Maas, Mary

Abstract Background - The phenotype and biological role of monocytes in B-cell non-Hodgkin lymphoma (NHL) is not fully understood, however, an increased absolute monocyte count in the peripheral blood of lymphoma patients is associated with a poor prognosis. We have previously reported that monocytes from patients with relapsed B-cell NHL displayed an immunosuppressive CD14+HLA-DRlow/- phenotype that correlated with a poor prognosis. However, the underlying mechanism by which CD14+HLA-DRlow/- monocytes develop in patients with B-cell NHL is unknown. The goal of this study was to determine whether cytokines are responsible for the increased number and phenotype of CD14+HLA-DRlow/-monocytes present in lymphoma patients. Methods – Whole blood from patients with newly diagnosed, untreated B-cell NHL (n=20) and healthy donors (n=20) was stained with a panel of antibodies and analyzed by 10-color flow cytometry. Cytokine levels in serum and culture supernatants were measured by Luminex and ELISA, respectively. Polarization of monocytes from healthy donors was performed by incubating CD14+ cells with specific cytokines or supernatants from B-cell NHL cell lines for 24 hours. Activation and proliferation of CD4+T cells cocultured with IL-10-pretreated monocytes were measured by flow cytometry. Results – By flow cytometry, we observed that the absolute number of peripheral monocytes was increased in newly-diagnosed lymphoma patients compared to healthy donors. A significant proportion of these monocytes displayed an immunosuppressive CD14+HLA-DRlow/- phenotype and the numbers of CD14+HLA-DRlow/- cells were significantly higher in lymphoma patients than in healthy donors. To identify the underlying mechanism by which CD14+HLA-DRlow/- monocytes develop thereby leading to increased numbers of CD14+HLA-DRlow/- monocytes in B-cell NHL, we tested a panel of cytokines and found that IL-10 played a key role in the process. Firstly, treatment of monocytes with IL-10 in vitro resulted in the generation of CD14+HLA-DRlow/- cells. Second, monocytes co-cultured with IL-10 producing lymphoma B-cells, or treated with supernatants from lymphoma cell cultures, developed a CD14+HLA-DRlow/- phenotype. Thirdly, IL-10 levels were increased in the serum of DLBCL (p<0.0001) and FL patients (p=0.010) compared to healthy controls, and serum IL-10 levels correlated with increased numbers of peripheral monocytes (p=0.02). Finally, IL-10-pretreated CD14+HLA-DRlow/- monocytes were significantly immunosuppressive and inhibited the proliferation and activation of CD4+T cells in co-culture assays. Conclusions- Taken together, our results suggest that IL-10 signaling contributes to the increased numbers of CD14+HLA-DRlow/- monocytes in B-cell NHL. Strategies to inhibit IL-10 production may therefore have therapeutic potential in B-cell NHL. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction: Immune suppression is a major component of lymphoma pathogenesis. Recent advances in lymphoma treatment have been immunotherapy. We present the preliminary results of our clinical trial testing 2 vaccine strategies in patients with indolent B-cell non-Hodgkin lymphoma (NHL). The primary objective is to determine the safety and feasibility of the vaccine approaches and secondary objectives are to describe clinical responses and identify corresponding immune changes. Methods: Autologous mature dendritic cells (mDC) were manufactured from leukapheresed cells of NHL pts. For patients with tumor lymph nodes deemed amenable to cryoablation by interventional radiologist (arm A), they received cryoablation of a node and injection of mDC into the cryoablated node followed by another 1 to 7 intratumoral mDC injections. Remaining patients had a tumor excised to generate tumor lysate ex vivo. mDC were pulsed with tumor lysate during DC maturation (arm B; DC-TL). The DC-TL vaccines were injected intradermally for 4 to 8 doses. Patients are monitored for one year after vaccines for adverse events and systemic tumor response. Correlative studies include cellular immune phenotype of peripheral blood and T cell intracellular cytokine productions. Planned accrual is 10 patients per arm (total = 20). Results: To date, 10 patients have accrued to arm A and 5 patients to arm B (Table 1). All pts tolerated vaccine treatments without major adverse events. Of the 10 evaluable patients, there