Critical influences on the pathogenesis of follicular lymphoma

Abstract The development of follicular lymphoma (FL) from a founder B cell with an upregulation of B-cell lymphoma 2 (BCL2), via the t(14;18) translocation, to a proliferating clone, poised to undergo further transformation to an aggressive lymphoma, illustrates the opportunistic Darwinian process of tumorigenesis. Protection against apoptosis allows an innocent cell to persist and divide, with dangerous accumulation of further mutational changes, commonly involving inactivation of chromatin-modifying genes. But this is not all. FL cells reflect normal B cells in relying on expression of surface immunoglobulin. In doing so, they add another supportive mechanism by exploiting the natural process of somatic hypermutation of the IGV genes. Positive selection of motifs for addition of glycan into the antigen-binding sites of virtually all cases, and the placement of unusual mannoses in those sites, reveals a posttranslational strategy to engage the microenvironment. A bridge between mannosylated surface immunoglobulin of FL cells and macrophage-expressed dendritic cell–specific ICAM-3–grabbing nonintegrin produces a persistent low-level signal that appears essential for life in the hostile germinal center. Early-stage FL therefore requires a triad of changes: protection from apoptosis, mutations in chromatin modifiers, and an ability to interact with lectin-expressing macrophages. These changes are common and persistent. Genetic/epigenetic analysis is providing important data but investigation of the posttranslational landscape is the next challenge. We have one glimpse of its operation via the influence of added glycan on the B-cell receptor of FL. The consequential interaction with environmental lectins illustrates how posttranslational modifications can be exploited by tumor cells, and could lead to new approaches to therapy.

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Concurrent Chromosomal Alterations at 3q27, 8q24 and 18q21 in An Atypical Form of Burkitt’s Lymphoma

Blood ◽

10.1182/blood.v112.11.5268.5268 ◽

2008 ◽

Vol 112 (11) ◽

pp. 5268-5268

Author(s):

Majdi SM Hamarshi ◽

Maha abu Kishk ◽

Mahmoud Mahafzah ◽

Jami Walloch

Keyword(s):

Bone Marrow ◽

Follicular Lymphoma ◽

B Cell ◽

Cell Lymphoma ◽

B Cell Lymphoma ◽

Burkitt’S Lymphoma ◽

Burkitt's Lymphoma ◽

High Grade ◽

Surface Immunoglobulin ◽

Cell Neoplasm

Abstract Introduction: Chromosomal translocations are common in non-Hodgkin’s lymphomas (NHL), most frequently involving the genes bcl-2 in the t(14;18) of follicular lymphoma (FL), c-myc in the t(8;14) of Burkitt’s lymphoma (BL) and bcl-6 in the t(3;14) of follicular or diffuse large B-cell (DLBC) lymphoma. We report the clinical features, pathology and genetic findings in an exceedingly rare case of Burkitt’s lymphoma that showed concurrent involvement of these three chromosomal loci. Case Report: This is a 65 year old Caucasian female who presented with a rapidly growing right supraclavicular lymph node over a few weeks. FNA biopsy showed typical morphology of Burkitt’s lymphoma. Similar morphologic features were found on the bone marrow biopsy. There was widespread disease with no CNS involvement. Flow cytometry from peripheral blood and immunohistochemistry on the cellblock showed B-cell phenotype positive for CD 10, CD19, CD20 (negative CD20 by immunohistochemistry), HLA-DR, cytoplasmic CD79a, and negative for CD34 and TdT. The interesting finding was the lack expression of surface or cytoplasmic immunoglobulin and expression of weak Bcl-6. Almost 90–95% expressed Ki67. The cytogenetic analysis reportedly demonstrated a complex karyotype t(3;8;14), and t(14;18) involving c-myc (8q24), bcl-2 (18q21), and bcl-6 (3q27). After 7 cycles of hyper CVAD-R she had bone marrow biopsy which showed residual disease. She also had a biopsy confirmed relapse as left arm nodule and left leg nodular infiltrate at 8 and 12 months form the diagnosis, respectively. Discussion: This is a complex case of high grade B-cell lymphoma with morphology suggestive of Burkitt’s lymphoma. However the classification was challenging by the lack of surface immunoglobulin expression that might be expected in mature B-cell neoplasm “DLBCL, FL”, and the lack of TdT and CD34 that might be expected in precursor B-cell neoplasm “BL”. The diagnosis was highly dependent on the cytogenetic findings, which was significant for the presence of t(8;14) albeit in a three way translocation t(3;8;14), and t(14;18) involving c-myc (8q24), bcl-2 (18q21), and bcl-6 (3q27). The lymphoma was therefore described as “Burkitt’s transformation”. This is a rare translocation pattern, but has been described in follicular lymphoma, grade 3; diffuse large cell lymphoma; and Burkitt’s lymphoma. Conclusion: BL might lack surface immunoglobulin expression making the diagnosis of high grade B-cell lymphoma challenging if based on the morphology and immunophenotyping alone. The cytogentetic findings better delineate sub-types of lymphoma. Molecular evidence of multiple oncogene deregulations, especially when involving the c-myc gene, appears to be associated with a dire clinical outcome.

