KIT Mutations Research Articles

Pathophysiologic implications of elevated prevalence of hereditary alpha-tryptasemia in all mastocytosis subtypes

Mastocytosis and monoclonal mast cell (MC) activation syndrome (MMAS) are heterogeneous conditions characterized by the accumulation of atypical MCs. Despite the recurrent involvement of KIT mutations, the pathophysiologic origin of mastocytosis and MMAS is unclear. Although hereditary α-tryptasemia (HαT, related to TPSAB1 gene duplication) is abnormally frequent in these diseases, it is not known whether the association is coincidental or causal. We evaluated the prevalence of HαT in all mastocytosis subtypes and MMAS and assessed the pathophysiologic association with HαT. Clinical data, laboratory data, KIT mutations, TPSAB1 duplication (assessed by droplet digital PCR), and HαT prevalence were retrospectively recorded for all patients with mastocytosis and MMAS registered in the French national referral center database and compared to a control cohort. To increase the power of our analysis for advanced systemic mastocytosis (advSM), we pooled our cohort with literature cases. We included 583 patients (27 with MMAS and 556 with mastocytosis). The prevalence of HαT in mastocytosis was 12.6%, significantly higher than in the general population (5.7%, P= .002) and lower than in MMAS (33.3%, P= .02). HαT+ patients were more likely to have anaphylactic reactions and less likely to have cutaneous lesions than HαT- patients (43.0% vs 24.4%, P= .006; 57.7% vs 75.6%, respectively, P= .006). In the pooled analysis, the prevalence of HαT was higher in advSM (11.5%) than in control cohorts (5.2%, P= .01). Here we confirm the increase incidence of anaphylaxis in HαT+ mastocytosis patients. The increased prevalence of HαT in all subtypes of systemic mastocytosis (including advSM) is suggestive of pathophysiologic involvement.

Golgi retention and oncogenic KIT signaling via PLCγ2-PKD2-PI4KIIIβ activation in gastrointestinal stromal tumor cells

Most gastrointestinal stromal tumors (GISTs) develop due to gain-of-function mutations in the tyrosine kinase gene, KIT. We recently showed that mutant KIT mislocalizes to the Golgi area and initiates uncontrolled signaling. However, the molecular mechanisms underlying its Golgi retention remain unknown. Here, we show that protein kinase D2 (PKD2) is activated by the mutant, which causes Golgi retention of KIT. In PKD2-inhibited cells, KIT migrates from the Golgi region to lysosomes and subsequently undergoes degradation. Importantly, delocalized KIT cannot trigger downstream activation. In the Golgi/trans-Golgi network (TGN), KIT activates the PKD2-phosphatidylinositol 4-kinase IIIβ (PKD2-PI4KIIIβ) pathway through phospholipase Cγ2 (PLCγ2) to generate a PI4P-rich membrane domain, where the AP1-GGA1 complex is aberrantly recruited. Disruption of any factors in this cascade results in the release of KIT from the Golgi/TGN. Our findings show the molecular mechanisms underlying KIT mislocalization and provide evidence for a strategy for inhibition of oncogenic signaling.

Bioinformatic analysis of KIT juxtamembrane domain mutations in Syrian GIST patients: jigsaw puzzle completed

BackgroundThe huge number of detected somatic KIT mutations highlights the necessity of in silico analyses that are almost absent in the relevant medical literature. The aim of this study is to report the mutation spectrum analysis of exon 11 encoding the juxtamembrane (JM) domain of the KIT gene in a group of Syrian GIST patients.MethodsForty-eight formalin-fixed paraffin-embedded GIST tissue samples, collected between 2006 and 2016, were retrieved from the pathological archives and analyzed for KIT exon 11 mutations by DNA sequencing. Structural/functional impact of detected variants was predicted using several bioinformatic tools.ResultsTwenty-one different variants have been detected in intron 10, exon 11, and intron 11 of the KIT gene, eight of which were novel changes. Mutations in exon 11 of the KIT gene were detected in 28 of 48 (58.3%) GIST patients and predicted to be pathogenic and cancer promoting. Specifically, age above 60 was very significantly associated with the negative selection of deletion mutations (p = .007), a phenomenon that points to deletion severity.ConclusionsSix bioinformatic tools have proved efficient in predicting the impact of detected KIT variations in view of published structural, experimental, and clinical findings.

