技术资料

Multiple myeloma (MM) cells are characterized by high protein synthesis resulting in chronic endoplasmic reticulum (ER) stress,which is adaptively managed by the unfolded protein response. Inositol-requiring enzyme 1? (IRE1?) is activated to splice X-box binding protein 1 (XBP1) mRNA,thereby increasing XBP1s protein,which in turn regulates genes responsible for protein folding and degradation during the unfolded protein response. In this study,we examined whether IRE1?-XBP1 pathway is a potential therapeutic target in MM using a small-molecule IRE1? endoribonuclease domain inhibitor MKC-3946. MKC-3946 triggered modest growth inhibition in MM cell lines,without toxicity in normal mononuclear cells. Importantly,it significantly enhanced cytotoxicity induced by bortezomib or 17-AAG,even in the presence of bone marrow stromal cells or exogenous IL-6. Both bortezomib and 17-AAG induced ER stress,evidenced by induction of XBP1s,which was blocked by MKC-3946. Apoptosis induced by these agents was enhanced by MKC-3946,associated with increased CHOP. Finally,MKC-3946 inhibited XBP1 splicing in a model of ER stress in vivo,associated with significant growth inhibition of MM cells. Taken together,our results demonstrate that blockade of XBP1 splicing by inhibition of IRE1? endoribonuclease domain is a potential therapeutic opt View Publication

B cell activation and Ab production in response to protein Ags requires presentation of peptides for recruitment of T cell help. We and others have recently demonstrated that B cells can also acquire innate help by presenting lipid Ags via CD1d to NKT cells. Given the newfound contribution of NKT cells to humoral immunity,we sought to identify the pathways that regulate CD1 molecule expression in human B cells. We show that ex vivo,activated and memory B cells expressed lower levels of CD1d compared with resting,naive,and marginal zone-like B cells. In vitro,CD1d was downregulated by all forms of B cell activation,leaving a narrow temporal window in which B cells could activate NKT cells. CD1c expression and function also decreased following activation by CD40L alone,whereas activation via the BCR significantly upregulated CD1c,particularly on marginal zone-like B cells. We found that the CD40L-induced downregulation of CD1d and CD1c correlated with diminished expression of retinoic acid receptor α (RARα) response genes,an effect that was reversed by RARα agonists. However,BCR-induced upregulation of CD1c was independent of the RAR pathway. Our findings that both CD1d and CD1c are upregulated by RARα signaling in human B cells is distinct from effects reported in dendritic cells,in which CD1c is inversely downregulated. One functional consequence of CD1d upregulation by retinoic acid was NKT cell cytotoxicity toward B cells. These results are central to our understanding of how CD1-restricted T cells may control humoral immunity. View Publication

B cell aggregates in the central nervous system (CNS) have been associated with rapid disease progression in patients with multiple sclerosis (MS). Here we demonstrate a key role of carcinoembryogenic antigen-related cell adhesion molecule1 (CEACAM1) in B cell aggregate formation in MS patients and a B cell-dependent mouse model of MS. CEACAM1 expression was increased on peripheral blood B cells and CEACAM1(+) B cells were present in brain infiltrates of MS patients. Administration of the anti-CEACAM1 antibody T84.1 was efficient in blocking aggregation of B cells derived from MS patients. Along these lines,application of the monoclonal anti-CEACAM1 antibody mCC1 was able to inhibit CNS B cell aggregate formation and significantly attenuated established MS-like disease in mice in the absence of any adverse effects. CEACAM1 was co-expressed with the regulator molecule T cell immunoglobulin and mucin domain -3 (TIM-3) on B cells,a novel molecule that has recently been described to induce anergy in T cells. Interestingly,elevated coexpression on B cells coincided with an autoreactive T helper cell phenotype in MS patients. Overall,these data identify CEACAM1 as a clinically highly interesting target in MS pathogenesis and open new therapeutic avenues for the treatment of the disease. View Publication

Chaetocin,a thiodioxopiperazine natural product previously unreported to have anticancer effects,was found to have potent antimyeloma activity in IL-6-dependent and -independent myeloma cell lines in freshly collected sorted and unsorted patient CD138(+) myeloma cells and in vivo. Chaetocin largely spares matched normal CD138(-) patient bone marrow leukocytes,normal B cells,and neoplastic B-CLL (chronic lymphocytic leukemia) cells,indicating a high degree of selectivity even in closely lineage-related B cells. Furthermore,chaetocin displays superior ex vivo antimyeloma activity and selectivity than doxorubicin and dexamethasone,and dexamethasone- or doxorubicin-resistant myeloma cell lines are largely non-cross-resistant to chaetocin. Mechanistically,chaetocin is dramatically accumulated in cancer cells via a process inhibited by glutathione and requiring intact/unreduced disulfides for uptake. Once inside the cell,its anticancer activity appears mediated primarily through the imposition of oxidative stress and consequent apoptosis induction. Moreover,the selective antimyeloma effects of chaetocin appear not to reflect differential intracellular accumulation of chaetocin but,instead,heightened sensitivity of myeloma cells to the cytotoxic effects of imposed oxidative stress. Considered collectively,chaetocin appears to represent a promising agent for further study as a potential antimyeloma therapeutic. View Publication