent somatic NGS testing via the Tempus xT assay (595-648 gene DNA panel) from 12/2017 to 07/2024. This assay assesses somatic tumor mutations (including SNVs, Indels, CNVs, and select SVs), MSI, TMB, and incidentally detected germline SNVs and small indels in matched normal tissue. Clinical characteristics and immunotherapy markers were compared between eoGEA and aoGEA by Wilcoxon Rank Sum or Chi-squared test. Somatic and germline mutations were compared between two age groups with false discovery rate adjustments. Results: We compared the demographic, clinical, and molecular features of a total of 5863 patients with eoGEA (n=785, median age 43) and aoGEA (n=5078, median age 68). Over 80% of patients were diagnosed with stage IV disease. The eoGEA group had a higher proportion of females, non-white, and Hispanic or Latino patients compared to the aoGEA group (p<0.001). Prevalence of MSI-H/ dMMR, and TMB-H was lower in eoGEA vs aoGEA (p<0.001), while PD-L1 expression was similar. Prevalence of somatic CDH1 , CDKN2A , and TP53 SNVs, and FGFR2 and KRAS CNAs were higher in eoGEA vs aoGEA (q<0.001). In a subset of 3286 patients with tumor/normal match testing (eoGEA=464 and aoGEA=2822), eoGEA also had a higher prevalence of germline CDH1 mutations (q<0.001). Conclusions: eoGEA has a unique somatic and germline mutation profile compared to aoGEA; further study evaluating the molecular landscape including epigenetic changes could shed light on underlying mechanisms responsible for the rising incidence of eoGEA. eoGEA (n=785) aoGEA (n=5078) p-value/q-value* Baseline characteristics Median age at diagnosis (IQR) 43 (38, 47) 68 (61,74) <0.001 Gender: male 509 (65%) 3798 (75%) <0.001 Race (white) 280 (69%) 2347 (80%) <0.001 Ethnicity (not hispanic or latino) 206 (60%) 1768 (86% <0.001 Stage IV 495 (85%) 2883 (81%) 0.073 Immunologic markers TMB ≥ 10 25 (3.2%) 519(10%) <0.001 MSI-H 13 (1.7%) 261 (5.1%) <0.001 dMMR 7 (2.2%) 120 (5.9%) 0.007 Somatic mutations profiles * CDH1 126 (16%) 334 (6.6%) <0.001 TP53 515 (66%) 3764 (74%) <0.001 CDKN2A 101 (13%) 1011 (20%) <0.001 KRAS 92 (12%) 931 (18%) <0.001 NOTCH1 12 (1.5%) 228 (4.5%) 0.002 Germline mutation profiles * eoGEA (N=464) aoGEA (N= 2,822) Overall prevalence 46 (9.9%) 207 (7.3%) CDH1 10 (2.2%) 8 (0.3%) 0.001 TP53 3 (0.6%) 0 (0%) 0.039 BRCA2 2 (0.4%) 38 (1.3%) 0.6 BRIP1 4 (0.9%) 10 (0.4%) 0.6

BRCA1 and BRCA2 mutations testing in prostate cancer: Detection in formalin fixed paraffin embedded (FFPE) and blood samples.

Prostate cancer (PC) represents one of the leading causes of cancer-related morbidity and mortality in men, requiring further understanding to improve diagnosis and treatment. Germline BRCA1/2 mutations, primarily identified in other hereditary cancers, confer an increased risk of developing PC; thus, testing is essential to assess cancer risk, guiding preventive strategies and screening. Recently, somatic BRCA1/2 mutations have emerged as pivotal predictive biomarkers of responsiveness to the poly ADP-ribose polymerase (PARP) inhibitors. This review provides a comprehensive overview of BRCA1/2 mutations testing in PC, focusing on the germline and somatic mutations frequencies and the technical approach for their identification. A revision of the main data reported in the literature regarding BRCA1/2 mutations identification will be presented, highlighting the critical issue for the detection both in formalin fixed paraffin embedded (FFPE) and blood samples.

