Metabolic analysis of radioresistant medulloblastoma stem-like clones and potential therapeutic targets

<div><p>Medulloblastoma is a fatal brain tumor in children, primarily due to the presence of treatment-resistant medulloblastoma stem cells. The energy metabolic pathway is a potential target of cancer therapy because it is often different between cancer cells and normal cells. However, the metabolic properties of medulloblastoma stem cells, and whether specific metabolic pathways are essential for sustaining their stem cell-like phenotype and radioresistance, remain unclear. We have established radioresistant medulloblastoma stem-like clones (rMSLCs) by irradiation of the human medulloblastoma cell line ONS-76. Here, we assessed reactive oxygen species (ROS) production, mitochondria function, oxygen consumption rate (OCR), energy state, and metabolites of glycolysis and tricarboxylic acid cycle in rMSLCs and parental cells. rMSLCs showed higher lactate production and lower oxygen consumption rate than parental cells. Additionally, rMSLCs had low mitochondria mass, low endogenous ROS production, and existed in a low-energy state. Treatment with the metabolic modifier dichloroacetate (DCA) resulted in mitochondria dysfunction, glycolysis inhibition, elongated mitochondria morphology, and increased ROS production. DCA also increased radiosensitivity by suppression of the DNA repair capacity through nuclear oxidization and accelerated the generation of acetyl CoA to compensate for the lack of ATP. Moreover, treatment with DCA decreased cancer stem cell-like characters (e.g., CD133 positivity and sphere-forming ability) in rMSLCs. Together, our findings provide insights into the specific metabolism of rMSLCs and illuminate potential metabolic targets that might be exploited for therapeutic benefit in medulloblastoma.</p></div

Diminution of mitochondrial respiration in ONS-F8 and -B11.

<p>(A) Mitochondria mass, (B) mitochondria membrane potential, (C) OCR (using MitoXpress) in ONS-76, -F8 and -B11 cells. All quantitative data are means ± S.D. *P<0.05, Welch’s t-test.</p

ONS-76, -F8 and DCA-treated cells exhibit different metabolic profiles.

<p>Schematic diagram of the metabolic pathway. The red and blue arrows represent increased and decreased metabolite concentrations in ONS-F8 compared with ONS-76 (A), and in DCA-treated cells compared with non-DCA-treated cells (B).</p

Relative glycolysis and TCA cycle related metabolites in ONS-76 and -F8 cells with and without DCA.

<p>Relative glycolysis and TCA cycle related metabolites in ONS-76 and -F8 cells with and without DCA.</p

ONS-F8 and -B11 showed low levels of ROS and nuclear oxidative stress.

<p>Levels of (A) intracellular ROS, (B) mitochondria-derived superoxide, (C) nuclear oxidative stress, (D) GSH in ONS-76, -F8 and -B11. All quantitative data are means ± S.D. *P<0.05, Welch’s t-test, n.s., non-significant.</p

DCA induces alteration of mitochondrial respiration and glycolysis.

<p>(A) OCR (using MitoXpress), (B) extracellular lactate production, (C) pyruvate kinase activity, (D) glucose uptake in ONS-76, -F8, and -B11 cells with and without DCA. All quantitative data are means ± S.D. *P<0.05, Welch’s t-test.</p