The ability of 2-deoxy-d-glucose (2-DG) to interfere with d-glucose metabolism demonstrates that nutrient and energy deprivation is an efficient tool to suppress cancer cell growth and survival. Acting as a d-glucose mimic, 2-DG inhibits glycolysis due to formation and intracellular accumulation of 2-deoxy-d-glucose-6-phosphate (2-DG6P), inhibiting the function of hexokinase and glucose-6-phosphate isomerase, and inducing cell death. In addition to glycolysis inhibition, other molecular processes are also affected by 2-DG. Attempts to improve 2-DG's drug-like properties, its role as a potential adjuvant for other chemotherapeutics, and novel 2-DG analogs as promising new anticancer agents are discussed in this review.using gluconeogenesis [5]. The hydrophilic nature of glucose requires specific glucose transporter proteins (GLUTs) to facilitate cellular uptake [6]. Higher glucose utilization by tumor cells requires overexpression of GLUT transporters to increase glucose uptake over 20-30 fold as compared to normal cells [7,8].Once inside the cell, glucose enters a cycle of changes to release energy in the form of ATP. Normal cells with access to oxygen utilize glycolysis to metabolize glucose into two molecules of pyruvate and form two molecules of ATP. The pyruvate is further oxidized in the mitochondria to acetyl-CoA via the pyruvate dehydrogenase complex. Acetyl-CoA then enters the Krebs cycle, in which it is oxidized into 2 molecules of CO 2 . The electrons derived from this process are used to create three molecules of NADH and one molecule of FADH 2 . These electron carrier molecules are reoxidized through the oxidoreductive systems of the respiratory chain, which drives ATP formation from ADP and inorganic phosphate (P i ) [9]. As a result of oxidative phosphorylation, 30 ATP molecules are generated from one molecule of glucose versus a net of 2 from glycolysis [9,10]. Oxygen is vitally important for this process as the final electron acceptor, allowing complete oxidation of glucose. In the case of insufficient oxygen concentrations, for example in skeletal muscle during periods of intense exertion, cells fall back on glycolysis, an ancient metabolic pathway evolved before the accumulation of significant atmospheric oxygen. Pyruvate, the end product of glycolysis, is reduced to lactate via lactic acid fermentation, cycling NADH back to NAD + [11]. The comparison of glucose metabolic pathways is presented in Figure 1.

Interleukin (IL)-8 is released both in visceral adipose tissue and in contracting skeletal muscles. In this study, we examined cellular pathways associated with muscle hypertrophy, chosen on the basis of microRNA profiling, in differentiating rat primary skeletal muscle cells (RSkMC) treated with IL-8 (1 ng/ml) for 11 days. IL-8 increased myocilin expression, Akt phosphorylation, FoxO3 dispersion throughout the cytoplasm, and reduced FoxO3 level. IL-8 decreased the expression of atrogin and MuRF1 and increased myotube length and diameter. We concluded that IL-8 present in extracellular environment of myoblasts induced to differentiation stimulates expression of myocilin, a protein important for skeletal muscle hypertrophy. This phenomenon was associated with: (a) activation of myogenic transcription, (b) increased phosphorylation and activation of PKB/Akt, leading to (c) cytoplasm distribution and degradation of a transcription factor FoxO3, (d) decreased expression of gene markers of proteolysis, atrogin and Murf1, and (e) increased myotube length and diameter. In this regard, IL-8 affects skeletal muscle cells similarly to IGF-I and can be considered as a potent anticatabolic factor for skeletal muscle.

Muscle cachexia is one of the most critical unmet medical needs. Identifying the molecular background of cancer-induced muscle loss revealed a promising possibility of new therapeutic targets and new drug development. In this review, we will define the signal transducer and activator of transcription 3 (STAT3) protein’s role in the tumor formation process and summarize the role of STAT3 in skeletal muscle cachexia. Finally, we will discuss a vast therapeutic potential for the STAT3-inhibiting single-agent treatment innovation that, as the desired outcome, could block tumor growth and generally prevent muscle cachexia.

Over the last decade, we have seen tremendous progress in research on 2-deoxy-D-glucose (2-DG) and its analogs. Clinical trials of 2-DG have demonstrated the challenges of using 2-DG as a monotherapy, due to its poor drug-like characteristics, leading researchers to focus on improving its bioavailability to tissue and organs. Novel 2-DG analogs such as WP1122 and others have revived the old concept of glycolysis inhibition as an effective anticancer strategy. Combined with other potent cytotoxic agents, inhibitors of glycolysis could synergistically eliminate cancer cells. We focused our efforts on the development of new combinations of anticancer agents coupled with 2-DG and its derivatives, targeting glioblastoma, which is in desperate need of novel approaches and therapeutic options and is particularly suited to glycolysis inhibition, due to its reliance on aerobic glycolysis. Herein, we present evidence that a combined treatment of 2-DG analogs and modulation of histone deacetylases (HDAC) activity via HDAC inhibitors (sodium butyrate and sodium valproate) exerts synergistic cytotoxic effects in glioblastoma U-87 and U-251 cells and represents a promising therapeutic strategy.

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