Background
IL-6 receptor/JAK/STAT is a major signalling pathway associated with pleiotropic functions including cell transformation and proliferation. STAT3, one of a family of 7 STAT members, sits ...at the apex of the signalling cascade and is a potential target for cancer therapy. Small molecular weight inhibitors either prevent STAT3 phosphorylation or target high constitutive levels of phosphorylated pSTAT3 (pSTAT3). Increased constitutive expression of pSTAT3 is a hallmark of solid tumors and is associated with increased morbidity. However recent studies suggest that this may not apply to hematological malignancies. Phospho-flow cytometry offers a novel approach for the quantitation of constitutive and cytokine induced pSTAT3 expression in subsets of hemopoietic cells. Constitutive pSTAT3 expression is not a prognostic factor for patients with either multiple myeloma (MM) or acute myeloid leukemia (AML), though we recently demonstrated that IL-6 induced pSTAT3 was associated with better prognosis in MM (χ2 =13.06; p<0.0003) (Leukemia 2015; 29:483) . There is considerable heterogeneity of pSTAT3 expression between patients which suggests that quantitation of these new biomarkers may help to identify those patients most likely to respond to STAT-targeted therapy. Methods
We have determined constitutive and IL-6 induced pSTAT3 and 5 in malignant plasma cells of patients with MM (n=25) and for comparison, the blast cells in AML (n=8) and CD5+ B cells in chronic lymphocytic leukemia (CLL) (n=12) as well as the non-malignant B and T cells in each sample. Normal BM cells (n=9) served as a control. We have also determined pSTAT3 and 5 expression in "side population" cells (SP), the putative myeloma stem cells, and determined whether MM and AML tumor cells induce pSTAT3 on normal lymphocytes in vitro by co-culture experiments. IL-6 receptor expression was also determined on all cells.
Results
Constitutive pSTAT3 expression was increased (>5% of normal lymphocytes) in the malignant plasma cells of 44% of patients with MM but by comparison was not increased in AML or B-CLL. Constitutive pSTAT5 was increased (>5%) in 68% of MM plasma cells and 75% of AML cells and was either normal or decreased in CLL cells. Patients with increased pSTAT3 or 5 in MM cells also had high expression in autologous normal T cells. The level of constitutive pSTAT3 and 5 was not related to the disease status (relapse vs remission). In patients with MM, IL-6 induced an increased pSTAT3 expression (induced/constitutive ratio >1.5) in both MM cells and T cells in 88% of samples. IL-6 induced pSTAT3 expression in blasts of 89% of AML patients (median ratio = 79). There was no correlation between the level of pSTAT3 induced by IL-6 and IL-6 receptor expression. IL-6 did not increase pSTAT5 levels in MM, AML or CLL. SP cells in the MM cell line RPMI 8226 had lower constitutive pSTAT3 than the non-SP population and a lower IL-6 receptor expression, but had a greater response to cytokine stimulation, suggesting that SP cells may be more sensitive than non-SP cells to inhibitors of STAT phosphorylation. Addition of RPMI 8226 cells or supernatant to normal T cells caused an increase in pSTAT3, suggesting that the upregulation of pSTAT3 is at least partly due to a tumor-derived soluble agent in the microenvironment.
Conclusions
These results demonstrate the heterogeneity of constitutive and cytokine induced pSTAT3 and 5 expression in MM, AML and CLL. Elevated levels of constitutive pSTAT3 (approx 44% of MM) and pSTAT5 (88% of MM and AML) in the malignant clone were associated with high levels in autologous non-malignant T cells and are not of prognostic significance. Therefore elevated pSTAT3 and 5 may not be an exclusive hallmark of the malignant clone, as reported in solid tumors, but rather a result of the microenvironment and a high IL6-R expression. Phospho-flow cytometry enables precise quantitation of constitutive and cytokine-induced pSTAT3 and 5, and thus can identify the patients most likely to respond to direct STAT-3 or 5 inhibitor therapies. SP cells (putative MM stem cells) appear to be potentially targetable. Inhibitors targeting signalling pathways may be more efficacious if therapy is directed to patients with targetable checkpoints.
Hart:DendroCyte BioTech Pty Ltd: Equity Ownership.