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Massive Parallel Sequencing of Full-Length B-Cell Receptor Sequences Reveals HLA-Dependent Shaping of the B-Cell Immune Repertoire

Blood ◽

10.1182/blood.v124.21.4143.4143 ◽

2014 ◽

Vol 124 (21) ◽

pp. 4143-4143

Author(s):

Marvyn T. Koning ◽

Sander A.J. van der Zeeuw ◽

Marcelo Navarrete ◽

Cornelis A.M. van Bergen ◽

Valeri Nteleah ◽

...

Keyword(s):

T Cell ◽

Follicular Lymphoma ◽

B Cell ◽

B Cell Lymphoma ◽

Cell Receptor ◽

B Cell Receptor ◽

Full Length ◽

Lymphoma Cells ◽

Hla Alleles ◽

Hla Binding

Abstract Peptides of the B-cell receptor (BCR) may be presented in HLA molecules and therefore be recognized as epitopes by T cells. Bioinformatic evidence indicates that follicular lymphoma cells are selected against expression of a clonal BCR with a high cumulative predicted binding of BCR-derived peptides to the respective patient's HLA complex (Strothmeyer, Blood 2010). This observation suggests T-cell-mediated immunosurveillance against outgrowth of follicular lymphoma cells according to BCR HLA binding strength. Here, we investigate whether this phenomenon pertains to peripheral B cells in 6 healthy donors: 2 donors homozygous for HLA A01*01 / B08*01, 2 homozygous for HLA A02*01 / B7*02, and 2 donors heterozygous for these alleles. Unbiased representation of full-length V(D)J sequences was considered essential for correct data interpretation. PCR primers annealing to conserved motifs of BCR variable regions (e.g. BIOMED-2 protocol) fail to amplify a fraction of BCR, particularly those modified by somatic hypermutation. Therefore, we developed an improved anchored PCR strategy: cDNA was synthesized from poly(A)-RNA from peripheral blood with primers that anneal to specific Ig constant regions. In the same reaction, the 3' cDNA end is extended by switching to an oligonucleotide template containing an anchor sequence (SMART technology; Clontech). Anchor-tagged cDNA was amplified with a primer annealing to the anchor in combination with a nested constant region-specific reverse primer. Dumbbell adapters were added to the termini of 250 ng of purified PCR products. Circular consensus sequencing of single molecules was performed on the PacBio platform (Pacific Biosciences). Using one SMRT PacBio cell per amplicon, separate sequence libraries were created for μ, γ, κ, and λ BCR transcripts. Sequences covered by at least five reads were selected with SMRT Portal software to obtain >95% of sequences without sequence errors as demonstrated on multiple B-cell lines. Selected sequences were analysed by HighV-QUEST software (Alamyar, Immunome Research 2012). After exclusion of non-BCR sequences and duplicate BCR transcripts, a median of 5318 (range: 670-8752) individual BCR sequences was obtained per library. Binding affinity of nonamers in in-silico-translated BCR were calculated for the 4 HLA alleles by the NetMHC 3.4 algorithm. The fractions of BCR lacking any weak HLA binding peptide (NetMHC IC50 <500nM) within a library were compared between donors positive or negative for any HLA molecule. μ VDJ transcripts without HLA binding peptides were significantly more frequent for all HLA alleles in donors that actually express that particular allele (Table). With the exception of HLA A01*01, similar results were observed for γ transcripts. While the fraction of κ VJ transcripts without an HLA binder was overall higher in HLA A01*01 and B08*01, HLA-positive individuals had higher proportions of non-HLA binding