David J. Chung

Indoleamine 2,3-dioxygenase–expressing mature human monocyte-derived dendritic cells expand potent autologous regulatory T cells

A comprehensive understanding of the complex, autologous cellular interactions and regulatory mechanisms that occur during normal dendritic cell (DC)-stimulated immune responses is critical to optimizing DC-based immunotherapy. We have found that mature, immunogenic human monocyte-derived DCs (moDCs) up-regulate the immune-inhibitory enzyme, indoleamine 2,3-dioxygenase (IDO). Under stringent autologous culture conditions without exogenous cytokines, mature moDCs expand regulatory T cells (Tregs) by an IDO-dependent mechanism. The priming of resting T cells with autologous, IDO-expressing, mature moDCs results in up to 10-fold expansion of CD4(+)CD25(bright)Foxp3(+)CD127(neg) Tregs. Treg expansion requires moDC contact, CD80/CD86 ligation, and endogenous interleukin-2. Cytofluorographically sorted CD4(+) CD25(bright)Foxp3(+) Tregs inhibit as much as 80% to 90% of DC-stimulated autologous and allogeneic T-cell proliferation, in a dose-dependent manner at Treg:T-cell ratios of 1:1, 1:5, and as low as 1:25. CD4(+)CD25(bright)Foxp3(+) Tregs also suppress the generation of cytotoxic T lymphocytes specific for the Wilms tumor antigen 1, resulting in more than an 80% decrease in specific target cell lysis. Suppression by Tregs is both contact-dependent and transforming growth factor-beta-mediated. Although mature moDCs can generate Tregs by this IDO-dependent mechanism to limit otherwise unrestrained immune responses, inhibition of this counter-regulatory pathway should also prove useful in sustaining responses stimulated by DC-based immunotherapy.

A phase 2 single-center study of carfilzomib 56 mg/m2 with or without low-dose dexamethasone in relapsed multiple myeloma

Standard carfilzomib (20 mg/m(2) cycle 1, 27 mg/m(2) thereafter; 2- to 10-minute infusion) is safe and effective in relapsed or refractory multiple myeloma (R/RMM). We report phase 2 results of carfilzomib 20 mg/m(2) on days 1 to 2 of cycle 1, 56 mg/m(2) thereafter (30-minute infusion), in R/RMM with the option of adding dexamethasone (20 mg) for suboptimal response/progression. Forty-four patients enrolled, all having prior bortezomib and immunomodulatory drugs and a median of 5 prior regimens. Of 42 response-evaluable patients, 23 (55%) achieved at least partial response (PR). Median (95% confidence interval) duration of response, progression-free, and overall survival were 11.7 (6.7-14.7), 4.1 (2.5-11.8), and 20.3 months (6.4-not estimable), respectively. High-risk cytogenetics did not impact outcomes. Treatment was active in bortezomib-refractory subgroups, but these patients tended to have poorer outcomes. Four/10 patients with prior allogeneic transplant achieved at least PR. Of 6 patients who responded, progressed and had dexamethasone added, 4 achieved at least stable disease. The most frequent grade 3/4 adverse events (AEs) possibly related to carfilzomib included lymphopenia (43%), thrombocytopenia (32%), hypertension (25%), pneumonia (18%), and heart failure (11%). Seven patients (16%) discontinued treatment due to AEs. Carfilzomib 56 mg/m(2) ± dexamethasone was tolerable and provided durable responses. This trial was registered at www.clinicaltrials.gov as #NCT01351623.

Peptide-Loaded Langerhans Cells, Despite Increased IL15 Secretion and T-Cell Activation In Vitro, Elicit Antitumor T-Cell Responses Comparable to Peptide-Loaded Monocyte-Derived Dendritic Cells In Vivo