Many acute myeloid leukemia (AML) patients achieve a complete remission (CR) with chemotherapy but relapse is common. Removal of residual disease remains the greatest challenge. Allogeneic ...transplantation (alloHCT) addresses this through an immune-mediated graft versus leukemia effect (GVL), but has high morbidity and mortality. Therapeutic dendritic cell (DC) vaccination has the potential to provide immune control with limited toxicity. Previous trials using monocyte-derived DC (Mo-DC) have demonstrated modest clinical effects. This is understandable as Mo-DC have demonstrably poor migration in vivo and relatively inferior antigen processing and presentation compared to blood dendritic cells (BDC). We have developed a more practical, functionally superior vaccine composed of natural blood DC (BDC). This is achieved using the human-mouse chimeric monoclonal antibody CMRF-56 to enrich BDC from patient peripheral blood after a short incubation.We assessed the potential for preparing a CMRF-56+ BDC vaccine from AML patients in CR.
We developed an extended flow cytometry panel to distinguish different BDC subsets from blasts in AML, sorted them to confirm morphology, then used TruCount methodology to enumerate them at diagnosis, post-chemotherapy (5-28 weeks) and post alloHCT. We correct previous reports that suggested BDC numbers are normal at AML diagnosis by demonstrating that the Lineage- HLA-DR+ CD11c+ cells commonly classified as myeloid DC contain myeloblasts. Exclusion of myeloblasts, revealed that CD1c and CD141 BDC are grossly depleted at AML diagnosis to 567/mL and 24/mL, 4% and 3% respectively of the the levels of healthy aged-matched controls (HC) (n=9; n=13), but recovered to 7323/mL and 294/mL, representing 57% and 39% HC levels (n=12) during CR1, and to 10282/mL and 299/mL, representing 80% and 40% of HC after alloHCT (n=6). In contrast, plasmacytoid dendritic cells (pDC) levels were 2229/mL and 27% of HC at diagnosis, but failed to recover further remaining at 1453/mL or 18% of HC at CR1 and at 1986/mL and 24% of HC post alloHCT. CD1c BDC from AML patients in CR upregulated the CMRF-56 antigen,. similarly to HC (n=5, p=0.4) but primary AML blasts did not, enabling myeloblast free, CMRF-56+ BDC purifications. CMRF-56+ BDC isolated from AML patients in CR expanded anti-viral and Wilms' Tumour 1-specific autologous CD8+ T cells in vitro. However, patients who failed standard induction chemotherapy and required fludarabine-containing salvage regimens produced good CMRF-56+ BDC preparations but did not expand functional T cells.
These data support the feasabillity of preparing a functional BDC vaccine from AML patients in CR using CMRF-56 immune selection and highlight the potential detrimental effects of specific chemotherapeutics on cellular therapy. BDC vaccination may consolidate chemotherapy induced CR in AML, or enhance GVL post alloHCT, by stimulating specific immune responses to control residual disease.
Hsu:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Bryant:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Fromm:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Papadimitrious:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Orellana:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Suen:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Yang:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Weatherburn:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Gasiorowski:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Iland:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Brown:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Joshua:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Ho:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Gibson:DendroCyte BioTech Ltd: Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Clark:DendroCyte BioTech Ltd: Equity Ownership, Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd. Hart:DendroCyte BioTech Ltd: Equity Ownership, Other: Laboratory IP contracted via ANZAC Research Institute to DendroCyte BioTech Ltd.
Many acute myeloid leukemia (AML) patients achieve a complete remission (CR) with chemotherapy, but relapse is common. Removal of residual disease remains the greatest challenge. The potential of the ...immune system to control chemotherapy resistant malignant cells is evident in the success of allogeneic transplantation (aTx), and early results with T cell checkpoint inhibition. However, these non-specific interventions lead to considerable morbidity.
Dendritic cell (DC) vaccination has the potential to generate leukemia-specific autologous immunity with little toxicity. Promising results have been achieved with vaccines developed in vitro from purified monocytes (Mo-DC) delivered to patients with limited residual disease after conventional therapy. To stimulate an effective cytotoxic T cell response to exogenous proteins, DC must be able to cross-present protein antigen. We have demonstrated that pre-formed blood DC (BDC) have superior function to Mo-DC. Both Mo-DC and CD1c+ mDC sustained presentation of surface-loading peptide, FMP58-66, in the context of HLA class I for at least 16 hours. CD1c+ mDC presented the peptide at higher density than Mo-DC (p=0.0004). Most notably, CD1c+ mDC had a strikingly increased capacity to cross-present FMP54-74 long peptide as FMP58-66 bound to HLA-A2 at 16 hours compared with Mo-DC (p=0.0032).