Comparison of efficacy between homoharringtonine, aclarubicin, cytarabine (HAA) and idarubicin, cytarabine (IA) regimens as induction therapy in patients with de novo core binding factor acute myeloid leukemia.

To compare efficacy between homoharringtonine combined with cytarabine and aclarubicin (HAA) and idarubicin and cytarabine (IA) regimens as first induction chemotherapy in patients with core binding factor acute myeloid leukemia (CBF-AML). Cox regression model and propensity score matching (PSM) were used to identify the regimen associated with a better remission rate and outcomes. In total, 374 patients with CBF-AML (243 with RUNX1::RUXN1T1 and 131 with CBFB::MYH11) were included in this study. The patients received the HAA or IA regimen (187 each) as the first induction therapy. For patients with RUNX1::RUXN1T1, multivariate analyses showed that the HAA regimen was significantly associated with a higher CR/CRi rate after the first induction (hazard ratio [HR] = 5.3 [95% CI 2.3, 12.2]; p < 0.001) and more favorable relapse-free survival (RFS) (HR = 0.5 [0.3, 0.8], p = 0.01). In PSM analysis, the HAA regimen also had a higher CR/CRi rate (96% vs. 77%, p < 0.001), especially for those harboring wild-type KIT (KITWT) (96% vs. 83%, p = 0.02) or non-D816 KIT mutation (100% vs. 63%, p = 0.002), as well as more favorable RFS (p = 0.01), compared with the IA regimen. However, there was no difference in the remission rate or outcomes between the two regimens for patients with CBFB::MYH11. The HAA regimen as first induction chemotherapy resulted in a higher CR/CRi rate in AML patients with RUNX1::RUNX1T1, especially those harboring KITWT and non-D816 KIT mutation, and a more favorable RFS compared with the IA regimen. The efficacy between the two regimens did not differ in those with CBFB::MYH11.

5'UTR Variant in KIT Associated With White Spotting in Horses.

Mutations in KIT, a gene that influences melanoblast migration and pigmentation, often result in mammalian white spotting. As of February 2023, over 30 KIT variants associated with white spotting were documented in Equus caballus (horse). Here we report an association of increased white spotting on the skin and coat with a variant in the 5'UTR of KIT (rs1149701677: g.79,618,649A>C). Horses possessing at least one alternate allele demonstrate phenotypic characteristics similar to other KIT mutations: clear borders around unpigmented regions on the body, face, and limbs. Using a quantitative measure of depigmentation, we observed an average white score of 10.70 among individuals with rs1149701677, while the average score of the control, homozygous reference sample was 2.23 (P=1.892e-11, n=109, t-test). The rs1149701677 site has a cross-species conservation score of 3.4, one of the highest scores across the KIT 5'UTR, implying regulatory importance for this site. Ensembl also predicted a "moderately impactful" functional effect for the rs1149701677 variant. We propose that this single nucleotide variant likely alters the regulation of KIT, which in turn may disrupt melanoblast migration causing an increase in white spotting on the coat. Alternatively, the rs1149701677 variant may be in linkage with another nearby variant with an as-yet-undiscovered functional impact. We propose to term this new allele "Holiday White" or W35 based on conventional nomenclature.

KIT and PDGFRA Variants and the Survival of Patients with Gastrointestinal Stromal Tumor Treated with Adjuvant Imatinib.

Adjuvant imatinib improves the recurrence-free survival and overall survival (OS) of patients with gastrointestinal stromal tumors (GISTs) who have a high risk of recurrence after surgery and is now considered standard treatment. Yet, OS benefit has been demonstrated in only one randomized study, the Scandinavian Sarcoma Group XVIII/AIO trial, where patients with high-risk GISTs were allocated to either 1 year or 3 years of adjuvant imatinib. SSGXVIII/AIO is also the only randomized trial in which adjuvant imatinib duration exceeding 2 years was evaluated. In this trial, the 3-year treatment led to a 45% reduction in the risk of death during the first 10 years that followed random allocation even though some of the patients did not have GISTs at tumor histology review, had mutations now known to be imatinib-resistant or had non-localized disease at study entry. In the subgroup of patients who had KIT exon 11 deletion/indel mutation, the reduction in the risk of death was 66% in favor of the longer treatment. Proper patient selection is of crucial importance since many patients are cured with surgery. Little evidence for OS benefit is available from randomized trials for patients whose GIST harbors KIT exon 9 mutation, KIT insertion mutation, PDGFRA D842V mutation, or lacks KIT and PDGFRA mutations. Adjuvant imatinib improves OS substantially if high-risk GISTs can be identified, treatment duration is long enough, and GISTs harbor an imatinib-sensitive mutation.

