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The original article [1] contained an error in the order of the citations in the manuscript which was mistakenly introduced by the production team of the journal and not by the authors of this article. The article has since been corrected to ensure that all citations correspond to their appropriate references.

Additional file 1. The CXCL12γ chemokine immobilized by heparan sulfate on stromal niche cells controls adhesion and mediates drug resistance in multiple myeloma.

Whereas for B cell lymphomas it is known that they occur more frequently in immunocompromised patients, such a relation has thus far not been clearly established for T cell lymphomas. Of 251 patients that were diagnosed with a T cell non-Hodgkin lymphoma in our center between 1999 and 2014, at least 25 were identified in immunocompromised patients. Here, we retrospectively analysed the clinical and pathological characteristics of these 25 cases. In addition, we searched the literature and present an overview of 605 previously published cases. The actual number of patients with B cell chronic lymphocytic leukemia and patients on immunosuppressive drugs for inflammatory bowel disease or rheumatoid arthritis in the total cohort of 251 patients diagnosed with T cell non-Hodgkin lymphoma was much higher than the number of patients expected to have these diseases in this cohort based on their prevalence in the general population. This, together with the large number of additional cases found in the literature, suggests that the risk of developing T cell non-Hodgkin lymphoma is increased in immunocompromised patients. Compared to T cell non-Hodgkin lymphoma in the general population these lymphomas are more often located extranodally, present at a younger age and appear to have a poor outcome. The observations made in this study should raise awareness of the possible development of T cell non-Hodgkin lymphoma in immunodeficient patients and challenge the prolonged use of immunosuppressive drugs in patients who are in clinical remission of their autoimmune disease

Pregledni rad o mogućnostima ciljane terapije difuznog B-velikostaničnog limfoma

Hepatosplenic T-cell lymphoma (HSTCL) is a rare malignancy of unknown incidence that has been associated with immune-mediated disease. This study explored the incidence and patient characteristics of HSTCL in a population of 15.5 million over a 13-year period using a comprehensive national pathology database in The Netherlands (Pathologisch-Anatomisch Landelijk Geautomatiseerd Archief) with 100% capture. Twelve cases of HSTCL were identified during this period. The overall incidence of HSTCL in the Dutch population over this period was estimated at 0.06 per million inhabitant-years. All but 2 of the patients were adults at the time of diagnosis (median age, 34.5 years), and most patients died within a year of diagnosis. Three patients had a history of immune-mediated disease, 1 of whom was receiving azathioprine at the time of HSTCL diagnosis. Azathioprine as well as anti-tumor necrosis factor-α agents have been reported as possibly being associated with HSTCL. None of the 12 HSTCL patients had been treated with an anti-tumor necrosis factor-α agent

P>Background Hyaluronic acid is expressed in atherosclerotic lesions, but its exact role in atherosclerotic disease remains unknown. As degradation of hyaluronic acid by hyaluronidase into low molecular weight hyaluronic acid (LMW-HA) is associated with inflammation and Matrix Metalloproteinase (MMP)-9 activity, we hypothesized that hyaluronic acid metabolism is increased in plaques with unstable characteristics like large lipid core, high number of macrophages, MMP-9 activity, low collagen and smooth muscle cell content. Materials and methods Protein was isolated from 68 carotid artery specimens. The adjacent plaque segment was characterized for the histological parameters: lipid core, macrophage, collagen, smooth muscle cell (SMC) content and the amount of intra-plaque thrombus. Hyaluronidase activity, total hyaluronic acid and LMW-HA expression, the standard hayaluronic acid receptor CD44s and the VEGF-A binding isoform CD44v3, MMP-9 activity and the plaque instability associated growth factor Vascular Endothial Growth Factor (VEGF)-A were analysed and correlated with histological characteristics. Results Hyaluronidase activity, LMW-HA and CD44 expression (CD44s, CD44v3) levels were increased in atheromatous plaques compared with fibrous plaques. Total hyaluronic acid did not correlate with plaque instability. MMP-9 activity correlated with CD44s, hyaluronidase and LMW-HA expression. CD44v3 correlated with the angiogenic factor VEGF-A. In vitro stimulation of macrophages with LMW-HA increased MMP-9 activity. Conclusions We show for the first time that increased hyaluronic acid metabolism and elevated CD44 levels are associated with plaque destabilization potentially by increased MMP-9 activity and stimulation of angiogenesis

