Glucose Metabolites Exert Opposing Roles in Tumor Chemoresistance

Abstract

Reprogrammed glucose metabolism and increased glycolysis have been implicated in tumor chemoresistance. The aim was to investigate the distinct roles of the glucose metabolites pyruvate and ATP in chemoresistance mechanisms, including cell death and proliferation. Our data showed higher glucose transporters in colorectal cancer (CRC) from non-responsive patients than those responsive to chemotherapy. Human CRC cell lines exposed to 5-fluorouracil (5-FU) displayed elevated cell viability and larger tumors in xenograft mouse models if cultured in high-glucose medium. Glucose conferred resistance to 5-FU-induced necroptosis via pyruvate scavenging of mitochondrial free radicals, whereas ATP replenishment had no effect on cell death. Glucose attenuated the 5-FU-induced G0/G1 shift but not the S phase arrest. Opposing effects were observed by glucose metabolites; ATP increased while pyruvate decreased the G0/G1 shift. Lastly, 5-FU-induced tumor spheroid destruction was prevented by glucose and pyruvate, but not by ATP. Our finding argues against ATP as the main effector for glucose-mediated chemoresistance and supports a key role of glycolytic pyruvate as an antioxidant for dual modes of action: necroptosis reduction and a cell cycle shift to a quiescent state.

Divergent Actions of Pyruvate and ATP in Glucose-mediated Irinotecan Chemoresistance in Colorectal Cancer

“…We further con rmed that the anti-necroptotic role of pyruvate was exerted through direct scavenging of ROS coupled to de novo acetate production in an ATP-independent manner. Notably, ATP failed to rescue cells from irinotecan-and 5-FU-induced necroptosis [15]but did prevent the irinotecan-induced apoptosis in the current study. The exact mechanisms for ATP-mediated resistance to apoptosis warrant further investigation.…”

Metabolic Reprogramming: A Friend or Foe to Cancer Therapy?

“…Notably, the ability of 5-FU to induce apoptosis was significantly diminished with the addition of antioxidants; confirming a key role for ROS in 5-FU induced apoptosis [153]. Conversely, 5-FU also reportedly enhances CRC cell survival in high-glucose conditions as a result of enhanced glycolysis and a subsequent elevation in intracellular pyruvate, which acts as a ROS scavenger to protect against oxidative stress-induced death [154]. Thus, 5-FU treatment can improve the ability of cancer cells to tolerate oxidative stress and evade apoptosis induced by high levels of ROS.…”

Invasive Pathobionts Contribute to Colon Cancer Initiation by Counterbalancing Epithelial Antimicrobial Responses

“…In other settings, cells exposed to bacteria for 4 hours were washed with PBS twice, incubated with gentamicin-containing medium for 24–48 hours, and evaluated for cell viability and cell-cycle progression by using a tetrazolium dye MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay and flow cytometry. 42 , 43 , 52 Briefly, the cells were fixed with ice-cold 70% ethanol, and incubated with anti-human Ki67 (1:400; Cell Signaling, Beverly, MA) followed by secondary antibody conjugated to Alexa-Fluor 488, and then stained with propidium iodide for 30 minutes at room temperature. A minimum of 10,000 propidium iodide–stained nuclei were analyzed by flow cytometry, and the percentages of cells in the G0–G1, S, and G2–M phases of the cell cycle and the ratio of cells with high to low intensity of Ki67 were determined using Mod Fit LT cell-cycle analysis software (Verity Software, Topsham, ME).…”

“…Human cell lines were plated as 3-dimensional spheroid cultures based on previous protocols. 42 , 43 , 52 Briefly, Caco-2 cells cocultured with bacteria for 4 hours were trypsinized and resuspended in culture medium containing gentamicin (300 μg/mL) to eliminate extracellular bacteria. The cells were immediately mixed with ice-cold Matrigel (354234; Corning, New York, NY) at a 3:1 ratio with cell culture medium, and a volume of 300 μL was seeded per well in 24-well plates.…”

“…) assay and flow cytometry. 42,43,52 Briefly, the cells were fixed with ice-cold 70% ethanol, and incubated with antihuman Ki67 (1:400; Cell Signaling Q28 ) followed by secondary antibody conjugated to Alexa-Fluor 488, and then stained with propidium iodide for 30 minutes at room temperature. A minimum of 10,000 propidium iodide-stained nuclei were analyzed by flow cytometry, and the percentages of cells in the G0-G1, S, and G2-M phases of the cell cycle and the ratio of cells with high to low intensity of Ki67 were determined using Mod Fit LT cell-cycle analysis software (Verity Software, Topsham, ME).…”