Register-based and genetic studies of Prader-Willi syndrome show a high frequency of gonadal tumors and a possible mechanism for tumorigenesis through imprinting relaxation.

Prader-Willi syndrome (PWS) is a rare disease caused by a lack of expression of inherited imprinted genes in the paternally derived Prader-Willi critical region on chromosome 15q11.2-q13. It is characterized by poor feeding and hypotonia in infancy, intellectual disability, behavioral abnormalities, dysmorphic features, short stature, obesity, and hypogonadism. PWS is not a known cancer predisposition syndrome, but previous investigations regarding the prevalence of cancer in these patients suggest an increased risk of developing specific cancer types such as myeloid leukemia and testicular cancer. We present the results from a Swedish national population-based cohort study of 360 individuals with PWS and 18,000 matched comparisons. The overall frequency of cancer was not increased in our PWS cohort, but we found a high frequency of pediatric cancers. We also performed whole-genome sequencing of blood- and tumor-derived DNAs from a unilateral dysgerminoma in a 13-year-old girl with PWS who also developed bilateral ovarian sex cord tumors with annular tubules. In germline analysis, there were no additional findings apart from the 15q11.2-q13 deletion of the paternal allele, while a pathogenic activating KIT mutation was identified in the tumor. Additionally, methylation-specific multiplex ligation-dependent probe amplification revealed reduced methylation at the PWS locus in the dysgerminoma but not in the blood. In conclusion, our register-based study suggests an increased risk of cancer at a young age, especially testicular and ovarian tumors. We found no evidence of a general increase in cancer risk in patients with PWS. However, given our limited observational time, further studies with longer follow-up times are needed to clarify the lifetime cancer risk in PWS. We have also described the second case of locus-specific loss-of-imprinting in a germ cell tumor in PWS, suggesting a possible mechanism of carcinogenesis.

Gastrointestinal Stromal Tumor (GIST)

&#x0D; &#x0D; &#x0D; Gastrointestinal stromal tumor (GIST) are the most common mesenchymal tumor of the gastrointestinal tract and most common malignancy of the small intestine. Although the exact prevalence of GIST is not known, GIST was recognized as tumor it's arise from interstitial cells of Cajal. Most of the GISTs driven by a KIT or platelet-derived growth factor receptor alpha (PDGFRA) mutation. Histologically, GISTs look like spindle cell tumors most of the time, but they can be epitheoid or mixed type. Clinically, patients with small GISTs remain asymptomatic. In another case, patients with larger GISTs present with various symptoms depending on the location of the GISTs. Most of GISTs are located in the stomach or small bowel. But, they can involve almost any segment of the gastrointestinal tract from distal esophagus to anus. Diagnosis is suspected on imaging and endoscopic studies, and confirmed by tissue acquisition with immunohistochemical staining. The various endoscopic modalities of resection are increasingly tried. Surgical resection is the treatment of choice. In management of larger GISTs, tyrosine kinase inhibitors are extremly useful. Treatment options for metastatic GISTs also include radiotherapy, chemotherapy, hepatic artery embolization, chemoembolization, and radiofrequency ablation.&#x0D; &#x0D; &#x0D;

Detection of Hybrid Fusion Transcripts, Aberrant Transcript Expression, and Specific Single Nucleotide Variants in Acute Leukemia and Myeloid Disorders with Recurrent Gene Rearrangements

