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Heterozygous (HET) truncating mutations in the TTN gene (TTNtv) encoding the giant titin protein are the most common genetic cause of dilated cardiomyopathy (DCM). However, the molecular mechanisms by which TTNtv mutations induce DCM are controversial. Here we investigated 127 clinically identified DCM human cardiac samples with next-generation sequencing (NGS), high-resolution gel electrophoresis, Western blot analysis and super-resolution microscopy in order to dissect the structural and functional consequences of TTNtv mutations. The occurrence of TTNtv was found to be 15% in the DCM cohort. Truncated titin proteins matching, by molecular weight, the gene-sequence predictions were detected in the majority of the TTNtv samples. The total amount of expressed titin, which includes the truncated fragments, was comparable in the TTNtv+ and TTNtv-samples, indicating that titin haploinsufficiency is not the leading cause of the molecular pathogenesis. Proteomic analysis of washed cardiac myofibrils and Stimulated Emission Depletion (STED) super-resolution microscopy of myocardial sarcomeres labeled with sequence-specific anti-titin antibodies revealed that truncated titin is structurally integrated in the sarcomere. Sarcomere lengthdependent anti-titin epitope position, shape and intensity analysis pointed at structural defects in the I/A junction and the M-band of TTNtv+ sarcomeres, which may contribute, via faulty mechanosensor function, to the development of manifest DCM.

Összefoglaló. Bevezetés: A krónikus myeloid leukaemia a diagnosztika fejlődésének és a tirozin-kináz-gátlók bevezetésének köszönhetően az elmúlt évtizedekben kiváló prognózisú betegséggé vált. Célkitűzés: A betegséggel kapcsolatos ismereteink nagy része klinikai vizsgálatokból származik, emiatt kiemelt szerepük van a nem szelektált beteganyagon végzett elemzéseknek. Módszer: Retrospektív elemzésünkben a Semmelweis Egyetem Belgyógyászati és Onkológiai Klinikáján 2003 és 2019 között tirozin-kináz-gátló kezelésben részesült betegek adatait tekintettük át. Eredmények: Klinikánkon összesen 88 beteg részesült terápiában, közülük 73 beteg az analízis időpontjában is kezelés alatt állt. A betegek 5 éves össztúlélése 86%, 5 éves progressziómentes túlélése 70% volt. 9 beteg halt meg, közülük 2 betegnél a halál oka a progrediáló alapbetegség volt. 38 betegnél volt szükség az első vonalban terápiaváltásra, a váltás oka akkor elsősorban az elégtelen terápiás válasz volt. A későbbi terápiaváltásokra elsősorban intolerancia miatt került sor. Az első vonalban a betegek több mint fele major molekuláris választ ért el, a jelenlegi kezelés mellett a betegek 85%-ánál major molekuláris választ detektáltunk. Megbeszélés: Adataink alapján az intézményünkben kezelt betegek túlélése és a betegek által elért terápiás válasz megfelel a nemzetközi adatoknak. Következtetés: Mivel nem válogatott beteganyagról van szó, a kapott eredmények pontosabb képet adhatnak a krónikus myeloid leukaemia tirozin-kináz-gátlóval történt kezelésének eredményeiről. Orv Hetil. 2021; 162(32): 1297–1302. Summary. Introduction: As a result of advances in diagnostic techniques and the introduction of tyrosine kinase inhibitors, the prognosis of chronic myeloid leukemia has improved over the last decades. Objective: Most of our knowledge about chronic myeloid leukemia results from clinical trials, therefore data derived from non-selected patient population is substantial. Method: Data of chronic myeloid leukemia patients treated with tyrosine kinase inhibitors at the Department of Internal Medicine and Oncology, Semmelweis University, between 2003 and 2019 were analysed retrospectively. Results: 88 patients received treatment, 73 patients were on therapy at the time of the analysis. Overall survival at 5 years was 86%, progression-free survival at 5 years was 70%. 9 patients died, 2 of them due to progressive disease. 38 patients needed 2nd line therapy, the main reason of treatment change was failure of therapy. Subsequent treatment modifications were conducted mostly because of intolerance. More than half of the patients on 1st line treatment reached major molecular response and 85% of the patients on treatment at the end of the analysis are in major molecular response. Discussion: Based on our data, survival and therapeutic response of patients in our center are similar to the international results. Conclusion: This analysis provides real-world data about treatment results of chronic myeloid leukemia in the tyrosine kinase inhibitor era. Orv Hetil. 2021; 162(32): 1297–1302.