were 1 CR (arm B: 1 / 4; total: 1/6) and 4 PR (arm A: 3/6; arm B: 1 / 4; total: 4/10) for an ORR of 50% for both arms (Figure 1). Time to next treatment ranged from 6.5 to 25 months (Figure 2). Correlative studies suggest that immune changes can be used as prognostic biomarkers to predict response. These include changes in vaccine induced cytokine secretion, and in the number and composition of the immune system. In addition, preliminary analysis of >40 immune phenotypes using flow cytometry and hierarchical clustering suggest there are characteristic immune system responses in patients responding to vaccine. Conclusions: Both cryoablation and intratumoral mDC vaccination are feasible and safe in NHL. Treatment responses may correlate with immune system changes. Biosystems analysis method can be used to develop novel assays as predictive biomarkers of treatment response and used to develop novel protocols that allow treating to response. Table 1. Patient Demographics Arm A (n = 10) Arm B (n = 5) Total (n = 15) Age (median, rage) 64 (55 – 80) 60 (31 – 86) 63 (31 – 86) Gender (M/F) 6/4 2/3 8/7 Histology (n, %) Follicular Marginal zone DLBCL 10 (100%) 0 (0%) 0 (0%) 3 (60%) 1 (20%) 1(20%) 13 (86.6%) 1 (6.7%) 1 (6.7%) Stage (N, %) II III IV 1 (10%) 1 (10%) 8 (80%) 2 (40%) 1 (20%) 2 (40%) 3 (20%) 2 (13.3%) 10 (66.7%) No of prior Tx (mean, range) 2.4 (0-8) 3.2 (0-7) 2.7 (0-8) FLIPI (n, %) 0-1 2 ≥ 3 1 (10%) 2 (20%) 7 (70%) 1 (20%) 2 (40%) 2 (45%) 2 (13.3%) 4 (26.7%) 9 (60%) Positive GELF criteria (n, %) 4 (40%) 1 (20%) 5 (30%) Figure 1. Waterfall plot. Figure 1. Waterfall plot. Figure 2. Time to next treatment. Figure 2. Time to next treatment. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 970 Despite advances in treatments for patients with non-Hodgkin's lymphoma (NHL), the relapse rates remain high and 40% of diffuse large B-cell NHL (DLBCL) patients die of disease. These patients have variable levels of immunodeficiency that may impact their prognosis. Previously we reported that monocytes in relapsed NHL patients suppress both autologous and allogeneic T cell proliferation and that these monocytes were unable to mature into dendritic cells in vitro. These suppressive functions were associated with increased frequency of CD14+HLA-DRneg monocytes in NHL patients (NHL: 29.4 ± 3.2%, n = 36; healthy donors 7.54 ± 0.97%, n = 27; p < 0.0001). This phenotype is distinct from other myeloid suppressors (Lin−CD33+HLA-DR−) or non-classical monocytes (CD16+), neither of which was different in numbers between NHL and healthy donors. We have now expanded our study cohort and found that the percentage of CD14+HLA-DRneg cells among circulating monocytes was increased in patients with more aggressive disease: DLBCL 37.5 ± 5.11%, n = 16 vs SLL and MALT lymphoma 15.8 ± 4.02%, n = 7; p = 0.01. Two newly diagnosed patients and three patients with localized disease amenable to resection all had frequencies of CD14+HLA-DRneg monocytes closer to that of healthy donors whereas 5 of the 6 patients with low grade NHL that transformed to DLBCL had significantly elevated percentage of these suppressive monocytes (49.1 ± 4.70%). To better understand the mechanism of immune suppression by CD14+HLA-DRneg monocytes, we investigated production of IFN-alpha induced by CpG oligodeoxynucleotide. Monocytes from NHL patients were less effective at IFN-alpha production (0.54 ± 0.22%, n = 4) compared to healthy donors (1.37 ± 0.25%, n = 4; p = 0.04). The corresponding culture supernatants also had a 4-fold reduction in IFN-alpha level by ELISA (p = 0.01). Reduced IFN-alpha production and subsequent decreased stimulatory response may contribute to diminished treatment response to CpG in NHL. Finally, we also found that the frequency of CD14+HLA-DRneg monocytes correlated with increasing plasma levels of arginase I, a known mediator of T cell suppression (n = 16, p = 0.06). Such correlation was not observed for circulating VEGF, IL-6 or IL-10. Taken together we have described a population of immunosuppressive CD14+HLA-DRneg monocytes in NHL patients that is more prevalent in aggressive disease and likely suppresses T cell function through multiple mechanisms including arginine metabolism. This work was supported through the University of Iowa and Mayo Clinic Lymphoma SPORE CA097274 and the Gerstner Family Foundation. Disclosures: Witzig: Novartis: Research Funding.