Development of an In Vitro Assay to Assess Pharmacological Compounds and Reversion of Tumor-Derived Immunosuppression of Dendritic Cells

Colorectal Cancer and Tumor Stromal Cells Have Different Effects on the Differentiation and Maturation of Dendritic Cells In Vitro

We compared the ability of SW837, SW480, HT-29, Caco-2, and HCT116 colorectal cancer lines and cancer-associated fibroblasts obtained from a colorectal adenocarcinoma biopsy specimen to modulate differentiation and maturation of dendritic cells in co-culture. The expression of surface markers of dendritic cell differentiation (CD1a) and maturation (CD83), as well as the expression of CD14 monocyte marker was evaluated by flow cytometry. Cancer-associated fibroblasts completely suppressed dendritic cell differentiation from peripheral blood monocytes induced by granulocyte-macrophage CSF and IL-4, but had no significant effect on their maturation under the influence of bacterial LPS. On the contrary, tumor cell lines did not interfere with monocyte differentiation, although some of them significantly reduced the level of CD1a expression. In contrast to cancer-associated fibroblasts, tumor cell lines and conditioned medium from primary tumor cell culture suppressed LPS-induced maturation of dendritic cells. These results suggest that tumor cells and cancer-associated fibroblasts can modulate different stages of the antitumor immune response.

Monocyte Infiltration and Differentiation in 3D Multicellular Spheroid Cancer Models

Tumor-associated macrophages often correlate with tumor progression, and therapies targeting immune cells in tumors have emerged as promising treatments. To select effective therapies, we established an in vitro 3D multicellular spheroid model including cancer cells, fibroblasts, and monocytes. We analyzed monocyte infiltration and differentiation in spheroids generated from fibroblasts and either of the cancer cell lines MCF-7, HT-29, PANC-1, or MIA PaCa-2. Monocytes rapidly infiltrated spheroids and differentiated into mature macrophages with diverse phenotypes in a cancer cell line-dependent manner. MIA PaCa-2 spheroids polarized infiltrating monocytes to M2-like macrophages with high CD206 and CD14 expression, whereas monocytes polarized by MCF-7 spheroids displayed an M1-like phenotype. Monocytes in HT-29 and PANC-1 primarily obtained an M2-like phenotype but also showed upregulation of M1 markers. Analysis of the secretion of 43 soluble factors demonstrated that the cytokine profile between spheroid cultures differed considerably depending on the cancer cell line. Secretion of most of the cytokines increased upon the addition of monocytes resulting in a more inflammatory and pro-tumorigenic environment. These multicellular spheroids can be used to recapitulate the tumor microenvironment and the phenotype of tumor-associated macrophages in vitro and provide more realistic 3D cancer models allowing the in vitro screening of immunotherapeutic compounds.