Normales Knochenmark und häufige reaktive Veränderungen

Zusammenfassung: Die histologische Knochenmarkuntersuchung spielt, wegen ihrer großen Aussagekraft bei relativ geringem Aufwand eine bedeutende Rolle in der Diagnostik von hämatologischen und nichthämatologischen Erkrankungen. Dafür ist die Kenntnis des normalen Knochenmarks mit seiner individuellen, insbesondere altersabhängigen, Variabilität, unentbehrlich. Neben entnahmebedingten Artefakten, die falsch interpretiert werden können, oder suboptimal fixierten bzw. verarbeiteten Biopsien, die diagnostisch überbewertet werden, gibt es eine Vielfalt von reaktiven Knochenmarkveränderungen, die einen neoplastischen Prozess vortäuschen und zu schwerwiegenden diagnostischen Fehlern führen können. Bei derartigen nichtneoplastischen Veränderungen können ein oder auch mehrere Kompartimente der Hämatopoiese qualitativ und quantitativ betroffen sein. Es kann zu Verteilungs- bzw. Architekturstörungen und/oder zu Veränderungen des Knochenmarkstromas kommen. Eine optimale Knochenmarkdiagnostik erfordert, neben Spezialfärbungen, zusätzlich oftmals immunhistochemische Untersuchungen und manchmal molekularpathologische Analysen. Mehr als bei anderen Organbiopsien ist die Kenntnis klinischer Befunde, insbesondere vorangegangener Therapien, relevant, um eine korrekte Diagnose zu stellen. In diesem Beitrag sind neben dem normalen Knochenmark die häufigsten reaktiven Veränderungen dargestell

Human gene-engineered calreticulin mutant stem cells recapitulate MPN hallmarks and identify targetable vulnerabilities

Calreticulin (CALR) mutations present the main oncogenic drivers in JAK2 wildtype (WT) myeloproliferative neoplasms (MPN), including essential thrombocythemia and myelofibrosis, where mutant (MUT) CALR is increasingly recognized as a suitable mutation-specific drug target. However, our current understanding of its mechanism-of-action is derived from mouse models or immortalized cell lines, where cross-species differences, ectopic over-expression and lack of disease penetrance are hampering translational research. Here, we describe the first human gene-engineered model of CALR MUT MPN using a CRISPR/Cas9 and adeno-associated viral vector-mediated knock-in strategy in primary human hematopoietic stem and progenitor cells (HSPCs) to establish a reproducible and trackable phenotype in vitro and in xenografted mice. Our humanized model recapitulates many disease hallmarks: thrombopoietin-independent megakaryopoiesis, myeloid-lineage skewing, splenomegaly, bone marrow fibrosis, and expansion of megakaryocyte-primed CD41+ progenitors. Strikingly, introduction of CALR mutations enforced early reprogramming of human HSPCs and the induction of an endoplasmic reticulum stress response. The observed compensatory upregulation of chaperones revealed novel mutation-specific vulnerabilities with preferential sensitivity of CALR mutant cells to inhibition of the BiP chaperone and the proteasome. Overall, our humanized model improves purely murine models and provides a readily usable basis for testing of novel therapeutic strategies in a human setting.Johannes Foßelteder, Gabriel Pabst, Tommaso Sconocchia, Angelika Schlacher, Lisa Auinger, Karl Kashofer, Christine Beham-Schmid, Slave Trajanoski, Claudia Waskow, Wolfgang Schöll, Heinz Sill, Armin Zebisch, Albert Wölfler, Daniel Thomas, and Andreas Reinisc

