Genetic and Drug Inhibition of LDH-A: Effects on Murine Gliomas

• Published in: Cancers 2022-05, Vol.14 (9), p.2306
• Main Authors: Maeda, Masatomo, Ko, Myat, Mane, Mayuresh M, Cohen, Ivan J, Shindo, Masahiro, Vemuri, Kiranmayi, Serganova, Inna, Blasberg, Ronald
• Format: Article
• Language: English
• Subjects: Antibodies; Brain cancer; Brain tumors; Carbon sources; Cell survival; Enzymes; Fatty acids; Gene expression; Glioma cells; Glucose; Glycolysis; Lactic acid; LDH-A gene; Lipid metabolism; Metabolic pathways; Metabolic rate; Metabolism; Oxidation; Phosphatase; Proteins; Pyruvic acid; Tricarboxylic acid cycle; Tumor cells; Tumors
• ISSN: 2072-6694; 2072-6694
• DOI: 10.3390/cancers14092306

The effects of the LDH-A depletion via shRNA knockdown on three murine glioma cell lines and corresponding intracranial (i.c.) tumors were studied and compared to pharmacologic (GNE-R-140) inhibition of the LDH enzyme complex, and to shRNA scrambled control (NC) cell lines. The effects of genetic-shRNA LDH-A knockdown and LDH drug-targeted inhibition (GNE-R-140) on tumor-cell metabolism, tumor growth, and animal survival were similar. LDH-A KD and GNE-R-140 unexpectedly increased the aggressiveness of GL261 intracranial gliomas, but not CT2A and ALTS1C1 i.c. gliomas. Furthermore, the bioenergetic profiles (ECAR and OCR) of GL261 NC and LDH-A KD cells under different nutrient limitations showed that (a) exogenous pyruvate is not a major carbon source for metabolism through the TCA cycle of native GL261 cells; and (b) the unique upregulation of LDH-B that occurs in GL261 LDH-A KD cells results in these cells being better able to: (i) metabolize lactate as a primary carbon source through the TCA cycle, (ii) be a net consumer of lactate, and (iii) showed a significant increase in the proliferation rate following the addition of 10 mM lactate to the glucose-free media (only seen in GL261 KD cells). Our study suggests that inhibition of LDH-A/glycolysis may not be a general strategy to inhibit the i.c. growth of all gliomas, since the level of LDH-A expression and its interplay with LDH-B can lead to complex metabolic interactions between tumor cells and their environment. Metabolic-inhibition treatment strategies need to be carefully assessed, since the inhibition of glycolysis (e.g., inhibition of LDH-A) may lead to the unexpected development and activation of alternative metabolic pathways (e.g., upregulation of lipid metabolism and fatty-acid oxidation pathways), resulting in enhanced tumor-cell survival in a nutrient-limited environment and leading to increased tumor aggressiveness.