Purpose: We compared the efficacy of human Langerhans cells (LC) as tumor immunogens in vivo with monocyte-derived dendritic cells (moDC) and investigated how interleukin 15 (IL15) supports optimal DC-stimulated antitumor immunity. Experimental Design: American Joint Committee on Cancer stage III/IV melanoma patients participated in this first clinical trial comparing melanoma peptide-pulsed LC with moDC vaccines (NCT00700167, www.ClinicalTrials.gov). Correlative studies evaluated mechanisms mediating IL15 support of DC-stimulated antitumor immunity. Results: Both DC vaccines were safe and immunogenic for melanoma antigens. LC-based vaccines stimulated significantly greater tyrosinase–HLA-A*0201 tetramer reactivity than the moDC-based vaccines. The two DC subtypes were otherwise statistically comparable, in contrast to extensive prior data in vitro showing LC superiority. LCs synthesize much more IL15 than moDCs and stimulate significantly more antigen-specific lymphocytes with a cytolytic IFN-γ profile even without exogenous IL15. When supplemented by low-dose IL15, instead of IL2, moDCs stimulate 5 to 6 logs more tumor antigen–specific effector memory T cells (TEMRA) over 3 to 4 weeks in vitro. IL2 and IL15 can be synergistic in moDC stimulation of cytolytic T cells. IL15 promotes T-cell expression of the antiapoptotic bcl-2 and inhibits candidate regulatory T-cell (Treg) expansion after DC stimulation, countering two effects of IL2 that do not foster tumor immunity. Conclusions: MoDC-based vaccines will require exogenous IL15 to achieve clinical efficacy. Alternatively, LCs can couple the endogenous production of IL15 with potent T-cell stimulatory activity. Optimization of full-length tumor antigen expression for processing into multiple immunogenic peptides for presentation by both class I and II MHC therefore merits emphasis to support more effective antitumor immunity stimulated by LCs. Clin Cancer Res; 17(7); 1984–97. ©2011 AACR.

T-cell Exhaustion in Multiple Myeloma Relapse after Autotransplant: Optimal Timing of Immunotherapy.

Autologous transplantation prolongs disease-free survival in multiple myeloma but is not curative. Regulatory T cells decline early after transplant, and T-cell exhaustion/senescence signals imminent relapse, providing therapeutic opportunities to revive antimyeloma immunity and counteract relapse. Multiple myeloma is the most common indication for high-dose chemotherapy and autologous stem cell transplantation (ASCT), and lenalidomide maintenance after transplant is now standard. Although lenalidomide doubles progression-free survival, almost all patients eventually relapse. Posttransplant immunotherapy to improve outcomes after ASCT therefore has great merit but first requires delineation of the dynamics of immune reconstitution. We evaluated lymphocyte composition and function after ASCT to guide optimal timing of immunotherapy and to identify potential markers of relapse. Regulatory T cells (Treg) decline as CD8+ T cells expand during early lymphocyte recovery after ASCT, markedly reducing the Treg:CD8+ effector T-cell ratio. These CD8+ T cells can respond to autologous dendritic cells presenting tumor antigen in vitro as early as day +12 after transplant, becoming antigen-specific cytolytic T-lymphocyte effectors and thereby demonstrating preservation of cellular reactivity. CD4+ and CD8+ T cells express the negative regulatory molecules, CTLA-4, PD-1, LAG-3, and TIM-3, before and after ASCT. A subpopulation of exhausted/senescent CD8+ T cells, however, downregulates CD28 and upregulates CD57 and PD-1, characterizing immune impairment and relapse after ASCT. Relapsing patients have higher numbers of these cells at +3 months after transplant, but before detection of clinical disease, indicating their applicability in identifying patients at higher risk of relapse. PD-1 blockade also revives the proliferation and cytokine secretion of the hyporesponsive, exhausted/senescent CD8+ T cells in vitro. Collectively, these results identify T-cell exhaustion/senescence as a distinguishing feature of relapse and support early introduction of immunotherapy to stimulate antitumor immunity after ASCT. Cancer Immunol Res; 4(1); 61–71. ©2015 AACR.

Factors impacting stem cell mobilization failure rate and efficiency in multiple myeloma in the era of novel therapies: experience at Memorial Sloan Kettering Cancer Center

Thalidomide, lenalidomide and bortezomib have increasingly been incorporated in first-line induction therapies for multiple myeloma. Concerns regarding the impact of these agents, especially lenalidomide, on stem cell mobilization prompted us to re-evaluate the risk factors that impact mobilization, including exposure to novel induction regimens. Among 317 patients who proceeded to stem cell collection after induction therapy between 2000 and 2009, the rate of mobilization failure, defined as the inability to collect 5 × 106 CD34+ cells/kg following the first collection attempt, was 13%. By multivariate analysis, independent risk factors associated with mobilization failure included older age (P=0.04), lower platelet count (P=0.002) and use of single-agent G-CSF for mobilization (P<0.0001). When considering for outcome measurement stem cell collection efficiency measured by the number of CD34+ cells yielded per pheresis performed during first collection attempt, lower platelet count, use of single-agent G-CSF and older age were also associated with lower efficiency. In this population mobilized mostly with cyclophosphamide and G-CSF, the use of lenalidomide during induction was not associated with a lower stem cell collection efficiency by multivariate analysis. The data support the current International Multiple Myeloma Working Group guidelines recommending the use of cyclophosphamide and G-CSF based mobilization for patients previously exposed to lenalidomide.

