Optimizing immunotherapy in multiple myeloma: restoring the function of patients' monocyte-derived dendritic cells by inhibiting p38 or activating MEK/ERK MAPK and neutralizing interleukin-6 in progenitor cells

Abstract

Previous studies demonstrated that circulating dendritic cells (DCs) in myeloma patients were functionally abnormal. However, the phenotype and function of patients' monocyte-derived DCs (MoDCs), which are commonly used for immunotherapy, were poorly defined. This study was undertaken to examine the quality of MoDCs from myeloma patients compared with cells from healthy donors. We found that patient-derived MoDCs are phenotypically and functionally defective. Compared with their normal counterparts, patient-derived, mature MoDCs expressed significantly lower levels of CD1a, CD40, CD80, and HLA-DR and were poor at activating alloreactive T cells, presenting recall antigen, and activating autologous antigen-and myeloma-specific T cells. These abnormalities may be attributed to elevated production of autocrine cytokines such as IL-6, activated p38 and STAT3, and inhibited MEK/ERK signaling pathways in the progenitor cells. Treatment with neutralizing IL-6-specific antibody and, more importantly, p38 inhibitor, or both, could correct these abnormalities. Treating patient-derived cells with these agents not only significantly increased cell yield but also produced MoDCs that were as functional as their normal counterparts. Thus, this study has delineated the mechanistic defects of MoDCs from myeloma patients and identi- IntroductionDendritic cells (DCs) are the sentinels of the immune system. [1][2][3] In their immature state, DCs are distributed primarily in tissues where they efficiently survey for incoming pathogens. Encounter with pathogens leads to DC activation and migration to secondary lymphoid organs, and during the migration they undergo maturation. Mature DCs not only acquire the ability to stimulate quiescent, naive CD4 ϩ and CD8 ϩ T cells and B cells and initiate primary immune responses but can also induce a strong secondary immune response with relatively small numbers of DCs and low levels of antigen. 2 Given their central role in controlling immunity, DCs are logical targets for many clinical situations that involve T cells, such as graft rejection, allergy, autoimmune diseases, resistance to infection and tumors, immunodeficiency, and vaccination.DC-based immunotherapy holds great promise for treating malignancies 4-6 including multiple myeloma (MM). [7][8][9][10] However, preliminary reports of DC-based immunotherapy in human MM have demonstrated minor clinical responses. [7][8][9][10] The lack of effectiveness of DC vaccines in tumor patients may be associated, at least in part, with defects in DCs. [11][12][13][14] Indeed, previous studies showed that the numbers of circulating DCs were significantly lower in patients with MM than in healthy individuals, 14 and the phenotype and function of these cells were also impaired. 13,14 The underlying mechanisms are largely unknown. Using the 5T2 myeloma mouse model, we have recently shown that myeloma cells or tumor-culture conditioning medium (TCCM) were able to inhibit differentiation and function of murine bone marrowderived DCs. 15 However, the phen...

Cellular immunotherapy in multiple myeloma: Lessons from preclinical models

“…Similar observations were made in the murine 5TGM1 MM model in which an inhibition of DC differentiation and function by MM cells via IL-6, IL-10, and TGF-β and activation of p38 mitogen-activated protein kinase (MAPK) signaling have been reported [54]. This inhibitory mechanism was confirmed in monocyte-derived DCs from myeloma patients and p38 inhibition resulted in a restoration of DC function [55]. Restoring or ensuring normal DC function might be of great interest for several cellular immunotherapy approaches that depend on it.…”

Toll-like receptors: lessons to learn from normal and malignant human B cells

“…[68][69][70] In MM, the monocyte-derived DCs generated by the patients are functionally defective; this was found to be due to cytokines released by MM cells. 71 TLR ligands may amplify these effects and inhibit DC maturation. Although recent reports show that Treg-cell function can be inhibited by directly targeting TLR8, 72 studies using other TLR ligands have observed enhanced Treg-cell induction and improved Treg-cell function.…”

RARα2 expression is associated with disease progression and plays a crucial role in efficacy of ATRA treatment in myeloma

“…Detailed protocol was described previously. 19 Primer sets used for these analyses were as follows: RAR␣1 forward, 5Ј-CCA TCT AGG AGT GGC ATC TTT T, reverse, 5Ј-ACT AAC TGG AAG CTG GTG CTG; RAR␣2 forward, 5Ј-GAG GAG GAA GTG CTC GTT GAC, reverse, 5Ј-GCC CGG TTC TGG TTA TAA AAA T; and GAPDH forward, 5Ј-GAC ACC CAC TCC TCC ACC T, reverse, 5Ј-ATG AGG TCC ACC ACC CTG T. GAPDH transcript levels were used to normalize the amount of cDNA in each sample. …”