Nirogacestat in patients with desmoid tumors and mutations of adenomatous polyposis coli ( APC ): Findings from the DeFi trial.

134 Background: Nirogacestat (niro) is an oral, targeted gamma secretase inhibitor FDA-approved for adults with progressing desmoid tumors (DT) who require systemic treatment. In the phase 3 DeFi trial (NCT03785964), niro demonstrated significant improvement vs placebo (pbo) in progression-free survival (PFS; HR 0.29 [95% CI: 0.15–0.55], P <.001) and objective response rate (ORR; 41% vs 8%, P <.001). Most DT are sporadic tumors characterized by somatic mutations in the CTNNB1 gene. About 10%–20% of DT are associated with APC mutations, the majority being germline that may cause familial adenomatous polyposis (FAP), an inheritable trait linked to an increased risk of colorectal cancer and may also confer more aggressive DT behavior. Methods: In DeFi, adult patients (pts) were randomized to oral niro (150 mg) or pbo twice daily. In pts with evaluable blood and tumor samples, descriptive post hoc analyses assessed effects of niro in pts with germline and/or somatic APC mutations, including pts with co-occurring somatic mutations of APC and CTNNB1 . Results: Of the 142 pts in DeFi, 29 pts had APC mutations (niro=13, pbo=16; 22 somatic, 21 germline, and 14 somatic and germline), including 3 pts (niro=2, pbo=1) with co-occurring somatic mutations of APC and CTNNB1 . Of these 29 pts, 19 (66%) were female, 16 (55%) were aged ≤30 y, 22 (76%) had a family history of FAP, and 22 (76%) were refractory to prior therapy (median of 3 prior lines of therapy). PFS was improved with niro vs pbo (HR 0.21 [95% CI: 0.05–1.00], P =.016). Confirmed ORR was 38% (5/13) for niro vs 13% (2/16) for pbo; median time to response with niro was 8.31 months. All 3 pts with co-occurring somatic mutations of APC and CTNNB1 were female, aged 18–56 y, had DT in the upper extremity or abdominal wall, and had no family history of FAP. The 2 pts on niro had received prior systemic therapy and/or surgery and the 1 pt on pbo had no prior therapy. Of the 2 pts on niro, both achieved a partial response (median time to response: 9.9 months). The 1 pt randomized to pbo experienced disease progression in 2.6 months. In pts with APC mutations, diarrhea was the most frequently reported adverse event. In niro-treated pts, increased rates of skin events (maculopapular rash, 62%; dermatitis acneiform, 38%) and stomatitis (46%) were reported in pts with APC mutations compared with those in the overall DeFi population (32%, 22%, and 29%, respectively). Conclusions: Improvement in PFS and ORR was observed with niro vs pbo in pts with DT harboring APC mutations. Efficacy and safety of niro in pts with APC mutations were generally consistent with findings for the overall DeFi population. Although analyses were limited due to small sample size, these results suggest that niro can provide clinically meaningful benefit to pts with progressing DT and APC mutations, including those with co-occurring somatic mutations of APC and CTNNB1 . Clinical trial information: NCT03785964 .

Emerging therapeutic strategies in Lynch syndrome-associated colorectal cancer and the role of MMR testing.

Lynch syndrome is the most common hereditary cancer predisposition, accounting for 1-5% of colorectal cancer cases, and is driven by germline mutations in DNA mismatch repair genes. Despite established diagnostic criteria, such as the Amsterdam guidelines, Lynch syndrome remains largely underdiagnosed. To address this gap, universal tumour screening has been introduced for all newly diagnosed cases of colorectal cancer and endometrial cancer, significantly improving early detection. The surgical management of colorectal cancer in patients with Lynch syndrome remains controversial. While extended colectomy reduces the risk of metachronous colorectal cancer, surgical strategies must be carefully individualised based on patient-specific factors. Chemoprevention with aspirin has shown promise in reducing the risk of colorectal cancer, with ongoing trials investigating optimal dosing. Immunotherapy, particularly immune checkpoint inhibitors, has revolutionised the treatment of Microsatellite Instability-High/deficient Mismatch Repair colorectal cancer, offering durable responses and significant survival benefits. In addition, the neoadjuvant use of immune checkpoint inhibitors is paving the way for non-surgical interventions, potentially transforming the management of colorectal cancer in patients with Lynch syndrome. A multidisciplinary approach and continued research are essential to optimise cancer prevention, treatment and quality of life for people with Lynch syndrome.

