Hsiuyi Tseng

Attainment of complete/very good partial response following rituximab-based therapy is an important determinant to progression-free survival, and is impacted by polymorphisms in FCGR3A in Waldenstrom macroglobulinaemia

The incorporation of rituximab into various regimens has improved depth of response in Waldenstrom macroglobulinaemia (WM), though the impact of achieving better responses remains to be determined. We examined response depth on progression‐free survival (PFS) in 159 rituximab‐naïve WM patients who received rituximab‐based therapy. The median follow‐up was 33·5 months, and categorical responses were as follows: complete response (CR, 8·8%); very good partial response (VGPR, 13·2%); partial response (50%); minor response (18·9%); Non‐Responders (8·8%). Sequencing for polymorphic variants of FCGR2A, FCGR2B, and FCGR3A was performed, and impact on response depth determined. Achievement of better categorical responses was incrementally associated with improved PFS (P < 0·0001). No separation was observed between CR and VGPR, and attainment of at least a VGPR was associated with improved time‐to‐progression. Neither age, serum IgM, haematocrit, platelet count, serum β2microglobulin, WM International Prognostic Scoring System score, and treatment group predicted for CR/VGPR. Polymorphisms at FCGR3A‐48 and ‐158 were associated with improved categorical responses, particularly attainment of CR/VGPR (P ≤ 0·03). The attainment of CR/VGPR was associated with significantly longer PFS in rituximab‐naïve WM patients undergoing rituximab‐based therapy, and was predicted by polymorphisms in FCGR3A.

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.

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.

Matrix Metalloproteinase-8 Is Overexpressed in Waldenström's Macroglobulinemia Cells, and Specific Inhibition of this Metalloproteinase Blocks Release of Soluble CD27

Soluble CD27 (sCD27) is produced by Waldenströms macroglobulinemia (WM) cells, with high levels found in WM patients which may facilitate disease expansion. Matrix metalloproteinases (MMP) may facilitate sCD27 release by cleavage of CD27. By gene expression analysis, we observed significantly higher transcription levels of MMP-8 and MMP-9, with 58.5 and 16.7 fold increase in mean transcription levels in WM cells relative to healthy donor peripheral blood B cells (P = .04, and .05, respectively). We developed a model for study of sCD27 release by transfecting BCWM.1 WM cells and BL2126 lymphoblastic B cells, both of which express MMP-8 and MMP-9 with a vector expressing FLAG-tagged CD27 (pFLAG-CD27) which in the presence of phorbol myristate acetate resulted in ≥ 10-fold increase in sCD27 release. MMP inhibitors against MMP-8, but not MMP 2, 3, or 9 blocked release of sCD27. The results suggest that MMP-8 may play a role in the pathogenesis of WM, and that its inhibition may be of therapeutic value 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.