Treatment outcome of atypical EGFR mutations in the German National Network Genomic Medicine Lung Cancer (nNGM).

BACKGROUND: Atypical EGFR mutations occur in 10%-30% of non-small-cell lung cancer (NSCLC) patients with EGFR mutations and their sensitivity to classical epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKI) is highly heterogeneous. Patients harboring one group of uncommon, recurrent EGFR mutations (G719X, S768I, L861Q) respond to EGFR-TKI. Exon 20 insertions are mostly insensitive to EGFR-TKI but display sensitivity to exon 20 inhibitors. Clinical outcome data of patients with very rare point and compound mutations upon systemic treatments are still sparse to date. PATIENTS AND METHODS: In this retrospective, multicenter study of the national Network Genomic Medicine (nNGM) in Germany, 856 NSCLC cases with atypical EGFR mutations including co-occurring mutations were reported from 12 centers. Clinical follow-up data after treatment with different EGFR-TKIs, chemotherapy and immune checkpoint inhibitors were available from 260 patients. Response to treatment was analyzed in three major groups: (i) uncommon mutations (G719X, S7681, L861Q and combinations), (ii) exon 20 insertions and (iii) very rare EGFR mutations (very rare single point mutations, compound mutations, exon 18 deletions, exon 19 insertions). RESULTS: Our study comprises the largest thus far reported real-world cohort of very rare EGFR single point and compound mutations treated with different systemic treatments. We validated higher efficacy of EGFR-TKI in comparison to chemotherapy in group 1 (uncommon), while most exon 20 insertions (group 2) were not EGFR-TKI responsive. In addition, we found TKI sensitivity of very rare point mutations (group 3) and of complex EGFR mutations containing exon 19 deletions or L858R mutations independent of the combination partner. Notably, treatment responses in group 3 (very rare) were highly heterogeneous. Co-occurring TP53 mutations exerted a non-significant trend for a detrimental effect on outcome in EGFR-TKI-treated patients in groups 2 and 3 but not in group 1. CONCLUSIONS: Based on our findings, we propose a novel nNGM classification of atypical EGFR mutations.

[Genetic evolution of in situ follicular neoplasia to t(14;18)-positive aggressive B-cell lymphoma]. / Die genetische Evolution der in situ follikulären Neoplasie zum t(14;18)-positiven aggressiven B­Zell-Lymphom.

BACKGROUND: In situ follicular neoplasia (ISFN) is a t(14;18)(q32;q21)+ precursor lesion of follicular lymphoma (FL), which in turn can transform into diffuse large B­cell lymphoma (DLBCL). For DLBCL that arise de novo, no precursor lesion is known. Given the high frequency of the t(14;18) translocation in de novo DLBCL as well, we investigated whether they can also arise from ISFN without FL as an intermediate step. OBJECTIVES: To investigate the clonal evolution of ISFN to DLBCL - transformed from FL and de novo. MATERIALS AND METHODS: Identification of ISFN lesions in patients with DLBCL was performed by BCL2 staining of reactive lymphoid tissues. ISFN and DLBCL were subsequently analyzed by fluorescence in situ hybridization, clonality analyses, sequencing of the t(14;18) breakpoint, and targeted next-generation sequencing. RESULTS: 10 cases with paired ISFN and DLBCL samples were identified, 6 of which were de novo DLBCL and 4 transformed from FL. 3 DLBCL carried MYC-rearrangements in addition to the t(14;18) and were classified as high-grade B­cell lymphoma (HGBL). The clonal relationship of ISFN and DLBCL/HGBL was confirmed for all cases. CREBBP, KMT2D, EZH2, TNFRSF14, and BCL2 were the genes most frequently mutated, with the distribution of private and shared mutations pointing to 2 different scenarios of clonal evolution. In most cases, DLBCL/HGBL, ISFN, and, if also present, FL had evolved divergently from a common progenitor, whereas linear evolution was less frequent. CONCLUSION: We show for the first time that t(14;18)+ DLBCL/HGBL can arise directly from ISFN without FL as an intermediate step and that during this progression, divergent evolution is common.

Epigenetic activation of O-linked ß-N-acetylglucosamine transferase overrides the differentiation blockage in acute leukemia.

