ALBERT

Description: Introduction LR11, which is also known as SorLA or SORL1, is a type-I membrane protein from which a large extracellular part, soluble LR11 (sLR11), is released by proteolytic shedding. We have demonstrated that serum sLR11 levels are significantly elevated in patients with acute leukemia and that sLR11 levels are associated with the peripheral blast percentage (Sakai et al. Clin Chim Acta. 2012). In addition, we found that high sLR11 levels have a significant negative prognostic impact on progression-free survival in patients with follicular lymphoma (FL; Kawaguchi et al. Br J Haematol. 2013). In this FL analysis, the immunohistological intensity of LR11 in lymph nodes of FL patients did not show a significant association with serum sLR11 levels. Therefore, a shedding mechanism is presumed to play a key role in the functions of LR11. A disintegrin and metalloproteinase 17 [ADAM17, also known as tumor necrosis factor (TNF)-α converting enzyme (TACE)] has been identified as the enzyme that cleaves TNF-α from its transmembrane precursor form, and it has been found to cleave the ectodomains of other cell surface proteins. LR11 is also shed by ADAM17. Tetraspanin CD9 has been recently shown to inhibit the shedding activity of ADAM17. Therefore, we investigated the role of CD9 in sLR11 release. Materials and methods First, we examined the gene expression levels of LR11 by quantitative real-time PCR and the cell surface expression of LR11 and CD9 by flow cytometric analysis in normal human peripheral-blood mononuclear cells (PBMCs). Second, we investigated the cellular expression and the released levels of LR11 and cellular CD9 in THP-1 monocytes, phorbol 12-myristate-13-acetate (PMA)-induced THP-1 macrophages (PMA/THP-1), and the B lymphoblastoid cell line CCRF-SB by immunoblot analysis. Furthermore, to assess the relationship between LR11 and CD9 in PMA/THP-1, we performed double immunofluorescence staining of these molecules followed by confocal microscopy analysis. Third, we examined the effects of ectopic neoexpression of CD9, anti-CD9 mAbs, and CD9 silencing. THP-1 cells stably interfered with CD9 were generated by the transfection of the shRNA expression vector that is specific for CD9. Results The gene expression levels of LR11 were significantly higher in CD3+ T cells than in CD14+ monocytes, and there was no difference between monocytes and CD19+ B cells. However, LR11 was only expressed on the cell surface of monocytes in normal PBMCs. CD9 was broadly expressed on the cell surface of every PBMCs. Because it has been reported that CD9 associates with ADAM-17 on the cell surface, we hypothesized that CD9 associates with the shedding of LR11 on the cell surface. To verify this hypothesis, we chose the monocytic cell line THP-1 because monocytes have both LR11 and CD9 on their surface. In addition, because the gene expression levels of LR11 were significantly higher in human monocyte-derived macrophages than that in monocytes, we investigated the levels in PMA/THP-1. LR11 was not expressed or released in undifferentiated THP-1 cells, but it was expressed or released in differentiated PMA/THP-1. CD9 was poorly expressed in THP-1 cells, and the CD9 expression levels were increased in PMA/THP-1. The confocal microscopy analysis showed colocalization of LR11 and CD9 proteins in PMA/THP-1. We next investigated the effects of ectopic neoexpression of CD9 in CD9-negative cells, neutralizing anti-CD9 mAbs (clone ALB-6) in CD9-positive cells, and CD9 silencing in THP-1 on the shedding of LR11. When CCRF-SB, LR11-positive and CD9-negative cells were transiently overexpressed with CD9, the amount of sLR11 released from CD9-overexpressing cells was decreased compared with that from control cells. The amount of sLR11 released from LR11-transfected THP-1 cells that were cultured with ALB-6 was significantly increased compared with that cultured with an isotypic control antibody. The PMA-stimulated release of sLR11 was significantly increased in CD9 shRNA-interfered THP-1 cells compared with cells that were transduced with the control shRNA. The increase in CD9 shRNA-interfered THP-1 was nullified by treatment with the metalloproteinase inhibitor GM6001 (Figure 1). Conclusion These results suggested that the tetraspanin CD9 inhibits ADAM17-mediated LR11 shedding in leukemia cells and that it may have a role in controlling the function of LR11. Disclosures: No relevant conflicts of interest to declare.

Description: Introduction: LR11 is a type I membrane protein that plays a key role in the migration of undifferentiated vascular smooth muscle cells, and circulating soluble LR11 (sLR11) has been known as a biomarker for coronary stenosis. We have previously found that LR11 is highly expressed in acute leukemia, diffuse large B cell lymphoma (DLBCL), and follicular lymphoma (FL) cells. Soluble LR11 were detected in the patients' serum, and our retrospective cohort demonstrated that serum sLR11 level is significantly increased at diagnosis and normalized at remission (Sakai et al. Clin Chim Acta. 2012, Ohwada et al. 2011 ASH annual meeting). Furthermore, high serum sLR11 level had a significant association with relapse and inferior progression-free survival (PFS) in patients with FL (Kawaguchi et al. Br J Haematol. 2013). Based on these findings, we have conducted a multicenter prospective observational study to validate the clinical impact of serum sLR11 in patients with newly diagnosed DLBCL. Patients and Methods: Ninety-seven consecutive patients with newly diagnosed DLBCL between 2010 and 2013 in Chiba University Hospital and affiliated hospitals were enrolled. Serum samples were collected at diagnosis and when the patients reached complete remission. Clinical and laboratorial data were collected prospectively. Serum sLR11 levels were measured with enzyme-linked immunosorbent assay. Normal control samples were obtained from 75 healthy adult volunteers who had given informed consent. Results: The patients had a median age of 69 years (range, 18-94). Ninety percent of patients were treated with R-CHOP-based regimen, and 80% of them achieved complete remission (CR). Serum sLR11 levels of DLBCL patients were significantly elevated than those of normal controls (21.2 ±27.6 ng/ml vs. 8.8 ±1.8 ng/ml, p

