Tumor cells can induce certain cytokines and soluble receptors that have a sup-pressive effect on the immune system. In this study, we showed that an extracellu-lar portion of a membrane-bound ligand of CD40 (soluble CD40 ligand; sCD40L) was significantly elevated in the serum of cancer patients compared with healthy donors. In addition, PBMCs from cancer patients had a relatively larger population of myeloid-derived suppressor cells (MDSCs), defined as CD33 HLA-DR cells, and these cells expressed higher levels of CD40. T-cell proliferation and IFN-production decreased when stimulated T cells were cocultured with an increased amount of autologous MDSCs. The addition of recombinant monomeric sCD40L enriched MDSCs and had an additive inhibitory effect on T-cell proliferation. PBMCs cultured in vitro with sCD40L also showed an expansion of regulatory T cells (CD4 CD25 high Foxp3), as well as induction of cytokines, such as IL-10 and IL-6. Moreover, sCD40L-induced enrichment of programmed death-1-expressing T cells was greater in cancer patients than in healthy donors. Preexisting sCD40L also inhibited IL-12 production from monocytes on activation. These data suggest that the higher levels of sCD40L seen in cancer patients may have an immunosuppressive effect. These studies were registered at www.clinicaltrials.gov as NCT00060528, NCT00019695, NCT00179309, NCT00514072, NCT00081848, and NCT00436956. (Blood. 2012;120(15):3030-3038)

The interaction between CD27 and its ligand CD70 has been implicated in regulating cellular immune responses to cancer. Here we report on the role of soluble CD27 (sCD27) in T-cell activation and its elevation in the serum of cancer patients after immunotherapy. In vitro, sCD27 is preferentially derived from activated CD4+ T cells. Adding sCD27 to stimulated peripheral blood mononuclear cells increases T-cell activation and proliferation, and is associated with the immunological synapse-related proteins myosin IIA, HMGB1, and the TCR Vβ chain. The pool of serum sCD27 is shown to be greater in healthy donors than in cancer patients. However, metastatic cancer patients treated with immunotherapy showed a significant increase in the serum sCD27-pool post-therapy (p < 0.0005); there was also an increased trend towards an association between enhanced sCD27-pool post-therapy and overall survival (p = 0.022). The identification of sCD27 as an immune modulator associated with enhanced human T-cell activation in vitro and in vivo provides a rationale for developing new immunotherapeutic strategies aimed at enhancing sCD27 for treating cancer and potentially other diseases.

The embryonic T-box transcription factor brachyury is aberrantly expressed in a range of human tumors. Previous studies have demonstrated that brachyury is a driver of the epithelial-mesenchymal transition (EMT), a process associated with cancer progression. Brachyury expression in human tumor cells enhances tumor invasiveness in vitro and metastasis in vivo, and induces resistance to various conventional therapeutics including chemotherapy and radiation. These characteristics, and the selective expression of brachyury for a range of human tumor types vs. normal adult tissues, make brachyury an attractive tumor target. Due to its intracellular localization and the “undruggable” character of transcription factors, available options to target brachyury are currently limited. Here we report on the development and characterization of an immunological platform for the efficient targeting of brachyury-positive tumors consisting of a heat-killed, recombinant Saccharomyces cerevisiae (yeast)–brachyury vector-based vaccine (designated as GI-6301) that expresses the full-length human brachyury protein. We demonstrate that human dendritic cells treated with recombinant yeast-brachyury can activate and expand brachyury-specific CD4+ and CD8+ T cells in vitro that, in turn, can effectively lyse human tumor cells expressing the brachyury protein. Vaccination of mice with recombinant yeast-brachyury is also shown here to elicit brachyury-specific CD4+ and CD8+ T-cell responses, and to induce anti-tumor immunity in the absence of toxicity. Based on these results, a Phase I clinical trial of GI-6301 is currently ongoing in patients with advanced tumors; to our knowledge, this is the first vaccine platform aimed at targeting a driver of tumor EMT that has successfully reached the clinical stage.