MR imaging of therapy-induced changes of bone marrow

MR imaging of bone marrow infiltration by hematologic malignancies provides non-invasive assays of bone marrow cellularity and vascularity to supplement the information provided by bone marrow biopsies. This article will review the MR imaging findings of bone marrow infiltration by hematologic malignancies with special focus on treatment effects. MR imaging findings of the bone marrow after radiation therapy and chemotherapy will be described. In addition, changes in bone marrow microcirculation and metabolism after anti-angiogenesis treatment will be reviewed. Finally, new specific imaging techniques for the depiction of regulatory events that control blood vessel growth and cell proliferation will be discussed. Future developments are directed to yield comprehensive information about bone marrow structure, function and microenvironment

Pitfalls in TCR gene clonality testing: teaching cases

Clonality testing in T-lymphoproliferations has technically become relatively easy to perform in routine laboratories using standardized multiplex polymerase chain reaction protocols for T-cell receptor (TCR) gene analysis as developed by the BIOMED-2 Concerted Action BMH4-CT98-3936. Expertise with clonality diagnostics and knowledge about the biology of TCR gene recombination are essential for correct interpretation of TCR clonality data. Several immunobiological and technical pitfalls that should be taken into account to avoid misinterpretation of data are addressed in this report. Furthermore, we discuss the need to integrate the molecular data with those from immunohistology, and preferably also flow cytometric immunophenotyping, for appropriate interpretation. Such an interactive, multidisciplinary diagnostic model guarantees integration of available data to reach the most reliable diagnosis

Repolarization of tumor infiltrating macrophages and increased survival in mouse primary CNS lymphomas after XPO1 and BTK inhibition

Altres ajuts: This work was supported by research funding from the Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias cofinanced by the European Regional Development Fund (ERDF); Fundación Asociación Española Contra el Cáncer (M.C. and P.A.) and Gilead Fellowships (GLD16/00144, GLD18/00047, F.B). M.C. holds a contract from Ministerio de Ciencia, Innovación y Universidades. S.B. is the recipient of a postdoctoral fellowship from Fundación Alfonso Martin Escudero.Patients diagnosed with primary central nervous system lymphoma (PCNSL) often face dismal outcomes due to the limited availability of therapeutic options. PCNSL cells frequently have deregulated B-cell receptor (BCR) signaling, but clinical responses to its inhibition using ibrutinib have been brief. In this regard, blocking nuclear export by using selinexor, which covalently binds to XPO1, can also inhibit BCR signaling. Selinexor crosses the blood-brain barrier and was recently shown to have clinical activity in a patient with refractory diffuse large B-cell lymphoma in the CNS. We studied selinexor alone or in combination with ibrutinib in pre-clinical mouse models of PCNSL. Orthotopic xenograft models were established by injecting lymphoma cells into the brain parenchyma of athymic mice. Tumor growth was monitored by bioluminescence. Malignant cells and macrophages were studied by immunohistochemistry and flow cytometry. Selinexor blocked tumor growth and prolonged survival in a bioluminescent mouse model, while its combination with ibrutinib further increased survival. CNS lymphoma in mice was infiltrated by tumor-promoting M2-like macrophages expressing PD-1 and SIRPα. Interestingly, treatment with selinexor and ibrutinib favored an anti-tumoral immune response by shifting polarization toward inflammatory M1-like and diminishing PD-1 and SIRPα expression in the remaining tumor-promoting M2-like macrophages. These data highlight the pathogenic role of the innate immune microenvironment in PCNSL and provide pre-clinical evidence for the development of selinexor and ibrutinib as a new promising therapeutic option with cytotoxic and immunomodulatory potential. The online version of this article (10.1007/s11060-020-03580-y) contains supplementary material, which is available to authorized users

