Response of myeloma to the proteasome inhibitor bortezomib is correlated with the unfolded protein response regulator XBP-1.

BACKGROUND: Multiple myeloma, a malignancy of the antibody-secreting plasma cells, remains incurable by current therapy. However, the proteasome inhibitor bortezomib and other new drugs are revolutionizing its treatment. It remains unclear why myelomas are peculiarly sensitive to bortezomib, or what causes primary or acquired resistance. The 'unfolded protein response' is necessary for folding and assembly of immunoglobulin chains in both normal and malignant plasma cells, as well as for the disposal of incorrectly folded or unpaired chains via the ubiquitin-proteasome pathway. We tested the hypothesis that levels of transcription factor XBP-1, a major regulator of the unfolded protein response, predict response to bortezomib. DESIGN AND METHODS: Expression of XBP-1 and other regulators of the unfolded protein response were measured in myeloma and other cancer cell lines and two cohorts of patients with refractory myeloma and correlated with sensitivity/response to bortezomib. Bortezomib-resistant myeloma cell lines were derived and the effects on expression of unfolded protein response regulators, immunoglobulin secretion, proteasome activity and cross-resistance to cytotoxic drugs and tunicamycin determined. The consequences of manipulation of XBP-1 levels for sensitivity to bortezomib were tested. RESULTS: Low XBP-1 levels predicted poor response to bortezomib, both in vitro and in myeloma patients. Moreover, myeloma cell lines selected for resistance to bortezomib had down-regulated XBP-1 and immunoglobulin secretion. Expression of ATF6, another regulator of the unfolded protein response, also correlated with bortezomib sensitivity. Direct manipulation of XBP-1 levels had only modest effects on sensitivity to bortezomib, suggesting it is a surrogate marker of response to bortezomib rather than a target itself. CONCLUSIONS: The unfolded protein response may be a relevant target pathway for proteasome inhibitors in the treatment of myeloma and its regulator XBP-1 is a potential response marker. (The BIR study was registered with Australian Clinical Trial Registry Number 12605000770662).

Children with islet autoimmunity and enterovirus infection demonstrate a distinct cytokine profile.

Cytokines are upregulated in prediabetes, but their relationship with Enterovirus (EV) infection and development of islet autoimmunity is unknown. Cytokines (n = 65) were measured using Luminex xMAP technology in a nested case-control study of 67 children with a first-degree relative with type 1 diabetes: 27 with islet autoantibodies (Ab(+)) and 40 age-matched persistently autoantibody negative (Ab(-)) control subjects. Of 74 samples, 37 (50%) were EV-PCR(+) in plasma and/or stool (EV(+)) and the remainder were negative for EV and other viruses (EV(-)). Fifteen cytokines, chemokines, and growth factors were elevated (P ≤ 0.01) in Ab(+) versus Ab(-) children (interleukin [IL]-1ß, IL-5, IL-7, IL-12(p70), IL-16, IL-17, IL-20, IL-21, IL-28A, tumor necrosis factor-α, chemokine C-C motif ligand [CCL]13, CCL26, chemokine C-X-C motif ligand 5, granulocyte-macrophage colony-stimulating factor, and thrombopoietin); most have proinflammatory effects. In EV(+) versus EV(-) children, IL-10 was higher (P = 0.005), while IL-21 was lower (P = 0.008). Cytokine levels did not differ between Ab(+)EV(+) and Ab(+)EV(-) children. Heat maps demonstrated clustering of some proinflammatory cytokines in Ab(+) children, suggesting they are coordinately regulated. In conclusion, children with islet autoimmunity demonstrate higher levels of multiple cytokines, consistent with an active inflammatory process in the prediabetic state, which is unrelated to coincident EV infection. Apart from differences in IL-10 and IL-21, EV infection was not associated with a specific cytokine profile.