sequences. λ transcripts were less likely to contain HLA binders with respect to HLA B07*02 and B08*01 but not to the HLA A alleles. Analogous analyses were performed for CDR3 regions as annotated by HighV-QUEST plus six amino acids on either flank. In 10 of 16 analyses, CDR3 sequences were less likely to contain an HLA binder in HLA-positive individuals; in three analyses an opposite effect was seen (Table). These results indicate that the peripheral BCR repertoire is shaped by HLA alleles in healthy individuals, most likely by T-cell mediated recognition of BCR peptides. Ongoing studies expand this fundamental finding with respect to the IC50 threshold, the number of nonamers, and additional HLA alleles. Our results warrant investigation of the potential role of HLA-dependent shaping of the BCR repertoire for the immune defense and the development of autoimmune disease and B-cell lymphoma. Table 1V(D)J without HLA binding peptideCDR3 without HLA binding peptideHLADonorμγκλμγΚλ A01*01Positive21%41%61%37%87%90%98%70%Negative16%42%59%38%92%92%96%65%P<0.001n.s.<0.01n.s.<0.001n.s.<0.01<0.001 A02*01Positive6%4%3%32%77%77%77%70%Negative4%1%2%32%75%69%78%78%P<0.001<0.001<0.01n.s.<0.01<0.001n.s.<0.001 B07*02Positive31%13%3%13%79%73%91%96%Negative27%8%2%6%79%69%90%98%P<0.001<0.01<0.01<0.001n.s.<0.05<0.05<0.001 B08*01Positive30%35%64%64%89%87%92%96%Negative14%28%62%61%88%82%90%93%P<0.001<0.001<0.01<0.001<0.01<0.001<0.01<0.001 Disclosures No relevant conflicts of interest to declare.

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Gastric MALT lymphoma B cells express polyreactive, somatically mutated immunoglobulins

Blood ◽

10.1182/blood-2009-06-228015 ◽

2010 ◽

Vol 115 (3) ◽

pp. 581-591 ◽

Cited By ~ 75

Author(s):

Vanessa J. Craig ◽

Isabelle Arnold ◽

Christiane Gerke ◽

Minh Q. Huynh ◽

Thomas Wündisch ◽

...

Keyword(s):

B Cell ◽

Malt Lymphoma ◽

Somatic Hypermutation ◽

Human Tumor ◽

B Cell Lymphoma ◽

Cell Receptor ◽

Gastric Malt Lymphoma ◽

Dependent Manner ◽

Antigen Specificity ◽

Show Evidence

Abstract Gastric B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) arises against a background of chronic inflammation caused by persistent Helicobacter pylori infection. The clinical and histopathologic features of the human tumor can be reproduced by Helicobacter infection of BALB/c mice. In this study, we have analyzed the antibody sequences and antigen specificity of a panel of murine and human MALT lymphoma–derived antibodies. We find that a majority of tumors in patients as well as experimentally infected mice are monoclonal. The tumor immunoglobulin heavy chain genes have undergone somatic hypermutation, and approximately half of all tumors show evidence of intraclonal variation and positive and/or negative selective pressure. Recombinantly expressed MALT lymphoma antibodies bind with intermediate affinity to various unrelated self- and foreign antigens, including Helicobacter sonicate, immunoglobulin G (IgG), DNA, and stomach extract; antigen binding is blocked in a dose-dependent manner in competitive enzyme-linked immunosorbent assays. A strong bias toward the use of VH gene segments previously linked to autoantibodies and/or polyreactive antibodies in B-cell malignancies or autoimmune pathologies supports the experimental finding of polyreactivity. Our results suggest that MALT lymphoma development may be facilitated by an array of local self- and foreign antigens, providing direct antigenic stimulation of the tumor cells via their B-cell receptor.