Specific recognition of foreign antigens and effective surveillance are the two mainstays of the body’s defense against microbial invasion. Evolution has created great antigen-receptor diversity and has equipped lymphocytes with exquisite motility and migratory properties to accomplish these tasks. As discovered more than four decades ago by Gowans and Knight, mature lymphocytes recirculate, moving continuously from blood to tissue and back to the bloodstream again.1 This recirculation is not random, but is guided by mechanisms allowing lymphocyte diapedesis at the correct site and directing their migration to the proper place in the tissues (for reviews, see 2-5]. Within the tissues, lymphocytes display a characteristic ‘amoeboid’ form of cell migration,6 which represents a physically optimized migration mode that allows easy cell traffic toward and between different tissue compartments. This movement is directed by chemokines and stromal cell networks in the lymphoid microenvironments.7,8 Lymphocyteendothelial recognition plays a central role in controlling the access of specialized lymphocyte subsets to particular tissues, thus influencing the nature of local immune and inflammatory responses. At the molecular level, this ‘homing’ process is regulated by adhesion molecules in concert with chemokines (chemoattractant cytokines): lymphocyte subsets as well as endothelial cells specifically program their expression of adhesion molecules and chemokines/chemokine receptors, allowing lymphocytes to move selectively to specific functional compartments of the immune system, such as the mucosal-associated lymphoid tissue (MALT) and the skin.2-5.

Primary follicular lymphoma of the gastrointestinal tract (GI-FL) is a rare so far poorly studied entity. We analyzed four FL cases located in the small intestine and duodenum to gain insight in their pathogenesis and to find an explanation for their low tendency to disseminate outside the GI tract. GI-FLs resemble nodal FLs with respect to morphology and expression of typical GC markers such as CD10, CD38, and BCL-6. We established that the high levels of the anti-apoptosis protein BCL-2 in the tumor cells are in all cases due to a t(14;18) involving the immunoglobulin heavy chain and BCL-2 loci. Detailed immunoglobulin gene analyses on microdissected tissue samples further supported the GC-cell derivation: GI-FLs carry extensively mutated variable heavy-chain genes. The mutation patterns indicated that at some time point in development stringent antigen receptor-based selection processes must have occurred. Interestingly, three of four neoplasms expressed surface IgA, an immunoglobulin class typical of the mucosal immune system and seldom found in nodal FL. In contrast to nodal FLs, the GI-FLs expressed the alpha4beta7 integrin, an established mucosa-homing receptor also expressed by normal intestinal B and T lymphocytes and by low-grade mucosa-associated lymphoid tissue lymphomas. However, the chemokine receptor CXCR3, expressed on low-grade mucosa-associated lymphoid tissue lymphomas, was not detected on the GI-FLs or on nodal FLs. The combined data suggests that primary FL of the small intestine is a distinct entity that originates from local antigen-responsive B cells

It is generally assumed that follicular lymphomas (FL) not only morphologically resemble normal germinal centers but have retained some functional characteristics of their non-neoplastic counterparts as well. Recent IgV gene analyses on a panel of FLs however, strongly suggested that FLs do not retain the capacity of somatic hypermutation and are not being selected on basis of the quality of their mIgV regions. To extend these findings, we investigated the follicular organization and class switching in a FL that consisted of both IgM- and IgG-expressing tumor cells with a high somatic mutation load and significant intraclonal V(H) gene diversity. V(H)-C(mu) and V(H)-Cgamma gene transcripts were amplified and sequenced from samples of approximately 50 tumor cells, isolated from frozen tissue sections by laser microdissection. We identified many different subclones and obtained limited evidence of subclone dominance in individual follicles. Remarkably, several subclones were found scattered over different follicles. All samples contained IgM- and IgG-expressing tumor cells with, in general, non-identical mutation patterns, which is not in support of ongoing class switching. Accordingly, no switch circle recombination products were found. The findings indicate that the neoplastic follicles lack the organization and functions typical of reactive germinal centers.