GATA2 mutated allele specific expression is associated with a hyporesponsive state of HSC in GATA2 deficiency syndrome

GATA2 germline mutations lead to a syndrome characterized by immunodeficiency, vascular disorders and myeloid malignancies. To elucidate how these mutations affect hematopoietic homeostasis, we created a knock-in mouse model expressing the recurrent Gata2 R396Q missense mutation. Employing molecular and functional approaches, we investigated the mutation’s impact on hematopoiesis, revealing significant alterations in the hematopoietic stem and progenitor (HSPC) compartment in young age. These include increased LT-HSC numbers, reduced self-renewal potential, and impaired response to acute inflammatory stimuli. The mature HSPC compartment was primarily affected at the CMP sub-population level. In the mutant LT-HSC population, we identified an aberrant subpopulation strongly expressing CD150, resembling aging, but occurring prematurely. This population showed hyporesponsiveness, accumulated over time, and exhibited allele-specific expression (ASE) favoring the mutated Gata2 allele, also observed in GATA2 mutated patients. Our findings reveal the detrimental impact of a Gata2 recurrent missense mutation on the HSC compartment contributing to its functional decline. Defects in the CMP mature compartment, along with the inflammatory molecular signature, explain the loss of heterogeneity in HPC compartment observed in patients. Finally, our study provides a valuable model that recapitulates the ASE-related pathology observed in GATA2 deficiency, shedding light on the mechanisms contributing to the disease’s natural progression.

Vaccines for cancer interception in familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an inherited autosomal dominant disorder caused by germline mutations in the adenomatous polyposis coli (APC) gene. FAP is associated with the development of hundreds of adenomas in the small and large intestines of individuals starting in the teenage years with a near 100% risk of developing colorectal cancer by adulthood. Eventually polyps develop throughout the gastrointestinal tract. Chemoprevention approaches have been somewhat successful in reducing polyp burden, but have not reduced the risk of the development of colorectal cancer or other cancers. The lack of efficacy of more standard drug approaches may be due to limited exposure to the agent only to specific periods while the drug is being metabolized, limited drug penetrance in the colon, and patient adherence to daily dosing and drug side effects. The success of immune therapy for the treatment of invasive cancer has led to research focused on the use of immune based approaches for polyp control in FAP, specifically polyp directed vaccines. Vaccines targeting antigens expressed in FAP lesions may be a superior method to control polyp burden and prevent disease progression as compared to classic chemoprevention drugs. A limited number of vaccines can be administered over a short period of time to generate a lasting immune response. Appropriately primed antigen specific T-cells can traffic to any site in the body where antigen is expressed, recognize, and eliminate the antigen expressing cell. Immunologic memory will allow the immune response to persist and the specificity of the immune response will limit toxicity to the targeted polyp. This review will examine the current state of vaccines directed against FAP lesions and highlight the challenges and opportunities of translating vaccines for cancer interception in FAP to the clinic.

The role of germline and somatic mutations in predicting cancer-associated thrombosis: a narrative review.

Patients with cancer have an increased risk of venous thromboembolism (VTE). Guidelines suggest to use risk assessment tools to guide decisions about thromboprophylaxis, but current tools have modest discriminatory ability. Genetic information from the germline or tumor has the potential to improve VTE prediction. Here, we provide a clinical overview of the current role of genetics in cancer-associated VTE. Germline mutations, such as factor V Leiden and prothrombin G20210A, are associated with a 2- to 2.5-fold increased VTE risk in patients with cancer. Tumor-specific somatic mutations also contribute to VTE risk, such as ALK rearrangements increasing the risk in nonsmall cell lung cancer and IDH1 mutations decreasing the risk in gliomas. Other somatic mutations associated with VTE independent of tumor type include KRAS, STK11, MET, KEAP1, CTNNB1, and CDKN2B. Incorporating data on germline or somatic mutations in risk scores improves discriminatory ability compared with the Khorana score. Specific germline and somatic mutations are associated with an increased VTE risk in patients with cancer and potentially improve performance of clinical risk scores. The increasing and widespread use of genetic testing in cancer care provides an opportunity for further development of prediction models incorporating genetic predictors.

