Interestingly when glucose is deleted in PCa cells GLUT is

Interestingly, when glucose is deleted in PCa cells, GLUT1 is increased. Also, AR is almost entirely located in the nucleus, correlating with the increment in GLUT1 levels. These results are in agreement with those reported by Vaz et al. [16], They described an increase in GLUT1 after DHT stimulation [16]. Furthermore, glucose deprivation fails to enhance GLUT1 expression when cells are grown in the absence of androgens. Hyperglycemia downregulates AR levels in Type 2 diabetes. Interestingly, diabetes type 2 is inversely related to prostate cancer incidence [44]. On the other hand, low glucose stimulates GLUT1 production, which might be concerned with the promotion of more aggressive tumors. Nuclear AR translocation, and consequently GLUT1 enhancement, are directly associated with cell proliferation. Since both proteins are found during S and G2/M R406 receptor phases, they could act synergistically to promote cell proliferation under androgenic stimulation or suppressing cell cycle arrest in the absence of glucose. On the contrary, it is known that glycolysis only affects cell cycle distribution from G1 to S [45]. In PCa, AMPK is considered a key metabolic regulator involved in proliferation and cell survival [46]. In PCa, androgens stimulate AMPK activation leading to OXPHOS [15]. AMPK is also able to induce GLUT1 expression and membrane translocation by inhibiting TXNIP [47], indicating that GLUT1 overexpression via AMPK can protect from cell death caused by glucose deprivation. More interestingly, H2O2 stimulates glucose uptake in cells overexpressing GLUT1 [48]. Accordingly, with these results, H2O2 increases nuclear AR levels and GLUT1 production via AMPK in LNCaP cells. The protective activation of AMPK by H2O2 has been already described, and recently it was proposed as a regulator of mitochondrial ROS [49], [50]. In PCa cells that overexpress GLUT1, as expected, glucose consumption is higher than in parental cells. Recent studies showed that the overexpression of GLUT1 drives with an inflammatory response because of the increase of ROS in macrophages due to a higher glucose uptake [51], [52]. Here it is shown that oxidative stress is enhanced in GLUT1-overexpressing cells in the presence of glucose, but not under glucose deprivation. To determine the mechanism by which GLUT1 protects cells from glucose removal, and given the oxidative signal caused by glucose removal, we analyzed several antioxidant pathways. The activity of mitochondrial SOD2, that fall after glucose removal in LNCaP cells, is sustained under glucose deprivation in GLUT1-overexpressing cells. Recently, it was described a role of this enzyme in the survival of renal carcinoma cells, as well as, in the promotion of cell proliferation of lung cancer cells via AMPK [53], [54]. Mainly GLUT1 overexpression increases reduced levels of glutathione. Since pentose phosphate pathway is not overstimulated after glucose withdrawal, the necessary NADPH to maintain GSH has to come from the mitochondria mainly. It was recently published that nicotinamide phosphoribosyltransferase (NAMPT), involved in NAD+ biosynthesis, protects cells from glucose deprivation-induced oxidative stress and that it is also regulated by AMPK [55], which confirms the role of mitochondria as the source of reducing power. The protective role of GLUT1 in PCa cells may come from the uptake of some compound included in culture medium or by the activation/inhibition of an intracellular signaling pathway. Besides glucose uptake, it is well-known that GLUT1 can transport other compounds. The treatment with phloretin, which is well-established as a GLUT blocker [56] enhances cell death by glucose deprivation, implying that this response is not only a consequence of intracellular signaling. The increase of cell death by serum deprivation strengthens this idea. Moreover, it was recently described that ROS production is enhanced in L6 myoblasts when GLUT1 is inhibited by phloretin, which it is in agreement with our results [57].