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miR-150 downregulation contributes to the high-grade transformation of follicular lymphoma by upregulating FOXP1 levels

Blood ◽

10.1182/blood-2018-06-855502 ◽

2018 ◽

Vol 132 (22) ◽

pp. 2389-2400 ◽

Cited By ~ 16

Author(s):

Katerina Musilova ◽

Jan Devan ◽

Katerina Cerna ◽

Vaclav Seda ◽

Gabriela Pavlasova ◽

...

Keyword(s):

B Cells ◽

Follicular Lymphoma ◽

B Cell ◽

Molecular Mechanisms ◽

B Cell Lymphoma ◽

Cell Receptor ◽

Upstream Region ◽

High Grade ◽

Histological Transformation ◽

High Grade Transformation

Follicular lymphoma (FL) is a common indolent B-cell malignancy with a variable clinical course. An unfavorable event in its course is histological transformation to a high-grade lymphoma, typically diffuse large B-cell lymphoma. Recent studies show that genetic aberrations of MYC or its overexpression are associated with FL transformation (tFL). However, the precise molecular mechanisms underlying tFL are unclear. Here we performed the first profiling of expression of microRNAs (miRNAs) in paired samples of FL and tFL and identified 5 miRNAs as being differentially expressed. We focused on one of these miRNAs, namely miR-150, which was uniformly downmodulated in all examined tFLs (∼3.5-fold), and observed that high levels of MYC are responsible for repressing miR-150 in tFL by binding in its upstream region. This MYC-mediated repression of miR-150 in B cells is not dependent on LIN28A/B proteins, which influence the maturation of miR-150 precursor (pri-miR-150) in myeloid cells. We also demonstrated that low miR-150 levels in tFL lead to upregulation of its target, namely FOXP1 protein, which is a known positive regulator of cell survival, as well as B-cell receptor and NF-κB signaling in malignant B cells. We revealed that low levels of miR-150 and high levels of its target, FOXP1, are associated with shorter overall survival in FL and suggest that miR-150 could serve as a good biomarker measurable in formalin-fixed paraffin-embedded tissue. Overall, our study demonstrates the role of the MYC/miR-150/FOXP1 axis in malignant B cells as a determinant of FL aggressiveness and its high-grade transformation.

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MiR-7e-5p downregulation promotes transformation of low-grade follicular lymphoma to aggressive lymphoma by modulating an immunosuppressive stroma through the upregulation of FasL in M1 macrophages

10.21203/rs.3.rs-38701/v3 ◽

2020 ◽

Author(s):

Xiaoli Lou ◽

Jianhong Fu ◽

Xin Zhao ◽

Xuemei Zhuansun ◽

Chao Rong ◽

...

Keyword(s):

