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Most B-cell malignancies strictly depend on signals from the microenvironment for their survival and proliferation. This niche-dependency can be regarded as their Achilles' heel and provides an excellent target for therapy. Waldenström's macroglobulinemia (WM) is characterized by the accumulation of neoplastic post-germinal center B cells within the bone marrow (BM). Interestingly, one third of the patients carry activating mutations in the chemokine receptor CXCR4, a key mediator of B cell and plasma cell homing to the BM. We have previously shown that signals from the B-cell antigen receptor (BCR) and from chemokine receptors play a central role in controlling the interaction of normal and malignant B cells with their microenvironment by regulating the activity of integrin adhesion molecules. Apart from controlling the homing and retention of lymphocytes within their growth- and survival niches, integrins also emit signals that directly promote cell growth and survival. By analogy to the successful treatment with BTK inhibitors, we propose that targeting pathways controlling integrin-mediated retention of the WM cells in the BM, thereby inducing ‘homelessness’ (anoikis) by mobilization of the malignant cells from their protective niches, may be an efficient treatment strategy for WM. [ABSTRACT FROM AUTHOR]

Background & Aims Resistance of metastatic human colorectal cancer cells to drugs that block epidermal growth factor (EGF) receptor signaling could be caused by aberrant activity of other receptor tyrosine kinases, activating overlapping signaling pathways. One of these receptor tyrosine kinases could be MET, the receptor for hepatocyte growth factor (HGF). We investigated how MET signaling, and its interaction with CD44 (a putative MET coreceptor regulated by Wnt signaling and highly expressed by intestinal stem cells [ISCs] and adenomas) affects intestinal homeostasis, regeneration, and adenoma formation in mini-gut organoids and mice. Methods We established organoid cultures from ISCs stimulated with HGF or EGF and assessed intestinal differentiation by immunohistochemistry. Mice with total epithelial disruption of MET ( Ah Cre /Met fl/fl /LacZ ) or ISC-specific disruption of MET ( Lgr5 Creert2 /Met fl/fl /LacZ ) and control mice ( Ah Cre /Met +/+ /LacZ , Lgr5 Creert2 /Met +/+ /LacZ ) were exposed to 10 Gy total body irradiation; intestinal tissues were collected, and homeostasis and regeneration were assessed by immunohistochemistry. We investigated adenoma organoid expansion stimulated by HGF or EGF using adenomas derived from Lgr5 Creert2 /Met fl/fl /Apc fl/fl and Lgr5 Creert2 /Met +/+ /Apc fl/fl mice. The same mice were evaluated for adenoma prevalence and size. We also quantified adenomas in Ah Cre /Met fl/fl /Apc fl/+ mice compared with Ah Cre /Met +/+ /Apc fl/+ control mice. We studied expansion of organoids generated from crypts and adenomas, stimulated by HGF or EGF, that were derived from mice expressing different CD44 splice variants ( Cd44 +/+ , Cd44 –/– , Cd44 s/s , or Cd44 v4–10/v4–10 mice). Results Crypts incubated with EGF or HGF expanded into self-organizing mini-guts with similar levels of efficacy and contained all differentiated cell lineages. MET-deficient mice did not have defects in intestinal homeostasis. Total body irradiation reduced numbers of proliferating crypts in Ah Cre /Met fl/fl /LacZ mice. Lgr5 Creert2 /Met fl/fl /LacZ mice had impaired regeneration of MET-deficient ISCs. Adenoma organoids stimulated with EGF or HGF expanded to almost twice the size of nonstimulated organoids. MET-deficient adenoma organoids did not respond to HGF stimulation, but did respond to EGF. ISC-specific disruption of Met ( Lgr5 Creert2 /Met fl/fl /Apc fl/fl mice) caused a twofold increase in apoptosis in microadenomas, resulting in an approximately 50% reduction of microadenoma numbers and significantly reduced average adenoma size. Total epithelial disruption of Met ( Ah Cre /Met fl/fl /Apc fl/+ mice) resulted in an approximate 50% reduction in (micro)adenoma numbers. Intestinal crypts from Cd44 –/– mice did not expand to the same extent as crypts from Cd44 +/+ mice on stimulation with HGF, but had the same response to EGF. The negative effect on HGF-mediated growth was overcome by expression of CD44v4–10, but not by CD44s. Similarly, HGF-mediated expansion of adenoma organoids required CD44v4–10. Conclusions In studies of intestinal organoid cultures and mice with inducible deletion of MET, we found HGF receptor signaling to regulate intestinal homeostasis and regeneration, as well as adenoma formation. These activities of MET are promoted by the stem cell CD44 isoform CD44v4–10. Our findings provide rationale for targeting signaling via MET and CD44 during anti-EGF receptor therapy of patients with colorectal cancer or in patients resistant to EGF receptor inhibitors. [ABSTRACT FROM AUTHOR]

Chronic kidney diseases (CKDs) are characterized by tubular atrophy and interstitial fibrosis. We previously showed that in obstructive nephropathy de novo CD44 renal expression contributes to renal fibrosis but attenuates tubular damage/apoptosis. As CD44-standard (CD44s) has been linked to TGF-β1-mediated actions and CD44-variant-3 (CD44v3) favors HGF-c-Met binding, we compared the functional properties of these CD44 isoforms in the progression of obstructive nephropathy, using specific CD44-variant knockout/knockin mice. The presence of CD44v3 diminished tubular damage during obstructive nephropathy, decreased apoptosis, and increased proliferation of tubular epithelial cells, and prevented renal fibrosis development. In contrast, expression of CD44s led to increased tubular damage and tubular epithelial cell apoptosis, and more renal fibrosis. A relative increase in renal β-catenin expression, HGF production, and HGF/c-Met signaling, together with a relative inhibition of TGF-β1 downstream signaling and TGF-β type I receptor expression, was found in CD44v3 mice compared with CD44s littermates. In line with this, Wnt3a/HGF treatment of tubular cells resulted in higher β-catenin/p-AKT levels in CD44v3+ tubular epithelial cells, whereas TGF-β1 induced a mild collagen I upregulation in CD44v3+ mouse embryonic fibroblasts as compared with CD44s+ cells. Thus, CD44s and CD44v3 exert opposite roles in the progression of obstructive nephropathy, with CD44v3-v10 being the protective isoform that delays evolution of the renal pathology. [ABSTRACT FROM AUTHOR]

