The brain has an exceptionally high requirement for energy metabolism, with glucose serving as the exclusive energy source. Cancers, including glioblastoma, have a high glucose uptake and rely on aerobic glycolysis for energy metabolism. The alternation of high-efficiency oxidative phosphorylation to a low-efficiency aerobic glycolysis pathway (Warburg effect) provides macromolecules for biosynthesis and proliferation. Current research indicates that the specific metabolism in the tumor tissue and normal brain tissue in the glioma allows the use of 5-aminolevulinic acid (5 ALA)-induced protoporphyrin IX (PpIX) and methylene blue (MB) to monitor and correct the development of the tumor. The focus is on the detection of the differences between tumor cells and tumor-associated macrophages/microglia using spectroscopic and microscopic methods, based on the fluorescent signals and the difference in the drug accumulation of photosensitizers (PSs). Since 5 ALA has long been used effectively in the clinic for fluorescent surgical navigation, it was employed as an agent to identify the localization of tumor tissue and study its composition, particularly tumor and immune cells (macrophages), which have also been shown to actively accumulate PpIX. However, since PpIX is photodynamically active, it can be considered effective as the main target of tumor tissue for further successful photodynamic therapy. MB was employed to visualize resident microglia, which is important for their activation/deactivation to prevent the reprogramming of the immune cells by the tumor. Thus, using two drugs, it is possible to prevent crosstalk between tumor cells and the immune cells of different geneses.
Keywords: 5-aminolevulinic acid (5 ALA); brain; fluorescent diagnostics; macrophages; methylene blue (MB); microglia; photosensitizer (PS); spectroscopic method; video fluorescent method.
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