Vargas, Doris M.

Abstract The PD-1:PD-L1 axis is a major immune regulatory pathway that blunts T cell activation in the tumor microenvironment. We recently identified that PD-1 is also upregulated on ovarian mouse tumor-infiltrating myeloid dendritic cells (TIDCs) that exhibit an immune suppressive phenotype. Extending those observations in this study, we now report that PD-1 is also expressed on human myeloid TIDCs of ovarian cancer patients, on which it suppresses the expression of co-stimulatory molecules (CD40 and CD80) as well as production of inflammatory cytokines. Mechanistic studies revealed that PD-1 on TIDCs is associated with Src homology domain-containing phosphatase-2 (SHP-2) and that PD-1-mediated blockade of NFkB-dependent cytokine release is SHP-2 dependent. PD-1 also inhibits NFkB-mediated antigen presentation which appears, however, to be independent of SHP-2. Thus, suppression of NFkB is critical in mediating PD-1-induced paralysis of ovarian tumor-associated immune TIDCs and is mediated through multiple signaling circuits that are both SHP-2 dependent and independent.

Abstract The PD-1:PD-L1 immune signaling axis mediates suppression of T-cell–dependent tumor immunity. PD-1 expression was recently found to be upregulated on tumor-infiltrating murine (CD11c+CD11b+CD8−CD209a+) and human (CD1c+CD19−) myeloid dendritic cells (TIDC), an innate immune cell type also implicated in immune escape. However, there is little knowledge concerning how PD-1 regulates innate immune cells. In this study, we examined the role of PD-1 in TIDCs derived from mice bearing ovarian tumors. Similar to lymphocytes, TIDC expression of PD-1 was associated with expression of the adapter protein SHP-2, which signals to NF-κB; however, in contrast to its role in lymphocytes, we found that expression of PD-1 in TIDC tonically paralyzed NF-κB activation. Further mechanistic investigations showed that PD-1 blocked NF-κB–dependent cytokine release in a SHP-2–dependent manner. Conversely, inhibition of NF-κB–mediated antigen presentation by PD-1 occurred independently of SHP-2. Collectively, our findings revealed that PD-1 acts in a distinct manner in innate immune cells compared with adaptive immune cells, prompting further investigations of the signaling pathways controlled by this central mediator of immune escape in cancer. Cancer Res; 76(2); 239–50. ©2015 AACR.

Abstract Purpose: It is well known that the immune system impacts the clinical course of ovarian cancer suggesting that immune-based approaches may effective in treating the disease. This has led to several clinical trials of novel treatments such as antibody, vaccine, and adoptive T cell therapy. PD-1:PD-L1 axis is a major immune regulatory pathway that blunts immune effectors in the tumor microenvironment. It is well known that high surface expression of PD-1 on tumor infiltrating T cells is a sign of their exhaustion. However, the complete mechanism behind the PD-1 regulation of T cell exhaustion is yet to be explored. Recently we identified that PD-1 is also expressed on ovarian tumor-infiltrating myeloid dendritic cells (DCs) that exhibit an immunosuppressive phenotype. Our goal in this study was to understand the mechanism by which PD-1 mediates the paralysis of ovarian cancer infiltrating DCs. Experimental procedures: PD-1+ DCs obtained from ID8 mouse model of ovarian cancer were used in this study. Data from this preclinical model was confirmed by using myeloid DCs obtained from ovarian cancer patient’s samples. Using standard flow cytometry, immunoassays (ELISA, multiplexed cytokine assay), PCR array, western blot and confocal microscopy, PD-1 mediated paralysis of ovarian cancer DCs was determined. Results: Our data shows that blockade of surface PD-1 on ovarian cancer infiltrating DCs results in their activation by, enhancing their surface co-stimulatory molecules expression, increasing their motility, enhancing their antigen presentation capacity, and increasing their production of immunostimulatory cytokines. Also, our results suggest that PD-1 expressed on tumor DCs mediates the suppression of NFkB which occurs through SHP-2 and IKK dependent mechanisms. Conclusion: Our study reveals that blockade of PD-1 on ovarian cancer infiltrating DCs results in the reversal of their paralysis to such an extent that it overrides their B7-H1 mediated suppression of T cells and this occurs through the reversal of PD-1 mediated tonic suppression of NFkB. Citation Format: Lavakumar Karyampudi James Krempski, Purushottam Lamichhane, Kimberly R. Kalli, Marshall D. Behrens, Doris M. Vargas, Lynn C Hartmann, Karen E Hedin, Ellen L. Goode, Keith L. Knutson. PD-1 mediated paralysis of ovarian cancer infiltrating dendritic cells [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-THER-1418.