Introduction: A variety of gene rearrangements and molecular alterations are key drivers in the pathobiology of acute leukemia and myeloid disorders; current classification systems increasingly incorporate these findings in diagnostic algorithms. Therefore, clinical laboratories require versatile tools, which can detect an increasing number and variety of molecular and cytogenetic alterations of clinical significance. Methods: We validated an RNA-based next-generation sequencing (NGS) assay that enables the detection of: (i) numerous hybrid fusion transcripts (including rare/novel gene partners), (ii) aberrantly expressed EVI1 (MECOM) and IKZF1 (Del exons 4–7) transcripts, and (iii) hotspot variants in KIT, ABL1, NPM1 (relevant in the context of gene rearrangement status). Results: For hybrid fusion transcripts, the assay showed 98–100% concordance for known positive and negative samples, with an analytical sensitivity (i.e., limit of detection) of approximately 0.8% cells. Samples with underlying EVI1 (MECOM) translocations demonstrated increased EVI1 (MECOM) expression. Aberrant IKZF1 (Del exons 4–7) transcripts detectable with the assay were also present on orthogonal reverse transcription PCR. Specific hotspot mutations in KIT, ABL1, and NPM1 detected with the assay showed 100% concordance with orthogonal testing. Lastly, several illustrative samples are included to highlight the assay’s clinically relevant contributions to patient workup. Conclusion: Through its ability to simultaneously detect various gene rearrangements, aberrantly expressed transcripts, and hotspot mutations, this RNA-based NGS assay is a valuable tool for clinical laboratories to supplement other molecular and cytogenetic methods used in the diagnostic workup and in clinical research for patients with acute leukemia and myeloid disorders.

Deep learning predicts patients outcome and mutations from digitized histology slides in gastrointestinal stromal tumor

Risk assessment of gastrointestinal stromal tumor (GIST) according to the AFIP/Miettinen classification and mutational profiling are major tools for patient management. However, the AFIP/Miettinen classification depends heavily on mitotic counts, which is laborious and sometimes inconsistent between pathologists. It has also been shown to be imperfect in stratifying patients. Molecular testing is costly and time-consuming, therefore, not systematically performed in all countries. New methods to improve risk and molecular predictions are hence crucial to improve the tailoring of adjuvant therapy. We have built deep learning (DL) models on digitized HES-stained whole slide images (WSI) to predict patients’ outcome and mutations. Models were trained with a cohort of 1233 GIST and validated on an independent cohort of 286 GIST. DL models yielded comparable results to the Miettinen classification for relapse-free-survival prediction in localized GIST without adjuvant Imatinib (C-index=0.83 in cross-validation and 0.72 for independent testing). DL splitted Miettinen intermediate risk GIST into high/low-risk groups (p value = 0.002 in the training set and p value = 0.29 in the testing set). DL models achieved an area under the receiver operating characteristic curve (AUC) of 0.81, 0.91, and 0.71 for predicting mutations in KIT, PDGFRA and wild type, respectively, in cross-validation and 0.76, 0.90, and 0.55 in independent testing. Notably, PDGFRA exon18 D842V mutation, which is resistant to Imatinib, was predicted with an AUC of 0.87 and 0.90 in cross-validation and independent testing, respectively. Additionally, novel histological criteria predictive of patients’ outcome and mutations were identified by reviewing the tiles selected by the models. As a proof of concept, our study showed the possibility of implementing DL with digitized WSI and may represent a reproducible way to improve tailoring therapy and precision medicine for patients with GIST.

Multiple intratumoral sources of kit ligand promote gastrointestinal stromal tumor.

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma and is typically driven by a single mutation in the Kit or PDGFRA receptor. While highly effective, tyrosine kinase inhibitors (TKIs) are not curative. The natural ligand for the Kit receptor is Kit ligand (KitL), which exists in both soluble and membrane-bound forms. While KitL is known to stimulate human GIST cell lines in vitro, we used a genetically engineered mouse model of GIST containing a common human KIT mutation to investigate the intratumoral sources of KitL, importance of KitL during GIST oncogenesis, and contribution of soluble KitL to tumor growth in vivo. We discovered that in addition to tumor cells, endothelia and smooth muscle cells produced KitL in KitV558Δ/+ tumors, even after imatinib therapy. Genetic reduction of total KitL in tumor cells of KitV558Δ/+ mice impaired tumor growth in vivo. Similarly, genetic reduction of tumor cell soluble KitL in KitV558Δ/+ mice decreased tumor size. By RNA sequencing, quantitative PCR, and immunohistochemistry, KitL expression was heterogeneous in human GIST specimens. In particular, PDGFRA-mutant tumors had much higher KitL expression than Kit-mutant tumors, suggesting the benefit of Kit activation in the absence of mutant KIT. Serum KitL was higher in GIST patients with tumors resistant to imatinib and in those with tumors expressing more KitL RNA. Overall, KitL supports the growth of GIST at baseline and after imatinib therapy and remains a potential biomarker and therapeutic target.