ROLE OF EZH2 METHYLTRANSFERASE ACTIVITY IN THE MAINTENANCE OF MYC-DRIVEN B CELL LYMPHOMAS

The Polycomb group protein Ezh2 catalyzes the Histone H3 lysine-27 trimethylation (H3K27me3) within the Polycomb Repressive Complex 2 (PRC2). PRC2 exerts a critical control over the expression of a large set of target genes controlling important biological functions, including cell proliferation, differentiation and stem cell self-renewal. Aberrant Ezh2 function is commonly observed in several cancer types and is due to deregulated enzymatic activity and/or expression of the Polycomb protein. Studies in preclinical models have started to reveal the importance of Ezh2 in B cell lymphomagenesis. In contrast, little is known about the effects of Ezh2 deregulated function/constitutive expression in B cell tumor maintenance and progression. The present study addresses this issue taking advantage of a MYC-driven mouse lymphoma model, featuring high Ezh2 expression as a result of malignant B cell transformation. Conditional, genetic inactivation of Ezh2 methyltransferase activity in aggressive primary Burkitt-like mouse B cell lymphomas led to the identification of two classes of tumors, differentially responding to the loss of Polycomb function. In type-1 lymphomas, Ezh2 inactivation impaired clonal tumor growth starting from single lymphoma cells. Instead, type-2 lymphomas were largely resistant to the loss of Ezh2 catalytic function, giving rise to a substantial number of Ezh2 mutant clones. Transcriptome analyses allowed the identification of a molecular signature discriminating type-1 from type-2 lymphomas, including genes controlling cell cycle progression, DNA replication and cell survival, which were more expressed in type-2 tumors. These results correlated with a more aggressive behavior of type-2 lymphomas when transplantated into immunoproficient hosts. The growth of rare Ezh2 mutant subclones, established from type-1 lymphomas, was impaired by the treatment with an Ezh1/2 small molecule inhibitor, identifying the Ezh2 paralog, Ezh1, as a determinant of resistance of tumor cells to Ezh2 inactivation. Ezh2 inhibition led to genome wide loss of H3K27me3, which was comparable between lymphoma types. However, while the loss of H3K27me3 at target genes in type-1 lymphomas failed to alter their expression, in type-2 lymphomas Ezh2 targets were in most cases deregulated following the loss of the histone mark. Based on these results, we propose that Ezh2 mutant subclones from type-1 lymphomas select an H3K27me3-independent mechanism to ensure correct regulation of Ezh2 target genes, which is needed for tumor growth. We also find that residual H3K27me3 is deposited at the promoter of new genes by a non-canonical PRC2/Ezh1, in Ezh2 mutant subclones from type-1 lymphomas. This activity alters the expression of target genes contributing to tumor growth. We finally report the isolation of clonal variants from type-1 lymphomas that acquire secondary resistance to pharmacological Ezh1/2 inhibition. The latter tumors (together with type-2 lymphomas) will be instrumental to unravel the genetic bases of resistance of MYC-driven lymphomas to PRC2 inhibition. Anti-Ezh2 inhibitors are currently being tested in phase-1 and -2 clinical trials for the treatment of both solid and blood cancers including B cell lymphomas. Our studies highlight the importance of understanding in more detail the mechanisms of action of Ezh2/PRC2 in tumors, in order to identify those that may benefit from anti-Ezh2 therapies. Our results also provide evidence for mechanisms of lymphoma resistance to Ezh2 inhibition and suggest strategies to circumvent such resistance

miR-155 gene: A typical multifunctional microRNA

In the last years small RNA molecules. i.e. microRNA (miRNA) encoded by miR genes, have been found to play a crucial role in regulating gene expression of a considerable part of plant's and animal's genome. Here, we report the essential information on biogenesis of miRNAs and recent evidence on their important role in human diseases. Emphasis has been given to miR-155, since this molecule represents a typical multifunctional miRNA. Recent data indicate that miR-155 has distinct expression profiles and plays a crucial role in various physiological and pathological processes such as haematopoietic lineage differentiation, immunity, inflammation, cancer, and cardiovascular diseases. Moreover, miR-155 has been found to be implicated in viral infections, particularly in those caused by DNA viruses. The available experimental evidence indicating that miR-155 is over expressed in a variety of malignant tumors allows us to include this miRNA in the list of genes of paramount importance in cancer diagnosis and prognosis. Exogenous molecular control in vivo of miR-155 expression could open up new ways to restrain malignant growth and viral infections, or to attenuate the progression of cardiovascular diseases. (C) 2009 Elsevier B.V. All rights reserved

