Adhesion to substrates induces dendritic cell endothelization and decreases immunological response

The role of angiogenic growth factors in the immune microenvironment of glioma

Angiogenic growth factors (AGFs) are a class of secreted cytokines related to angiogenesis that mainly include vascular endothelial growth factors (VEGFs), stromal-derived factor-1 (SDF-1), platelet-derived growth factors (PDGFs), fibroblast growth factors (FGFs), transforming growth factor-beta (TGF-β) and angiopoietins (ANGs). Accumulating evidence indicates that the role of AGFs is not only limited to tumor angiogenesis but also participating in tumor progression by other mechanisms that go beyond their angiogenic role. AGFs were shown to be upregulated in the glioma microenvironment characterized by extensive angiogenesis and high immunosuppression. AGFs produced by tumor and stromal cells can exert an immunomodulatory role in the glioma microenvironment by interacting with immune cells. This review aims to sum up the interactions among AGFs, immune cells and cancer cells with a particular emphasis on glioma and tries to provide new perspectives for understanding the glioma immune microenvironment and in-depth explorations for anti-glioma therapy.

Effect of laminin environments and tumor factors on the biology of myeloid dendritic cells

Dendritic cells (DCs) are immune cells that surveil the organism for infections or malignancies and activate specific T lymphocytes initiating specific immune responses. Contrariwise, DCs have been show to participate in the development of diseases, among them some types of cancer by inducing angiogenesis or immunosuppression. The ultimate fate of DC functions regarding their role in disease or health is prompted by signals from the microenvironment. We have previously shown that the interaction of DCs with various extracellular matrix components modifies the immune properties and angiogenic potential of these cells. The objective of the current studies was to investigate the angiogenic and immune profile of murine myeloid DCs upon interaction with laminin environments, with a particular emphasis on ovarian cancer. Our results show that murine ovarian tumors produce several types of laminins, as determined by PCR analysis, and also that tumor-associated DCs, both from ascites or solid tumors express adhesion molecules capable of interacting with these molecules as determined by flow cytometry and PCR analysis. Further, we established that DCs cultured on laminin upregulate both AKT and MEK signaling pathways, and that long-term culture on laminin surfaces decreases the immunological capacities of these cells when compared to the same cells cultured on synthetic substrates. In addition, we observed that tumor conditioned media was able to modify the metabolic status of these cells, and also reprogram the development of DCs from bone marrow precursors towards the generation of myeloid-derived suppressor cells. Overall, these studies demonstrate that the interaction between soluble factors and extracellular matrix components of the ovarian cancer microenvironment shape the biology of DCs and thus help them become co-conspirators of tumor growth.

Dendritic cells in inflammatory angiogenesis and lymphangiogenesis

Lymph node (LN) expansion during inflammation is essential to establish immune responses and relies on the development of blood and lymph vessels. Human dendritic cells (DCs), subdivided into two main subsets, namely conventional DCs (cDCs) and plasmacytoid DCs (pDCs), are professional antigen presenting cells endowed with the capability to produce soluble mediators regulating inflammation and tissue repair. cDCs support angiogenesis in secondary LNs both directly and indirectly through the secretion of vascular endothelial growth factor-A (VEGF)-A and VEGF-C and the production of several other mediators endowed with angiogenic properties. Finally, cDCs can affect neovascular formation via a transdifferentiation process. At variance with cDCs, the angiogenic properties of pDCs still remain poorly explored.

Regulation of inflammatory factors by double-stranded RNA receptors in breast cancer cells

Malignant cells are not the only components of a tumor mass since other cells (e.g., fibroblasts, infiltrating leukocytes and endothelial cells) are also part of it. In combination with the extracellular matrix, all these cells constitute the tumor microenvironment. In the last decade the role of the tumor microenvironment in cancer progression has gained increased attention and prompted efforts directed to abrogate its deleterious effects on anti-cancer therapies. The immune system can detect and attack tumor cells, and tumor-infiltrating lymphocytes (particularly CD8 T cells) have been associated with improved survival or better response to therapies in colorectal, melanoma, breast, prostate and ovarian cancer patients among others. Contrariwise, tumor-associated myeloid cells (myeloid-derived suppressor cells [MDSCs], dendritic cells [DCs], macrophages) or lymphoid cells such as regulatory T cells can stimulate tumor growth via inhibition of immune responses against the tumor or by participating in tumor neoangiogenesis. Herewith we analyzed the chemokine profile of mouse breast tumors regarding their capacity to generate factors capable of attracting and sequestering DCs to their midst. Chemoattractants from tumors were investigated by molecular biology and immunological techniques and tumor infiltrating DCs were investigated for matched chemokine receptors. In addition, we investigated the inflammatory response of breast cancer cells, a major component of the tumor microenvironment, to double-stranded RNA stimulation. By using molecular biology techniques such as qualitative and quantitative PCR, PCR arrays, and immunological techniques (ELISA, cytokine immunoarrays) we examined the effects of dsRNA treatment on the cytokine secretion profiles of mouse and human breast cancer cells and non-transformed cells. We were able to determine that tumors generate chemokines that are able to interact with receptors present on the surface of tumor infiltrating DCs. We observed that PRR signaling is able to modify the production of chemokines by breast tumor cells and normal breast cells, thereby constituting a possible player in shaping the profile of the leukocyte population in the TME.