We hypothesized that different BC subtypes are characterized by spatially distinct tumor immune microenvironment (TIME) and that immune gene assembly of metastatic (Met) and non-metastatic (Ctrl) BCs vary across subtypes. Peritumoral, stromal and intratumoral TIL was assessed on 309 BC cases. Hot, cold and immune-excluded groups were defined, and the prognostic role of this classification was assessed. CD4+/CD8+ positivity was analyzed in 75 cases in four systematically predefined tumor regions. Immune gene expression of Met and Ctrl HER2-negative BCs was compared by using NanoString nCounter technology. The amount of TIL infiltration varied greatly within all BC subtypes. Two-third of the cases were cold tumors with no significant survival difference compared to hot tumors. A lower CD4+/CD8+ ratio at the stromal internal tumor region was significantly associated with longer distant metastasis-free survival. The differentially expressed immune genes between Met and Ctrl varied across the studied BC subtypes with TNBC showing distinct features from the luminal subtypes. The TIME is characterized by a considerable heterogeneity; however, low level of TILs does not equate to disease progression. The differences in immune gene expression observed between Met and Ctrl breast carcinomas call attention to the important role of altered immune function in BC progression.

Absztrakt: Az akut myeloid leukemia (AML) osztalyozasanak es rizikobecslesenek alapjaul a citogenetikai elteresek szolgalnak, azonban az elmult evekben az uj generacios szekvenalasnak (NGS) koszonh...

Absztrakt: A molekularis genetikai vizsgalatok nagyleptekű fejlődese az elmult evekben lehetőve tette a malignus myeloid korkepek hattereben allo genetikai elteresek detektalasat. Ennek koszonhetően az akut myeloid leukemiaban (AML) gyakoribb mutaciok egyre teljesebb korű vizsgalata jelentősen javitotta a korkep diagnosztikajat, prognosztikai ertekeleset, valamint a terapiara adott valasz es a relapszus valoszinűsegenek előrejelzeset. Az AML patogeneziseben fontos szerepet jatszanak a kulonboző transzkripcios faktorok genetikai elteresei, amelyek a hematopoetikus őssejt myeloid iranyba tortenő differenciaciojat segitik elő. Ezen feherjek koze tartozik a CEBPA (CCAAT/enhancer binding protein alpha) gen altal kodolt, leucincipzar-motivumot tartalmazo transzkripcios faktor is. A CEBPA feherje a granulocytak differenciaciojaban vesz reszt, mig a mutacioja a myeloid blastok kontrollalatlan proliferaciojat okozhatja. Sporadikus AML-ben a betegek korulbelul 5–10%-aban mutathato ki a CEBPA gen mutacioja, leggyakr...

Richter syndrome (RS) represents the development of high-grade lymphoma in patients with chronic lymphocytic leukaemia (CLL) or small lymphocytic lymphoma (SLL) and presents a diagnostic and therapeutic challenge with an adverse prognosis. The genetic background and morphology of RS in CLL patients treated with chemoimmunotherapy is extensively characterised; however, our knowledge about RS in patients treated with targeted oral therapies should be extended. To understand the morphologic and molecular changes leading to RS in CLL patients treated with the Bruton's tyrosine kinase inhibitor, ibrutinib, and the BCL2 inhibitor, venetoclax, sequential samples from six CLL/SLL patients undergoing RS were collected in both the CLL and RS phases. A detailed immunophenotypic analysis of formalin-fixed, paraffin-embedded tissue specimens of RS phase was performed, followed by extensive molecular characterisation of CLL and RS samples, including the immunoglobulin heavy chain gene (IGH) rearrangement, TP53 mutations, drug-induced resistance mutations in BTK and BCL2 genes and various copy number changes and point mutations detectable with multiplex ligation-dependent probe amplification (MLPA). Rare, non-diffuse large B-cell lymphoma phenotypes of RS were observed in 3/6 cases, including plasmablastic lymphoma and a transitory entity between diffuse large B-cell lymphoma and classical Hodgkin lymphoma. The majority of cases were clonally related and harboured an unmutated variable region of the immunoglobulin heavy chain gene. Abnormalities affecting the TP53 gene occurred in all patients, and every patient carried at least one genetic abnormality conferring susceptibility to RS. In the background of RS, 2/5 patients treated with ibrutinib showed a BTK C481S resistance mutation. One patient developed a BCL2 G101V mutation leading to venetoclax resistance and RS. In conclusion, our findings contribute to better understanding of RS pathogenesis in the era of targeted oral therapies. Rare phenotypic variants of RS do occur under the treatment of ibrutinib or venetoclax, and genetic factors leading to RS are similar to those identified in patients treated with chemoimmunotherapy. To our best knowledge, we have reported the first BCL2 G101V mutation in an RS patient treated with venetoclax.