To assess the capacity to isolate and target DC in AML patients. We performed a visualised stochastic neighbour embedding (ViSNE) analysis that allowed us to directly compare healthy and patient BDC populations (HD, n=8, Relapsed refractory, n=6; in CR post-chemotherapy, n=18 or >12 months post-ATx, n=7) by visualising high dimensional cytometry data structures in two dimensions. All orthodox BDC subsets were identified in HD and AML CR patients, but were reduced in active AML. Within 12 weeks following chemotherapy, CD1c+ myeloid DC recovered while CD141+ DC and plasmacytoid DC showed partial recovery. We saw no significant difference in BDC subset recovery between different chemotherapy regimens used or in patients undergoing ATx.
To determine whether the T cell landscape will permit an active vaccination strategy in AML CR patients, we compared patients receiving non-fludarabine regimens (NFR), fludarabine-containing regimens (FR) with those receiving those post-ATx with age-matched HD. Patients receiving NFR have relatively normal T cell number, phenotype and function at CR, whereas patients who have received FR as salvage therapy have persistent T cell abnormalities including reduced number, altered subset distribution, as well as a failure to expand and increased activation-induced cell death upon ligation of the T cell receptor. A comprehensive analysis of T cell landscape demonstrated increased PD-1 and TIM-3 on CD4+ T cells, particularly within the memory CD28+CD45RO+ population in FR (PD-1 p=0.0005, TIM-3 p=0.001) and ATx (PD-1 p=0.044, TIM-3 p=0.027) patients. In the NFR group there was a trend to increased PD-1 expression by CD4+ T cells (p=0.06, Figure 6A). Peripheral blood CD8+ T cells showed no significant increase in PD-1 or TIM-3 expression.
We utilised the window of opportunity following induction of CR in NFR or ATx patients to combine active vaccination with BDC in combination with checkpoint inhibition against PD-1 and TIM-3. BDC priming was able to directly enhance functional T cell responses to viral (CMV, Influenza) and the tumour associated Wilms tumour 1 antigen, generating both CD4 and CD8 responses. Checkpoint blockade using anti-PD-1 and anti-TIM-3 antibodies demonstrated additive effects on the enhancement of antigen specific, cytotoxic, interferon gamma producing CD8+ T cells.
The generation of capable functional responses in AML requires intact antigen processing and presentation as well functional effector T cells. In AML we have demonstrated that DC function is intact and there is a window of opportunity for active immune intervention in CR following either chemotherapy or ATx. Chemotherapy regimens have a profound impact on the function of effector T cells, notably fludarabine profoundly inhibits the capacity of T cells to respond to antigen priming and induces susceptibility to activation induced cell death. Clinical targeting with active DC vaccination in conjunction PD-1 and TIM-3 blockade may provide a new avenue for targeting residual disease and relapse in poor prognosis patients with AML.
Hart:DendroCyte BioTech Pty Ltd: Equity Ownership. Clark:DendroCyte BioTech Pty Ltd: Equity Ownership.
Abstract Dendritic cells (DC) are a heterogeneous population of bone marrow derived leucocytes that are essential in the initiation of primary T lymphocyte responses. DC are identified as Lineage ...negative, HLA-DR+ blood cells that can be further subdivided by CD11c to distinguish CD11c+ DC and the CD11c− plasmacytoid DC. Plasmacytoid DC are the primary IFNα producing cells and express CD303, CD304 and CD123. The CD11c+ myeloid DC can be divided into populations by CD1c, CD16 and CD141 expression. Despite DC being a functionally unique population, they share many cell surface antigens with myeloid lineage cells and B lymphocytes. We used flow cytometry to screen fresh human blood DC populations with the HLDA9 panel of 63 directly labelled mAb which included mAb specific for a number of B lymphocyte antigens. Of this panel, 23 mAb did not bind Lin− HLA-DR+ DC and 10 bound all four populations. Eight mAb bound to the three CD11c+ DC populations whilst no mAb tested bound to only pDC. Some of the mAb expected to bind to DC populations failed in this analysis. Overall, this screening highlighted similarities between the CD11c+ DC subsets and the relatively immature state of peripheral blood DC.