Follicular Lymphoma ◽

B Cell ◽

Target Gene ◽

Fas Ligand ◽

B Cell Lymphoma ◽

Differentially Expressed ◽

Aggressive Lymphoma ◽

Low Grade ◽

M1 Macrophages ◽

M1 Macrophage

Abstract Background: In follicular lymphoma (FL), histologic transformation to high-grade FL and diffuse large B-cell lymphoma (DLBCL) is a critical adverse step in disease progression. Activation of the oncogene c-MYC and tumor microenvironment remodeling account for FL progression. A panel of microRNA (miRNA) was downregulated in transformed FL. Methods: Differentially expressed miRNAs were systematically analyzed compared in eleven lymph nodes tissue samples from patients at different stages of disease. Expression of miR-7e-5p was analyzed in 46 B-cell lymphomas, including 30 FLs and 16 DLBCLs. In FL cells, transcriptional regulation of the oncogene c-MYC on its target miR-7e-5p was revealed by Chromatin Immunoprecipitation (ChIP) assay. Exosome, carrying differentially expressed miR-7e-5p was isolated and visualized by transmission electron microscope and fluorescence tracing. The effect of miR-7e-5p on recipient macrophage was determined by target gene quantification, flow cytometry, and TUNEL method in a cocultured system with miR-7e-5p-mimics or inhibitor treatment. Expression of miR-7e-5p targets, macrophage proportions, and clinical parameters were included for correlation analysis. Results: We determined that downregulation of miR-7e-5p, driven by c-MYC overexpression, was associated with poorer prognosis in FL patients. The decreased expression of miR-7e-5p in lymphoma cells led to a reduced exosomal transfer to surrounding macrophages. As a result, the target gene of miR-7e-5p, Fas ligand (FasL), was upregulated and activated the caspase signaling, which led to the apoptosis of M1 macrophages in tumor stroma. Finally, in transformed FL tissues, overexpression of FasL and activation of caspase proteins was detected in tumor stromal macrophages. Downregulation of miR-7e-5p was associated with poorer clinical outcomes. Conclusion: Downregulation of exosomal miR-7e-5p induces stromal M1 macrophage apoptosis, which leads to immunosurveillance and transformation of FL.

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Aberrant Somatic Hypermutation of Follicular Lymphoma Transformed To Diffuse Large B-Cell Lymphoma.

Blood ◽

10.1182/blood.v108.11.2413.2413 ◽

2006 ◽

Vol 108 (11) ◽

pp. 2413-2413

Author(s):

Margareta Fruehwirth ◽

Alexander J.A. Deutsch ◽

Philipp B. Staber ◽

Ariane Aigelsreiter ◽

Werner Linkesch ◽

...

Keyword(s):

Follicular Lymphoma ◽

B Cell ◽

Somatic Hypermutation ◽

B Cell Lymphoma ◽

Initiation Site ◽

Sequence Variants ◽

Paired Samples ◽

Genome Wide ◽

Histological Transformation ◽

Large B Cell

Abstract Follicular Lymphoma (FL) accounts for approximately 20–30% of all malignant lymphomas and the frequency of histological transformation (HT) into diffuse large B-cell lymphomas (DLBCL) varies from 10% to 70%. Many genetic lesions have already been described in histological transformation, but a mechanism of genome-wide instability during histological transformation (HT) has not been reported. We have shown that the somatic hypermutation process (SHM) physiologically aimed at mutating the immunoglobulin variable gene (IgV) aberrantly targets multiple proto-oncogenes in >50% of DLCBL (Pasqualucci et al., Nature 412:341, 2001). Consequently, multiple mutations are introduced in the 5′ region of genes including known proto-oncogenes such as PIM-1, PAX-5, Rho/TTF and c-MYC. To further investigate whether aberrant somatic hypermutation (ASHM) also occurs in histological transformation of follicular lymphoma in DLBCL we studied the mutational profile of these genes in a total of 26 cases consisting of 10 paired samples of follicular lymphoma together with the corresponding DLBCL and 6 single cases of transformed DLBCL. Genomic DNA from histologically confirmed, macrodissected tissue obtained from formalin fixed and paraffin embedded tissue or cryoconserved samples was directly sequenced. Mutations in one or more genes were detected in 6 of 10 (60%) cases of pre-HT follicular lymphoma and in 13 of 16 (81.2%) post-HT cases. Two ore more genes were affected in 1 of 10 (10%) of FL and in 7 of 16 (43.7%) cases with DLBCL. Mutations in PIM-1 occurred in 3 of 10 (30%) cases of follicular lymphoma and in 9 of 16 (56.2%) in DLBCL. For PAX-5, the distribution of the mutated cases between FL and DLBCL was 2 of 10 (20%) and 7 of 16 (43.7%), for RhoH/TTF 2 of 10 (20%) and 3 of 16 (18.7%) and for c-MYC none of 10 (0%) FL and 2 of 16 (12.5%) DLBCL. A total of 38 single base pair substitutions were found in 19 cases, 10 sequence variants in 6 FL cases and 28 sequence variants in 13 DLBCL cases. The mutations were of somatic origin and share features of the IgV SHM process including bias for transition over transversion, elevated ratio of G+C over A+T substitutions and restriction to the first 1-2Kb from the promoter initiation site. The mean mutation frequency in mutated follicular lymphoma was with 0.024 ×10−2/bp 1.4 fold lower compared to 0.032 ×10−2/bp in the transformed DLBCLs. Further in PIM-1 and c-MYC some of the mutations were found to affect coding exons, leading to amino acid exchanges, thus potentially altering gene function. These data support a role of aberrant SHM in the histological transformation of FL to overt DLBCL.