Összefoglaló. Bevezetés: A krónikus myeloid leukaemia a diagnosztika fejlődésének és a tirozin-kináz-gátlók bevezetésének köszönhetően az elmúlt évtizedekben kiváló prognózisú betegséggé vált. Célkitűzés: A betegséggel kapcsolatos ismereteink nagy része klinikai vizsgálatokból származik, emiatt kiemelt szerepük van a nem szelektált beteganyagon végzett elemzéseknek. Módszer: Retrospektív elemzésünkben a Semmelweis Egyetem Belgyógyászati és Onkológiai Klinikáján 2003 és 2019 között tirozin-kináz-gátló kezelésben részesült betegek adatait tekintettük át. Eredmények: Klinikánkon összesen 88 beteg részesült terápiában, közülük 73 beteg az analízis időpontjában is kezelés alatt állt. A betegek 5 éves össztúlélése 86%, 5 éves progressziómentes túlélése 70% volt. 9 beteg halt meg, közülük 2 betegnél a halál oka a progrediáló alapbetegség volt. 38 betegnél volt szükség az első vonalban terápiaváltásra, a váltás oka akkor elsősorban az elégtelen terápiás válasz volt. A későbbi terápiaváltásokra elsősorban intolerancia miatt került sor. Az első vonalban a betegek több mint fele major molekuláris választ ért el, a jelenlegi kezelés mellett a betegek 85%-ánál major molekuláris választ detektáltunk. Megbeszélés: Adataink alapján az intézményünkben kezelt betegek túlélése és a betegek által elért terápiás válasz megfelel a nemzetközi adatoknak. Következtetés: Mivel nem válogatott beteganyagról van szó, a kapott eredmények pontosabb képet adhatnak a krónikus myeloid leukaemia tirozin-kináz-gátlóval történt kezelésének eredményeiről. Orv Hetil. 2021; 162(32): 1297-1302.As a result of advances in diagnostic techniques and the introduction of tyrosine kinase inhibitors, the prognosis of chronic myeloid leukemia has improved over the last decades.Most of our knowledge about chronic myeloid leukemia results from clinical trials, therefore data derived from non-selected patient population is substantial.Data of chronic myeloid leukemia patients treated with tyrosine kinase inhibitors at the Department of Internal Medicine and Oncology, Semmelweis University, between 2003 and 2019 were analysed retrospectively.88 patients received treatment, 73 patients were on therapy at the time of the analysis. Overall survival at 5 years was 86%, progression-free survival at 5 years was 70%. 9 patients died, 2 of them due to progressive disease. 38 patients needed 2nd line therapy, the main reason of treatment change was failure of therapy. Subsequent treatment modifications were conducted mostly because of intolerance. More than half of the patients on 1st line treatment reached major molecular response and 85% of the patients on treatment at the end of the analysis are in major molecular response.Based on our data, survival and therapeutic response of patients in our center are similar to the international results.This analysis provides real-world data about treatment results of chronic myeloid leukemia in the tyrosine kinase inhibitor era. Orv Hetil. 2021; 162(32): 1297-1302.

Acute lymphoblastic leukemia is the most common pediatric cancer characterized by a heterogeneous genomic landscape with copy number aberrations occurring at various stages of pathogenesis, disease progression, and treatment resistance. In this study, disease-relevant copy number aberrations were profiled in bone marrow samples of 91 children with B- or T-cell precursor acute lymphoblastic leukemia using digital multiplex ligation-dependent probe amplification (digitalMLPA(TM)). Whole chromosome gains and losses, subchromosomal copy number aberrations, as well as unbalanced alterations conferring intrachromosomal gene fusions were simultaneously identified with results available within 36 hours. Aberrations were observed in 96% of diagnostic patient samples, and increased numbers of copy number aberrations were detected at the time of relapse as compared with diagnosis. Comparative scrutiny of 24 matching diagnostic and relapse samples from 11 patients revealed three different patterns of clonal relationships with (i) one patient displaying identical copy number aberration profiles at diagnosis and relapse, (ii) six patients showing clonal evolution with all lesions detected at diagnosis being present at relapse, and (iii) four patients displaying conserved as well as lost or gained copy number aberrations at the time of relapse, suggestive of the presence of a common ancestral cell compartment giving rise to clinically manifest leukemia at different time points during the disease course. A newly introduced risk classifier combining cytogenetic data with digitalMLPA(TM)-based copy number aberration profiles allowed for the determination of four genetic subgroups of B-cell precursor acute lymphoblastic leukemia with distinct event-free survival rates. DigitalMLPA(TM) provides fast, robust, and highly optimized copy number aberration profiling for the genomic characterization of acute lymphoblastic leukemia samples, facilitates the decipherment of the clonal origin of relapse and provides highly relevant information for clinical prognosis assessment.

Absztrakt: A follicularis lymphoma terapiajaban a rituximab alkalmazasanak koszonhetően a betegek varhato elettartama szamottevően megnőtt, azonban a betegseg jelenlegi tudasunk szerint tovabbra is...

