Glucose deprivation increases nuclear DNA repair protein Ku and resistance to radiation induced oxidative stress in human cancer cells

Abstract

Recent studies have indicated that nutrient deprivation particularly glucose may play a major role in tumor cell tolerance to a generally oxidative stress environment in solid tumors. Here, we studied the impact of glucose deprivation on the response of human colon (HT29)0020and prostate (DU145) cancer cells to γ radiation. A significant decrease in intracellular glucose level was observed in glucose deprived cells as measured by bioreductive assay. The survival of HT29 and DU145 were increased by 30 and 100% respectively when these cells were exposed to γ radiation in the absence of glucose compared to that in the presence of glucose. In glucose depleted medium, glutathione (GSH), a free radical scavenger, content remained the same, and showed no correlation with the radiation resistance induced by glucose deprivation. GRP78, a stress response survival protein, was not significantly increased in cells deprived of glucose for 4 hours compared to those cells in glucose. DNA repair protein Ku, which is known to play a major role in cellular resistance to radiation, was significantly increased in glucose deprived cancer cells that showed enhanced radiation resistance. These results have demonstrated, for the first time, that glucose deprivation mediated stress increased the expression of nuclear Ku and resistance to radiation induced oxidative stress in human cancer cells. The additional resistance caused by glucose deprivation in cancer cells has clinical significance since solid tumors are known to have low level of glucose due to diffusion limited blood supply and higher metabolic activity.

A bioactive probe of the oxidative pentose phosphate cycle: Novel strategy to reverse radioresistance in glucose deprived human colon cancer cells

“…The intracellular non protein thiol (NPSH) was determined by DTNB assay as described previously (Li et al, 2009). Cells in the dish with the desired medium were rinsed twice and the attached cells were mixed with 1 ml of ice cold 50 mM SSA buffer.…”

“…This modification of the Active Motif nuclear extract preparation is necessary to avoid the reversal of HEDS mediated oxidation of protein thiols including Ku protein thiols by DTT (Ayene et al 2002). The nuclear proteins were prepared by membrane disruption using Active Motif hypotonic buffer, detergent and complete lysis buffer and centrifugation as per the manufacturer’s instructions (Li et al, 2009). The nuclear proteins were stored at −80°C.…”

“…In cancer cells, this question has intensified with direct evidence that steady-state concentrations of glucose are significantly reduced in solid tumors (Aronen et al, 2000; Izuishi et al, 2000; Rajendran et al, 2004). Unlike cells in normal tissue, where glucose deprivation is injurious, cancer cells in solid tumors can often adapt to glucose-deprivation induced oxidative stress by mechanisms that also permit them to acquire therapeutiuc resistance (Kato et al, 2002; Lee 2001; Li et al, 2009; Park et al, 2007; Wyld et al, 2002; Yun et al, 2005). While the effects of glucose deprivation have received significant attention, the specific role of glucose deprivation without the confounding effects of other nutrient, growth factors and oxygen depletion on the cellular control of thiol homeostasis and its subsequent effects on protein function, cell survival and response to free radicals induced oxidative stress have not been demonstrated in either cancer or normal cells.…”

Potential Pathways Involved in Elaidic Acid Induced Atherosclerosis in Human Umbilical Vein Endothelial Cells

“…Some other proteins related to DNA damage were also downregulated in HUVEC treated with 400 mol/L elaidic acid, such as XRCC 5 (spot (23)), PSME 3 (spot (3)), and SAE 1 (spot (20)). XRCC 5 , a subunit of the Ku heterodimer protein, played a major role in cellular resistance to radiation [52]. However, the expression of P53 was increased ( Figure 5); this indicated that the DNA damage level was increased.…”

A bioactive probe for glutathione-dependent antioxidant capacity in breast cancer patients: Implications in measuring biological effects of arsenic compounds

“…We have recently demonstrated in a series of publications that GSH recycling (GSH → GSSG (oxidized GSH) → GSH), which is dependent on several GSH dependent pathways, is required for the metabolic conversion of hydroxyethyldisulfide (HEDS) into mercaptoethanol (ME) (Ayene, Biaglow, Kachur, Stamato, & Koch, 2008; Ayene, et al, 2000; Ayene, et al, 2002; Biaglow, et al, 2003; Biaglow, et al, 2000; Biaglow, et al, 2006; Biaglow, et al, 1998; Li, Ayene, Ward, Dayanandam, & Ayene, 2009; Li, et al, 2013; Li, Zhang, Ward, Prendergast, & Ayene, 2012; Tuttle, et al, 2007). Unlike all the previous assays that measured just the glutathione level, a functional assay for glutathione such as HEDS metabolism will measure the “GSH dependent antioxidant capacity” of cells, a process that requires “glutathione recycling” by oxidative pentose phosphate cycle (OPPC) in conjunction with other GSH dependent pathways (Ayene, et al, 2002; Biaglow, et al, 2003; Lushchak, 2012).…”