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IGHV sequencing reveals acquired N-glycosylation sites as a clonal and stable event during follicular lymphoma evolution

Blood ◽

10.1182/blood.2019002279 ◽

2020 ◽

Vol 135 (11) ◽

pp. 834-844 ◽

Cited By ~ 4

Author(s):

Mariette Odabashian ◽

Emanuela Carlotti ◽

Shamzah Araf ◽

Jessica Okosun ◽

Filomena Spada ◽

...

Keyword(s):

Follicular Lymphoma ◽

B Cell ◽

Dna Sequences ◽

Somatic Hypermutation ◽

Variable Region ◽

Cell Receptor ◽

Tumor Evolution ◽

Growth And Survival ◽

Calcium Dependent ◽

Glycosylation Sites

Abstract Follicular lymphoma B cells undergo continuous somatic hypermutation (SHM) of their immunoglobulin variable region genes, generating a heterogeneous tumor population. SHM introduces DNA sequences encoding N-glycosylation sites asparagine-X-serine/threonine (N-gly sites) within the V-region that are rarely found in normal B-cell counterparts. Unique attached oligomannoses activate B-cell receptor signaling pathways after engagement with calcium-dependent lectins expressed by tissue macrophages. This novel interaction appears critical for tumor growth and survival. To elucidate the significance of N-gly site presence and loss during ongoing SHM, we tracked site behavior during tumor evolution and progression in a diverse group of patients through next-generation sequencing. A hierarchy of subclones was visualized through lineage trees based on SHM semblance between subclones and their discordance from the germline sequence. We observed conservation of N-gly sites in more than 96% of subclone populations within and across diagnostic, progression, and transformation events. Rare N-gly-negative subclones were lost or negligible from successive events, in contrast to N-gly-positive subclones, which could additionally migrate between anatomical sites. Ongoing SHM of the N-gly sites resulted in subclones with different amino acid compositions across disease events, yet the vast majority of resulting DNA sequences still encoded for an N-gly site. The selection and expansion of only N-gly-positive subclones is evidence of the tumor cells’ dependence on sites, despite the changing genomic complexity as the disease progresses. N-gly sites were gained in the earliest identified lymphoma cells, indicating they are an early and stable event of pathogenesis. Targeting the inferred mannose-lectin interaction holds therapeutic promise.

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Self-antigen recognition by follicular lymphoma B-cell receptors

Blood ◽

10.1182/blood-2012-05-427534 ◽

2012 ◽

Vol 120 (20) ◽

pp. 4182-4190 ◽

Cited By ~ 62

Author(s):

Kacey L. Sachen ◽

Michael J. Strohman ◽

Jonathan Singletary ◽

Ash A. Alizadeh ◽

Nicole H. Kattah ◽

...

Keyword(s):

Follicular Lymphoma ◽

B Cell ◽

Tumor Cells ◽

Somatic Hypermutation ◽

Cell Receptor ◽

Antigen Recognition ◽

Variable Regions ◽

B Cell Malignancy ◽

Unique Cell ◽

Self Antigen

Abstract Follicular lymphoma is a monoclonal B-cell malignancy with each patient's tumor expressing a unique cell surface immunoglobulin (Ig), or B-cell receptor (BCR), that can potentially recognize antigens and/or transduce signals into the tumor cell. Here we evaluated the reactivity of tumor derived Igs for human tissue antigens. Self-reactivity was observed in 26% of tumor Igs (25 of 98). For one follicular lymphoma patient, the recognized self-antigen was identified as myoferlin. This patient's tumor cells bound recombinant myoferlin in proportion to their level of BCR expression, and the binding to myoferlin was preserved despite ongoing somatic hypermutation of Ig variable regions. Furthermore, BCR-mediated signaling was induced after culture of tumor cells with myoferlin. These results suggest that antigen stimulation may provide survival signals to tumor cells and that there is a selective pressure to preserve antigen recognition as the tumor evolves.