The graft-versus-myeloma (GVM) effect represents a powerful form of immune attack exerted by alloreactive T cells against multiple myeloma cells, which leads to clinical responses in multiple myeloma ...transplant recipients. Whether myeloma cells are themselves able to induce alloreactive T cells capable of the GVM effect is not defined. Using adoptive transfer of T naive cells into myeloma-bearing mice (established by transplantation of human RPMI8226-TGL myeloma cells into CD122(+) cell-depleted NOD/SCID hosts), we found that myeloma cells induced alloreactive T cells that suppressed myeloma growth and prolonged survival of T cell recipients. Myeloma-induced alloreactive T cells arising in the myeloma-infiltrated bones exerted cytotoxic activity against resident myeloma cells, but limited activity against control myeloma cells obtained from myeloma-bearing mice that did not receive T naive cells. These myeloma-induced alloreactive T cells were derived through multiple CD8(+) T cell divisions and enriched in double-positive (DP) T cells coexpressing the CD8αα and CD4 coreceptors. MHC class I expression on myeloma cells and contact with T cells were required for CD8(+) T cell divisions and DP-T cell development. DP-T cells present in myeloma-infiltrated bones contained a higher proportion of cells expressing cytotoxic mediators IFN-γ and/or perforin compared with single-positive CD8(+) T cells, acquired the capacity to degranulate as measured by CD107 expression, and contributed to an elevated perforin level seen in the myeloma-infiltrated bones. These observations suggest that myeloma-induced alloreactive T cells arising in myeloma-infiltrated bones are enriched with DP-T cells equipped with cytotoxic effector functions that are likely to be involved in the GVM effect.
Adenosylhomocysteine hydrolase-like protein 1 (AHCYL1) is a novel intracellular protein with ~50% protein identity to adenosylhomocysteine hydrolase (AHCY), an important enzyme for metabolizing ...S-adenosyl-L-homocysteine, the by-product of S-adenosyl-L-homomethionine-dependent methylation. AHCYL1 binds to the inositol 1,4,5-trisphosphate receptor, suggesting that AHCYL1 is involved in intracellular calcium release. We identified two zebrafish AHCYL1 orthologs (zAHCYL1A and -B) by bioinformatics and reverse transcription-PCR. Unlike the ubiquitously present AHCY genes, AHCYL1 genes were only detected in segmented animals, and AHCYL1 proteins were highly conserved among species. Phylogenic analysis suggested that the AHCYL1 gene diverged early from AHCY and evolved independently. Quantitative reverse transcription-PCR showed that zAHCYL1A and -B mRNA expression was regulated differently from the other AHCY-like protein zAHCYL2 and zAHCY during zebrafish embryogenesis. Injection of morpholino antisense oligonucleotides against zAHCYL1A and -B into zebrafish embryos inhibited zAHCYL1A and -B mRNA translation specifically and induced ventralized morphologies. Conversely, human and zebrafish AHCYL1A mRNA injection into zebrafish embryos induced dorsalized morphologies that were similar to those obtained by depleting intracellular calcium with thapsigargin. Human AHCY mRNA injection showed little effect on the embryos. These data suggest that AHCYL1 has a different function from AHCY and plays an important role in embryogenesis by modulating inositol 1,4,5-trisphosphate receptor function for the intracellular calcium release.
Abstract 1982
Dendritic cells (DC) are centrally involved in the development of acute graft-versus-host disease (GvHD) following allogeneic hemopoietic cell transplantation (alloHCT). We previously ...showed that the activation status, as assessed by CMRF-44 antigen expression, of CD11c+ myeloid blood DC is highly associated with the onset and severity of acute GvHD (Transplantation. 2007;83:839–846). We also reported a positive correlation between acute GvHD and the expression of the chemokine receptor CCR5 on CD11c+ myeloid DC (Blood. 2009;114 Suppl.:2251). Given the phenotypic and functional heterogeneity of the CD11c+ DC population, we investigated CCR5 expression on the CD11c+ DC subsets and then monitored the informative CD11c+ CD16+ DC subset expression of CCR5 in the peripheral blood of 42 patients post alloHCT, and correlated the findings with GvHD.
Peripheral blood was collected twice weekly up to Day 100 post transplant from 42 alloHCT patients. The expression of CCR5 receptor on CD11c+ and CD11c- DC subsets was evaluated using multiparameter flow cytometry.