CD44 variant isoforms expressed by breast cancer cells are functional E-selectin ligands under flow conditions

Adhesion of circulating tumor cells to vascular endothelium is mediated by specialized molecules that are functional under shear forces exerted by hematogenous flow. Endothelial E-selectin binding to glycoforms of CD44 mediates shear-resistant cell adhesion in numerous physiological and pathological conditions. However, this pathway is poorly understood in breast cancer and is the focus of the present investigation. All breast cancer cell lines used in this study strongly expressed CD44. In particular, BT-20 cells expressed CD44s and multiple CD44v isoforms, whereas MDA-MB-231 cells predominantly expressed CD44s but weakly expressed CD44v isoforms. CD44 expressed by BT-20, but not MDA-MB-231, cells possessed E-selectin ligand activity as detected by Western blotting and antigen capture assays. Importantly, CD44 expressed by intact BT-20 cells were functional E-selectin ligands, regulating cell rolling and adhesion under physiological flow conditions, as found by shRNA-targeted silencing of CD44. Antigen capture assays strongly suggest greater shear-resistant E-selectin ligand activity of BT-20 cell CD44v isoforms than CD44s. Surprisingly, CD44 was not recognized by the HECA-452 MAb, which detects sialofucosylated epitopes traditionally expressed by selectin ligands, suggesting that BT-20 cells express a novel glycoform of CD44v as an E-selectin ligand. The activity of this glycoform was predominantly attributed to N-linked glycans. Furthermore, expression of CD44v as an E-selectin ligand correlated with high levels of fucosyltransferase-3 and -6 and epithelial, rather than mesenchymal, cell phenotype. Together, these data demonstrate that expression of CD44 as a functional E-selectin ligand may be important in breast cancer metastasis.

Perspectives on reprograming cancer-associated dendritic cells for anti-tumor therapies

In recent years, the relevance of the tumor microenvironment (TME) in the progression of cancer has gained considerable attention. It has been shown that the TME is capable of inactivating various components of the immune system responsible for tumor clearance, thus favoring cancer cell growth and tumor metastasis. In particular, effects of the TME on antigen-presenting cells, such as dendritic cells (DCs) include rendering these cells unable to promote specific immune responses or transform them into suppressive cells capable of inducing regulatory T cells. In addition, under the influence of the TME, DCs can produce growth factors that induce neovascularization, therefore further contributing to tumor development. Interestingly, cancer-associated DCs harbor tumor antigens and thus have the potential to become anti-tumor vaccines in situ if properly reactivated. This perspective article provides an overview of the scientific background and experimental basis for reprograming cancer-associated DCs in situ to generate anti-tumor immune responses.

Dendritic cells: In vitro culture in two- and three-dimensional collagen systems and expression of collagen receptors in tumors and atherosclerotic microenvironments

Dendritic cells (DCs) are immune cells found in the peripheral tissues where they sample the organism for infections or malignancies. There they take up antigens and migrate towards immunological organs to contact and activate T lymphocytes that specifically recognize the antigen presented by these antigen presenting cells. In the steady state there are several types of resident DCs present in various different organs. For example, in the mouse, splenic DC populations characterized by the co-expression of CD11c and CD8 surface markers are specialized in cross-presentation to CD8 T cells, while CD11c/SIRP-1α DCs seem to be dedicated to activating CD4 T cells. On the other hand, DCs have also been associated with the development of various diseases such as cancer, atherosclerosis, or inflammatory conditions. In such disease, DCs can participate by inducing angiogenesis or immunosuppression (tumors), promoting autoimmune responses, or exacerbating inflammation (atherosclerosis). This change in DC biology can be prompted by signals in the microenvironment. We have previously shown that the interaction of DCs with various extracellular matrix components modifies the immune properties and angiogenic potential of these cells. Building on those studies, herewith we analyzed the angiogenic profile of murine myeloid DCs upon interaction with 2D and 3D type-I collagen environments. As determined by PCR array technology and quantitative PCR analysis we observed that interaction with these collagen environments induced the expression of particular angiogenic molecules. In addition, DCs cultured on collagen environments specifically upregulated the expression of CXCL-1 and -2 chemokines. We were also able to establish DC cultures on type-IV collagen environments, a collagen type expressed in pathological conditions such as atherosclerosis. When we examined DC populations in atherosclerotic veins of Apolipoprotein E deficient mice we observed that they expressed adhesion molecules capable of interacting with collagen. Finally, to further investigate the interaction of DCs with collagen in other pathological conditions, we determined that both murine ovarian and breast cancer cells express several collagen molecules that can contribute to shape their particular tumor microenvironment. Consistently, tumor-associated DCs were shown to express adhesion molecules capable of interacting with collagen molecules as determined by flow cytometry analysis. Of particular relevance, tumor-associated DCs expressed high levels of CD305/LAIR-1, an immunosuppressive receptor. This suggests that signaling through this molecule upon interaction with collagen produced by tumor cells might help define the poorly immunogenic status of these cells in the tumor microenvironment. Overall, these studies demonstrate that through interaction with collagen proteins, DCs can be capable of modifying the microenvironments of inflammatory disease such as cancer or atherosclerosis.