Tumor-derived lactic acid modulates dendritic cell activation and antigen expression.
The tumor milieu can influence dendritic cell (DC) differentiation. We analyzed DC differentiation in a 3-dimensional tumor model and propose a new mechanism of DC modulation by the tumor environment. Monocytes were cultured in the presence of IL-4 and GM-CSF within multicellular tumor spheroids (MCTSs) generated from different tumor cell lines. Monocytes invaded the MCTSs and differentiated into tumor-associated dendritic cells (TADCs). The antigen expression was altered on TADCs independent of the culture conditions (immature/mature DCs, Langerhans cells) and IL-12 secretion was reduced. Supernatants of MCTSs could partially transfer the suppressive effect. Conditioned media from urotheli…
Proliferative activity and tumorigenic conversion: impact on cellular metabolism in 3-D culture
Oxygen consumption, glucose, lactate, and ATP concentrations, as well as glucose and lactate turnover rates, have been studied in a three-dimensional carcinogenesis model of differently transformed rat embryo fibroblasts (spontaneously immortalized Rat1 and myc-transfected M1, and the ras-transfected, tumorigenic descendants Rat1-T1 and MR1) to determine metabolic alterations that accompany tumorigenic conversion. Various bioluminescence techniques, thymidine labeling, measurement of[Formula: see text] distributions with microelectrodes, and determination of cellular oxygen uptake rates (Q˙[Formula: see text]) have been applied. In the ras-transfected, tumorigenic spheroid types, the size d…
Metabolic classification of human rectal adenocarcinomas: a novel guideline for clinical oncologists?
Based on previous findings in SCC of the human uterine cervix and of the head and neck, metastasis- and survival-related metabolic classification was performed in human rectal adenocarcinomas. Such a characterization is suggested as basis of a novel clinical guideline for an appropriate therapy of epithelium-derived malignancies.Tissue concentrations of ATP, glucose, and lactate in viable tumor regions of 33 pretherapeutically taken cryobiopsies from 24 patients were measured at a microscopic level using the technique of imaging bioluminescence.In metastatic carcinomas, lactate levels were significantly higher (mean+/-SD: 13.4+/-3.8 vs 6.9+/-2.5 micro mol/g, P = 0.0046) and glucose levels s…
Multicellular tumor spheroids: an underestimated tool is catching up again.
The present article highlights the rationale, potential and flexibility of tumor spheroid mono- and cocultures for implementation into state of the art anti-cancer therapy test platforms. Unlike classical monolayer-based models, spheroids strikingly mirror the 3D cellular context and therapeutically relevant pathophysiological gradients of in vivo tumors. Some concepts for standardization and automation of spheroid culturing, monitoring and analysis are discussed, and the challenges to define the most convenient analytical endpoints for therapy testing are outlined. The potential of spheroids to contribute to either the elimination of poor drug candidates at the pre-animal and pre-clinical …
Impact of exogenous lactate on survival and radioresponse of carcinoma cells in vitro
Tumour lactate levels have been shown to correlate with high radioresistance in tumour models in vivo. The study aimed to evaluate the impact of pathophysiological extracellular lactate concentrations and acidosis on the in vitro survival and radioresponse of various cancer cell lines.HCT-116, HT29 (colorectal) and FaDu (HNSCC) carcinoma cells were studied. Lactate release rates were determined, and expression of the monocarboxylate transporter MCT1 and its cofactor CD147 were monitored by immunofluorescence and flow cytometry. Colony formation was compared for cells exposed to 20 mM exogenous lactate, acidosis (pH 6.4) and lactate plus acidosis relative to control and dose response curves …
Lactate adversely affects the in vitro formation of endothelial cell tubular structures through the action of TGF-beta1.
When lactate accumulation in a tumor microenvironment reaches an average concentration of 10-20 mM, it tends to reflect a high degree of malignancy. However, the hypothesis that tumor-derived lactate has a number of partially adverse biological effects on malignant and tumor-associated host cells requires further evidence. The present study attempted to evaluate the impact of lactate on the process of angiogenesis, in particular on the formation of tubular structures. The endothelial cell (EC) network in desmoplastic breast tumors is primarily located in areas of reactive fibroblastic stroma. We employed a fibroblast-endothelial cell co-culture model as in vitro angiogenesis system normally…
Metabolic Imaging in Multicellular Spheroids of Oncogene-transfected Fibroblasts
Four rat embryo fibroblast (REF) cell lines with defined oncogenic transformation were used to study the relationship between tumorigenic conversion, metabolism, and development of cell death in a 3D spheroid system. Rat1 (spontaneously immortalized) and M1 ( myc-transfected) fibroblasts represent early nontumorigenic transformation stages, whereas Rat1-T1 (T24Ha- ras-transfected Rat1) and MR1 ( myc/T24Ha- ras-co-transfected REF) cells express a highly tumorigenic phenotype. Localized ATP, glucose, and lactate concentrations in spheroid median sections were determined by imaging bioluminescence. ATP concentrations were low in the nonproliferating Rat1 aggregates despite sufficient oxygen an…
Lactate enhances motility of tumor cells and inhibits monocyte migration and cytokine release.
In solid malignant tumors, lactate has been identified as a prognostic parameter for metastasis and overall survival of patients. To investigate the effects of lactate on tumor cell migration, Boyden chamber assays were applied. We could show here that lactate enhances tumor cell motility of head and neck carcinoma cell lines significantly in a dose-dependent manner. The changes in tumor cell migration could be attributed to L-lactate or a conversion of lactate to pyruvate, as only these two substances were able to increase migration. Addition of D-lactate or changes in osmolarity or intracellular pH did not alter the migratory potential of the cells investigated. Because lactate was shown …
Three-dimensional cell culture induces novel proliferative and metabolic alterations associated with oncogenic transformation
To date, cell biological characteristics of oncogene-transfected cells have been investigated either in relatively homogeneous monolayer cultures or in heterogeneous tumors in vivo. To evaluate the emergence of cellular heterogeneity during tumor formation, we have established a multicellular spheroid system from an oncogene-dependent, genetically determined 2-stage carcinogenesis model for 3-dimensional growth under well-defined conditions. The effect of T24Ha-ras transfection on cellular growth, proliferation, cell viability and oxygenation was investigated using spontaneously immortalized (Rat1) and c-myc-transfected (M1) Fisher 344 rat embryo fibroblasts and a tumorigenic T24Ha-ras-tran…