In the germinal center (GC), B cells are either selected to become memory cells or are eliminated through the process of programmed cell death. FDC which are intimately associated with the GC B cells are thought to be important in this selection process. Previously, we have shown that the LFA-1 (CD11a/CD18)-ICAM-1 (CD54) and VLA-4 (CD49d)-VCAM-1 (CD106) adhesion pathways are involved in FDC-B cell interaction. In the present study, we have explored whether these adhesive interactions contribute to the process of B cell selection by studying the effects on apoptosis of GC B cells. Using FDC and B cells derived from human tonsils, we found that only B cells adherent to FDC remain viable: disruption of FDC-B-cell clusters with mAb against LFA-1 alpha (CD11a), VLA-4 (CD49d), ICAM-1 (CD54), or VCAM-1 (CD106) results in apoptosis of the B cells. Furthermore, we found that GC B cells, upon adhesion to plastic-coated purified ICAM-1 (CD54) or VCAM-1 (CD106), show diminished apoptosis. Importantly, we observed that, at low concentration, ICAM-1 (CD54) and VCAM-1 (CD106) act synergistically with anti-IgM, in inhibiting apoptosis. Together, our data strongly suggest that adhesion of B cells via the LFA-1 (CD11a/CD18)-ICAM-1 (CD54) pathway and VLA-4 (CD49d)-VCAM-1 (CD106) pathway contributes to B cell selection.

Colorectal cancer derives from epithelial cells lining the crypts and develops through a series of genetic modifications that transforms normal epithelium to an adenoma and then ultimately adenocarcinoma. Active Wnt signaling in the intestinal crypt compartment is crucial to maintain a proliferating and multipotent pool of intestinal stem cells. CD44 is a prominent Wnt-responsive gene in these cells. CD44 comprises a versatile family of transmembrane adhesion receptors capable of binding extracellular matrix components. The occurrence of variable exons, mainly involving the extracellular domain, allows for the expression of various isoforms. Importantly, certain CD44 isoforms function as a coreceptor for growth factors that are present in the ISC microenvironment. It’s involvement in sensing, integrating and transducing microenvironmental signals makes CD44 a putative factor in regulating ISC fate decisions and in promoting intestinal tumorigenesis. These concepts are strengthened by the sustained expression of CD44 on colon cancer cells with stem-cell like properties. Aberrant CD44 expression in invasive CRC is associated with increased tumorigenic and metastatic potential, indicating a functional role throughout disease. The elucidation of tumor-specific CD44 isoforms, or signaling pathways affected by these isoforms, may contribute to the development of targeted treatment strategies. However, the functional contribution of CD44, and in particular individual splice variants of CD44, to the onset and progression of intestinal cancer has remained elusive. This thesis investigates the contribution of CD44 and variant isoforms to intestinal tumorigenesis and focuses on its role in affecting signaling cascades that regulate cell fate, cancer growth and progression.

