Jenny Sun

The Cell Type-Specific Expression of the Murine IL-13 Gene Is Regulated by GATA-3

IL-13, a Th2 cell-specific cytokine, is a major effector molecule mediating several pathological features of allergic asthma. However, the transcriptional regulation of the IL-13 gene remains unclear. Here we demonstrate, by using intracellular cytokine staining, that IL-13 is not always coexpressed with other Th2 cytokines in normal Th cells on a single cell basis. In addition, we identified and cloned a minimal inducible and cell type-specific promoter of the murine IL-13 gene. The cell type specificity of the minimal IL-13 promoter is mediated by a functionally critical GATA-3 site that binds endogenous GATA-3 proteins, whereas the induction by PMA/ionomycin is mediated by distinct cis-acting elements. Furthermore, by expressing GATA-3 in wild-type and c-maf transgenic Th1 cells, we demonstrate that the expression of IL-13 is regulated by a mechanism distinct from that regulating the expression of IL-4, and that the expression of Th1 and Th2 cytokine genes does not have to be mutually exclusive in effector Th cells.

A Mammalian Homolog of Drosophila schnurri, KRC, Regulates TNF Receptor-Driven Responses and Interacts with TRAF2

The cytokine TNFalpha launches cascades of gene activation that control inflammation and apoptosis through NFkappaB and JNK/SAPK signal transduction pathways. Here we describe a function for the zinc finger transcription factor kappa recognition component (KRC) in regulating patterns of gene activation in response to proinflammatory stimuli. We demonstrate that KRC overexpression inhibits while antisense or dominant-negative KRC enhances NFkappaB-dependent transactivation and JNK phosphorylation and consequently, apoptosis and cytokine gene expression. The effect of KRC is mediated through its interaction with the adaptor protein TRAF2, which intersects both pathways. KRC is a hitherto unrecognized participant in the signal transduction pathway leading from the TNF receptor to gene activation and may play a critical role in inflammatory and apoptotic responses.

IgA and IgG hypogammaglobulinemia in Waldenström’s macroglobulinemia

Background Hypogammaglobulinemia is common in Waldenström’s macroglobulinemia. The etiology of this finding remains unclear, but it has been speculated to be based on tumor-induced suppression of the ‘uninvolved’ immunoglobulin production Design and Methods We evaluated the incidence of IgA and IgG hypogammaglobulinemia in 207 untreated patients with Waldenström’s macroglobulinemia and investigated the associated clinicopathological findings and impact of therapy. We also sequenced eight genes (AICDA, BTK, CD40, CD154, NEMO, TACI, SH2D1A, UNG) implicated in immunoglobulin deficiency in 19 Waldenström’s macroglobulinemia patients with IgA and/or IgG hypogammaglobulinemia. Results At baseline 63.3%, 58.0% and 49.3% of the 207 patients had abnormally low serum levels of IgA, IgG, or both. No association between IgA and IgG hypogammaglobulinemia and disease burden, serum IgM levels, β2-microglobulin, International Prognostic Scoring System score, or incidence of recurrent infections was observed, although the presence of adenopathy and/or splenomegaly was associated with a lower incidence of hypogammaglobulinemia. Lower IgA and IgG levels were associated with disease progression in patients managed with a ‘watch and wait’ strategy. IgA and/or IgG levels remained abnormally low despite response to treatment, including complete remissions. A missense mutation in the highly conserved catalytic site of UNG was observed in a patient with hypogammaglobulinemia, warranting further study of this pathway in Waldenström’s macroglobulinemia. Conclusions IgA and IgG hypogammaglobulinemia is common in Waldenström’s macroglobulinemia and persists despite therapeutic intervention and response. IgA and IgG hypogammaglobulinemia does not predict the risk of recurrent infections in patients with Waldenström’s macroglobulinemia, although lower levels of serum IgA and IgG are associated with disease progression in Waldenström’s macroglobulinemia patients being managed with a ‘watch and wait’ strategy.

Hepcidin Is Produced by Lymphoplasmacytic Cells and Is Associated With Anemia in Waldenström's Macroglobulinemia

Waldenströms macroglobulinemia (WM) patients often present with anemia as their primary disease manifestation that may be related to hepcidin, an important regulator of iron homeostasis. We therefore determined hepcidin levels in 53 WM patients, and 20 age-matched healthy patient donors by hepcidin-25 ELISA. Serum hepcidin levels were elevated in WM patients versus healthy patients (P=.04), and correlated with BM disease involvement (P=.004), beta-2-microglobulin levels (P=.029), and inversely with hemoglobin (P=.05). No correlation with serum iron indices was observed, though in patients with high hepcidin levels, increased iron deposition in bone marrow macrophages was observed. Importantly, hepcidin transcripts and protein were produced by primary WM cells. Hepcidin levels correlated with serum IL-6 (P<.001) and C-Reactive Protein (P=.033) levels. The results of this study implicate hepcidin as a contributor to anemia in WM, and suggest that an iron re-utilization defect accompanies hepcidin overproduction leading to its sequestration in WM patients.