Mastocytose als oorzaak van osteoporotische fracturen: casusbespreking en literatuurstudie

Mastocytosis as a cause of osteoporotic fractures: a case report and literature review Systemic mastocytosis is a rare cause of secondary osteoporosis. Mastocytosis is a myeloproliferatic disease characterized by abnormal growth and proliferation of mast cells. The disease is associated with activating KIT mutations. There are 2 major types of mastocytosis: cutaneous mastocytosis and systemic mastocytosis with extracutaneous infiltration. Systemic mastocytosis needs to be considered in the differential diagnosis of unexplained osteoporosis, unexplained spinal fractures (especially in men and premenopausal women) and in patients with osteoporosis with severe bone pain. Bone involvement is one of the most frequent expressions of systemic mastocytosis, especially in adults. The clinical presentation is diverse: from osteoporosis with fragility fractures and poorly localized bone pain to asymptomatic osteolytic and/or focal sclerotic lesions and diffuse osteosclerosis. Osteoporosis in patients with systemic mastocytosis is caused by neoplastic infiltration or, more likely, local release of mediators. Screening for mastocytosis is possible by determining the serum basal tryptase and searching for a p.D816V KIT mutation, but the final diagnosis requires a bone marrow examination. The first-line treatment of osteoporosis secondary to mastocytosis consists of bisphosphonates and denosumab. Teriparatide can be considered in patients with new vertebral fractures under treatment with antiresorptive therapy, but more research is needed to evaluate its effectivity and safety. In case of refractory osteoporosis caused by mastocytosis, cytoreductive therapy, whether or not in combination with bisphosphonates, can be administered. In this article, the authors report a case of a 48-year-old patient with osteoporosis as the first manifestation of underlying mastocytosis. A literature review was performed to describe the etiology, pathophysiology, diagnostic process and treatment options of bone involvement in patients with mastocytosis.

The 2023 Updated Classification and Diagnostic Criteria of Mastocytosis

Mastocytosis is an uncommon hematologic malignancy characterized by accumulation of abnormal mast cells in various organs or tissues. A somatic point mutation in the KIT gene at codon 816 is detected in more than 90% of patients with systemic Masto cytosis (SM). The 2022 WHO classification continues to recognize three disease types: systemic mastocytosis, cutaneous mastocytosis and mast cell sarcoma. Bone marrow mastocytosis is a new separate subtype of SM. The classification also recognizes well-differentiated systemic mastocytosis, a morphologic pattern that can occur in any SM subtype. Diagnostic criteria for SM have been modified. The expression of CD30 and the presence of any KIT mutation causing ligand-independent activation have been accepted as minor diagnostic criteria. Classical B-findings and C-findings have undergone minor refinements. Most notably, variant allele frequency of D816V mutation ≥ 10% in bone marrow cells or peripheral blood leukocytes is qualified as a B-finding.

A mutation-based radiomics signature predicts response to imatinib in Gastrointestinal Stromal Tumors (GIST)

ObjectivesTo develop a mutation-based radiomics signature to predict response to imatinib in Gastrointestinal Stromal Tumors (GISTs). MethodsEighty-two patients with GIST were enrolled in this retrospective study, including 52 patients from one center that were used to develop the model, and 30 patients from a second center to validate it. Reference standard was the mutational status of tyrosine-protein kinase (KIT) and platelet-derived growth factor α (PDGFRA). Patients were dichotomized in imatinib sensitive (group 0 - mutation in KIT or PDGFRA, different from exon 18-D842V), and imatinib non-responsive (group 1 - PDGFRA exon 18-D842V mutation or absence of mutation in KIT/PDGFRA). Initially, 107 texture features were extracted from the tumor masks of baseline computed tomography scans. Different machine learning methods were then implemented to select the best combination of features for the development of the radiomics signature. ResultsThe best performance was obtained with the 5 features selected by the ANOVA model and the Bayes classifier, using a threshold of 0.36. With this setting the radiomics signature had an accuracy and precision for sensitive patients of 82 % (95 % CI:60–95) and 90 % (95 % CI:73–97), respectively. Conversely, a precision of 80 % (95 % CI:34–97) was obtained in non-responsive patients using a threshold of 0.9. Indeed, with the latter setting 4 patients out of 5 were correctly predicted as non-responders. ConclusionsThe results are a first step towards using radiomics to improve the management of patients with GIST, especially when tumor tissue is unavailable for molecular analysis or when molecular profiling is inconclusive.