The Mechanisms of Telomere and Telomerase Regulation in Hematologic Malignancies

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The Mechanisms of Telomere and Telomerase Regulation in Hematologic Malignancies

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Genetic Basis of Familial Lymphoma Predisposition

Lymphomas are classified into Hodgkin and non-Hodgkin lymphomas (HL and NHL), and they are further categorized into tens of different subtypes. This thesis has focused on two rare lymphoma subtypes: nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) and primary mediastinal large B-cell lymphoma (PMBCL). Although the majority of lymphomas are sporadic, a familial component has been observed in both HL and NHL. The aim of this thesis was to study the genetic background of familial NLPHL and PMBCL predisposition. HL is classified into NLPHL and classical Hodgkin lymphoma (cHL). Germline mutations of the KLHDC8B gene have been observed in some families with cHL. In this study, the KLHDC8B gene was analyzed in four families with NLPHL, but mutations were not detected. The results suggest that germline mutations of KLHDC8B do not underlie familial NLPHL susceptibility. To clarify the genetic basis of NLPHL predisposition, a Finnish family with NLPHL susceptibility was studied with new genome-wide methods, SNP microarray and exome sequencing. Data from these two efforts were integrated, and a germline deletion of two nucleotides (c.2437-2438delAG) was observed in the NPAT gene. Subsequently, NPAT was screened in a number of familial and sporadic HL cases, and an in-frame deletion of one serine residue was found to be more frequent in the cases versus healthy controls (odds ratio 4.11, p = 0.018). Thus, NPAT was identified as a candidate gene for NLPHL predisposition. The familial risk in NLPHL was studied by using the Finnish Cancer Registry (FCR) and the Finnish Population Registries. Altogether 693 patients with NLPHL were identified, and a family member cohort comprising of the first-degree relatives of 692 patients was collected. Cancer data for the relatives was derived from the FCR. We calculated the standardized incidence ratios (SIRs) for all cancers, NHL, cHL and NLPHL in the family member cohort. In addition, the primary tumor samples from 20 first-degree relatives with HL diagnosis were histopathologically reviewed. In the family member cohort, the SIR for NLPHL was 19. Thus, a high familial risk in NLPHL was observed, suggesting that familial factors contribute to NLPHL susceptibility. An increased relative risk for NHL and cHL was also observed. We studied a family of three siblings with PMBCL and a cousin affected by diffuse large B-cell lymphoma (DLBCL). Re-examination of tumor samples revealed that all four tumors resembled each other histopathologically, proposing a common background. Genome-wide SNP array, linkage analysis and exome sequencing were performed to identify the genetic factor underlying PMBCL/DLBCL in this family. A missense change c.5533C>A (His1845Asn) was detected in the MLL gene and was the only non-database variation residing in linked regions and segregating in lymphoma affected family members. To our knowledge, this is the first description of familial clustering of PMBCL. Our findings suggest that sometimes PMBCL may