Primary cutaneous follicle center lymphoma (PCFCL) is an indolent variant of follicular lymphoma (FL) with limited information available on the genetic background of the disease. The genetic hallmark of nodal FL, the t(14;18) translocation, affecting the BCL2 gene, is rare in PCFCL. Loss of 1p36, the most common secondary chromosomal abnormality in nodal FL, has been recently reported in 16.7% of PCFCL cases. In order to further characterize PCFCL, 21 cases were analyzed using interphase fluorescence in situ hybridization with BCL2 break apart and 1p36/1q25 dual color probes. Sanger sequencing was used to investigate TNFRSF14 and EZH2 mutations and immunohistochemistry to assess BCL2, EZH2 protein expressions. 1p36 deletion occurred in 22% (5/21), BCL2 gene break in 10% (2/20) of the PCFCL cases. Mutations of the candidate tumor suppressor gene of the 1p36 region, TNFRSF14 mutations were detected in 4/17 (23.5%) cases with 2 cases presenting with concurrent 1p36 deletion. EZH2 hotspot mutations at Y641, A682, and A692 were not found. High EZH2 protein expression associated with a BCL2 negative phenotype was observed in 43% (9/21) of the cases. BCL2 gene break or 1p36 deletion did not impact the prognosis; however, they showed association with advanced stages at diagnosis (p = 0.016) and a tendency with shorter event free survival (p = 0.052). In conclusion, 1p36 deletion co-occurs with acquired TNFRSF14 mutations, suggesting a role of this tumor suppressor gene in the development of a subgroup of PCFCL. High EZH2 protein expression associated with BCL2 negative phenotype is common and might represent an ideal therapeutic target.

Abstract: Genetic abnormalities associated with the development, progression and treatment resistance of hematological malignancies are extensively characterized. Rapid, reliable and cost-efficient techniques are needed to screen the clinically relevant aberrations in routine diagnostics. Multiplex ligation-dependent probe amplification is an efficient tool to analyze genomic copy number aberrations at 55–60 different genomic loci. The method allows the profiling of prognostic and predictive markers; thus, it can efficiently be combined with karyotyping and fluorescence in situ hybridization, the most commonly used diagnostic techniques to detect cytogenetic lesions. Furthermore, the method can interrogate methylation status and unravel point mutations at specific sites, providing results in 24 hours. Here, we describe the technical background of multiplex ligation-dependent probe amplification, summarize its advantages and limitations as well as discuss its role in oncohematological diagnostics and research. Finally, future outlook is provided, with emphasis on recent technological advances related to next-generation sequencing. Orv Hetil. 2018; 159(15): 583–592.

Absztrakt: A kronikus limfocitas leukemia klinikailag heterogen megjelenese genetikai diverzitassal parosul. Hazankban fluoreszcens in situ hibridizacio terjedt el a betegekben előfordulo, prognosz...

Background Philadelphia negative myeloproliferative neoplasms (MPNs) are characterized by frequent mutations of driver genes including JAK2, CALR and MPL. While the influence of JAK2 V617F mutant allele burden on the clinical phenotype of MPN patients is well-described, the impact of CALR mutant allele burden on clinical features needs further investigation. Patients and methods Quantitative assessment of JAK2 and CALR mutations was performed on diagnostic DNA samples from 425 essential thrombocythemia (ET) and 227 primary myelofibrosis patients using real-time quantitative PCR and fragment length analysis. Characterization of CALR mutations and detection of MPL mutations were performed by Sanger sequencing. Results Twelve novel CALR mutations have been identified. ET patients with CALRmut load exceeding the median value exhibited lower hemoglobin values (12.0 vs. 13.6 g/dL), higher LDH levels (510 vs. 351 IU/L) and higher rate of myelofibrotic transformation (19% vs. 5%). The CALRmut load was higher among ET patients presenting with splenomegaly compared to those without splenomegaly (50.0% vs. 43.5%). Conclusion Our study confirms the clinical significance of driver mutational status and JAK2mut load in MPNs; in addition, unravels a novel clinical association between high CALRmut load and a more proliferative phenotype in ET.

Although genetic predisposition to haematological malignancies has long been known, genetic testing is not yet the part of the routine diagnostics. In the last ten years, next generation sequencing based studies identified novel germline mutations in the background of familial aggregation of certain haematologic disorders including myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML). This is supported by the fact that the myeloid neoplasms with genetic predisposition represent a new category in the revised 2016 World Health Organization classification. According to the new classification, these disorders are subdivided based on the clinical and genetic features, including myeloid neoplasms with germline predisposition alone, or with pre-existing platelet disorder, cytopaenias or other organ failures. The predisposing genetic factors include mutations in the RUNX1, CEBPA, GATA2, ANKRD26, ETV6, DDX41, TERC or TERT and SRP72 genes. The genes affected in these syndromes are important regulators of haemopoiesis and are frequently implicated in leukaemogenesis, providing deeper insight into the understanding of normal and malignant haemopoiesis. Despite the growing knowledge of germline predisposing events in the background of familial myeloid malignancies, the germline genetic component is still unknown in a subset of these pedigrees. Here, we present the first study of inherited myeloid malignancies in Hungary. We identified three families with apparent clustering of myeloid malignancies with nine affected individuals across these pedigrees. All tested individuals were negative for CEBPA, GATA2, RUNX1, ANKRD26, ETV6, DDX41, TERC or TERT and SRP72 mutations, suggesting the presence of so far unidentified predisposing mutations.

