Objectives: This study aimed to systematically analyze changes in mitochondrial-related protein expression in bladder cancer cells and tumor-associated fibroblasts and to investigate the characteristics of bladder cancer cell energy metabolism.
Methods: In this study, we utilized the following techniques to achieve the objectives: (1) a co-culture system of bladder tumor cells and fibroblasts was built using a microfluidic chip as a three-dimensional culture system; (2) the concentration of lactic acid in the medium from the different groups was determined using an automatic micro-plate reader; (3) a qualitative analysis of mitochondria-related protein expression was performed by immunofluorescent staining; and (4) a quantitative analysis of mitochondrial-associated protein expression was conducted via Western blot. SPSS software was utilized to analyze the data.
Results: (1) Determination of lactic acid concentration: The lactic acid concentration was determined to be highest in the experimental group, followed by the T24 cell control group and then the fibroblast control group. (2) Qualitative results: In the control group, the mitochondrial-related protein fluorescence intensity was higher in the fibroblasts compared with the cancer cells, and the fluorescence intensity of the fibroblasts was reduced compared with the experimental group. The mitochondrial-related protein fluorescence intensity of the cancer cells was higher in the experimental group compared with the control group, and the opposite results were obtained with the fibroblasts. (3) Quantitative results: The expression of mitochondria-related proteins was higher in fibroblasts compared with cancer cells in the control group, and the opposite results were obtained in the experimental group (P<0.05). The expression of mitochondria-related proteins was increased in cancer cells in the experimental group compared with the control group; the opposite results were observed for the fibroblasts (P<0.05).
Conclusions: The energy metabolism of bladder tumor cells does not parallel the "Warburg effect" because even under sufficient oxygen conditions, cancer cells still undergo glycolysis. Bladder cancer cells also have an efficient oxidative phosphorylation process wherein cancer cells promote glycolysis in adjacent interstitial cells, thereby causing increased formation of nutritional precursors. These high-energy metabolites are transferred to adjacent tumor cells in a specified direction and enter the Krebs Cycle. Ultimately, oxidative phosphorylation increases, and sufficient ATP is produced.
Keywords: Energy metabolism; microfluidic chip; three-dimensional cell culture; tumorigenesis; warburg effect.