Lenalidomide Polarizes Th1-specific Anti-tumor Immune Response and Expands XBP1 Antigen-Specific Central Memory CD3+CD8+ T cells against Various Solid Tumors

Introduction: Effective combination immunotherapeutic strategies may be required to enhance effector cells’ anti-tumor activities and improve clinical outcomes. Methods: XBP1 antigen-specific cytotoxic T lymphocytes (XBP1-CTL) generated using immunogenic heteroclitic XBP1 US184-192 (YISPWILAV) and XBP1 SP367-375 (YLFPQLISV) peptides or various solid tumor cells over-expressing XBP1 target antigen were evaluated, either alone or in combination with lenalidomide, for phenotype and immune functional activity. Results: Lenalidomide treatment of XBP1-CTL increased the proportion of CD45RO+ memory CD3+CD8+ T cells, but not the total CD3+CD8+ T cells. Lenalidomide upregulated critical T cell activation markers and costimulatory molecules (CD28, CD38, CD40L, CD69, ICOS), especially within the central memory CTL subset of XBP1-CTL, while decreasing TCRαβ and T cell checkpoint blockade (CTLA-4, PD-1). Lenalidomide increased the anti-tumor activities of XBP1-CTL memory subsets, which were associated with expression of Th1 transcriptional regulators (T-bet, Eomes) and Akt activation, thereby resulting in enhanced IFN-γ production, granzyme B upregulation and specific CD28/CD38-positive and CTLA-4/PD-1-negative cell proliferation. Conclusions: These studies suggest the potential benefit of lenalidomide treatment to boost anti-tumor activities of XBP1-specific CTL against a variety of solid tumors and enhance response to an XBP1-directing cancer vaccine regime

Inhibition of wild-type p53-expressing AML by novel small molecule HDM2 inhibitor, CGM097

The tumor suppressor, p53, is a key regulator of apoptosis and functions upstream in the apoptotic cascade by both indirectly and directly regulating Bcl-2 family proteins. In cells expressing wild-type (wt) p53, the Human Double Minute 2 (HDM2) protein binds to p53 and blocks its activity. Inhibition of HDM2:p53 interaction activates p53 and causes apoptosis or cell cycle arrest. We have characterized the novel HDM2 inhibitor, CGM097, as having significant activity against wt p53-expressing acute myeloid leukemia (AML). Specifically, CGM097 potently and selectively inhibited the proliferation of human AML cell lines and primary AML cells expressing wt p53, but not mutant p53, in a target-specific manner. Several patient samples that harbored mutant p53 were comparatively unresponsive to CGM097. Synergy was observed when CGM097 was combined with FLT3 inhibition against mutant FLT3-expressing cells, as well as when combined with MEK inhibition in cells with activated MAPK signaling. Finally, CGM097 was effective in reducing leukemia burden in vivo. Taken together, these data suggest that CGM097 might be a promising treatment for AML characterized as harboring wt p53 as a single agent, as well as possibly in combination with another targeted therapy using tyrosine kinase inhibitors (TKIs) against oncogenes that drive AML

Lenalidomide Enhances Immune Checkpoint Blockade-Induced Immune Response in Multiple Myeloma

International audiencePurpose: PD-1/PD-L1 signaling promotes tumor growth while inhibiting effector cell-mediated antitumor immune responses. Here, we assessed the impact of single and dual blockade of PD-1/ PD-L1, alone or in combination with lenalidomide, on accessory and immune cell function as well as multiple myeloma cell growth in the bone marrow (BM) milieu. Experimental Design: Surface expression of PD-1 on immune effector cells, and PD-L1 expression on CD138 þ multiple mye-loma cells and myeloid-derived suppressor cells (MDSC) were determined in BM from newly diagnosed (ND) multiple myelo-ma and relapsed/refractory (RR) multiple myeloma versus healthy donor (HD). We defined the impact of single and dual blockade of PD-1/PD-L1, alone and with lenalidomide, on auto-logous anti-multiple myeloma immune response and tumor cell growth. Results: Both ND and RR patient multiple myeloma cells have increased PD-L1 mRNA and surface expression compared with HD. There is also a significant increase in PD-1 expression on effector cells in multiple myeloma. Importantly, PD-1/PD-L1 blockade abrogates BM stromal cell (BMSC)-induced multiple myeloma growth, and combined blockade of PD-1/PD-L1 with lenalidomide further inhibits BMSC-induced tumor growth. These effects are associated with induction of intracellular expression of IFNg and granzyme B in effector cells. Importantly, PD-L1 expression in multiple myeloma is higher on MDSC than on antigen-presenting cells, and PD-1/PD-L1 blockade inhibits MDSC-mediated multiple myeloma growth. Finally, lenalido-mide with PD-1/PD-L1 blockade inhibits MDSC-mediated immune suppression. Conclusions: Our data therefore demonstrate that checkpoint signaling plays an important role in providing the tumor-promoting , immune-suppressive microenvironment in multiple myeloma, and that PD-1/PD-L1 blockade induces anti-multiple myeloma immune response that can be enhanced by lenalido-mide, providing the framework for clinical evaluation of combination therapy

Inhibition of wild-type p53-expressing AML by the novel small molecule HDM2 inhibitor CGM097

The tumor suppressor p53 is a key regulator of apoptosis and functions upstream in the apoptotic cascade by both indirectly and directly regulating Bcl-2 family proteins. In cells expressing wild-type (WT) p53, the HDM2 protein binds to p53 and blocks its activity. Inhibition of HDM2:p53 interaction activates p53 and causes apoptosis or cell-cycle arrest. Here, we investigated the ability of the novel HDM2 inhibitor CGM097 to potently and selectively kill WT p53-expressing AML cells. The antileukemic effects of CGM097 were studied using cellbased proliferation assays (human AML cell lines, primary AML patient cells, and normal bone marrow samples), apoptosis, and cell-cycle assays, ELISA, immunoblotting, and an AML patient-derived in vivo mouse model. CGM097 potently and selectively inhibited the proliferation of human AML cell lines and the majority of primary AML cells expressing WT p53, but not mutant p53, in a target-specific manner. Several patient samples that harbored mutant p53 were comparatively unresponsive to CGM097. Synergy was observed when CGM097 was combined with FLT3 inhibition against oncogenic FLT3-expressing cells cultured both in the absence as well as the presence of cytoprotective stromal-secreted cytokines, as well as when combined with MEK inhibition in cells with activated MAPK signaling. Finally, CGM097 was effective in reducing leukemia burden in vivo. These data suggest that CGM097 is a promising treatment for AML characterized as harboring WT p53 as a single agent, as well as in combination with other therapies targeting oncogene-activated pathways that drive AML