Multiple myeloma (MM) is a genetically heterogeneous disease with a diverse clinical outcome. Copy number alterations (CNAs), including whole chromosome and subchromosomal gains and losses, are common contributors of the pathogenesis and have demonstrated prognostic impact in MM. We tested the performance of digital multiplex ligation-dependent probe amplification (digitalMLPA), a novel technique combining MLPA and next-generation sequencing, to detect disease-related CNAs. Copy number status at 371 genomic loci was simultaneously analyzed in 56 diagnostic bone marrow samples, which were also examined by conventional MLPA and interphase fluorescence in situ hybridization (iFISH). On average, digitalMLPA identified 4.4 subchromosomal CNAs per patient. The increased number of probes compared with conventional MLPA allowed a detailed mapping of CNAs, especially on chromosome 1, where 24 different patterns were observed in 38 patients harboring loss(1p) and/or gain(1q). iFISH, MLPA, and digitalMLPA results at loci investigated by multiple methods showed a congruency of 95%. Besides precise characterization of hyperdiploid karyotypes not efficiently achievable by iFISH or MLPA, digitalMLPA unraveled 156 CNAs not detected by the other two methods in 45 patients (80%). In addition, we provide proof of principle that digitalMLPA can detect known point mutations, in this case the BRAFV600E. Our study demonstrates the robustness of digitalMLPA to profile CNAs and to screen point mutations in MM, which could efficiently be used in myeloma diagnostics.

Mutations of the multifunctional protein calreticulin (CALR) are recognised as one of the main driver alterations involved in the pathogenesis of Philadelphia negative myeloproliferative neoplasms (Ph- MPN) and also represent a major diagnostic criterion in the most recent World Health Organization classification of myeloid neoplasms. Nowadays, quantitative assessment of the driver mutations is gaining importance, as recent studies demonstrated the clinical relevance of the mutation load reflecting the size of the mutant clone. Here, we performed for the first time a manual and automated quantitative assessment of the CALR mutation load at protein level using CAL2, a recently developed CALR mutation specific monoclonal antibody, on a cohort of 117 patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) and compared the CALR protein mutation loads with the CALR mutation load values established by a molecular assay. Eighteen different CALR mutations were detected in the cohort of the 91 CALR mutant cases. Mutation loads of the CALR mutations were between 13% and 94% with mean value in PMF cases significantly higher than ET cases (49.94 vs 41.09; t-test, p=0.004). Cases without CALR mutation (n=26) showed no or only minimal labelling with the CAL2 antibody, while all 18 different types of CALR mutations were associated with CAL2 labelling. The CALR mutation load showed a significant correlation (p=0.03) with the occurrence of major thrombotic events, with higher mutation load in patients presenting with these complications. We report a 100% concordance between the mutation status determined by immunohistochemistry and the CALR molecular assay, and we extend the applicability of this approach to 16 rare CALR mutations previously not analysed at protein level.

Genetic abnormalities associated with the development, progression and treatment resistance of hematological malignancies are extensively characterized. Rapid, reliable and cost-efficient techniques are needed to screen the clinically relevant aberrations in routine diagnostics. Multiplex ligation-dependent probe amplification is an efficient tool to analyze genomic copy number aberrations at 55-60 different genomic loci. The method allows the profiling of prognostic and predictive markers; thus, it can efficiently be combined with karyotyping and fluorescence in situ hybridization, the most commonly used diagnostic techniques to detect cytogenetic lesions. Furthermore, the method can interrogate methylation status and unravel point mutations at specific sites, providing results in 24 hours. Here, we describe the technical background of multiplex ligation-dependent probe amplification, summarize its advantages and limitations as well as discuss its role in oncohematological diagnostics and research. Finally, future outlook is provided, with emphasis on recent technological advances related to next-generation sequencing. Orv Hetil. 2018; 159(15): 583-592.