A real-world study of adjuvant anti-PD -1 immunotherapy on stage III melanoma with BRAF, NRAS, and KIT mutations.

Melanoma frequently harbors BRAF, NRAS, or KIT mutations which influence both tumor development and treatment strategies. For example, it is still controversial whether adjuvant anti-PD-1 monotherapy or BRAF/MEK inhibitors may better improve the survival for resected BRAF-mutant melanoma. Furthermore, outcomes for melanoma with NRAS and KIT mutation receiving adjuvant immunotherapy remain unclear. One hundred seventy-four stage III melanoma patients who underwent radical surgery in Fudan University Shanghai Cancer Center (FUSCC) during January 2017 to December 2021 were included in this real-world study. Patients were followed up until death or May 30th, 2022. Pearson's chi-squared test or Fisher's exact test was performed for univariable analysis of the different category groups. Log-rank analysis was used to identify the prognostic factors for disease-free survival (DFS). There were 41 (23.6%) patients with BRAF mutation, 31 (17.8%) with NRAS mutation, 17 (9.8%) with KIT mutation, and 85 (48.9%) wild-type patients without either genomic alteration of those three genes. Most ( n = 118, 67.8%) of them were acral melanoma, while 45 (25.9%) were cutaneous subtype, and 11 were (6.3%) primary unknown. Among them, 115 (66.1%) patients received pembrolizumab or toripalimab monotherapy as adjuvant therapy; 22 (12.6%) patients received high-dose interferon (IFN), and 37 (21.3%) patients were just for observation. There was no statistical difference in clinicopathologic factors between anti-PD-1 group and IFN/OBS group. Of all the enrolled patients, anti-PD-1 group had a better DFS than IFN/OBS group ( p = 0.039). In anti-PD-1 group, patients with BRAF or NRAS mutations had poorer DFS than wild-type group. No survival difference was found among patients harboring different gene mutations in IFN/OBS group. In wild-type patients, anti-PD-1 group had a better DFS than IFN/OBS group ( p = 0.003), while no survival benefits were found for patients with BRAF, NRAS, or KIT mutations. Although anti-PD-1 adjuvant therapy provides a better DFS in the general population and in wild-type patients, patients with BRAF, KIT or, especially, NRAS mutation may not benefit further from immunotherapy than conventional IFN treatment or observation.

A Peptide Vaccine Design Targeting KIT Mutations in Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is a leading blood cancer subtype that can be caused by 27 gene mutations. Previous studies have explored potential vaccine and drug treatments against AML, but many were proven immunologically insignificant. Here, we targeted this issue and applied various clinical filters to improve immune response. KIT is an oncogenic gene that can cause AML when mutated and is predicted to be a promising vaccine target because of its immunogenic responses when activated. We designed a multi-epitope vaccine targeting mutations in the KIT oncogene using CD8+ and CD4+ epitopes. We selected the most viable vaccine epitopes based on thresholds for percentile rank, immunogenicity, antigenicity, half-life, toxicity, IFNγ release, allergenicity, and stability. The efficacy of data was observed through world and regional population coverage of our vaccine design. Then, we obtained epitopes for optimized population coverage from PCOptim-CD, a modified version of our original Java-based program code PCOptim. Using 24 mutations on the KIT gene, 12 CD8+ epitopes and 21 CD4+ epitopes were obtained. The CD8+ dataset had a 98.55% world population coverage, while the CD4+ dataset had a 65.14% world population coverage. There were five CD4+ epitopes that overlapped with the top CD8+ epitopes. Strong binding to murine MHC molecules was found in four CD8+ and six CD4+ epitopes, demonstrating the feasibility of our results in preclinical murine vaccine trials. We then created three-dimensional (3D) models to visualize epitope-MHC complexes and TCR interactions. The final candidate is a non-toxic and non-allergenic multi-epitope vaccine against KIT mutations that cause AML. Further research would involve murine trials of the vaccine candidates on tumor cells causing AML.

