Pirh2 mediates the sensitivity of myeloma cells to bortezomib via canonical NF-κB signaling pathway

Clinical success of the proteasome inhibitor established bortezomib as one of the most effective drugs in treatment of multiple myeloma （MM）. While survival benefit of bortezomib generated new treatment strategies, the primary and secondary resistance of MM cells to bortezomib remains a clinical concern. This study aimed to highlight the role of p53-induced RING-H2 （Pirh2） in the acquisition of bortezomib resistance in MM and to clarify the function and mechanism of action of Pirh2 in MM cell growth and resistance, thereby providing the basis for new therapeutic targets for MM. The proteasome inhibitor bortezomib has been established as one of the most effective drugs for treating MM. We demonstrated that bortezomib resistance in MM cells resulted from a reduction in Pirh2 protein levels. Pirh2 overexpression overcame bortezomib resistance and restored the sensitivity of myeloma cells to bortezomib, while a reduction in Pirh2 levels was correlated with bortezomib resistance. The levels of nuclear factor- kappaB （NF-κB） p65, pp65, plKBa, and IKKa were higher in bortezomib-resistant cells than those in parental cells. Pirh2 overexpression reduced the levels of plKBa and IKKa, while the knockdown of Pirh2 via short hairpin RNAs increased the expression of NF-κB p65, plKBa, and IKKa. Therefore, Pirh2 suppressed the canonical NF- κB signaling pathway by inhibiting the phosphorylation and subsequent degradation of IKBa to overcome acquired bortezomib resistance in MM cells.

TLR4 inactivation protects from graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Graft-versus-host disease （GVHD） is the most common complication after hematopoietic stem cell transplantation. To clarify the role of Toll-like receptor 4 （TLR4）, which is a major receptor for bacterial lipopolysaccharides （LPS）, in the development of acute GVHD, we used a TLR4-knockout （TLR4-/-） mouse GVHD model and analyzed the underlying immunological mechanisms. When TLR4-/- mice were used as bone marrow and splenocyte cell graft donors or recipients, GVHD symptom occurrence and mortality were delayed compared to wild-type （TLR4＋/＋） mice. In addition, histopathological analyses revealed that in TLR4-/-→BALB/c chimeras, liver and small intestine tissue damage was reduced with minimal lymphocytic infiltration. In contrast to TLR4＋/＋, TLR4-/- mice dendritic cells did not express CD80, CD86, CD40, MHC-II or IL-12 during LPS induction and remained in an immature state. Furthermore, the ability of TLR4-/- mice spleen dendritic cells to promote allogeneic T-cell proliferation and, in particular, T-helper cell 1 （Th 1） development was obviously attenuated compared with TLR4＋/＋ mice dendritic cells, and the levels of interferon-T （IFN-γ） and IL-IO, Th2-cell specific cytokines, were significantly higher in the serum of TLR4-/-→BALB/c than in TLR4＋/＋→BALB/c chimeric mice. Overall, our data revealed that TLR4 may play a role in the pathogenesis of GVHD and that targeted TLR4 gene therapy might provide a new treatment approach to reduce the risk of GVHD.

High levels of serum IL-10 indicate disease progression,extramedullary involvement,and poor prognosis in multiple myeloma

Multiple myeloma(MM)is a common malignant hematological tumor in adults,which is characterized by clonal malignant proliferation of plasma cells in the bone marrow and secretion of a large number of abnormal monoclonal immunoglobulins(M protein),leading to bone destruction,hypercalcemia,anemia,and renal insufficiency(Alexandrakis et al.,2015;Yang et al.,2018).Since a large number of new drugs,represented by proteasome inhibitors and immunomodulators,have been successfullyused to treat MM.