Multidimensional imaging provides evidence for down-regulation of T cell effector function by MDSC in human cancer tissue.

A high intratumoral frequency of neutrophils is associated with poor clinical outcome in most cancer entities. It is hypothesized that immunosuppressive MDSC (myeloid-derived suppressor cell) activity of neutrophils against tumor-reactive T cells contributes to this effect. However, direct evidence for such activity in situ is lacking. Here, we used whole-mount labeling and clearing, three-dimensional (3D) light sheet microscopy and digital image reconstruction supplemented by 2D multiparameter immunofluorescence, for in situ analyses of potential MDSC-T cell interactions in primary human head and neck cancer tissue. We could identify intratumoral hotspots of high polymorphonuclear (PMN)-MDSC and T cell colocalization. In these areas, the expression of effector molecules Granzyme B and Ki67 in T cells was strongly reduced, in particular for T cells that were in close proximity or physically engaged with PMN-MDSC, which expressed LOX-1 and arginase I. Patients with cancer with evidence for strong down-regulation of T cell function by PMN-MDSC had significantly impaired survival. In summary, our approach identifies areas of clinically relevant functional interaction between MDSC and T cells in human cancer tissue and may help to inform patient selection in future combination immunotherapies.

Stromal versus tumoral inflammation differentially contribute to metastasis and poor survival in laryngeal squamous cell carcinoma.

In solid tumors the biology and clinical course are strongly influenced by the interaction of tumor cells and infiltrating stromal host cells. The aim of this study was to assess the relative importance of stromal vs. tumoral inflammation for metastasis and survival in patients with laryngeal squamous cell carcinoma (LSCC). In 110 patients with tissues from histologically proven LSCC the expression of CD45, CD11b, CD3, MMP-9 and COX-2 was semiquantitatively analyzed in stromal regions and tumor nests. CD45, CD11b, CD3 and MMP-9 positive cells were more abundant in stroma whereas COX-2 was predominantly expressed in epithelial tumor nests. High expression of stromal CD45 and CD11b on immune cells in tumor regions correlated with COX-2 expression on tumor cells. High levels of CD45 in stroma as well as CD11b and COX-2 in tumor nests were associated with increased metastasis. In contrast, high frequencies of CD3 cells in the tumor core area were associated with reduced metastasis. Overall survival was reduced in patients with high stromal CD45, high tumoral CD11b and high tumoral COX-2 expression. This is the first study which separately analyzes peritumoral stroma and tumor core area in laryngeal squamous cell carcinoma in terms of CD45, CD11b, CD3, MMP-9 and COX-2 expression. Our results indicate that stroma and tumor islands need to be considered as two separate compartments in the inflammatory tumor microenvironment. Inflammatory stromal leukocytes, abundant myeloid cells in tumor regions and high expression of COX-2 on tumor cells are linked to metastatic disease and poor overall survival.

Tumor-specific CD4+ T cells develop cytotoxic activity and eliminate virus-induced tumor cells in the absence of regulatory T cells.

The important role of tumor-specific cytotoxic CD8(+) T cells is well defined in the immune control of the tumors, but the role of effector CD4(+) T cells is poorly understood. In the current research, we have used a murine retrovirus-induced tumor cell line of C57BL/6 mouse origin, namely FBL-3 cells, as a model to study basic mechanisms of immunological control and escape during tumor formation. This study shows that tumor-specific CD4(+) T cells are able to protect against virus-induced tumor cells. We show here that there is an expansion of tumor-specific CD4(+) T cells producing cytokines and cytotoxic molecule granzyme B (GzmB) in the early phase of tumor growth. Importantly, we demonstrate that in vivo depletion of regulatory T cells (Tregs) and CD8(+) T cells in FBL-3-bearing DEREG transgenic mice augments IL-2 and GzmB production by CD4(+) T cells and increases FV-specific CD4(+) T-cell effector and cytotoxic responses leading to the complete tumor regression. Therefore, the capacity to reject tumor acquired by tumor-reactive CD4(+) T cells largely depends on the direct suppressive activity of Tregs. We suggest that a cytotoxic CD4(+) T-cell immune response may be induced to enhance resistance against oncovirus-associated tumors.