RF05 A national report on incidence, patient demographics and tumour characteristics of melanoma by BRAF, NRAS and KIT genotype: England 2016–2019

Abstract Although studies have shown variation between countries in the incidence and characteristics of patients and tumours associated with melanoma BRAF, NRAS and KIT mutations, no national molecular genetics data from England have been published. In 2022, the National Institute for Health and Care Excellence highlighted the need for national cohort studies to evaluate the role of biomarkers. This descriptive national observational study used National Disease Registration Service (NDRS) data to identify all site melanoma cases that were diagnosed and underwent molecular genetic testing in England between 2016 and 2019. The NDRS collects molecular genetics data from most genomic laboratories nationally but does not routinely receive results for BRAF testing by immunohistochemistry (IHC) done at local pathology laboratories. Molecular genetic testing and incidence of wild-type (WT), BRAF mutant (+), NRAS+ and KIT+ melanomas were described. Demographic (sex, age, ethnicity, deprivation, geographical region) and tumour factors (site, stage) of BRAF+, NRAS+, KIT+ and WT tumours were described. In total, 61 514 new melanomas were registered in England between 2016 and 2019. Thirteen per cent (n = 7925), 5.0% (n = 3084) and 1.2% (n = 743) of tumours underwent BRAF, NRAS and KIT testing, respectively. BRAF testing rates varied across regions from 19.9% (n = 1040/5217) in the West Midlands to 5.5% (n = 227/4114) in the North East. Thirty-four per cent (n = 2674/7925), 30.5% (n = 942/3084) and 8.6% (n = 64/743) of tumours were BRAF+, NRAS+ and KIT+, respectively. Thirty-four per cent (n = 1523/4479) of males and 37.6% (n = 1132/3014) of females with cutaneous melanomas were BRAF+. Forty-six per cent (n = 1693/3712) of patients aged &amp;lt; 70 years and 20.5% (n = 332/1622) aged ≥ 80 years were BRAF+. The highest proportion of BRAF+ cutaneous melanoma were identified in the North East (46.7%, n = 106/227) and the lowest in the West Midlands (32.6%, n = 339/1040). Thirty-two per cent (n = 560/1760) of males and 30.0% (n = 349/1167) of females with cutaneous melanoma were NRAS+. Twenty-six per cent (n = 356/1354) of patients aged &amp;lt; 70 years and 31.8% (n = 229/718) aged ≥ 80 years were NRAS+. The highest proportion of NRAS+ cutaneous melanoma were in the West Midlands (40%, n = 14/35) and the lowest in the North East (28.3%, n = 36/127). We report the largest and most complete dataset for national molecular genetics of melanoma ever published. Regional differences in BRAF testing may be explained by variations in local practice and methods used, and differences in population age, but could impact on treatment options. Lack of IHC, testing nonuniformity and lack of whole melanoma population data (early-stage nonrecurrent tumours and tumours in frail elderly patients may be excluded) were limitations.