Direct and indirect effects of multiplex genome editing of F5H and FAD2 in oil crop camelina.

Mutants with simultaneous germline mutations were obtained in all three F5H genes and all three FAD2 genes (one to eleven mutated alleles) in order to improve the feed value of the seed meal and the fatty acid composition of the seed oil. In mutants with multiple mutated F5H alleles, sinapine in seed meal was reduced by up to 100%, accompanied by a sharp reduction in the S-monolignol content of lignin without causing lodging or stem break. A lower S-lignin monomer content in stems can contribute to improved stem degradability allowing new uses of stems. Mutants in all six FAD2 alleles showed an expected increase in MUFA from 8.7% to 74% and a reduction in PUFA from 53% to 13% in the fatty acids in seed oil. Remarkably, some full FAD2 mutants showed normal growth and seed production and not the dwarfing phenotype reported in previous studies. The relation between germline mutation allele dosage and phenotype was influenced by the still ongoing activity of the CRISPR/Cas9 system, leading to new somatic mutations in the leaves of flowering plants. The correlations between the total mutation frequency (germline plus new somatic mutations) for F5H with sinapine content, and FAD2 with fatty acid composition were higher than the correlations between germline mutation count and phenotypes. This shows the importance of quantifying both the germline mutations and somatic mutations when studying CRISPR/Cas9 effects in situations where the CRISPR/Cas9 system is not yet segregated out.

Proteomic Profiling of Medullary Thyroid Cancer Identifies CAPN1 as a Key Regulator of NF1 and RET Fueled Growth.

Background: Medullary thyroid cancer (MTC) is a frequently metastatic tumor of the thyroid that develops from the malignant transformation of C-cells. These tumors most commonly have activating mutations within the RET or RAS proto-oncogenes. Germline mutations within RET result in C-cell hyperplasia, and cause the MTC pre-disposition disorder, multiple endocrine neoplasia, type 2A (MEN2A). Single-agent therapies for MTC, including vandetanib (VAN) and cabozantinib for all MTCs and selpercatinib (SEL) for RET-mutated MTC, lead to partial responses but are not curative. Methods: To identify new therapeutic targets for MTC, we conducted proteomic profiling of normal C-cells, MTC cells, pre-malignant MEN2A patient samples, and MTC tumors. Results: From this analysis, we identified CAPN1, a member of the CALPAIN (CAPN) family endopeptidases, as widely upregulated in MTC samples. We found that short hairpin RNA-mediated depletion of CAPN1 or inhibitors of CAPN1 significantly reduced MTC cell growth, colony formation, and xenograft tumor growth invivo. In addition, we show that CAPN1 inhibitors synergize with VAN and SEL in vitro, maximizing apoptosis. Mechanistic experiments implicate CAPN1 in inhibiting neurofibromin, encoded by NF1, and CAPN1 inhibitors stabilize NF1 protein levels and diminish downstream RAS/RET activation of AKT and ERK. Conclusions: Our data suggest that increased CAPN1 levels support RET and RAS-fueled growth by reducing NF1 levels. We find that combinatorial therapies between CAPN1 inhibitors and VAN or SEL show maximal efficacy in MTC cells.