BACKGROUND: Overriding the differentiation blockage in acute myeloid leukemia (AML) is the most successful mode-of-action in leukemia therapy - now curing the vast majority of patients with acute promyelocytic leukemia (APL) using all-trans retinoic acid (ATRA)-based regimens. Similar approaches in other leukemia subtypes, such as IDH1/2-mutated AML, are under active investigation. We herein present successful release of the differentiation blockage upon treatment with the natural (-)-Δ9-Tetrahydrocannabinol isomer dronabinol in vitro and in vivo. METHODS: Cellular maturation and differentiation were followed in two patients employing whole genome methylation profiling, proteome analyses, NGS deep sequencing and multispectral imaging flow cytometry. For functional studies lentiviral OGT knock-down in vitro and ex vivo cell models were created to evaluate proliferative, apoptotic and differentiating effects of OGT in acute leukemia. FINDINGS: In here, we provide molecular evidence that dronbinol is capable to override the differentiation blockage of acute leukemia blasts at the state of the leukemia-initiating clone. We further identify the O-linked ß-N-acetyl glucosamine (O-GlcNAc) transferase (OGT) to be crucial in this process. OGT is a master regulator enzyme adding O-GlcNAc to serine or threonine residues in a multitude of target proteins. Aberrant O-GlcNAc modification is implicated in pathologies of metabolic, neurodegenerative and autoimme diseases as well as cancers. We provide evidence that dronabinol induces transcription of OGT via epigenetic hypomethylation of the transcription start site (TSS). A lentiviral OGT-knock out approach proves the central role of OGT exerting antileukemic efficacy via a dual-mechanism of action: High concentrations of dronabinol result in induction of apoptosis, whereas lower concentrations drive cellular maturation. Most intriguingly, overriding of the differentiation blockage of acute leukemia blasts is validated in vivo following two patients treated with dronabinol. INTERPRETATION: In conclusion, we provide evidence for overcoming the differentiation blockage in acute leukemia in subentities beyond promyelocytic and IDH1/2-mutated leukemia and thereby identify O-GlcNAcylation as a novel (drugable) field for future leukemia research. FUNDING: Unrestricted grant support by the IZKF Program of the Medical Faculty Tübingen (MMS) and Brigitte Schlieben-Lange Program as well as the Margarete von Wrangell Program of the Ministry of Science, Research and the Arts, Baden-Württemberg, Germany (KKS) and Athene Program of the excellence initiative University of Tübingen (KKS).

Pediatric Langerhans cell histiocytosis: the impact of mutational profile on clinical progression and late sequelae.

Langerhans cell histiocytosis (LCH) is a clonal histiocytic disorder with recurrent mutations of BRAF and MAP2K1, but data on the impact of genetic features on progression and long-term sequelae are sparse. Cases of pediatric LCH with long-term follow-up from our institution were analyzed for mutations in BRAFV600 and MAP2K1 exons 2 and 3 by immunostaining with mutation-specific VE1 antibody, as well as allele-specific PCR and sequencing, respectively. Clinical and follow-up data were obtained from our files and a questionnaire sent to all former patients. Sixteen of 37 (43%) evaluable cases showed BRAFV600E, one case a BRAFV600D and eleven (30%) a MAP2K1 mutation. Nine cases were unmutated for both genes. All cases with risk organ involvement showed either BRAFV600 or MAP2K1 mutation. Patients with BRAFV600 mutation excluding Hashimoto-Pritzker cases had a significantly higher risk for relapses (p = 0.02). Long-term sequelae were present in 19/46 (41%) patients (median follow-up 12.5 years, range 1.0 to 30.8) with a trend for higher rates in mutated cases (mutated = 9/17, 53% versus non-BRAFV600/MAP2K1 mutated = 2/7, 29%). In addition, 8/9 cases with skin involvement including all Hashimoto-Pritzker cases (n = 3) were positive for BRAFV600E. Infants below 2 years more frequently had BRAFV600 mutations (p = 0.013). Despite favorable prognosis, pediatric LCH shows a high frequency of relapses and long-term medical sequelae.

Multicenter validation of cancer gene panel-based next-generation sequencing for translational research and molecular diagnostics.

