Summary TGF-β blockade significantly slows tumor growth through many mechanisms, including activation of CD8+ T-cells and macrophages. Here, we show that TGF-β blockade also increases neutrophil-attracting chemokines resulting in an influx of CD11b+/Ly6G+ tumor-associated neutrophils (TAN) that are hypersegmented, more cytotoxic to tumor cells, and express higher levels of pro-inflammatory cytokines. Accordingly, following TGF-β blockade, depletion of these neutrophils significantly blunts anti-tumor effects of treatment and reduces CD8+ T-cell activation. In contrast, in control tumors, neutrophil depletion decreases tumor growth and results in more activated CD8+ T-cells intra-tumorally. Together, these data suggest that TGF-β within the tumor microenvironment induces a population of TAN with a pro-tumor phenotype. TGF-β blockade results in the recruitment and activation of TAN with an anti-tumor phenotype.

Cell-cell and cell-substratum interactions are mediated through several different families of receptors. In addition to targeting cell adhesion to specific extracellular matrix proteins and ligands on adjacent cells, these receptors influence many diverse processes including cellular growth, differentiation, junction formation, and polarity. Several families of adhesion receptors have been identified. These include: 1) the integrins, heterodimeric molecules that function both as cell-substratum and cell-cell adhesion receptors; 2) the adhesion molecules of the immunoglobulin superfamily, which are involved in cell-cell adhesion and especially important during embryo-genesis, wound healing, and the inflammatory response; 3) the cadherins, developmentally regulated, calcium-dependent homophilic cell-cell adhesion proteins; 4) the LEC-CAMs, cell adhesion molecules with lectin-like domains that mediate white blood cell/endothelial cell adhesion; and 5) homing receptors that target lymphocytes to specific lymphoid tissue. In this review we summarize recent data describing the structure and function of some of these cell adhesion molecules (with special emphasis on the integrin family) and discuss the possible role of these molecules in development, inflammation, wound healing, coagulation, and tumor metastasis.

Purpose: Myeloid suppressor (Gr-1 + /CD11b + ) cells accumulate in the spleens of tumor-bearing mice where they contribute to immunosuppression by inhibiting the function of CD8 + Tcells and by promoting tumor angiogenesis. Elimination of these myeloid suppressor cells may thus significantly improve antitumor responses and enhance effects of cancer immunotherapy, although to date few practical options exist. Experimental Design: The effect of the chemotherapy drug gemcitabine on the number of (Gr-1 + /CD11b + ) cells in the spleens of animals bearing large tumors derived from five cancer lines grown in both C57Bl/6 and BALB/c mice was analyzed. Suppressive activity of splenocytes from gemcitabine-treated and control animals was measured in natural killer (NK) cell lysis and Winn assays. The impact of myeloid suppressor cell activity was determined in an immunogene therapy model using an adenovirus expressing IFN-h. Results:This study shows that the chemotherapeutic drug gemcitabine, given at a dose similar to the equivalent dose used in patients, was able to dramatically and specifically reduce the number of myeloid suppressor cells found in the spleens of animals bearing large tumors with no significant reductions in CD4 + T cells, CD8 + T cells, NK cells, macrophages, or B cells. The loss of myeloid suppressor cells was accompanied by an increase in the antitumor activity of CD8 + T cells and activated NK cells. Combining gemcitabine with cytokine immunogene therapy using IFN-h markedly enhanced antitumor efficacy. Conclusions: These results suggest that gemcitabine may be a practical strategy for the reduction of myeloid suppressor cells and should be evaluated in conjunction with a variety of immunotherapy approaches.

Mesothelin is a cell-surface molecule over-expressed on a large fraction of carcinomas, and thus is an attractive target of immunotherapy. A molecularly targeted therapy for these cancers was created by engineering T cells to express a chimeric receptor with high affinity for human mesothelin. Lentiviral vectors were used to express a single-chain variable fragment that binds mesothelin and that is fused to signaling domains derived from T-cell receptor zeta, CD28, and CD137 (