Patterns of relapse and progression in multiple myeloma patients after auto-SCT: implications for patients’ monitoring after transplantation

Auto-SCT (ASCT) is widely used in first-line treatment of multiple myeloma (MM). However, most patients eventually relapse or have progression of disease (R/POD). Although precise knowledge of R/POD patterns would be important to generate evidence-based surveillance recommendations after ASCT, such data is limited in the literature, especially after introduction of the free light chain assay (FLCA). This retrospective study examined the patterns of R/POD after first-line ASCT in 273 patients, using established criteria. At the time of R/POD, only 2% of patients had no associated serological evidence of R/POD. A total of 85% had asymptomatic R/POD, first detected by serological testing, whereas 15% had symptomatic R/POD with aggressive disease, early R/POD and short survival, with poor cytogenetics and younger age identified as risk factors. Although occult skeletal lesions were found in 40% of asymptomatic patients tested following serological R/POD, yearly skeletal surveys and urine testing were poor at heralding R/POD. We found a consistent association between paraprotein types at diagnosis and R/POD, allowing informed recommendations for appropriate serological monitoring and propose a new needed criterion using FLCA for patients relapsing by FLC only. Our findings provide important evidence-based recommendations that strengthen current monitoring guidelines after first-line ASCT in MM.

Upfront plerixafor plus G-CSF versus cyclophosphamide plus G-CSF for stem cell mobilization in multiple myeloma: efficacy and cost analysis study

Cyclophosphamide plus G-CSF (C+G-CSF) is one of the most widely used stem cell (SC) mobilization regimens for patients with multiple myeloma (MM). Plerixafor plus G-CSF (P+G-CSF) has demonstrated superior SC mobilization efficacy when compared with G-CSF alone and has been shown to rescue patients who fail mobilization with G-CSF or C+G-CSF. Despite the proven efficacy of P+G-CSF in upfront SC mobilization, its use has been limited, mostly due to concerns of high price of the drug. However, a comprehensive comparison of the efficacy and cost effectiveness of SC mobilization using C+G-CSF versus P+G-CSF is not available. In this study, we compared 111 patients receiving C+G-CSF to 112 patients receiving P+G-CSF. The use of P+G-CSF was associated with a higher success rate of SC collection defined as ⩾5 × 106 CD34+ cells/kg (94 versus 83%, P=0.013) and less toxicities. Thirteen patients in the C+G-CSF arm were hospitalized owing to complications while none in the P+G-CSF group. C+G-CSF was associated with higher financial burden as assessed using institutional-specific costs and charges (P<0.001) as well as using Medicare reimbursement rates (P=0.27). Higher rate of hospitalization, increased need for salvage mobilization, and increased G-CSF use account for these differences.

Treatment of multiple myeloma with monoclonal antibodies and the dilemma of false positive M-spikes in peripheral blood

OBJECTIVES To characterize the effect of three humanized IgG κ monoclonal antibodies (daratumumab, isatuximab, and elotuzumab) on the interpretation of results generated by protein electrophoresis, immunofixation, free light chain, and heavy/light chain assays performed on human serum. METHODS Healthy volunteer serum and serum from multiple myeloma patients were supplemented with clinically relevant concentrations of each of the three monoclonal antibodies. These specimens then underwent analysis via serum protein electrophoresis, immunofixation, serum free light chain quantification, heavy/light chain quantification, total IgG, and total protein. In addition, serum specimens from patients who had undergone treatment with elotuzumab for multiple myeloma underwent similar analysis. RESULTS Addition of the study drugs to serum from both the healthy donor as well as multiple myeloma patients resulted in a visible and quantifiable M-protein on SPEP and a visible IgGκ band by IFE. Increases were also noted in total IgG, IgGκ, and IgGκ/IgGλ-ratios. Analysis of serum from multiple myeloma patients receiving study drug showed similar findings with an additional IgGκ band and quantifiable M-protein with similar migration patterns in specimens drawn after administration. CONCLUSION The treatment of multiple myeloma patients with monoclonal antibodies results in a visible and quantifiable M-protein that has the potential to falsely indicate poor response to therapy.

