No abstract

Bacillus cereus is a growing concern as a cause of life-threatening infections in patients with hematologic malignancies. However, the risk factors for patients with unfavorable outcomes have not been fully elucidated. At our institution, we observed the growth of B. cereus in blood culture in 68 patients with (23) or without (45) hematologic malignancies treated from September 2002 to November 2009. We defined a case as having sepsis when more than two blood culture sets were positive for B. cereus or only a single set was positive in the absence of other microorganisms in patients who had definite infectious lesions. We determined 12 of 23 patients with hematologic malignancies as having sepsis, as well as 10 of 45 patients without hematologic malignancies (p = 0.012). Of the 12 patients with hematologic malignancies, four patients with acute leukemia died of B. cereus sepsis within a few days. In our cohort, risk factor analysis demonstrated that a neutrophil count of 0/mm(3), central venous (CV) catheter insertion, and the presence of central nervous system (CNS) symptoms were significantly associated with a fatal prognosis (p = 0.010, 0.010, and 0.010, respectively). Analysis of data from our cohort in conjunction with those from 46 previously reported patients with B. cereus sepsis identified similar risk factors, that is, acute leukemia, extremely low neutrophil count, and CNS symptoms (p = 0.044, 0.004, and 0.002, respectively). These results indicate that appropriate prophylaxis and early therapeutic intervention against possible B. cereus sepsis are crucially important in the treatment of hematologic malignancies.

Linear ubiquitin chain assembly complex (LUBAC) is a key regulator of NF-kB signaling. Activating single-nucleotide polymorphisms of HOIP, the catalytic subunit of LUBAC, are enriched in patients with activated B cell-like diffuse large B-cell lymphoma (ABC-DLBCL), and expression of HOIP which parallels LUBAC activity is elevated in ABC-DLBCL samples. Thus, to clarify the precise roles of LUBAC in lymphomagenesis, we generated a mouse model with augmented expression of HOIP in B cells. Interestingly, augmented HOIP expression facilitated DLBCL-like B-cell lymphomagenesis driven by MYD88-activating mutation. The developed lymphoma cells partly shared somatic gene mutations with human DLBCLs, with increased frequency of a typical AID mutation pattern. In vitro analysis revealed that HOIP overexpression protected B cells from DNA damage-induced cell death through NF-kB activation, and the analysis of human DLBCL database showed that expression of HOIP positively correlated with gene signatures representing regulation of apoptosis signaling, as well as NF-kB signaling. These results indicate that HOIP facilitates lymphomagenesis by preventing cell death and augmenting NF-kB signaling, leading to accumulation of AID-mediated mutations. Furthermore, a natural compound that specifically inhibits LUBAC was shown to suppress the tumor growth in a mouse transplantation model. Collectively, our data indicates that LUBAC is crucially involved in B-cell lymphomagenesis through protection against DNA damage-induced cell death, and is a suitable therapeutic target for B-cell lymphomas.

A 64-year-old woman suffering from progressive amyloid A (AA) amyloidosis of the gastrointestinal (GI) tract, associated with active rheumatoid arthritis, was transferred to our hospital due to hypovolemic shock. Although intensive care, including treatment with prednisolone and methotrexate, improved the hypovolemic shock, paralytic ileus became dominant instead of the marked diarrhea, suggesting the terminal stage of AA amyloidosis of the GI tract. Thus, we administered tocilizumab, a humanized anti-interleukin 6 receptor antibody (8 mg/kg, repeated every 4 weeks). Two weeks after the first injection of tocilizumab, serum AA rapidly returned to their normal ranges in accordance with the amelioration of paralytic ileus and systemic joint pain. Surprisingly, after three courses of tocilizumab treatment, colon biopsy revealed no amyloid deposition. Tocilizumab is a promising agent to treat secondary AA amyloidosis by strongly suppressing serum AA levels.

A 70-year-old male was admitted because of back pain due to peri-vertebral tumors. The histologic picture of a needle-biopsied tumor specimen showed pleomorphic large cell infiltration into the collagen fibers. On immunohistochemistry, these abnormal cells were positive for CD68, CD163 and lysozyme but negative for CD1a, 21, 30, and S100. Flow cytometric analysis also demonstrated that these cells were positive for CD13, 14, 38, 45, 56, and HLA-DR. A bone marrow aspirate showed the marked infiltration of abnormal large cells with the same surface antigens as described above. A diagnosis of HS was made. He showed monocytosis in the peripheral blood of more than 1.0 x 10(9)/L from presentation. The karyotype of bone marrow cells was 46,XY,+8. Fluorescent in situ hybridization (FISH) analysis with a probe for chromosome no. 8 showed that all these monocytes carried +8, indicating that he had another disorder of chronic myelomonocytic leukemia (CMML). FISH analysis with a probe for chromosome no. 12 demonstrated that the abnormal large cells in the bone marrow were all tetraploid, while analysis with the chromosome no. 8 probe showed more than 8 signals per cell, indicating that HS cells carried octasomy to decasomy of chromosome no. 8. These findings strongly suggest that HS in the present patient originated from underlying CMML.

