Quality of tumor lysates used for pulsing dendritic cells is influenced by the method used to harvest adherent tumor cells.

BACKGROUND: Lysates from tumor cells are reported to induce maturation of dendritic cells (DCs) and are used in clinical settings for DC-based vaccination against solid tumors. Nevertheless, the maturation inducing effect of tumor lysates on DCs is discussed controversially and the efficacy of tumor vaccines varies significantly. FINDINGS: Using three individual adherent colorectal tumor cell lines we also faced the difficulty to obtain consistent results regarding maturation inducing effect of tumor lysates on DCs. Therefore, we compared different methods to prepare tumor cell lysate and could demonstrate that trypsinizing as a method to harvest adherent tumor cells has a significant negative impact on biologic activity of tumor lysates. Specifically, we assessed induction of maturation markers CD40, CD80, and CD86 on DCs which were treated with differently prepared lysates. CONCLUSIONS: Trypsinizing is a very common way of harvesting adherent cells from culture flasks. Our results shall call investigators' attention to the enzymatic activity of trypsin degrading some possibly important proteins on the surface of cultured cells. Specifically for DC-based vaccination against tumor antigens investigators should avoid trypsin.

Human mesenchymal stem cells respond to native but not oxidized damage associated molecular pattern molecules from necrotic (tumor) material.

Necrosis is a characteristic feature of advanced solid tumors. Released necrotic factors, also referred to as damage associated molecular patterns (DAMPs), are known to critically impact the tumor microenvironment by enhancing angiogenesis or influencing the immune response. We have recently shown that DAMPs can act as chemoattractants and activators of granulocytes. We demonstrate that necrotic material from both normal and tumor cells promotes proliferation and trafficking of human mesenchymal stem cells (MSCs). We characterize the protein high mobility group box 1 (HMGB1) as a crucial member of DAMPs within necrotic material. In addition, we show that DAMPs interfere with expression of indoleamine 2, 3-dioxygenase (IDO) in MSCs. The biological activity of necrotic material toward MSCs is abolished once these DAMPs are oxidized. MSCs found within tumor tissue can act as immunoregulatory cells and are able to promote tumor metastasis, thus playing a crucial role within the tumor microenvironment. Here, we reveal DAMPs to be crucial factors in the setting of MSC biology within the tumor microenvironment. The tumor microenvironment is characterized by reducing and hypoxic conditions that protect DAMPs from oxidation. Based on our results, oxidizing conditions should be considered for therapeutic approaches that target the tumor microenvironment.