O-08 AGGRESSIVE PARAGANGLIOMA-PHEOCHROMOCYTOMA: AN UNDER-TOLD STORY OF THE SDH-D MUTATION

Abstract Introduction Hereditary paraganglioma-pheochromocytoma (PGL/PCC) syndromes are defined by the occurrence of paragangliomas derived from the autonomic nervous system and pheochromocytomas that are localized to the adrenal medulla. While pheochromocytomas and sympathetic paragangliomas cause catecholamine hypersecretion, parasympathetic paragangliomas are mostly nonsecretory. A diagnosis of hereditary PGL/PCC is based on a personal and family history of recurrent, multiple, early-onset PGL/PCC and the identification of mutations in the disease-related genes. Germline mutations in succinate dehydrogenase (SDH) genes are among the most common susceptibility genes. Some of these tumors, particularly those related to SDH-B, exhibit a significant malignant potential. However, mutations in the SDH-D gene do not often predispose to aggressive disease. Clinical Case A 24-year-old male patient presented to the outpatient clinic with a headache and right flank pain. There was not family history of the disease, except for the sudden death of his father at the age of 43. An MRI of the abdomen revealed a 45x44 mm lesion in the right adrenal gland. The patient's urinary normetanephrine levels were found to be significantly elevated. Subsequently, a right adrenalectomy was performed, and the pathology report confirmed a diagnosis of pheochromocytoma. The patient was referred to our clinic after 123 - Iodine MIBG SPECT/CT scan revealed the presence of a 24x15 mm lesion at the left cervical level 3 and a 21x35 mm lesion at the right paraaortic level. Concurrent plasma and urinary catecholamine levels were within the normal range. Both were surgically excised, and the pathology result was reported as paraganglioma. The molecular analysis revealed a pathogenic SDH-D gene variant:c.147dupA (p.His50fs).The patient was started to be monitored annually. In the third year of follow-up, a 14x12 mm nodular lesion was detected in the aorticopulmonary space. The lesion was not excised due to its proximity to vital structures and the patient was continued to be monitored. During the four-year period, there was not significant growth was observed in the lesion. However, in the fifth year detection of the lesion, it's size was reaching to 28x26 mm. It was excised via thoracic surgery. The pathology result was consistent with paraganglioma, with positive surgical margins and a Ki-67 index of 6%.Despite the recommendation for genetic screening, the patient's family members declined. Ten years after the initial diagnosis, the patient's cousin presented with cervical paraganglioma at the age of 19. Conclusion The presented case demonstrates the significance of molecular testing for patients with PGL/PCC and the necessity of long-term follow-up. Furthermore, it suggests that individuals carrying the SDH-D gene mutation may be at an increased risk of an aggressive disease course. Therefore, the precision of genetic counseling is of vital importance in establishing clinical screening and follow-up strategies.Figure 1:Transvers view of Chest CT showing paraganglioma located in aortopulmonary space. Table 1:Catecholamine metabolites in 24 hour urine at diagnosis

Abstract A005: 18F-Fluorthanatrace PARP inhibitor PET tracer: Potential implications for theranostics

Abstract Objective: PARP (poly [ADP-ribose] polymerase) inhibitors are approved for a variety of malignancies including those with a breast, prostate, and ovarian carcinoma, particularly in the setting of a germline or somatic pathogenic BRCA mutation. There is active interest in the development of theranostics including those with a PARP inhibitor backbone. Methods: We evaluate a novel PARP inhibitor (PARPi) PET tracer 18-Fluorine [18F] Fluorthanatrace (FTT). Patients with primary or metastatic solid tumors with measurable disease initiating therapy with a PARP inhibitor monotherapy or in combination with another systemic agent were eligible. Patients underwent 18F-FTT PET/CT prior to initiation of PARPi and a second 18F-FTT PET 2-4 weeks after initiation of a PARP inhibitor. Hematologic toxicity on PARPi monotherapy or combination was assessed using the CTCAEv5.0 criteria. Regions of interest were drawn over the uninvolved bone marrow (usually taken at L3) and normal muscle to obtain the maximum standardized uptake value. Bone marrow to muscle ratio (B/M) was calculated at baseline and on PARPi. Spearman rank correlation coefficient was used. Results: A total of 21 patients were enrolled and underwent 18F-FTT PET. Patients had a median of 0 (range 0-7) prior lines of systemic therapy. The primary disease site included breast (9), ovary (6), primary peritoneal (1), pancreas (1)and other (4). Measurable uptake of 18F-FTT within the tumor and bone marrow was observed in all patients. Median L3 SUVmax at baseline was 4.3 (range 2.1-11.8) vs. 2.33 (range 1.4-2.9) while on PARP inhibitor. Baseline B/M was associated with highest grade hematologic toxicity in patients (n=10) who received talazoparib monotherapy or combination (r=0.65, p=0.042). While B/M was not associated with hematologic toxicity in patients (n=11) who received olaparib monotherapy or combination (r=0.098, p=0.77). Conclusions: 18F-FTT PET can measure target engagement of PARP inhibitors in bone marrow and may have implications for PARP inhibitor-based theranostics and dosing. Results suggest there may be differential impact of different PARPi on bone marrow and should be considered when selecting a backbone for theranostics. Citation Format: Lilie Lin, Mahmoud Hammad, Franklin Wong, Timothy A. Yap. 18F-Fluorthanatrace PARP inhibitor PET tracer: Potential implications for theranostics. [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Targeted Therapies in Combination with Radiotherapy; 2025 Jan 26-29; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(2_Suppl):Abstract nr A005.