Lymphoma-associated hemophagocytic syndrome (LAHS) is a serious disorder, and its early diagnosis and treatment with appropriate chemotherapy are very important. However, reliable markers for early diagnosis of LAHS have not been identified. We screened serum cytokines using a newly introduced assay system, cytometric bead array (CBA), and identified interferon-inducible protein 10 (IP-10)/CXCL10 and monokine induced by interferon gamma (MIG)/CXCL9 as useful markers. Serum concentrations of IP-10 and MIG at the time of LAHS diagnosis were greater than 500 and 5,000 pg/ml, respectively. The sensitivity and specificity for LAHS diagnosis were 100 and 95 %, respectively, when we set the above values as the cut-off levels. Serum levels of these two chemokines were already elevated at the time of admission and significantly decreased after successful treatment, indicating their usefulness for both the diagnosis and therapeutic outcomes for LAHS. IP-10 and MIG were also useful in distinguishing severe from moderate/mild LAHS, and B-cell-type LAHS from T-cell/natural killer cell-type LAHS. Furthermore, IP-10 and MIG were of use to distinguish LAHS from sepsis in patients with hematologic malignancies. Rapid measurement of IP-10 and MIG by CBA appeared to be important for early diagnosis and treatment of LAHS.

The Notch-signaling pathway in a variety of mature B-cell neoplasms is often activated by gene alterations, but its role remains unclear. Here, we show that B cells harboring dysregulated activation of Notch1 signaling have an immunomodulatory effect on T cells by amplifying regulatory T (Treg) and T helper 2 (Th2) cell responses in an interleukin-33 (IL-33)-dependent manner. A conditional mouse model, in which constitutive expression of an active form of Notch1 is induced in B cells by gene promoter-driven Cre recombinase, revealed no obvious phenotypic changes in B cells; however, mice demonstrated an expansion of Treg and Th2 cell subsets and a decrease in cytokine production by Th1 and CD8 T cells. The mice were susceptible to soft tissue sarcoma and defective production of CD8 T cells specific for inoculated tumor cells, suggesting impaired antitumor T-cell activity. Gene-expression microarray revealed that altered T-cell responses were due to increased IL-33 production by Notch1-activated B cells. Knockout of or blockade of IL-33 by a receptor-blocking antibody abrogated the Treg and Th2 cell-dominant T-cell response triggered by B cells. Gene-expression data derived from human diffuse large B-cell lymphoma (DLBCL) samples showed that an activated Notch-signaling signature correlates positively with expression and Treg cell-rich gene-expression signatures. These findings indicate that B cells harboring dysregulated Notch signaling alter T-cell responses via IL-33, and suggest that aberrant activation of Notch signaling plays a role in fostering immune privilege in mature B-cell neoplasms.

Background SLFN11 has recently been reported to execute cancer cells harboring replicative stress induced by DNA damaging agents. However, the roles of SLFN11 under physiological conditions remain poorly understood. Germinal center B-cells (GCBs) undergo somatic hypermutations and class-switch recombination, which can cause physiological genotoxic stress. Hence, we tested whether SLFN11 expression needs to be suppressed in GCBs during B-cell development. Objective To clarify the expression profile of SLFN11 in different developmental stages of B-cells and B-cell-derived cancers. Methods We analyzed the expression of SLFN11 by mining cell line databases for different stages of normal B-cells and various types of B-cell-derived cancer cell lines. We performed dual immunohistochemical staining for SLFN11 and B-cell specific markers in normal human lymphatic tissues. We tested the effects of two epigenetic modifiers, an EZH2 inhibitor, tazemetostat (EPZ6438) and a histone deacetylase inhibitor, panobinostat (LBH589) on SLFN11 expression in GCB-derived lymphoma cell lines. We also examined the therapeutic efficacy of these drugs in combination with cytosine arabinoside and the effects of SLFN11 on the efficacy of cytosine arabinoside in SLFN11-overexpressing cells. Results SLFN11 mRNA level was found low in both normal GCBs and GCB-DLBCL (GCB like-diffuse large B-cell lymphoma). Immunohistochemical staining showed low SLFN11 expression in GCBs and high SLFN11 expression in plasmablasts and plasmacytes. The EZH2 and HDAC epigenetic modifiers upregulated SLFN11 expression in GCB-derived lymphoma cells and made them more susceptible to cytosine arabinoside. SLFN11 overexpression further sensitized GCB-derived lymphoma cells to cytosine arabinoside. Conclusions The expression of SLFN11 is epigenetically suppressed in normal GCBs and GCB-derived lymphomas. GCB-derived lymphomas with low SLFN11 expression can be treated by the combination of epigenetic modifiers and cytosine arabinoside.