Langerhans-type and monocyte-derived human dendritic cells have different susceptibilities to mRNA electroporation with distinct effects on maturation and activation: implications for immunogenicity in dendritic cell-based immunotherapy

BackgroundmRNA electroporation of dendritic cells (DCs) facilitates processing and presentation of multiple peptides derived from whole antigen, tailored to different HLA molecules. Clinical responses to electroporated moDC vaccines, however, have been suboptimal. Human Langerhans-type DCs (LCs) are the most potent conventional DC subtype for inducing CD8+ cytotoxic T lymphocytes (CTLs) in vitro. We recently demonstrated that Wilms’ tumor 1 (WT1) mRNA-electroporated LCs are superior to moDCs as stimulators of tumor antigen-specific CD8+ CTLs, even though they are comparable stimulators of allogeneic T cell proliferative responses. A detailed comparative evaluation of the effects of mRNA electroporation on LCs versus moDCs, however, is needed.MethodsImmature and partially-matured human moDCs and LCs electroporated with mRNA were compared for transfection efficiency, phenotypic changes, viability, retention of transgene expression after cryopreservation, and immunogenicity. Student t test was used for each pairwise comparison. One-way analysis of variance was used for multiple group comparisons.ResultsTransfection efficiency after electroporation with enhanced green fluorescent protein (eGFP) mRNA was higher for immature than for partially-matured moDCs. In contrast, transfection efficiency was higher for partially-matured than for immature LCs, with the additional benefit that electroporation itself increased maturation and activation of CD83+HLA-DRbright LCs but not moDCs. Electroporation did not impair final maturation and activation of either DC subtype, after which both mRNA-electroporated LCs and moDCs were functionally similar in stimulating allogeneic T cell proliferation, a standard assay of DC immunogenicity.ConclusionsThese findings support mRNA electroporation of DCs, and in particular LCs, as an effective non-viral method to stimulate specific, potent CD8+ CTL responses. The differences between LCs and moDCs regarding this form of antigen-loading have important implications for DC-based immunotherapies.

Human Dendritic Cells Mitigate NK-Cell Dysfunction Mediated by Nonselective JAK1/2 Blockade

Broad JAK inhibitors can improve graft-versus-host disease caused by stem cell transplants, but they reduce NK-cell numbers and activity. Selective inhibitors of JAK2, in concert with moDCs or Langerhans cells, preserve STAT5 signaling and NK-cell proliferation and function. Janus kinase (JAK) inhibitors have achieved positive responses in myeloproliferative neoplasms, but at the expense of decreased natural killer (NK) cell numbers and compromised function. Selective JAK2 inhibition may also have a role in preventing and treating graft-versus-host disease after allogeneic hematopoietic stem cell transplantation. Although JAK inhibitors can impair monocyte-derived dendritic cell (moDC) activation and function and suppress effector T-cell responses, the effects on NK cells and the relevant mechanisms remain undefined. Using common γc cytokines and distinct human dendritic cell (DC) subtypes, we compared the effects of a JAK2-specific (TG101348) with a less selective JAK1/2 (ruxolitinib) inhibitor on NK-cell activation and function. Ruxolitinib treatment completely blocked IL2, IL15, and DC-mediated STAT5 phosphorylation, along with the capacity of NK cells to secrete IFNγ or lyse NK cell–sensitive targets. Only NK-cell proliferation stimulated by moDCs resisted ruxolitinib treatment. In contrast, TG101348 treatment of stimulated NK cells resulted in far less functional compromise. TG101348 completely inhibited only soluble IL15-mediated STAT5 phosphorylation, which Langerhans-type DCs (LCs), presenting membrane-bound IL15 in trans, could salvage. These results demonstrate that ruxolitinibs nonselective inhibition of JAK1/2 results in profound NK-cell dysfunction by blocking downstream pSTAT5, hence providing a persuasive rationale for the development of selective JAK2 inhibitors for immunotherapeutic applications. Cancer Immunol Res; 5(1); 52–60. ©2016 AACR.