P105 Adult-onset mastocytosis: a retrospective review

Abstract Mastocytosis is characterized by an abnormal proliferation of mast cells in different organs, with the skin being the most frequently affected site. Adult-onset mastocytosis often follows a chronic course and is more likely to have extracutaneous involvement. We undertook a retrospective case note review of adult patients with a diagnosis of mastocytosis in our dermatology department between 2021 and 2022. Fourteen patients were identified with a female-to-male ratio of 1.8 : 1. Median age at disease onset was 46 years (range 25–75). Lesions were described as maculopapular (n = 8), macular (n = 3), telangiectatic (n = 2) and urticated (n = 1). The torso was affected in 12 patients (86%). The most commonly reported symptom was pruritus (n = 9). Other complaints included flushing (n = 3), abdominal pain (n = 2), dizziness (n = 2), weight loss (n = 2), night sweats (n = 2), syncope (n = 1), musculoskeletal pain (n = 1) and symptoms of recurrent anaphylaxis (n = 1). Two patients were asymptomatic. Darier sign was elicited in five patients and negative in two (not documented in seven). Eight patients were assessed for lymphadenopathy and organomegaly, with no detected abnormality. Eleven patients had skin biopsies; 10 (91%) had mastocytosis in the skin confirmed on histology; one patient had a nondiagnostic histological finding, but mastocytosis was diagnosed on the basis of clinical presentation. Seven patients had elevated serum tryptase levels (&amp;gt; 20 ng mL−1) on at least one occasion. Bone densitometry was done in five patients with elevated serum tryptase: two had osteopenia and one had osteoporosis. Eleven patients underwent bone marrow examination. Mast cell infiltration of the bone marrow was detected in four patients; KIT mutations in bone marrow were subsequently identified in three patients. Twelve patients remain under long-term follow-up. Treatments prescribed included antihistamine (n = 10), epinephrine autoinjector (n = 6), topical steroids (n = 5), vitamin D (n = 5), calcium (n = 4), H2 blocker (n = 2), bisphosphonates (n = 2), phototherapy (n = 2), leukotriene antagonists (n = 2), cosmetic camouflage (n = 1), oral sodium cromoglicate (n = 1) and KIT–tyrosine kinase inhibitor (n = 1). Despite treatments, none of the patients had regression (partial or complete) of cutaneous disease, although no fatal outcome was observed. Four (29%) cases had a final diagnosis of indolent systemic mastocytosis (all had elevated serum tryptase levels, two had anaemia). Our findings were consistent with the literature, where serum tryptase levels rather than systemic symptoms were a reliable predictor of systemic mastocytosis. Interestingly, 10 (71%) patients had mastocytosis limited to the skin, which is in contrast to the published literature, where the majority of people with adult-onset mastocytosis have systemic forms of the disease.

Clinical and prognostic profile of SRSF2 and related spliceosome mutations in patients with acute myeloid leukemia.

Mutations in splicing factor (SF) genes are frequently detected in myelodysplastic syndrome, but their clinical and prognostic relevance in acute myeloid leukemia (AML) have rarely been reported. A total of 368 newly diagnosed non-M3 AML patients were included in this study. Next generation sequencing including four SF genes was performed on the genomicDNA. The clinical features and survival were analyzed using statistical analysis. We found that 64 of 368 patients harbored SF mutations. The SF mutations were much more frequently found in older or male patients. SRSF2 mutations were shown obviously co-existed with IDH2 mutation. The level of measurable residual disease after first chemotherapy was higher in SF-mutated patients compared to that in SF-wild patients, while the complete remission rate was significantly decreased. And the overall survival of SF-mutated patients was shorter than that of SF-wild patients. Moreover, our multivariable analysis suggests that the index of male, Kit mutation or ZRSR2 mutation was the independent risk factor for overall survival. SRSF2mut was associated with older age, higher proportion of peripheral blasts or abnormal cell proportion by flow cytometry. SF mutation is a distinct subgroup of AML frequently associated with clinic-biological features and poor outcome. SRSF2mut could be potential targets for novel treatment in AML.

Co-occurring mutations in ASXL1, SRSF2, and SETBP1 define a subset of myelodysplastic/ myeloproliferative neoplasm with neutrophilia

Identification of genomic signatures with consistent clinicopathological features in myelodysplastic/myeloproliferative neoplasm (MDS/MPN) is critical for improved diagnosis, elucidation of biology, inclusion in clinical trials, and development of therapies. We describe clinical and pathological features with co-existence of mutations in ASXL1 (missense or nonsense), SRSF2, and SKI homologous region of SETBP1, in 18 patients. Median age was 68 years with a male predominance (83%). Leukocytosis and neutrophilia were common at presentation. Marrow features included hypercellularity, granulocytic hyperplasia with megakaryocytic atypia, while the majority had myeloid hyperplasia and/or erythroid hypoplasia, myeloid dysplasia, and aberrant CD7 expression on blasts. Mutations in growth signaling pathways (RAS or JAK2) were noted at diagnosis or acquired during the disease course in 83% of patients. Two patients progressed upon acquisition of FLT3-TKD (acute myeloid leukemia) or KIT (aggressive systemic mastocytosis) mutations. The prognosis is poor with only two long-term survivors, thus far, who underwent blood or marrow transplantation. We propose that the presence of co-occurring ASXL1, SRSF2, and SETBP1 mutations can be diagnostic of a subtype of MDS/MPN with neutrophilia if clinical and morphological findings align. Our report underscores the association between genotype and phenotype within MDS/MPN and that genomic signatures should guide categorization of these entities.