The ATP (adenosine 5'-triphosphate) molecule is an important extracellular signaling molecule, as it is able to control most aspects of tissue functions. This is primarily facilitated by purine receptors, whose plasticity and diversity are responsible for a wide range of effective responses in the target cell. Since ATP is very rapidly degraded in the extracellular environment, observing only nucleotide P2 receptors and extracellular ATP concentrations is not sufficient - it is important to monitor the overall image of the dynamic equilibrium between extracellular ATP concentrations in its degradation molecules, particularly adenosine. While incresed ATP concentrations in the adenosynergic system act as a signal for danger, increased adenosine concentrations can be associated with the immunosuppressive function of the tumor milieu. Cancer is a complex disease that is dictated both by cell-intrinsic and cell-extrinsic processes and represents a complicated regulatory and metabolic network of processes. In contrast to healthy differentiated cells that concentrate mainly on mitochondrial oxidative phosphorylation for the production of energy, most cancer cells rely on the production of ATP by aerobic glycolysis. In addition, recent research suggests the ability of cancer cells to internalize extracellular ATP by macropinosis, since concentrations of extracellular ATP are significantly higher in the tumor microenviroment compared to healthy tissue microenviroment. The detection and development of enzyme inhibitors and hypoxic-adenosine pathways present a promising area for new immunotherapeutic agents; however, a wider consideration of the problem of non-selectivity and side effects is essential. In the future, we can expect the discovery of sophisticated methods that would offer us integrated knowledge of tumor milieu, which is one of the main obstacles in the development of new treatments for cancer.
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