Lactic Acidosis in the Presence of Glucose Diminishes Warburg Effect in Lung Adenocarcinoma Cells

Abstract

Lactic acidosis (3 to 40 mM, pH < 6.9) is a condition found in solid tumors because tumor cells have a high rate of glucose consumption and lactate production even in the presence of oxygen; nevertheless, the microenvironment might still provide a sufficient glucose supply. Lactic acidosis has been proposed to shift metabolism from aerobic glycolysis toward oxidative phosphorylation (OXPHOS). We tested if lung tumor cells cultured under lactic acidosis shift their metabolism from glycolysis to OXPHOS by consuming extracellular lactate, increasing growth rate. We analyzed lung adenocarcinoma (A-549, A-427) cell lines and non-transformed fibroblast cells (MRC-5), which were cultured using RPMI-1640 medium initially containing lactate (2 mM) and glucose (10 mM), at pH 7.2 or 6.2 and oxygen tension 21% O 2 (normoxia) or 2% O 2 (hypoxia). We obtained growth curves, as well as glucose consumption and lactate production rates (measured during exponential growth) for each cell line. HIF-1α (Hypoxia-inducible factor 1 α), CS (citrate synthase) and AMPK (AMP-activated protein kinase) transcript levels were analyzed using RT-qPCR. By flow cytometry, we determined: (a) expression of glucose transporters (GLUT)1 and 4; (b) lactate transporters (MCT)1 and 4; (c) cell cycle profile, and (d) protein levels of HIF-1α, total and phosphorylated AMPK (pAMPK). Mitochondrial functionality was evaluated by measuring O 2 consumption in tumor cells using polarography and a Clark-type electrode. Tumor and non-transformed cells used both aerobic glycolysis and OXPHOS for obtaining energy. As of 48 h of culture, lactate levels ranged from (4.5-14 mM), thus forming a lactic environment. Lactic acidosis diminished GLUT1/GLUT4 expression and glucose consumption in A-549, but not in A-427 cells, and induced differential expression of HIF-1α, AMPK, and CS transcripts. A-427 cells increased pAMPK and HIF-1α levels and shifted their metabolism increasing OXPHOS; thus supporting cell growth. Conversely, A-549 cells increased HIF-1α protein levels, but did not activate AMPK and diminished OXPHOS. A-549 cells survived by arresting cells in G1-phase. Our findings show that lactic acidosis diminishes Warburg effect in tumor cells, but this change does not necessarily promote a shift to OXPHOS. Hence, lung adenocarcinomas show a differential metabolic response even when they are under the same microenvironmental conditions.

Platelet-rich plasma improves chronic inflammatory pain by inhibiting PKM2-mediated aerobic glycolysis in astrocytes

“…Our study found that PKM2 expression was increased in the spinal cord after CFA injection and was accompanied by altered pain behavior. Simultaneously, we detected an increase in GLUT1 and glycolysis product lactic acid levels, which may be due to increased glucose uptake and increased glycolysis activity (52). These results show that PKM2 may be involved in the development of CFA inflammatory pain.…”

Correlation between electrical characteristics and biomarkers in breast cancer cells

“…4 d. LDHA expression was consistent with the lactic acid measurement; its expression was lower in MCF-7 cells than in normal MCF-10A cells, although there was no significant difference between the two groups. LDHA expression is regulated by hypoxia-inducible factor alpha (HIF-1α) 16 , 17 . The expression of HIF-1α was very low in MCF-10A cells, and the level of expression increased as the degree of malignancy of the breast cancer cells increased.…”

A Transcriptomic Analysis of Head and Neck Squamous Cell Carcinomas for Prognostic Indications

“…In our previous work, altered glucose metabolism—the Warburg effect [ 90 ]—promoted the progression of HNSCC, which is partially attributed to the solute carrier family 2 member A4 (SLC2A4, or glucose transporter 4, GLUT4) and tripartite motif-containing 24 (TRIM24) pathway [ 91 , 92 ]. Lactic acidosis-induced GLUT4 overexpression was also found in lung cancer cells [ 93 ]. Currently, pembrolizumab and nivolumab’s success has been based on a common biomarker (e.g., PD-1) in several types of cancer.…”