Abstract: Adoptive transfer of retrovirally transduced stem cells has recently been described for instant transgenesis in the hematopoietic compartment of mice. This method circumvents the need to manipulate the germline. However, cell type specific gene expression in this ‘retrogenic’ mouse model has remained tedious. Here we report a single retroviral vector-based method to rapidly generate conditional retrogenic mice. For this purpose, mutated loxP-flanked DNA segments are transduced into hematopoietic stem cells isolated from Cre recombinase transgenic mice, which are subsequently transferred into immunodeficient mice. In this way gene expression can be restricted to hematopoietic cell lineages of choice in the acquired immune system. [Copyright &y& Elsevier]

Background: Current immunosuppressive drug treatments for renal transplant recipients result in high one-year graft survival rates. Despite adequate suppression of the immune response directed to the allograft, the immune system remains able to cope with many infectious agents.Methods: To define the influence of distinct immunosuppressive treatment protocols, primary and secondary cellular and humoral immune responses in groups of renal transplant recipients were studied: patient treated with prednisolone and cyclosporine A (P/CsA); with IgA CD3 monoclonal antibody as a rejection treatment superimposed on prednisolone and cyclosporine A (IgA CD3 mAb+P/CsA); and with prednisolone, cyclosporine A and mycophenolate mofetil (P/CsA/MMF).Results: Primary in vitro proliferative responses to the protein antigen keyhole limpet hemocyanin (KLH) were not significantly disturbed in P/CsA treated patients, or in IgA CD3 mAb+P/CsA and P/CsA/MMF treated patients. In vitro proliferative responses to the recall antigen tetanus toxoid (TT) were similarly unaffected. Antigen-specific antibody responses to immunization with KLH and TT were not affected by treatment with P/CsA, or by IgA CD3 mAb+P/CsA, but were severely disturbed in patients treated with P/CsA/MMF. All patients displayed a profound inhibition of the delayed-type hypersensitivity skin reactivity to KLH and recall antigens. Nevertheless, in most patients with P/CsA treatment, T cell infiltrates were observed in skin biopsies from the site of KLH challenge, while expression of intercellular cell adhesion molecule-1 (ICAM-1) expression in challenged skin was significantly decreased in these patients. The balance between T helper 1 and T helper 2 cells was unaffected by immunosuppressive treatments during one year of follow-up.Conclusions: Immunosuppressive drug treatment with P/CsA inhibits delayed-type hypersensitivity skin reactions to both primary and frequently encountered antigens. Histological studies indicate an effect on ICAM-1 expression, leaving the influx of CD3pos T cells unaffected. Administration of a 10-day course of IgA CD3 mAb does not add profound immunosuppressive effects on the measured parameters. In contrast, addition of treatment with MMF profoundly decreases both primary and secondary humoral immune responsiveness in vivo. Finally, no effect of the studied immunosuppressive drugs on Th1/Th2 balance in vivo was measured. [ABSTRACT FROM AUTHOR]

Close contact between T lymphocytes and keratinocytes is an important feature of many inflammatory skin diseases. In vitro studies showed that stimulation of keratinocytes with interferon-γ or tumor necrosis factor-α and of T cells with phorbol esters results in a leukocyte function-associated antigen (LFA)-1/intercellular adhesion molecule (ICAM)-1-mediated adhesion. The present study was performed to investigate the role of the CD44 molecule in keratinocyte/T-cell binding. The CD44 class of lymphocyte adhesion receptors is involved in lymphocyte binding to high endothelial venules and to extracellular matrix compounds and is therefore important in lymphocyte recirculation and homing. Moreover, CD44 can act as a co-stimulating signal in T-cell activation and promotes homotypic adhesion of in vitro cultured CD3-stimulated T cells. Using a cell adhesion assay a sixfold increase in T-cell/keratinocyte adhesion was found after pre-incubating the T cells with anti-CD44. This increased adhesion was found to require an intact cytoskeleton, to be energy and magnesium dependent, and could be completely inhibited by anti-LFA-1 and anti-ICAM-1. Pretreatment of T cells with hyaluronic acid, a ligand for CD44 and an extracellular matrix compound in the dermis and epidermis, did not affect T-cell/keratinocyte adhesion. [ABSTRACT FROM AUTHOR]

Abstract: Extra-nodal marginal zone B cell lymphomas (MZBCLs) of the mucosa-associated lymphoid tissues (MALT) arise at sites of chronic antigenic stimulation due to organ-specific autoimmunity or infections, like Helicobacter pylori-associated chronic gastritis and Borrelia burgdorferi dermatitis. Recently, conflicting data have been published regarding a possible association between Chlamydia psittaci and ocular adnexal MZBCL. In the present study, we analyzed a cohort of ocular adnexal MZBLs from the Netherlands for the presence of C. psittaci DNA. We found no evidence for the presence of C. psittaci DNA in any of the tumor samples studied. Our data do not support a role for C. psittaci in the pathogenesis of ocular adnexal lymphomas in patients from the Netherlands. [Copyright &y& Elsevier]