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MiR-7e-5p downregulation promotes transformation of low-grade follicular lymphoma to aggressive lymphoma by modulating an immunosuppressive stroma through the upregulation of FasL in M1 macrophages

10.21203/rs.3.rs-38701/v2 ◽

2020 ◽

Author(s):

Xiaoli Lou ◽

Jianhong Fu ◽

Xin Zhao ◽

Xuemei Zhuansun ◽

Chao Rong ◽

...

Keyword(s):

Follicular Lymphoma ◽

B Cell ◽

Target Gene ◽

Fas Ligand ◽

B Cell Lymphoma ◽

Differentially Expressed ◽

Aggressive Lymphoma ◽

Low Grade ◽

M1 Macrophages ◽

M1 Macrophage

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MiR-7e-5p downregulation promotes transformation of low-grade follicular lymphoma to aggressive lymphoma by modulating an immunosuppressive stroma through the upregulation of FasL in M1 macrophages

Journal of Experimental & Clinical Cancer Research ◽

10.1186/s13046-020-01747-z ◽

2020 ◽

Vol 39 (1) ◽

Author(s):

Xiaoli Lou ◽

Jianhong Fu ◽

Xin Zhao ◽

Xuemei Zhuansun ◽

Chao Rong ◽

...

Keyword(s):

Follicular Lymphoma ◽

B Cell ◽

Target Gene ◽

Fas Ligand ◽

B Cell Lymphoma ◽

Differentially Expressed ◽

Aggressive Lymphoma ◽

Low Grade ◽

M1 Macrophages ◽

M1 Macrophage

Abstract Background In follicular lymphoma (FL), histologic transformation to high-grade FL and diffuse large B-cell lymphoma (DLBCL) is a critical adverse step in disease progression. Activation of the oncogene c-MYC and tumor microenvironment remodeling account for FL progression. A panel of microRNA (miRNA) was downregulated in transformed FL (tFL). Methods Differentially expressed miRNAs were systematically compared in 11 lymph nodes from patients at different stages of disease. Expression of miR-7e-5p was analyzed in 46 B-cell lymphomas, including 30 FL tissues and 16 DLBCL tissues. In FL cells, transcriptional regulation of the oncogene c-MYC on its target miR-7e-5p was revealed by Chromatin Immunoprecipitation (ChIP) assay. Exosome, carrying differentially expressed miR-7e-5p was isolated and visualized by transmission electron microscope and fluorescence tracing. The effect of miR-7e-5p on recipient macrophage was determined by target gene quantification, flow cytometry, and TUNEL method in a cocultured system with miR-7e-5p-mimics or inhibitors treatment. Expression of miR-7e-5p targets, macrophage proportions, and clinical parameters were included for correlation analysis. Results We determined that downregulation of miR-7e-5p, driven by c-MYC overexpression, was associated with poorer prognosis in FL patients. The decreased expression of miR-7e-5p in lymphoma cells led to a reduced exosomal transfer to surrounding macrophages. As a result, the target gene of miR-7e-5p, Fas ligand (FasL), was upregulated and activated the caspase signaling, which led to the apoptosis of M1 macrophages in tumor stroma. Finally, in transformed FL tissues, overexpression of FasL and activation of caspase proteins was detected in tumor stromal macrophages. Downregulation of miR-7e-5p was associated with poorer clinical outcomes. Conclusion Downregulation of exosomal miR-7e-5p induces stromal M1 macrophage apoptosis, which leads to immunosurveillance and transformation of FL.

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