Epigenetic regulation of CD44 in Hodgkin and non-Hodgkin lymphoma

<p>Abstract</p> <p>Background</p> <p>Epigenetic inactivation of tumor suppressor genes (TSG) by promoter CpG island hypermethylation is a hallmark of cancer. To assay its extent in human lymphoma, methylation of 24 TSG was analyzed in lymphoma-derived cell lines as well as in patient samples.</p> <p>Methods</p> <p>We screened for TSG methylation using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) in 40 lymphoma-derived cell lines representing anaplastic large cell lymphoma, Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), Hodgkin lymphoma and mantle cell lymphoma (MCL) as well as in 50 primary lymphoma samples. The methylation status of differentially methylated <it>CD44 </it>was verified by methylation-specific PCR and bisulfite sequencing. Gene expression of <it>CD44 </it>and its reactivation by DNA demethylation was determined by quantitative real-time PCR and on the protein level by flow cytometry. Induction of apoptosis by anti-CD44 antibody was analyzed by annexin-V/PI staining and flow cytometry.</p> <p>Results</p> <p>On average 8 ± 2.8 of 24 TSG were methylated per lymphoma cell line and 2.4 ± 2 of 24 TSG in primary lymphomas, whereas 0/24 TSG were methylated in tonsils and blood mononuclear cells from healthy donors. Notably, we identified that <it>CD44 </it>was hypermethylated and transcriptionally silenced in all BL and most FL and DLBCL cell lines, but was usually unmethylated and expressed in MCL cell lines. Concordant results were obtained from primary lymphoma material: <it>CD44 </it>was not methylated in MCL patients (0/11) whereas <it>CD44 </it>was frequently hypermethylated in BL patients (18/29). In cell lines with <it>CD44 </it>hypermethylation, expression was re-inducible at mRNA and protein levels by treatment with the DNA demethylating agent 5-Aza-2'-deoxycytidine, confirming epigenetic regulation of <it>CD44</it>. CD44 ligation assays with a monoclonal anti-CD44 antibody showed that CD44 can mediate apoptosis in CD44⁺lymphoma cells. <it>CD44 </it>hypermethylated, CD44^-lymphoma cell lines were consistently resistant towards anti-CD44 induced apoptosis.</p> <p>Conclusion</p> <p>Our data show that <it>CD44 </it>is epigenetically regulated in lymphoma and undergoes <it>de novo </it>methylation in distinct lymphoma subtypes like BL. Thus <it>CD44 </it>may be a promising new epigenetic marker for diagnosis and a potential therapeutic target for the treatment of specific lymphoma subtypes.</p

Keratoacanthoma: a clinically distinct variant of well differentiated squamous cell carcinoma

Keratoacanthomas are distinct skin lesions that occur most often as solitary tumors in sun-exposed areas in elderly, fair-skinned patients. Clinically, these tumors are characterized by a rapid onset and regression within months. Keratoacanthomas display distinct histological features including a keratin-filled crater lined by a proliferating squamous epithelium. Cytologically, there may be overlap with classical well differentiated squamous cell carcinoma. Rarely, otherwise typical keratoacanthomas show intravascular and perineural invasion and lymph node metastases. Keratoacanthomas should, therefore, be considered to be a clinically distinct variant of well differentiated squamous cell carcinoma capable of spontaneous regression. This view is supported by their common etiology, occasional concurrent occurrence, and a multitude of studies revealing no substantial differences between these two lesions. Regression is immunologically mediated and activated by a variety of molecular mechanisms. Considering the common nature of keratoacanthomas and well differentiated squamous cell carcinomas, and the lack of any features predicting prognosis, surgical excision of keratoacanthoma is advisable

Chlamydia psittaci infection in nongastrointestinal extranodal MALT lymphomas and their precursor lesions

Extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT) are associated with various infectious pathogens. We analyzed the presence of Chlamydia psittaci, Chlamydia pneumoniae, and Chlamydia trachomatis DNA in 47 nongastrointestinal and 14 gastrointestinal MALT lymphomas, 37 nonmalignant control samples, and 27 autoimmune precursor lesions by polymerase chain reaction amplification and direct sequencing. In 47 nongastrointestinal MALT lymphomas, 13 (28%) were positive for C psittaci DNA compared with 4 (11%) of 37 nonmalignant control samples (P = .09). C psittaci was detected at variable frequencies in MALT lymphomas of different sites: lung, 100% (5/5; P .05); salivary gland, 13% (2/15; P > .05); ocular adnexa, 15% (2/13); and skin, 25% (1/4). Of 27 autoimmune precursor lesions (11 Hashimoto thyroiditis and 16 Sjögren syndrome), 11 (41%) contained C psittaci DNA. Only 1 (7%) of 14 gastrointestinal MALT lymphomas was positive for C psittaci. All specimens were negative for C trachomatis and C pneumoniae. Besides ocular adnexal lymphomas, C psittaci infection is associated with nongastrointestinal MALT lymphomas and autoimmune precursor lesions, suggesting possible involvement of C psittaci-induced antigenic-driven MALT lymphomagenesis

Response to Harrison et al. ‘Clinically relevant differences between BCSH and WHO diagnostic criteria for ET

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