Malignancy cells are characterized by a metabolic shift in cellular energy production, orchestrated by the transcription factor HIF-1, from mitochondrial oxidative phosphorylation to increased glycolysis, regardless of oxygen availability (Warburg effect). heterogeneity and to studies that explored tumor pH imaging for assessing treatment response to anticancer therapies. tumor pH maps. Magnetic resonance imaging methods Magnetic resonance spectroscopy Magnetic resonance spectroscopy (MRS) has been proposed in the D-106669 early days of nuclear magnetic resonance (NMR) applications as a direct approach to the detection and quantification of metabolites in living tissues. In the oncological field, MRS allows the assessment of abnormal metabolic profiles that may act as useful prognostic biomarkers. In addition to metabolites, MRS has also been exploited for assessing pHi and pHe compartments of tumors cells by combining acceptable sensitivity threshold with spatial resolution. Intense efforts have been devoted to design suitable pH reporters with the aim of satisfying the criteria of favorable pharmacokinetics, pdue to the dependence of its chemical shift on pH changes in the physiological range (pby exploiting the intracellular pH reporter 2-deoxyglucose (2DG), that is phosphorylated to 2DG6P and accumulates within cells overcoming the glycolytic process [15]. 31P-MRS of fibrosarcoma xenograft tumors revealed a good correspondence between pH values obtained from Pi and from 2DG6P measurements, confirming that Pi-MRS measurements definitely statement on intracellular pH. To supply the lack of extracellular pH reporter probes for 31P-MRS, exogenous phosphonate brokers have also been developed. Despite the fact that several extracellular phosphonate-based probes showed good characteristics [16], most applications have historically involved the use of 3-aminopropylphosphonate (3-APP). This compound shows a pthe concept of the cellular pH gradient of tumors, indicating that intracellular pH in tumor is usually more alkaline in comparison to normal tissue, whereas extracellular pH is generally more acidic. This peculiar information has been exploited in several studies aiming at reverting the acidic-base pH gradient as a potential approach for treating malignancy. This idea is based on the fact that this kinetic uptake of drugs strongly depends on their ionization state in relation to a specific pHi/pHe condition [19]. Several investigations showed increased cytotoxic activity of chemotherapeutic drugs as mitoxantrone and doxorubicin upon induced tumor alkalinization with sodium bicarbonate, which raises the extracellular pH of 0.4C0.8?models. [20, 21] Moreover, inhibitors of mitochondrial metabolism in combination with hyperglycemic conditions induced selective acidification of human melanoma xenografts, with a significant decrease of both intra and extracellular pH [22]. Furthermore, 31P-MRS approach was recently used in a mouse model to evaluate early intracellular pH changes upon antiangiogenic treatment of recurrent glioblastoma [23]. This approach can therefore provide assessments of both intra- and extracellular tumor pH by combining endogenous and exogenous D-106669 31P-made up of molecules. However, the potential neurotoxicity of 3-APP (analog of the -aminobutyric TNFSF10 acid neurotransmitter) in the presence of compromised blood brain barriers is a concern for human use and the low spatial resolution and long acquisition times combined with the requirement of dedicated coils limit its application application relies on the minimal NMR background interference from endogenous transmission and the large chemical shift range (~?300?ppm) that allowed the development of several fluorinated probes able to statement microenvironment changes of pO2, hypoxia, enzyme D-106669 activity, and pH [24]. Aromatic molecules, such as the vitamin B6 analogue fluoropyridoxol, were reported for assessing pH thanks to the larger chemical shift response (~?9.5?ppm) to changes in pH in comparison to fluoroalanine-based probes (~?2?ppm) [25]. Early studies demonstrated the capability of 6-fluoropyridoxol (6-FPOL) to simultaneously measure the dynamic changes of pHe/pHi in perfused rat hearth with a time resolution of 2?min [24]. As the papplications are the relative instability of fluorinated probes and their nonspecific accumulation in tissues due to their hydrophobicity. To overcome these issues, new formulations based on the encapsulation of 19F compounds have been proposed. Promising results were obtained with PEGylated nanogels that showed variation in size in accordance with pH.