Only the CD11c+ CD16+ DC subset lacked CCR5 and induced it upon alloactivation. Seventeen of 42 patients developed acute GvHD (5 grade I, 12 grades II-IV). The percentage of CD11c+ CD16+ DC expressing CCR5 correlated with the development of acute GvHD grades II-IV. The maximum CCR5 expression detected on CD11c+ CD16+ DC in patients prior to developing grades II-IV GvHD (mean 22.7 ± 4.3%, n=12) was higher than in those with grades 0-I GvHD (11.4 ± 1.7%, n=30) (p=0.0285). CCR5 levels >20% on CD16+ myeloid DC predicted grades II-IV GvHD with a sensitivity of 66.7% and specificity of 86.7%. Levels of expression of CCR5 on the CD11c+ CD16- DC and CD123+ plasmacytoid DC were not predictive of GvHD.
Expression of CCR5 on circulating CD11c+ CD16+ myeloid DC post alloHCT correlated with the development of moderate to severe GvHD. This observation may reflect DC activation or altered DC homing during the alloimmune response. Detection of increased CCR5+ CD11c+ CD16+ DC may allow pre-emptive therapeutic intervention prior to the clinical diagnosis of GvHD.
No relevant conflicts of interest to declare.
Introduction: CD83 is an important marker of activated dendritic cells (DC) but it is also expressed on other immune cells. Polyclonal anti-CD83 antibody depletes activated DC and prevents human ...peripheral blood mononuclear cell (PBMC) induced xenogeneic graft versus host disease (GVHD) in immunosuppressed SCID mice (J Exp Med 2009;206;387). We therefore generated a potential therapeutic human anti-CD83 mAb (3C12C), which had similar efficacy and T cell sparing effects in the same model (Leukemia 2015; in press). To investigate the specific immunosuppressive effect of 3C12C further, we undertook a comprehensive analysis of CD83 expression and its glycosylation pattern on various immune cell populations and tested the effect of 3C12C on T cell function using preclinical models, including a human CD83 (hCD83) knock in (KI) mouse.
Methods: A panel of mouse and recombinant mAbs to hCD83 were used to analyse its expression by flow cytometry on resting and activated healthy donor PBMC. The expression of potential CD83 splice variants was examined by PCR. T cell expression was examined by flow cytometry and confocal microscopy after PHA, CD3/CD28 beads and allogeneic mixed leukocyte reaction (alloMLR) culture. Control human IgG1 (trastuzumab) and 3C12C mAbs were tested (0.125mg d-1) in a xenogeneic model of GVHD utilizing human PBMC transplanted into total body irradiation and anti-NK conditioned SCID mice. The genetically engineered hCD83 KI mouse was shown to be immune-competent and used to test the effect of 3C12C on LPS activated DC and T cells.
Results: There were distinct CD83 splice variants (full length CD83, splicing variant CD83a, CD83b and CD83c) in different immune cells. CD83 glycosylation status also differed with high glycosylation required for surface expression on activated DC, whereas its expression on activated B cells and monocytes was resistant to de-glycosylation. Increases in CD83 expression on T cells occurred early with different kinetics, underlining the distinct signal pathway involved. The 3C12C mAb reduced T cell proliferation in the alloMLR but did not affect cytomegalovirus (CMV) or influenza (Flu) specific CD8+T cell numbers. Treatment with 3C12C prevented GVHD in human PBMC transplanted SCID mice, which otherwise developed histological GVHD between d8-13. Human DC were activated by d2 and expressed the CMRF-44 activation marker plus CD83, CD80 and CD86. Treatment with 3C12C mAb eliminated CD83+ CMRF44+ DC early post-transplant and reduced T cell activation. Further studies, established CMV and Flu specific T cells were retained and responded to antigen by IFNg production. Furthermore, Treg numbers were preserved. The 3C12C mAb depleted LPS activated DC in hCD83 KI mice in experiments performed prior to commencing transplant studies.
Conclusion: These findings suggest that the potential therapeutic human anti-CD83 mAb induced significant immune suppression, by depletion of activated DC and consequential modulation of T cell activation. The reduction in allo/xeno activated T cells may result in part from a direct effect of anti-CD83 on early T cell responses. This apparently selective immunosuppressive effect preserves anti-viral T cell immunity and Treg pathways, suggesting that 3C12C merits further investigation as a novel agent for GVHD prophylaxis.
Hart:DendroCyte BioTech Pty Ltd: Equity Ownership. Clark:DendroCyte BioTech Pty Ltd: Equity Ownership.