Introduction: Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy characterized by a heterogeneous genomic landscape. Copy number aberrations (CNA) emerge during the development, progression and treatment resistance of ALL, and can serve as genomic markers for prognostic classification of patients or for scrutinizing clonal evolution associated with relapse. While identification of distinct CNAs with well-characterized prognostic significance has its own value, uncovering the co-segregation of driver aberrations in individual patient samples could allow for a more personalized risk assessment and treatment response prediction. Methods: Disease-relevant CNAs were profiled in children with B- or T-cell precursor ALL using a next-generation sequencing based digital multiplex ligation-dependent probe amplification (digitalMLPA) assay containing 598 probes specific for 54 genes with key relevance in ALL. Besides the diagnostic samples of 91 patients treated according to the BFM protocols, 14 matching samples drawn at the time of first or second relapse were comparatively analyzed. Clonal relationship between B-cell precursor cell populations prevailing at different time points during the disease course was also investigated by screening immunoglobulin heavy-chain gene rearrangements in matching diagnostic and relapse samples using Illumina deep-sequencing with >20,000x coverage. Results: Whole chromosome gains and losses, subchromosomal CNAs as well as alterations conferring intrachromosomal gene fusions were simultaneously identified by digitalMLPA with results available within 36 hours. Aberrations were observed in 96% of diagnostic patient samples and increased numbers of CNAs were detected in individual samples at the time of relapse as compared to diagnosis. DigitalMLPA results were successfully validated by conventional MLPA, FISH and PCR data. Comparative scrutiny of 24 matching diagnostic and relapse samples from 11 patients harboring CNAs revealed three different patterns of clonal relationships with (i) one patient displaying identical CNA profiles at diagnosis and relapse, (ii) six patients showing clonal evolution with all lesions detected at diagnosis being present at relapse and (iii) four patients displaying conserved as well as lost or gained CNAs at the time of relapse, suggestive of the presence of a common ancestral cell compartment giving rise to clinically manifest leukemia at different time points during the disease course. Time between diagnosis and first relapse of T-ALL patients displaying altered CNA profiles suggested a prolonged time requirement of clonal evolution, and of the development of manifest leukemia from an ancestral clone compared to the quick return of an identical clone at the time of relapse. Comparison of the IGH gene rearrangements identified at diagnoses and relapse revealed identical compositions of the most abundant clonotypes in all but one B-ALL patients analyzed; hence, IGH repertoire did not reveal an additional depth of clonal history in our cohort, e.g. by demonstrating the presence of an ancestral clone as the major source of clonal expansion at disease progression in a patient with altered CNA profiles suggesting direct clonal evolution between diagnosis and relapse. Copy number profiles acquired by digitalMLPA were used for determining CNA-based risk groups (Table 1) which were combined with karyotyping and molecular cytogenetic data in order to establish an extended prognostic classifier for patients with B-cell precursor ALL. This novel classifier distinguished four combined genetic risk groups showing significantly different 5-year survival rates (GR: 97%, IR: 84%, IHR: 63% and PR: 13%). Conclusions: DigitalMLPA allows for a rapid, scalable and highly optimized copy number profiling of genomic regions recurrently altered by driver aberrations in pediatric ALL. Based on the comparison of CNA profiles at diagnosis and relapse, clonal evolution and emergence of relapse from an ancestral clone are the predominant driving mechanisms of disease progression. Comprehensive copy number profiling by digitalMLPA identifies distinct prognostic groups for risk assessment in B-cell precursor ALL. Supporting grants : LP95021, K_16 #119950, NVKP_16-1-2016-0004, KH17-126718, BO/00320/18/5, FK_19 #131476, ÚNKP-19-4-SE-77 Disclosures Benard-Slagter: MRC Holland: Employment. de Groot:MRC Holland: Employment. Savola:MRC Holland: Employment.

