Construction of SLC16A1/3 Targeted Gallic Acid-Iron-Embelin Nanoparticles for Regulating Glycolysis and Redox Pathways in Cervical Cancer

Cancer cells rewire their metabolism to promote growth, survival, proliferation, and long-term maintenance. The common feature of this altered metabolism is the increased glucose uptake and fermentation of glucose to lactate. This phenomenon is observed even in the presence of completely functioning mitochondria and, together, is known as the 'Warburg Effect'. The Warburg Effect has been documented for over 90 years and extensively studied over the past 10 years, with thousands of papers reporting to have established either its causes or its functions. Despite this intense interest, the function of the Warburg Effect remains unclear. Here, we analyze several proposed explanations for the function of Warburg Effect, emphasize their rationale, and discuss their controversies.

Increased glucose uptake and accumulation of lactate, even under normoxic conditions (i.e., aerobic glycolysis or the Warburg Effect), is a common feature of cancer cells. This phenomenon clearly indicates that lactate is not a surrogate of tumor hypoxia. Tumor lactate can predict for metastases and overall survival of patients, as shown by several studies of different entities. Metastasis of tumors is promoted by lactate-induced secretion of hyaluronan by tumor-associated fibroblasts that create a milieu favorable for migration. Lactate itself has been found to induce the migration of cells and cell clusters. Furthermore, radioresistance has been positively correlated with lactate concentrations, suggesting an antioxidative capacity of lactate. Findings on interactions of tumor metabolites with immune cells indicate a contribution of lactate to the immune escape. Furthermore, lactate bridges the gap between high lactate levels in wound healing, chronic inflammation, and cancer development. Tumor cells ensure sufficient oxygen and nutrient supply for proliferation through lactate-induced secretion of VEGF, resulting in the formation of new vessels. In summary, accumulation of lactate in solid tumors is a pivotal and early event in the development of malignancies. The determination of lactate should enter further clinical trials to confirm its relevance in cancer biology. ©2011 AACR

Among viability assays that depend on the conversion of substrate to chromogenic product by live cells, the MTT assay is still among one of the most versatile and popular assays. The MTT assay involves the conversion of the water-soluble yellow dye MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] to an insoluble purple formazan by the action of mitochondrial reductase. Formazan is then solubilized and the concentration determined by optical density at 570 nm. The result is a sensitive assay with excellent linearity up to ∼106 cells per well. As with the alamarBlue assay, small changes in metabolic activity can generate large changes in MTT, allowing one to detect cell stress upon exposure to a toxic agent in the absence of direct cell death. The assay has been standardized for adherent or nonadherent cells grown in multiple wells. The protocol uses a standard 96-well plate. This can be scaled up, however, to suit a different plate format. Plate 500-10,000 cells per well in a 96-well plate. The assay has good linearity up to 106 cells.