P27Kip1 and Tumors: Characterization of CDKN1B Variants Identified in MEN4 and Breast Cancer

p27Kip1 is a key cell cycle gatekeeper governing the timing of Cyclin-dependent kinase (CDK) activation/inactivation and, consequently, cell proliferation. Structurally, the protein is largely unfolded, a feature that strongly increases its plasticity and interactors and enhances the number of regulated cellular processes. p27Kip1, like other intrinsically unstructured proteins, is post-translationally modified on several residues. These modifications affect its cellular localization and address p27Kip1 for specific interactions/functions. Several germline or somatic CDKN1B (the p27Kip1 encoding gene) mutations have been demonstrated to be associated with multiple endocrine neoplasia type 4 (MEN4), hairy cell leukemia, small-intestine neuroendocrine tumors, and breast and prostate cancers. Here, we analyzed the effect of four CDKN1B missense and nonsense mutations found in patients affected by MEN4 or cancers, namely, c.349C>T, p.P117S; c.397C>A, p.P133T; c.487C>T, p.Q163*; and c.511G>T, p.E171*. By transfecting breast cancer cell lines, we observed increased growth and cell motility for all the investigated mutants compared to wild-type p27Kip1 transfected cells. Furthermore, we discovered that the mutant forms exhibited altered phosphorylation on key residues and different localization or degradation mechanisms in comparison to the wild-type protein and suggested a possible region as crucial for the lysosome-dependent degradation of the protein. Finally, the loss of p27Kip1 ability in blocking cell proliferation was in part explained through the different binding efficiency that mutant p27Kip1 forms exhibited with Cyclin/Cyclin-dependent Kinase complexes (or proteins involved indirectly in that binding) with respect to the WT.

Identification of new candidate genes for the hereditary predisposition to uveal melanoma: IGCMU trial

IntroductionUveal melanoma (UM) is a rare ocular cancer. While germline mutations in genes such as BAP1 and MBD4 account for approximately 20% of familial UM cases, the hereditary factors underlying the remaining cases remain unknown. Epidemiological studies have suggested an increased risk of prostate cancer, thyroid cancer, and leukemia among patients with UM, indicating potential unidentified genetic predispositions. This study aims to identify new candidate genes associated with a hereditary predisposition to UM.MethodsThis single-center study, conducted at Centre Jean Perrin, will involve the exome sequencing of 50 patients with UM who do not harbor known pathogenic variants in the BAP1 or MBD4 genes. The primary objective is to identify novel candidate genes associated with hereditary cancer predisposition among UM patients. A several-step-bioinformatic analysis will be conducted to identify the genes of interest. A secondary objective is to explore genes known to be involved in predisposition to other cancers, already described in the occurrence of uveal melanoma, but where an association has not been fully established yet. The study has begun in October 2024, with patient recruitment lasting 12 months. No follow-up period is planned, but the duration of the genetic analyses is estimated at six months, with the final study report expected by October 2026.DiscussionThe identification of novel hereditary predisposition genes for UM could significantly enhance genetic counselling and surveillance strategies for families affected. This study could also contribute to a better understanding of the genetic landscape of UM, potentially leading to more personalized and effective options for its detection.Trial registrationClinicalTrials.gov, identifier NCT06550674, registered in August 2024. Protocol: version 1.0, January 18th, 2024.