Abstract 1818
There is clinical evidence for the presence of a limited degree of host-tumor control in patients with multiple myeloma (MM) but the exact mechanisms involved are not known. Patients ...who survive for more than ten years are likely to have the most active immunological host-tumour control and are an ideal cohort to study. We now add to our preliminary observations using a range of immunological biomarkers in the 29 of these patients who attend our clinic.
51% of MM patients (n=264) had expanded CD3+CD8+ TCRVβ+ CD57+T cell clones detected by TCRVβ analysis (Beckman, BetaMark). Clonality was confirmed by IgH CDR3 sequencing. These clones accounted for 14.3% (median) of the CD3 cells (range 4–49%). CFSE tracking demonstrated the anergic nature of these clonal T cells (median 6% proliferation) compared with other CD8 cells (70% proliferation) while Geneset analysis of mRNA microarrays (Affymetrix U133) identified that anergy was caused by upregulated RAS, CSK, TOB and suppressed ERK pathways. Unlike recent reports for T-LGL, microarray analysis suggested that there was no evidence of STAT3 upregulation in the MM T cell clones. Functional studies suggested that these non-proliferating clones have split anergy as interferon-γ production was normal. In contrast, all ten year survivors had expanded T cell clones and serial studies demonstrated a >8 year persistence of the same clone in 8 out of 12 patients studied. More importantly, unlike the other MM patients, the T cell clones in 19 out of 21 of the ten year survivors studied were not anergic. The Treg/Th17 ratio in the ten year survivors was significantly lower than other MM patients (median 1.9 vs 12.0; p<0.0002) and even lower than age matched normals (median 5.6; p<0.006). This difference in the ten year survivors was due to an increased absolute Th17 cell (p<0.005) number and a reduced absolute Tregnumber (p<0.05). MM patients had a reduced number of absolute 6-Sulfo-LacNAc (SLAN)-DCs, a major source of IL-12, compared to both age matched controls and long term survivors (p < 0.01). Allo SLAN-DCs stimulated a higher proliferative response by MM T cells than could be achieved with mononuclear preparations.
In conclusion, MM patients have expanded clones of cytotoxic T cells that exhibit split anergy and these cells are potential candidates for restoring immunological control of MM and other cancers. The normalised Treg/Th17 ratio suggests that the induced tolerance associated with increased Treg cell numbers is also absent in these patients. Our observations that the ten year MM survivors do not have anergy in their clonal T cells and have less Treg suppression offers a unique cohort for future studies.
No relevant conflicts of interest to declare.
Abstract 3212
Vascular endothelial growth factor (VEGF), produced by many tumours including multiple myeloma (MM), has been reported to regulate the function of myeloid cells inducing myeloid-derived ...suppressor cells that suppress T cell responses. Little is known about the effect of VEGF on human myeloid cells including myeloid dendritic cells (MDC) and monocytes during their lifespan in bone marrow (BM) and peripheral blood (PB). We analysed the capacity of rhVEGF165 to regulate. MDC (CD11c+CD16+MDC and CD11c+CD16−MDC) and CD14+ monocytes that reside in the BM of humanised (hu)NOD/SCID mice or in peripheral blood (PB) of adult healthy subjects.
The CD11c+CD16−MDC and monocytes located in the femur, tibia and pelvic bones had elevated VEGFR-1 and VEGFR-2 surface expression compared to those located in the vertebrae and skull. Surface expression of VEGFR-1 and VEGFR-2 was negligible on CD11c+CD16+MDC, CD11c+CD16−MDC and monocytes in PB, however, VEGFR-1 mRNA was detected in CD11c+CD16+MDC and monocytes, and VEGFR-1 and VEGFR-2 mRNA in CD11c+CD16−DC. Treatment with rhVEGF165 had no effect on maturation status of MDC and monocytes residing in BM and PB, as measured by MHC-class II, CD40, CD86, CD83 expression. However, rhVEGF165 treatment regulated the capacity of MDC and monocytes to stimulate T cell responses by inducing several disparate outcomes, enhancing the capacity of CD11c+CD16−MDC, diminishing the capacity of monocytes and no effect on CD11c+CD16+MDC.
Our data suggests that the paradigm of VEGF-induced myeloid-derived suppressor cells is not as simple as originally predicted and it is likely that VEGF regulates myeloid cells to varying degrees depending on their developmental status.
No relevant conflicts of interest to declare.
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