The heme precursor 5-aminolevulinic acid disrupts the Warburg effect in tumor cells and induces caspase-dependent apoptosis

Abstract

Abstract. Our previous study demonstrated that 5-aminolevulinic acid (ALA) administered to mice stimulates oxidative phosphorylation by upregulation of the mitochondrial respiratory chain complex IV enzyme cytochrome c oxidase (COX). The present study investigated whether ALA disrupts the Warburg effect, which represents a shift in ATP generation from oxidative phosphorylation to glycolysis, protecting tumor cells against oxidative stress-mediated apoptosis. The human lung carcinoma cell line A549 exposed to ALA exhibited enhanced oxidative phosphorylation, which was indicated by an increase in COX protein expression and oxygen consumption. Furthermore, ALA suppressed glycolysis-mediated acidosis. This normalization of the ATP metabolic pathways significantly increased the generation of superoxide anion radical (O 2 •-) and the functional expression of active caspase-3, leading to caspase-dependent apoptosis. These data demonstrate that ALA inhibits the Warburg effect and induces cancer cell death. Use of this endogenous compound might constitute a novel approach to cancer therapy.

5-Aminolevulinic acid strongly enhances delayed intracellular production of reactive oxygen species (ROS) generated by ionizing irradiation: Quantitative analyses and visualization of intracellular ROS production in glioma cells in vitro

“…The biological effect of administration of the heme precursor 5-ALA is not only high accumulation of PpIX within the mitochondria of tumor cells, but also generation of antitumor immunity via activation of heat-shock protein as well as inhibition of heme-oxygenase-1 with photoactivation and hyperthermia (26). Moreover, recent studies have reported that 5-ALA can improve the function of the mitochondrial respiratory chain (particularly COX activity) and thereby disrupt the warburg effect and induce caspase-dependent apoptosis in tumor cells (27,28). In our previous study, we demonstrated that multi-dose ionizing radiation induced strong aggregation of activated macrophages with phagocytic features within tumors, causing strong inhibition of tumor growth in glioma cells in vivo (19).…”

“…This delayed ROS production is induced primarily in the mitochondria of tumor cells (24,25). Meanwhile, the heme precursor 5-ALA presents not only a high accumulation of PpIX in the mitochondria of tumor cells, but also improves dysfunction of the mitochondrial respiratory chain in tumor cells (26)(27)(28). Thus, we hypothesized that 5-ALA-induced PpIX may operate upon mitochondria, and cause changes in delayed production of ROS after ionizing irradiation in tumor cells.…”

The Effect of 5-Aminolevulinic Acid on Cytochrome P450-Mediated Prodrug Activation

“…We previously reported that the expression and activity of the hemeprotein cytochrome c oxidase is elevated in ALA-treated cells [ 11 , 12 ]. Moreover, we found that the expression of PEPT1, a transporter involved in the uptake of ALA, is higher in tumor tissues compared with that in normal tissues [ 13 ].…”

Inverse correlation between heme synthesis and the Warburg effect in cancer cells

“…Injection of ALA induced expression and activity of COX in mice liver [22]. It also enhanced COX expression and oxygen consumption in a lung cancer cell line, A549 [23]. Accordingly, we expected that regulation of heme synthesis using ALA, SFC, and SA should affect mitochondrial activity.…”

“…Owing to the fact that COX is a heme protein, ALA-mediated increase in the amount of heme was thought to induce the expression COX. We also reported that addition of ALA leads to activation of ETS in cancer cells [23].…”