A case of de novo neuroendocrine prostate cancer presented with elevated level of serum CEA carrying BRCA2 mutation: case report and literature review

BackgroundDe novo neuroendocrine prostate cancer (NEPC) is a rare subtype of prostate cancer (PCa) and few markers are available for screening and monitoring. Potential circulating or fluid markers might facilitate early diagnosis thus improving prognosis of NEPC, especially for de novo NEPC.Case presentationA man of 71-year was presented with elevated level of serum carcinoembryonic antigen (CEA) (1296.5 ng/ml) and normal PSA (0.47ng/ml). Gastrointestinal endoscopy showed no signs of gastric or colorectal cancer. Fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) and prostate-specific membrane antigen PET-CT (PSMA PET-CT) indicated prostate cancer with metastases including pelvic lymph nodes, bone as well as lung metastases. Biopsy of prostate revealed mixed carcinoma including small cell neuroendocrine carcinoma (SCNEC) and adenocarcinoma (Gleason score of 4 + 5). Immunohistochemistry (IHC) staining and next generation sequencing demonstrated a strong expression of chromogranin A (CgA), synaptophysin (SYN) and CEA, and a germline mutation in BRCA2, respectively. After a prostatic massage, an increased level of CEA (137 ng/ml vs 5 ng/ml) was detected in urine. Olaparib, a Poly ADP-ribose polymerase inhibitor (PARPi), combined with androgen deprivation therapy (ADT) were administrated. FDG PET-CT indicated tumor regression in both quantity and size three months later, and CEA levels of serum and urine decreased to 23 ng/ml and 2.4 ng/ml 4 months later, respectively.ConclusionThis is the first report of a de novo NEPC presented with an elevated level of CEA, in which CEA was also detected in urine specimen post a prostatic massage. After a combination treatment of ADT for 3 months, levels of CEA in both serum and urine decreased sharply when tumor regressed radiologically. CEA might be a marker of screening and monitoring of NEPC.

Paediatric paraganglioma with variant of unknown significance on genetic testing.

Introduction: Sympathetic paragangliomas (PGLs), are rare neuroendocrine tumours originating from chromaffin cells, primarily in the thorax, abdomen, and pelvis. Paediatric paragangliomas are particularly uncommon, but they represent a notable cause of secondary hypertension in children. These tumours frequently have a genetic basis, with up to 40% of patients carrying germline mutations, including variants of unknown significance (VUS), which present diagnostic and management challenges. Case presentation: In this case report, we describe a 10-year-old male who presented with seizures and hypertensive crisis, later diagnosed with a functional PGL. Biochemical tests confirmed elevated catecholamines, and imaging revealed a 3 cm para-aortic tumour. Genetic testing identified a heterozygous mutation in the FH gene classified as VUS. Surgical resection of the tumour was curative, with no recurrence after two years of follow-up. Conclusion: This case underscores the complexities of interpreting VUS in paediatric PGL and highlights the need for long-term follow-up and further research into the clinical significance of these genetic findings.

Paradoxical dominant negative activity of an immunodeficiency-associated activating PIK3R1 variant.