Histone deacetylase inhibitors demonstrate significant preclinical activity as single agents, and in combination with bortezomib in Waldenström's macroglobulinemia.

We studied the role of histone deacetylase inhibitors in Waldenstroms macroglobulinemia (WM). Gene expression profiling of bone marrow CD19+ cells from 30 patients and 10 healthy donors showed overexpression of HDAC4, HDAC9, and Sirt5, with validation of HDAC9 overexpression by q-PCR in primary and BCWM.1 cells. Suberoylanilide hydroxamic acid, trichostatin A, panobinostat, and sirtinol demonstrated dose-dependent killing of BCWM.1 cells. TSA showed the greatest potency with IC50 of 70 nM. Importantly, HDAC9 activity was decreased following TSA treatment suggesting an essential role for this HDAC in WM therapy. The combination of bortezomib plus HDAC inhibitors resulted in at least additive tumor cell killing in BCWM.1 cells. TSA and bortezomib-induced apoptosis depended on a similar set of caspase activation, whereas their effect on cell cycle regulators was distinctly different. These results provided a framework for examining HDAC inhibitors as monotherapy, as well as combination therapy with bortezomib in WM.

Soluble CD27 Is a Faithful Marker of Disease Burden and Is Unaffected by the Rituximab-Induced IgM Flare, as Well as by Plasmapheresis, in Patients with Waldenström's Macroglobulinemia

BACKGROUND The assessment of disease burden is often difficult in patients with Waldenströms macroglobulinemia (WM) who receive rituximab due to the induction of an IgM flare, and following the removal of serum IgM by plasmapheresis. Soluble CD27 (sCD27) is a tumor necrosis factor family member secreted by WM cells which is strongly correlated with serum IgM levels and clinical responses in patients with WM. As such, we attempted to delineate its potential role in WM patients experiencing a rituximab-induced IgM flare and following plasmapheresis. PATIENTS AND METHODS sCD27 levels were serially measured by serum-based ELISA in 8 patients who ultimately demonstrated a response to therapy, and in whom a rituximab-mediated IgM flare was observed, as well as in 3 WM patients undergoing plasmapheresis. RESULTS Among the 8 patients who experienced a rituximab-mediated IgM flare, IgM levels rose from 3515 to a peak of 5270 mg/dL (P = .008), while sCD27 levels decreased from 174.1 to 155.9 U/mL (P = .012), with a decline observed in all patients. Among 3 patients undergoing plasmapheresis, IgM levels declined from a median of 6940 to 4770 mg/dL (P = .031), while median sCD27 levels remained without significant change (P = .317). CONCLUSION sCD27 is a faithful marker of disease burden and is unaffected by the rituximab-induced IgM flare, as well as plasmapheresis in WM. The use of this marker may aid in correctly predicting clinical outcome in patients undergoing treatment with rituximab and/or plasmapheresis in WM.

Vorinostat induced cellular stress disrupts the p38 mitogen activated protein kinase and extracellular signal regulated kinase pathways leading to apoptosis in Waldenström macroglobulinemia cells

Histone deacetylases (HDACs) are aberrantly expressed, and inhibitors of HDACs induce apoptosis in lymphoplasmacytic cells (LPCs) in Waldenström macroglobulinemia (WM). The molecular profile by which these agents induce apoptosis in WM LPCs remains to be delineated. We examined the activity of the histone deacetylase inhibitor, vorinostat, and dissected its pro-apoptotic pathways in WM LPCs. Vorinostat induced apoptosis in WM cells through activating specific caspases at varying times. Inhibitors of apoptosis (IAPs) were down-regulated after vorinostat treatment. Cellular stress induced in vorinostat-treated WM cells was reflected by changes in the mitogen activated protein kinase (MAPK) pathways. Activated phospho-p38 MAPK was up-regulated at 12 h, while phospho-extracellular signal-regulated kinase (Erk) abruptly decreased at 24 h. Bortezomib did not augment vorinostat induced primary WM cell killing as reported in other B-cell disorders. These studies support that stress induced apoptosis in vorinostat-treated WM LPCs is mediated through disrupting the activity of the Erk and p38 MAPK pathways.