No abstract

During a search for genes that maintain T cell quiescence, we determined that Tob, a member of an anti-proliferative gene family, was highly expressed in anergic T cell clones. Tob was also expressed in unstimulated peripheral blood T lymphocytes and down-regulated during activation. Forced expression of Tob inhibited T cell proliferation and transcription of cytokines and cyclins. In contrast, suppression of Tob with an antisense oligonucleotide augmented CD3-mediated responses and abrogated the requirement of costimulation for maximal proliferation and cytokine secretion. Tob associated with Smad2 and Smad4 and enhanced Smad DNA-binding. The inhibitory effect of Tob on interleukin 2 (IL-2) transcription was not mediated by blockade of NFAT, AP-1 or NF-kappaB transactivation but by enhancement of Smad binding on the -105 negative regulatory element of the IL-2 promoter. Thus, T cell quiescence is an actively maintained phenotype that must be suppressed for T cell activation to occur.

We have developed a cancer vaccine in which autologous tumor is fused with dendritic cells (DCs) resulting in the presentation of tumor antigens in the context of DC mediated costimulation. In clinical trials, immunologic responses have been observed, however responses may be muted by inhibitory pathways. The PD1/PDL1 pathway is an important element contributing to tumor mediated immune suppression. In this study, we demonstrate that myeloma cells and DC/tumor fusions strongly express PD-L1. Compared to a control population of normal volunteers, increased PD-1 expression was observed on T cells isolated from patients with myeloma. Interestingly, following autologous transplantation, T cell expression of PD-1 returned to levels seen in normal controls. We examined the effect of PD-1 blockade on T cell response to DC/tumor fusions ex-vivo. Presence of CT-011, an anti-PD1 antibody, promoted the vaccine induced T cell polarization towards an activated phenotype expressing Th1 as compared to Th2 cytokines. A concomitant decrease in regulatory T cells and enhanced killing in a cytotoxicity assay was observed. In summary, we demonstrate that PD-1 expression is increased in T cells of patients with active myeloma, and that CT-011 enhances activated T cell responses following DC/tumor fusion stimulation.

Background A multiple myeloma (MM) vaccine has been developed whereby patient derived tumor cells are fused with autologous dendritic cells (DCs), creating a hybridoma that stimulates a broad anti-tumor response. We report on the results of a phase II trial in which patients underwent vaccination following autologous stem cell transplantation (ASCT) to target minimal residual disease. Methods Twenty-four patients received serial vaccinations with DC/myeloma fusion cells following post-transplant hematopoietic recovery. A second cohort of 12 patients received a pre-transplant vaccine followed by post-transplant vaccinations. DCs generated from adherent mononuclear cells cultured with GM-CSF, IL-4 and TNFα were fused with autologous bone marrow-derived MM cells using polyethylene glycol (PEG). Fusion cells were quantified by determining the percentage of cells that co-express DC and MM antigens. Findings The post-transplant period was associated with reduction in general measures of cellular immunity; however, an increase in CD4 and CD8+ myeloma specific T cells was observed after ASCT that was significantly expanded following post-transplant vaccination. Seventy-eight percent of patients achieved a best response of CR+VGPR and 47% achieved a CR/nCR. Remarkably, 24% of patients who achieved a partial response following transplant were converted to CR/nCR after vaccination and at over 3 months post-transplant, consistent with a vaccine-mediated effect on residual disease. Interpretation The post-transplant period for patients with multiple myeloma provides a unique platform for cellular immunotherapy in which vaccination with DC/MM fusions resulted in the marked expansion of myeloma specific T cells and cytoreduction of minimal residual disease.