The simultaneous detection of multiple somatic mutations in the context of molecular diagnostics of cancer is frequently performed by means of amplicon-based targeted next-generation sequencing (NGS). However, only few studies are available comparing multicenter testing of different NGS platforms and gene panels. Therefore, seven partner sites of the German Cancer Consortium (DKTK) performed a multicenter interlaboratory trial for targeted NGS using the same formalin-fixed, paraffin-embedded (FFPE) specimen of molecularly pre-characterized tumors (n = 15; each n = 5 cases of Breast, Lung, and Colon carcinoma) and a colorectal cancer cell line DNA dilution series. Detailed information regarding pre-characterized mutations was not disclosed to the partners. Commercially available and custom-designed cancer gene panels were used for library preparation and subsequent sequencing on several devices of two NGS different platforms. For every case, centrally extracted DNA and FFPE tissue sections for local processing were delivered to each partner site to be sequenced with the commercial gene panel and local bioinformatics. For cancer-specific panel-based sequencing, only centrally extracted DNA was analyzed at seven sequencing sites. Subsequently, local data were compiled and bioinformatics was performed centrally. We were able to demonstrate that all pre-characterized mutations were re-identified correctly, irrespective of NGS platform or gene panel used. However, locally processed FFPE tissue sections disclosed that the DNA extraction method can affect the detection of mutations with a trend in favor of magnetic bead-based DNA extraction methods. In conclusion, targeted NGS is a very robust method for simultaneous detection of various mutations in FFPE tissue specimens if certain pre-analytical conditions are carefully considered.

[Differential diagnostic specific skin infiltrates in chronic myelomonocytic leukemia]. / Differenzialdiagnose spezifischer Hautinfiltrate bei chronischer myelomonozytärer Leukämie.

A 72-year-old male patient presented with multiple erythematous plaques on the lower arms, lower legs and feet. The patient suffered from rheumatoid arthritis and accompanying interstitial granulomatous dermatitis under treatment with tocilizumab. Several months prior to presentation a chronic myelomonocytic leukemia (CMML) had been diagnosed. The skin biopsy showed a perivascular infiltration of medium-sized cells with positivity for CD123, CD303 and CD4 with a low proliferation activity so that a diagnosis of a CMML-associated proliferation of plasmacytoid dendritic cells was made. The differential diagnosis of specific cutaneous infiltrates in CMML is discussed.

[Predictive biomarkers for tumor-relevant signaling pathways in molecular pathology]. / Prädiktive Biomarker tumorrelevanter Signalwege in der molekularen Pathologie.

In the era of personalized medicine, targeted cancer treatments aim to improve therapy and overall survival. Specific therapies are individually customized for patients based on molecular alterations of the neoplastic cells. The pathologist has a central role in the identification and characterization of a variety of molecular markers that can be used to better predict outcome and assess therapeutic success of specific targeted approaches.

Increasing genomic and epigenomic complexity in the clonal evolution from in situ to manifest t(14;18)-positive follicular lymphoma.

Follicular lymphoma (FL) is characterized besides the t(14;18)(q32;q21), by recurrent chromosomal alterations and somatic mutations. In this study, we analyzed cases of FL in situ (FLIS) without manifest FL (mFL), partial involvement by FL (PFL) and paired cases of FLIS and mFL to detect possible early chromosomal imbalances, mutations, as well as DNA-methylation patterns of genomic regions of selected genes. We demonstrate that all paired FLIS and mFL cases were clonally related, based on IGH rearrangement patterns and BCL2 breakpoint sequences. FLIS and PFL had no or few secondary chromosomal imbalances detectable by array comparative genomic hybridization (FLIS 0.8 copy number alterations (CNA)/case; PFL 2.0 CNA/case; mFL 6.3 CNA/case) and a lower level of DNA methylation of genes recurrently de novo methylated in lymphomas, as compared with mFL. EZH2 Tyr641 mutations were detected in a subset of both FLIS (2/9) and PFL (1/3) cases. In conclusion, these findings provide evidence that FLIS represents a FL precursor lesion of long-lived clonal B cells carrying the t(14;18) with no or few secondary genetic changes. Our data suggest that there may be more than one distinct lesion driving the progression from FLIS to manifest lymphoma.

[Bone marrow biopsy: processing and use of molecular techniques]. / Knochenmarkbiopsie: Aufarbeitung und Einsatzmöglichkeiten molekularpathologischer Methoden.

