Downregulating PD-L1 Expression Research Articles

Continuous Therapy for Elderly Newly Diagnosed Multiple Myeloma

e28 Immunomodulatory drugs (IMiDs) directly trigger multiple myeloma (MM) cell apoptosis, abrogate adhesion to bone marrow (BM), modulate cytokines, inhibit angiogenesis, and augment T-cell, NK-cell, andNK-T cell function while downregulating Tregs. Binding to cereblon is implicated in both their direct cytotoxic and immunerelated effects. Importantly, they can augment immune therapies in MM, evidenced by increasing antibody-dependent cellular cytotoxicity and clinical activity of the mAbs elotuzumab, daratubumab, and SAR650984, and immunotoxin indatuximab ravtansine. MM cells and accessory cells that augment MM cell growth and suppress host immune function, including myeloid derived suppressor cells (MDSCs) and plasmacytoid dendritic cells (pDCs), express PD-L1; immune effector T and NK cells express PD-1. Moreover, PD-L1 expression increases with progression from normal to MGUS to active MM, and with progression from newly diagnosed to relapsed and refractory disease. Preclinical studies show that anti-PD-1 Ab, -PD-L1 Ab, or both can induce autologous effector cell-mediated cytotoxicity. Anti-PD-L1 Ab can induce MM-cell specific CD4 and CD8 CTLs and NK cell cytotoxicity, even in the presence of MDSCs and pDCs, thereby inhibiting MM cell growth in the BM. PD-L1 is induced on MM and accessory cells in the BM, as is PD-1 on immune effector cells. Importantly, IMiDs downregulate PDL-1 expression on MM and accessory cells and PD-1 on immune effector cells, thereby enhancing CD4, CD8, and NK-cell mediated MM cytotoxicity in the presence of BM accessory cells. Peptide-based vaccine strategies are also being evaluated in smouldering MM to block progression to active disease, as are MM cell/DC fusion vaccines to treat minimal residual disease posttransplant and improve outcome. In both cases, CD4 and CD8 MM-specific immune responses have been triggered by vaccination; this can be increased by lenalidomide (LEN) and/or checkpoint inhibition. A randomized trial is now comparing LEN with LEN plus MM cell/DC fusion vaccine posttransplant; it is likely that LEN and checkpoint inhibition will be combined, to generate sustained autologous memory anti-MM immunity. Immune approach combinations including mAbs, vaccines, IMiDs, and checkpoint inhibitors offer great potential to overcome effects of immune suppressive cytokines and accessory cells in the BM microenvironment, restore host CD4, CD8, and NK cell antitumour immunity, and so improve patient outcome in MM.

Mucin-1 (MUC1) Oncoprotein in Multiple Myeloma Cells Inhibits the Th1 Responses By Down Regulating the Expression of Mir-200c and up-Regulating the PDL1 Expression

Introduction: The PDL1/PD-1 pathway is a critical mediator of immune escape in patients with multiple myeloma (MM). Regulation of this pathway has not been well characterized. MicroRNAs (miRNAs) are a conserved class of small (~22 nucleotides) RNAs that post-transcriptionally regulate gene expression by interacting with the 3′ untranslated region (3′ UTR) and, in some settings, coding regions of target mRNAs. MiRNAs suppress gene expression by promoting mRNA degradation or inhibiting translation. Of note, the 3’UTR of the PDL1 gene contains putative binding sites for miR-200 family of micro-RNA’s, suggesting a possible role of miR-200’s in regulation of PDL1 expression. We have previously demonstrated that miR-200c is suppressed by the MUC1 oncoprotein, and hypothesized that MUC1 expression on myeloma cells upregulates the expression of PDL1, via suppressing miR-200c. In the present study, we investigated the relationship between MUC1, miR-200c and PDL1 in multiple myeloma.Methods and Results: Lentivirus vectors expressing miR-200c or a control vector with green fluorescence protein (GFP) were transduced in two different MM cell lines (MM-RPMI, MM-U266). Cells were harvested sorted by Fluorescence-Activated Cell Sorting (FACS) after 72 hours of transduction, using a dual fluorescence for GFP and anti-PDL1 antibody to analyze the changes in PDL1 expression. MiR-200c transduction of U266 cells resulted in a decrease in mean expression of PDL1 from 69.55% to 1.4% (n=2). Similarly, RPMI cells demonstrated a reduction in mean expression of PDL1 from 62.5% to 1.9% (n=2) following miR-200c transduction. The abrogation of PDL1 expression in MM cells by ectopic expression of miR-200c was confirmed using western immunoblot analysis. Having previously demonstrated that miR-200c is suppressed by MUC1 in a solid tumor model, we evaluated the effect of silencing MUC1 in U266 and RPMI cell lines on miR-200c and PDL1 expression. MUC1 silenced stable cell lines of RPMI and U266 cells were generated using lentivirus shRNA vectors against MUC1 or a scrambled vector control. MUC1 silenced cells demonstrated an increase in miR-200c expression (> 2 fold, p value <0.05). Notably, PDL1 expression decreased from 52% to 3.7% and from 62.5% to 6.1% following silencing of MUC1 on U266 and RPMI cells respectively.Conclusions: Ectopic expression of micro-RNA miR-200c in RPMI-MM and U266-MM cell lines results in down regulation of PDL1 expression. Silencing MUC1 in RPMI-MM and U266-MM cell lines results in both increased expression of miR-200c and downregulation of PDL1 expression. These results support the hypothesis that MUC1 expression on myeloma cells contributes to tumor mediated immunosuppression, by suppressing miR-200c thereby enhancing PDL1 expression. Interfering with MUC1 mediated signaling represents a novel approach towards augmenting immune mediated targeting of myeloma. DisclosuresNo relevant conflicts of interest to declare.

Absence of donor CD40 protects renal allograft epithelium and preserves renal function

Blocking the CD40-CD154 pathway prevents allograft rejection and induces donor-specific tolerance in various experimental models. However, the translation to clinical studies has been hampered by unexpected thromboembolic complications of CD154-blocking antibodies. Thus, blocking CD40 instead is now considered as an alternative strategy. Here, we evaluated the role of donor CD40 in allospecific T-cell responses in vitro and in an in vivo model for renal transplantation. Fully MHC-mismatched allografts from CD40-deficient donors displayed better renal function than wild type. These functional data correlated with a lower level of apoptosis in renal tubular epithelial cells and higher expression of PD-L1, which is most probably because of a reduced Th17 response in recipients of a CD40-deficient donor. This hypothesis was supported in vitro, where donor CD40 expression was important for the induction of direct allospecific T-cell responses. Especially the induction of Th17 cells was critically dependent on donor CD40. IL-17A in conjunction with interferon-γ in turn rendered renal tubular epithelial cells to a more costimulatory state by upregulating CD40 and downregulating PD-L1 expression. In conclusion, CD40 blockade not only reduces the allospecific T-cell responses, but might also lead to protection of tubular epithelium from apoptosis and thereby preserve kidney allograft function.