Introduction: The irreversible Bruton tyrosine kinase (BTK) inhibitor ibrutinib is changing the paradigm of the treatment of chronic lymphocytic leukemia (CLL) with remarkable outcomes in first line as well as in relapsed CLL, including high risk patients with TP53 aberration. While the majority of patients demonstrate durable responses, with a median follow up of 3 years, approximately 18% of them develop resistance and relapse. Mutations in the BTK and PLCG2 genes emerged as predominant mechanisms conferring secondary ibrutinib resistance with BTK and/or PLCG2 mutations detected in the majority of resistant patients, often even 10 months before the clinical relapse. Given the very poor outcome of patients discontinuing ibrutinib, comprehensive understanding of the mechanisms of ibrutinib resistance and changes in the clonal architecture induced by the selective pressure of the drug are of major clinical importance. To dissect the clonal evolution in the context of all relevant mutation targets in CLL, we performed a temporal mutation profiling of 31 genes in paired pre- and post-treatment samples of patients receiving ibrutinib therapy. Methods: Sequential samples from 18 patients treated with single-agent ibrutinib were included in this study. Pre-treatment peripheral blood samples were available in all patients, with post-treatment samples at 18 months for 6 patients, at 12 months for 7 patients, at 8 months for 3 patients and at 3 months for 2 patients, with a median follow up of 12 months. Targeted deep NGS analysis of 31 recurrently mutated target genes, including ATM, BCOR, BIRC3, BRAF, BTK, CHD2, DDX3X, EGR2, EIF2A, EP300, FBXW7, HIST1H1E, IGLL5, KLHL6, KMT2D, LRP1B, MAPK1, MED12, MGA, MYD88, NFKBIE, NOTCH1, PLCG2, POT1, RIPK1, RPS15, SAMHD1, SF3B1, TP53, XPO1 and ZMYM3 was performed using the TruSeq Custom Amplicon approach (Illumina) on genomic DNA specimens extracted from peripheral blood mononuclear cells. Variant calling was performed using the VariantStudio3.0 application (Illumina) and only variants supported with more than 100 mutant reads were considered. Our cohort represented a heavily pretreated patient group with a median of 2.5 (range: 1-5) lines of prior therapies. Results: The ultra-deep NGS analysis revealed a total of 473 somatic mutations in the 18 paired samples with a median allelic depth of 25.550x across the 31 genes analyzed. The post-treatment samples carried a considerably higher number of mutations compared to the pre-treatment samples (114 vs 359 mutations) with more than half of the variants representing subclonal alterations with variant allele frequencies (VAF) of Conclusions: The ultra-deep NGS analysis performed on paired samples of CLL patients treated with ibrutinib provided a significant insight into the mutational repertoire as well as subclonal dynamics of the leukemic compartment. Furthermore, it has revealed a profound subclonal heterogeneity that seems to be further enhanced by ibrutinib therapy, as demonstrated by a higher frequency of subclonal variants in the post-treatment samples. The clinical significance and the potential role of the novel BTK and PLCG2 variants identified in our study will require a longer follow up time, as currently all patients harboring these subclonal variants are still on ibrutinib therapy. Disclosures No relevant conflicts of interest to declare.

The last fifteen years brought a revolution both in treatment and diagnostics of chronic myeloid leukemia. Nowadays, the main method for monitoring of the disease is molecular monitoring with real-time PCR technology which can indicate treatment modification. With the development of the international scale and inter-laboratory standardization the residual tumor mass can be measured accurately and the results are comparable between the different laboratories. By the growing experience in the field of molecular responses we can now accurately predict treatment outcome early on with the so called early molecular response and BCR-ABL1 kinetics, allowing the selection of the best TKI with the treatment-free remission representing real option of the near future. Nevertheless, further advancements can be expected, including the workflow automatization and detection of even deeper molecular responses.Az elmúlt másfél évtized a krónikus mieloid leukémia területén nemcsak a kezelésben, hanem a diagnózisban és monitorozásban is forradalmat hozott, így már valós idejû PCR-vizsgálat eredménye is indikálhat módosítást a terápiában. A nemzetközi skálának és a laboratóriumok közötti standardizációnak köszönhetõen lehetséges a reziduális tumortömeg pontos mérése. A molekuláris válaszok terén szerzett tapasztalatoknak köszönhetõen egyre pontosabb és korábbi prognózisalkotás lehetséges a korai molekuláris válasz és a BCR-ABL1 kinetika segítségével. Mindezeknek köszönhetõen könnyebb kiválasztani a leghatékonyabb terápiát, és a kezelés tartós felfüggesztése is realitássá válhat a közeljövõben. Mindazonáltal a jövõben további fejlõdés várható, egyrészt az automatizálás, másrészt a még mélyebb molekuláris válaszok és érzékenyebb monitorozás tekintetében.