Description: Recently, novel agents such as bortezomib and lenalidomide have been introduced for multiple myeloma (MM) treatment and have improved patients' survival drastically. However, dexamethasone remains a mainstay in the treatment of MM. Dexamethasone effectively induces tumor cell death when used for the initial treatment of MM. In addition, dexamethasone has a synergistic effect with novel agents and is hence used in combination with such agents. However, prolonged dexamethasone exposure may lead to drug resistance. To elucidate the mechanism of dexamethasone resistance, we generated a dexamethasone-resistant subline of the MM cell line RPMI8226. We cultured RPMI8226 cells with 1 µM dexamethasone for 7 weeks and established the dexamethasone-resistant cell line Dex-R. This cell line showed no difference in survival in the presence or absence of 1 µM dexamethasone. We then examined differences in gene expression between RPMI8226 and Dex-R cells using cDNA microarray. Expression of the FARP1 gene, which is a transforming growth factor beta (TGF-b) target gene in myeloma cells, was increased approximately 50-fold in Dex-R cells compared to that in RPMI8226 cells. In some myeloma patients who become chemoresistant, myeloma cells show high levels of FARP1 expression at the initial stage. FARP1 has a Rho-GEF domain and can associate with proteins on the cell membrane through the FERM domain. In the nervous system, FARP1 is involved in synaptogenesis via the activation of Rac1. Based on these observations, we hypothesize that Dex-R cells acquires dexamethasone resistance with an increase in the level of FARP1 expression via the activation of Rac1. To verify this hypothesis, we established inducible FARP1 knockdown Dex-R cells using the TET-ON lentiviral system. We cultivated these cells for 24 h with doxycycline and added 1 µM dexamethasone. A total of 48 h after adding dexamethasone, we measured cell viability using the MTS assay. We cultured Dex-R cells with a Rac1 inhibitor (NSC23766) and added dexamethasone 12 h later. FARP1 expression decreased to approximately 10% in FARP1 knockdown cells 24 h after the addition of doxycycline. Without dexamethasone, there was no difference in survival in the presence or absence of doxycycline. However, when cells were cultured with dexamethasone, the growth of FARP1 knockdown Dex-R cells was significantly inhibited compared with that of the control (Fig 1). Next, we examined the change in dexamethasone resistance on the addition of the Rac1 inhibitor. The number of cells increased after 96 h without dexamethasone. On the other hand, the number of cells significantly decreased when cultured with dexamethasone (Fig 2). These data suggest that resistance to dexamethasone in Dex-R cells was mitigated by the inhibition of Rac1. We conclude that the activation of Rac1 through FARP1 is one mechanism of dexamethasone resistance in MM. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: Intravascular large B-cell lymphoma (IVLBCL) is a rare disease entity characterized by selective growth of lymphoma cells in the lumina of small vessels. IVLBCL has been listed in the WHO classification, which improves recognition of the disease. However, no standard therapy has been established based on the results of prospective studies. We previously reported promising efficacy of rituximab (R)-containing chemotherapy for IVLBCL (JCO 2008) and a high incidence of central nervous system (CNS) recurrence (25% at 3 y) after R-chemotherapy (Lancet Oncol 2009, Cancer Sci 2010). To explore a more effective first-line treatment, we conducted a phase 2 trial of R-CHOP combined with CNS prophylaxis including R-high-dose methotrexate (R-HDMTX) and intrathecal chemotherapy with MTX, cytarabine (Ara-C), and prednisolone (PSL) (IT). Methods: Major inclusion criteria were untreated, histologically confirmed IVLBCL, age 20-79 y, ECOG PS 0-3, and no apparent CNS involvement at diagnosis. Patients received 3 cycles of R-CHOP followed by 2 cycles of R-HDMTX (3.5 g/m2; 2 g/m2 for ≥70 y) every 2 weeks, and 3 additional cycles of R-CHOP. IT (MTX 15 mg, Ara-C 40 mg, PSL 10 mg) was performed twice during the first 3 cycles of R-CHOP and twice during the final 3 cycles of R-CHOP (4 times in total). If patients achieved complete response (CR), they were observed without any therapy until relapse or disease progression. The primary endpoint was 2-y progression-free survival (PFS), and secondary endpoints included 2-y overall survival (OS), CR rate, cumulative incidence of CNS recurrence at 2 y, patterns of progression, and adverse events. The threshold 2-y PFS was estimated to be 35%, with expected 2-y PFS estimated to be 60%. With a statistical power of 90% and a one-sided, type I error of 5%, a projected sample size of 37 was calculated in anticipation of 10% ineligible patients. The trial was registered in the UMIN Clinical Trials Registry (UMIN000005707). Results: 38 IVLBCL patients were enrolled between June 2011 and July 2016. One patient was found to be ineligible after completion of the protocol treatment due to a past history of lymphoma. The protocol treatment was completed in 34 (89%) of 38 patients. The diagnosis of IVLBCL was histologically confirmed by central pathological review in all enrolled patients. The baseline characteristics of the 37 eligible patients were: male sex, 16 (43%); median age, 66 (range 38-78) y; ECOG PS 〉1, 15 (41%); stage IV, 37 (100%); serum LDH 〉ULN, 36 (97%); WBC