The rapid technological development in diagnostic pathology, especially of immunohistochemical and molecular techniques, also has a significant impact on diagnostic procedures for the evaluation of bone marrow trephine biopsies. The necessity for optimal morphology, combined with preservation of tissue antigens and nucleic acids on one hand and the wish for short turnaround times on the other hand require careful planning of the workflow for fixation, decalcification and embedding of trephines. Although any kind of bone marrow processing has its advantages and disadvantages, formalin fixation followed by EDTA decalcification can be considered a good compromise, which does not restrict the use of molecular techniques. Although the majority of molecular studies in haematological neoplasms are routinely performed on bone marrow aspirates or peripheral blood cells, there are certain indications, in which molecular studies such as clonality determination or detection of specific mutations need to be performed on the trephine biopsy. Especially, the determination of B- or T-cell clonality for the diagnosis of lymphoid malignancies requires stringent quality controls and knowledge of technical pitfalls. In this review, we discuss technical aspects of bone marrow biopsy processing and the application of diagnostic molecular techniques.

[Peripheral NK/T-cell lymphoma]. / Periphere NK/T-Zell-Lymphome.

Peripheral T-cell lymphomas comprise 8% of the malignant lymphomas in Germany. About 25% of these cases present primarily in extranodal localizations. Such localizations are typical for the respective disease and form the basis for the classification of extranodal peripheral T-cell lymphoma. The morphology, immunophenotype and lineage specificity of the tumor cells (originating from T- or NK-cells) is only secondary for the classification. Extranodal NK/T-cell lymphomas of the nasal type are characterized by an angiocentric growth pattern and large confluent areas of necrosis. In addition, there is a clonal infection by Epstein-Barr virus in the T-lymphocytes. In the differential diagnosis, B-cell lymphomas are more frequent at all localizations than T- or NK-cell lymphomas.

Nodal peripheral T-cell lymphomas correspond to distinct mature T-cell populations.

Peripheral T-cell lymphomas (PTCL) have not been successfully correlated with specific developmental stages of reactive T-cells. Mature T-cells pass through distinct stages upon antigen encounter. Naïve T-cells are CD45RA(+)/CD45R0(-)/CD27(+)/CCR7(+). After antigen contact they replace CD45RA expression with CD45R0. The mature T-cells differentiate to central memory cells, which retain CD27 and CCR7, or to effector memory cells, which lose expression of both molecules depending on the strength of the antigen interaction. In this study, we evaluated lymph node biopsies from eight PTCL-not otherwise specified (PTCL-NOS), seven angioimmunoblastic T-cell lymphomas (AILT), and 15 anaplastic large cell lymphomas (ALCL). Detection of tumour cells with antibodies that recognize specific rearranged T-cell receptor Vbeta segments allowed us to investigate the expression of various differentiation-associated molecules. Results were analysed by hierarchical cluster analysis. All AILT and ALCL showed a homogeneous effector cell phenotype (CD45RA(-)/CD45R0(+)/CD27(-)), but differed in the cytotoxic and activation markers expressed. Several (5/8) PTCL-NOS clustered together; these cases all exhibited a CD4(+) central memory cell phenotype (CD45RA(-)/CD45R0(+)/CD27(+)) and four expressed the lymph node homing receptor CCR7. In conclusion, AILT and ALCL tumour cells correspond to different subsets of effector cells, while a subset of PTCL-NOS correlates with a non-effector T-cell population.

[Anaplastic large cell lymphomas lack the expression of T-cell receptor molecules]. / Fehlende T-zell Rezeptor Expression in grosszellig anaplastischen T-Zell Lymphomen.

Anaplastic large cell lymphoma (ALCL) designates a heterogeneous group of CD30+ (systemic or primary cutaneous) peripheral T-cell lymphomas (PTCLs). A subgroup of systemic ALCL is transformed by anaplastic lymphoma kinase (ALK). We compared 46 ALCL with 22 PTCLs in terms of T-cell receptor (TCR) rearrangements, expression of TCRs and TCR-associated molecules [CD3, ZAP-70 (zeta-associated protein 70)]. Despite their frequent clonal rearrangement for TCRbeta, only 4% of ALCLs expressed TCRbeta protein, whereas TCRs were detected in 86% of PTCLs. Moreover, both TCRbeta+ ALCLs lacked CD3 and ZAP-70 (ie, molecules indispensable for the transduction of cognate TCR signals). Defective expression of TCRs is a common characteristic of all types of ALCL, which may contribute to the dysregulation of intracellular signaling pathways controlling T-cell activation and survival. This molecular hallmark of ALCL is analogous to defective immunoglobulin expression distinguishing Hodgkin lymphoma from other B-cell lymphomas.