Introduction: Bruton tyrosine kinase inhibitor ibrutinib has altered the therapeutic landscape of chronic lymphocytic leukemia (CLL) with remarkable responses in relapsed or refractory CLL. Despite mostly durable responses, approximately 20% of patients experience disease progression with, in many cases, BTK or phospholipase Cg2 (PLCG2) resistance mutations predating the clinical progression by up to 15 months. Longitudinal studies have shed some light on the temporal aspects of clonal evolution processes leading to ibrutinib resistance, however, the spatial heterogeneity within the various environmental niches has not been described in detail yet. Here, we report the case of a CLL patient in which we are able to document, for the first time, an example of ibrutinib driven spatial convergent evolution leading to disease progression. The patient developed ibrutinib resistance after 21 months of treatment with simultaneous lymphadenomegaly and lymphocytosis. Sanger sequencing revealed a canonical BTK p.C481S mutation in peripherial blood and a PLCG2 p.D993H mutation in the lymph node with the absence of the BTK p.C481S mutation present in the peripherial blood suggesting convergent evolution in terms of the BTK and PLCG2 variants with both commonly associated with ibrutinib resistance. The patient was subsequently treated with venetoclax but due to further progression despite of high-dose salvage chemotherapy and autologous stem cell transplantation the patient died. Methods: Serial samples at ten different timepoints during the disease course were analysed. Genomic DNA was isolated from peripheral blood mononuclear cells and native lymph node tissue. Circulating cell-free DNA (ccfDNA) was isolated from peripheral blood samples. The fraction of tumor cells was determined by flow cytometry. During the Sanger sequencing BTK exons 11, 15, 16, and PLCG2 exon 12, 19, 20, 24, 27 and 30 were examined. Targeted ultra-deep next-generation sequencing (NGS) analysis of the BTK and PLCG2 genes was performed on a MiSeq platform (Illumina). Abundances of the PLCG2 p.P993H and BTK p.C481S variants were quantified using custom assays on a QX200 droplet digital PCR system (ddPCR, BioRad). Results: To dissect this spatial heterogeneity, BTK and PLCG2 mutations were screened by NGS which confirmed the Sanger finding and in addition to the dominant PLCG2 p.D993H variant, identified the BTK p.C481S mutation as a minor clone in the lymph node, with the BTK p.C481S mutation remaining the exclusive for the peripheral blood. Next, we tested the presence of these mutations in the circulating ccfDNA with ddPCR. Notably, both mutations were identified in the ccfDNA with a VAF of 1%. The ddPCR analysis revealed that both variants were absent in the pre-ibrutinib peripheral blood sample, however their emergence predated the clinical progression by 15 months. We observed a gradual expansion of these variants in the sequential samples, demonstrating clonal selection under the selective pressure of ibrutinib. Of note, the ddPCR assay identified the PLCG2 p.D993H mutation as a minor clone (VAF: 0.2%), previously unseen in the peripheral blood by NGS at the time of ibrutinib relapse. Intriguingly, the two subclones displayed differential sensitivity to the venetoclax therapy. In the peripheral blood, we observed a reduction of the BTK p.C481S positive subclone accompanied by expansion of the subclone harbouring PLCG2 p.D993H which was previously dominant in the lymph node. With these dynamic changes in the subclonal architecture, the disease progressed and ultimately led to death of the patient. Conclusions: Clonal evolution is a major driving force of disease progression in CLL. Several studies have traced the effect of treatment on temporal evolutionary trajectories in the context of standard and targeted therapies and identified subclonal heterogeneity and active clonal selection. However, the spatial aspect of subclonal dynamics has not been appreciated until recently. Here, we presented a unique case of CLL, developing ibrutinib resistance via multiple routes simultaneously, with the observed spatial heterogeneity leading to progression and aggressive transformation of the disease. This case highlights the importance of genetic profiling of multiple affected sites as investigations restricted to peripheral blood may underestimate the repertoire of clinically relevant genetic alterations. Disclosures No relevant conflicts of interest to declare.

Primary myelofibrosis (PMF) is a Philadelphia chromosome negative, clonal myeloproliferative neoplasm characterised by a progressive nature. Morphologically, the bone marrow biopsy shows features of abnormal proliferation of terminally differentiated megakaryocytes and subsequent bone marrow fibrosis. The molecular landscape of PMF includes phenotypic driver mutations (JAK2 V617F, CALR and MPL) which represent major diagnostic criteria, and subclonal mutations that also occur in several other myeloid diseases, but have a prognostic value in disease progression of MF. The most important subclonal mutations affect the genes ASXL1, TET2, IDH1/2, EZH2 and TP53. Triple negative genotype and the high molecular risk genotype and CALR-/ASXL1+ are associated with adverse survival with the latest indicating stem cell transplantation independently of the DIPSS-plus score.A primer mielofibrózis (PMF) klonális, a Philadelphia-kromoszóma-negatív mieloproliferatív neopláziák csoportjába tartozó, hemopoetikus õssejt eredetû megbetegedés. Diagnózisa csontvelõi morfológián alapszik, amely mellett major diagnosztikus kritérium a driver mutációk: a JAK2 V617F pontmutáció, az MPL és kalretikulin (CALR) génmutációk egyikének megléte. A mielofibrózis progressziójában szubklonális mutációk jelentõs szerepet játszanak, amelyek közül a leglényegesebbek az ASXL1, TET2, IDH1/2, EZH2, SRSF2 és TP53 mutációi. A progresszió folyamatos, azonban esetenként eltérõ idõbeli lefutást mutat. Klinikai adatoktól független rizikófaktornak bizonyult az úgynevezett „tripla-negatív” genotípus, a magas molekuláris rizikócsoport (HMR, high molecular risk) és a CALR-/ASXL1+ genotípus, amelyek közül a legutóbbi önmagában indikálja a csontvelõ-transzplantációt a jelenleg legelfogadottabb, klinikai adatokon alapuló rizikócsoport-besorolástól, a DIPSS-Plus rizikócsoporttól függetlenül.