PIK3R1 encodes three regulatory subunits of class IA phosphoinositide 3-kinase (PI3K), each associating with any of three catalytic subunits, namely p110α, p110β, or p110δ. Constitutional PIK3R1 mutations cause diseases with a genotype-phenotype relationship not yet fully explained: heterozygous loss-of-function mutations cause SHORT syndrome, featuring insulin resistance and short stature attributed to reduced p110α function, while heterozygous activating mutations cause immunodeficiency, attributed to p110δ activation and known as APDS2. Surprisingly, APDS2 patients do not show features of p110α hyperactivation, but do commonly have SHORT syndrome-like features, suggesting p110α hypofunction. We sought to investigate this. In dermal fibroblasts from an APDS2 patient, we found no increased PI3K signalling, with p110δ expression markedly reduced. In preadipocytes, the APDS2 variant was potently dominant negative, associating with Irs1 and Irs2 but failing to heterodimerise with p110α. This attenuation of p110α signalling by a p110δ-activating PIK3R1 variant potentially explains co-incidence of gain-of-function and loss-of-function PIK3R1 phenotypes.

MLH1 promoter hypermethylation and Lynch Syndrome: When to test for constitutional epimutations of MLH1 gene?

Lynch syndrome is a genetic condition predisposing to cancer, particularly colorectal cancer and endometrial cancer, due to germline mutations in MisMatch Repair genes. More rarely, Lynch syndrome is the result of a constitutional MLH1 promoter methylation. This review summarizes the current knowledge about the role of this epigenetic mechanism in the Lynch syndrome. Universal Tumor Screening, performed on tumoral specimens to identify features suggestive of Lynch syndrome, shows the same features both in the case of sporadic cancers and Lynch syndrome-cancers due to a constitutional MLH1 methylation: microsatellite instability, deficiency of MisMatch Repair proteins, and methylation of MLH1 gene. Over the last few years, identifying methylation of MLH1 promoter on tumors was used to discern sporadic tumors from Lynch syndrome tumors: the methylation of the MLH1 promoter was usually explained as a somatic event and this could lead to a missed diagnosis of some Lynch syndrome cases. Therefore, establishing criteria to decide when to test patients for constitutional MLH1 methylation is urgent. In the case of microsatellite instability/deficiency of MisMatch Repair tumors with MLH1 methylation, a germline genetic test could be requested for all colorectal cancer patients aged 55 years or younger and all endometrial cancer patients younger than 50 years old, independently from family history. The prevalence of germline MLH1 epimutations is not precisely known and possibly underestimated. The associated cancer risk could be similar to that due to a MLH1 sequence variant. MLH1 epimutations could be secondary to other genetic defects and follow an autosomal dominant inheritance. On the contrary, primary epimutations are often "de novo" events, and their transmission does not follow Mendelian rules.

Colorectal cancer in Lynch syndrome families: consequences of gene germline mutations and the gut microbiota

BackgroundLynch syndrome (LS)-associated colorectal cancer (CRC) always ascribes to pathogenic germline mutations in mismatch repair (MMR) genes. However, the penetrance of CRC varies among those with the same MMR gene mutation. Thus, we hypothesized that the gut microbiota is also involved in CRC development in LS families.MethodsThis prospective, observational study was performed from December 2020 to March 2023. We enrolled 72 individuals from 9 LS families across six provinces in China and employed 16S rRNA gene amplicon sequencing to analyze the fecal microbiota components among LS-related CRC patients (AS group), their spouses (BS group), mutation carriers without CRC (CS group), and non-mutation carriers (DS group) using alpha and beta diversity indices.ResultsThere were no apparent differences in age or gender among the four groups. Alpha and beta diversity indices exhibited no significant differences between the AS and BS groups, verifying the role of germline mutations in the occurrence of CRC in LS families. Beta diversity analysis exhibited significant differences between the AS and CS groups, revealing the importance of the gut microbiota for the occurrence of CRC in LS families. A greater difference (both alpha and beta diversity indices) was shown between the AS and DS groups, demonstrating the combined impact of the gut microbiota and genetic germline mutations on the occurrence of CRC in LS families. Compared with those in the CS and DS groups, we identified ten microbial genera enriched in the AS group, and one genus (Bacteroides) decreased in the AS group. Among the elevated genera in the AS group, Agathobacter, Coprococcus and Prevotellaceae_NK3B31_group were butyrate-producing genera.ConclusionThis study found the development of CRC in the LS families can be attributed to the combined effects of gene germline mutations as well as the gut microbiota and provided novel insights into the prevention and treatment of CRC in the LS families.