The Interplay Between Oxidative Phosphorylation and Glycolysis as a Potential Marker of Bladder Cancer Progression in Vitro and in Vivo

Abstract

BackgroundUrothelial bladder cancer (UBC) is the most common tumor of the urinary system, the ninth most common cancer worldwide and the one with the most expensive treatment from diagnosis to death. One of the biggest problems related to this disease is the lack of sufficiently accurate markers that can anticipate the progression of the cancer from a low-grade non-muscle invasive to a high-grade muscle invasive UBC. Genomics and transcriptomics have recently added a number of molecular markers to traditional observations based on pathological parameters, which have greatly improved the prediction of risk of recurrence and progression. The inclusion of information from other omics sciences, such as metabolomics, could significantly improve this scenario.MethodsIn this study, we present the metabolic characterization using 1H-NMR of three UBC cell lines representing tumors with low-risk of progression, RT4, high-risk, 5637, and a cell line that shares characteristics with both, RT112. The metabolic profiles were classified by multivariate analysis. To validate the in vitro results, concentrations of two metabolites were measured in vivo in the urine of 91 patients with non-invasive and invasive tumors.ResultsRT4 cells mainly use oxidative phosphorylation to produce ATP and biomass, 5637 cells depend mainly on glycolysis, while RT112 cells show a mixed state with both metabolisms partially activated. The lactate/alanine ratio proved to be the most sensitive marker to the different type of metabolism active in the cells in vitro. By measuring its value in vivo in urine, we have found a two-fold increase among patients with high-grade tumors compared to low-grade ones.ConclusionsOur results reveal for the first time the relative importance of glycolysis and oxidative phosphorylation in the growth and maintenance of different UBC cell lines, and the relationship with their genomic signatures. They suggest that oxidative and non-oxidative metabolic states are primarily related to cell lines with low and high risk of progression, respectively. From this observation and our preliminary in vivo results, it appears that the lactate/alanine ratio in patients' urine is a good candidate to become a new marker to predict the conversion of low-grade tumors into more malignant forms.