arise in the context of familial predisposition, and MLL was identified as a candidate gene for PMBCL susceptibility. However, our observations are preliminary, and need to be confirmed in future studies.Lymfoomat ovat imukudoksen kasvaimia, jotka luokitellaan Hodgkinin ja non-Hodgkin lymfoomiin (HL ja NHL), sekä edelleen useisiin eri alatyyppeihin. Suurin osa lymfoomista on sattumalta syntyneitä, mutta pienen osan on havaittu esiintyvän perheittäin. Perheittäin esiintyvien lymfoomien etiologia ja geenitausta on kuitenkin huonosti tunnettu. Väitöskirjatutkimuksessa selvitettiin kahden harvinaisen lymfoomatyypin, nodulaarisen lymfosyyttivaltaisen Hodgkinin lymfooman (NLPHL) sekä primaarin mediastinaalisen suurisoluisen B-solulymfooman (PMBCL), periytyvän muodon geenitaustaa. HL:n päätyypit ovat klassinen HL sekä NLPHL. Klassisen HL:n periytyvän muodon taustalta on kuvattu geenivirheitä KLHDC8B-geenissä. Tutkimuksessa selvitetiin, löytyykö myös NLPHL-suvuissa geenivirheitä kyseisestä geenistä. KLHDC8B-geeni analysoitiin neljästä tunnetusta NLPHL-suvusta. Geenivirheitä ei todettu, mikä viittaa siihen, että KLHDC8B-geenin geenivirheet eivät ole perheittän esiintyvän NLPHL:n syy. Tutkimuksen toisessa osassa tavoitteena oli tunnistaa NLPHL:lle altistava geenivirhe suomalaisessa NLPHL-suvussa. Menetelminä käytettiin genominlaajuista SNP-mikrosirua sekä eksomisekvenointia. Menetelmien tuottamaa tietoa yhdistämällä tunnistetiin suomalaisessa NLPHL-suvussa NPAT-geenin geenivirhe. Kyseessä oli kahden emäksen deleetio c.2437-2438delAG. Jatkoselvityksissä tutkittiin suurta määrää suomalaisia ja englantilaisia HL-potilaita, ja tunnistettiin toinen NPAT-geenin muutos, jota esiintyi merkittävästi enemmän HL-potilailla kuin terveillä henkilöillä. Näin ollen tutkimuksessa tunnistettiin mahdollinen perinnöllisen NLPHL:n alttiusgeeni. Väitöstyön kolmannessa osassa arvioitiin Suomen syöpärekisteristä kerätyn tiedon avulla erityyppisten lymfoomien riskiä NLPHL-potilaiden ensimmäisen asteen sukulaisilla. Syöpärekisteristä löydettiin 693 NLPHL-potilasta, ja heidän ensimmäisen asteen sukulaisensa selvitettiin. Sukulaisten syöpätiedot kerättiin syöpärekisteristä, ja niiden perusteella tarkasteltiin eri lymfoomien esiintyvyyttä sukulaisjoukossa. Lisäksi HL:an sairastuneiden sukulaisten kasvainnäytteitä tutkittiin uudelleen hematopatologin toimesta. Tutkimuksessa havaittiin, että lähisukulaisilla oli noin 19-kertainen sairastumisriski NLPHL:an muuhun väestöön verrattuna. Tutkimustulos viittaa siihen, että familiaaliset tekijät, kuten ympäristö- tai geneettiset tekijät, voivat vaikuttaa NLPHL:n riskiin. Myös klassisen HL:n sekä NHL:n riski oli sukulaisjoukossa suurempi kuin muulla väestöllä. Väitöskirjan neljännessä osassa tunnistettiin suomalainen PMBCL-suku, joka on tiettävästi ensimmäinen raportoitu tapaus, jossa PMBCL esiintyy perheittäin. Sukua tutkittiin genominlaajuisen SNP-mikrosirun ja eksomisekvensoinnin avulla. Suvussa tunnistettiin MLL-geenin variantti c.5533C>A (His1845Asn), jota ei löytynyt terveiltä henkilöiltä tai geneettisistä tietokannoista. Näin ollen MLL-geenin muutokset saattavat liittyä perinnölliseen PMBCL-alttiuteen. Tutkimustulokset mahdollistavat uusien PMBCL-perheiden tunnistamisen, mikä edesauttaisi tämän uuden tautikokonaisuuden kliinistä ja geneettistä karakterisointia