Multiple myeloma (MM) is a largely incurable hematological malignancy characterized by a clonal expansion of malignant plasma cell in the bone marrow (BM). The survival and proliferation of MM cells in the BM is highly dependent on signals emanating from the BM microenvironment. In most MMs, aberrant activation of the Wnt/β-catenin signaling drives proliferation and is associated with disease progression, however, canonical Wnt-pathway activation mutations are rare, indicating that Wnt pathway activation in MM is driven by autocrine and/or paracrine Wnt ligands. In chapter 2 , we uncover a previously unknown role for the R-spondin/LGR4 axis in regulating Wnt/β-catenin activation in MM. These results advocate LGR4 as a therapeutic target in MM. High expression of syndecan-1 is a hallmark of plasma cell and its malignant counterpart MM. In chapter 3 , we showed that HS chains decorating syndecan-1 bind Wnts and R-spondins to promote aberrant Wnt signaling activation and cell growth in MM. BMSCs secreted CXCL12α plays an important role in MM cell homing and adhesion in the BM niche. However, the role of its alternative splicing isoform CXCL12γ in MM BM microenvironment is still unknown. In chapter 4 , we showed that BMSC-derived CXCL12γ functions as a ‘niche chemokine’ that, in conjunction with cell surface HSPGs, plays a unique role in controlling MM cell adhesion, BM retention, and drug resistance. In chapter 5 , we reviewed the critical role of HSPGs in the interaction between normal and malignant plasma cells and the BM microenvironment.

Multiple myeloma (MM) is a clonal expansion of malignant plasma cells in the bone marrow (BM). Whereas numerous genetic and epigenetic abnormalities have been implicated in MM tumorigenesis, MM cells are highly dependent on a protective BM niche for growth and survival. The aim of the studies described in this thesis was to investigate the reciprocal interaction between multiple myeloma tumor cells and the bone marrow microenvironment. In particular, we focused on mechanisms that facilitate aberrant activation of the canonical Wnt signaling pathway in tumor cells. Oncogenic Wnt signaling typically results from mutations in core pathway components, which cause constitutive, ligand-independent signaling. Whereas most MMs display activation of the canonical Wnt pathway, these cell-intrinsic mutations are rare. Instead, aberrant Wnt signaling activation in MM cells was proposed to be driven by both autocrine Wnt ligands and paracrine Wnts produced in the MM niche. This thesis describes the identification of several genetic and epigenetic abnormalities in MM that sensitize tumor cells to Wnt ligands. Since Wnt signaling in MM cells is largely ligand dependent, it can be targeted by drugs/antibodies that act upstream in the pathway, interfering with Wnt secretion, sequestering Wnts, or blocking Wnt (co)receptors. In addition, the transcriptional effect of hypoxia in MM cells was studied, which identified ADM as an important regulator of angiogenesis in MM.

The transcription factor FOXP1 is prominently expressed in mature B cells and is a potential oncogene in B cell non-Hodgkin lymphomas; however, the functions of FOXP1 in mature B cells and B cell lymphomagenesis have not yet been fully explored. In the first part of this thesis, the roles of FOXP1 in B cell biology and lymphomagenesis are studied. Our studies show that FOXP1 directly represses a set of pro-apoptotic genes and key regulators of plasma cell differentiation in primary human mature B cells. Overexpression of FOXP1 promotes survival and outgrowth of these cells by cooperating with the NF-κB pathway. Furthermore, FOXP1 downregulation is required for efficient plasma cell differentiation. We also identified the nature of the smaller FOXP1 isoform that is highly expressed in ABC-type diffuse large B cell lymphoma (DLBCL). We showed that upon overexpression in primary human B cells, this isoform regulates the same set of genes and exerts an equally strong effect on survival and plasma cell differentiation, as compared to FOXP1 full-length. DLBCL is a heterogeneous diagnostic class of lymphomas comprising molecularly distinct subtypes. Various mutations affecting the NF-κB pathway occur in ABC-DLBCL, of which MyD88 and CD79B mutations are among the most prevalent. In the second part of this thesis the prevalence of oncogenic CD79B and MYD88 mutations, and their relation to clinical, phenotypic, and molecular parameters is explored in a large panel of DLBCL patients. Our studies show specific high prevalence of these mutations in DLBCLs presenting at immune privileged sites.