Inhibition of Mitochondrial Complex II by the Anticancer Agent Lonidamine

Abstract

The antitumor agent lonidamine (LND; 1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxylic acid) is known to interfere with energy-yielding processes in cancer cells. However, the effect of LND on central energy metabolism has never been fully characterized. In this study, we report that a significant amount of succinate is accumulated in LND-treated cells. LND inhibits the formation of fumarate and malate and suppresses succinate-induced respiration of isolated mitochondria. Utilizing biochemical assays, we determined that LND inhibits the succinate-ubiquinone reductase activity of respiratory complex II without fully blocking succinate dehydrogenase activity. LND also induces cellular reactive oxygen species through complex II, which reduced the viability of the DB-1 melanoma cell line. The ability of LND to promote cell death was potentiated by its suppression of the pentose phosphate pathway, which resulted in inhibition of NADPH and glutathione generation. Using stable isotope tracers in combination with isotopologue analysis, we showed that LND increased glutaminolysis but decreased reductive carboxylation of glutamine-derived α-ketoglutarate. Our findings on the previously uncharacterized effects of LND may provide potential combinational therapeutic approaches for targeting cancer metabolism.

The anti-tumour agent lonidamine is a potent inhibitor of the mitochondrial pyruvate carrier and plasma membrane monocarboxylate transporters

“…3B confirm that LND inhibits both with IC 50 values of 25 and 150 μM, respectively. The data with succinate closely match similar data obtained in uncoupled mouse liver mitochondria where we also demonstrated that LND inhibits succinate-ubiquinone reductase activity of respiratory complex II with an IC 50 of about 300 μM [28]. This is substantially higher than the K i for the MPC and IC 50 for pyruvate and glutamate + malate oxidation.…”

“…Intracellular and extracellular L-lactate was measured as previously described [28] with modification. DB-1 cells were washed twice with phosphate-buffered saline (PBS) followed by scraping into 750 μL of ice-cold methanol/water (4:1, v/v) containing 2.5 Og of [ 13 C 3 ] lactate as internal standard.…”

Effect of Lonidamine on Systemic Therapy of DB-1 Human Melanoma Xenografts with Temozolomide

“…Our recent publications (11,38) confirmed that LND inhibits lactate export by the proton-linked MCTs and specifically measured inhibition by MCT1and MCT4 that commonly are expressed in many tumor types; however, our studies demonstrated that an even more potent inhibition of pyruvate export from the cytosol into the mitochondria via the mitochondrial pyruvate carrier (MPC) was augmenting cytosolic acidification and also explained a marked decrease in tumor ATP production by oxidative phosphorylation. This inhibition of mitochondrial respiration was further increased at higher LND concentration by inhibition of electron-transport at Complex II at the ubiquinone reductase step (11,39). Our studies, therefore, confirm inhibition of the MCTs but indicate that inhibition of the MPC may play an important role in retention of lactic acid and pyruvate in the cytosol.…”

2-Methoxyestradiol Affects Mitochondrial Biogenesis Pathway and Succinate Dehydrogenase Complex Flavoprotein Subunit A in Osteosarcoma Cancer Cells

“…One mechanism that has been described for SDH-induced apoptosis involves its disassembly in the low pH environment of distressed cells that results in excessive production of reactive oxygen species from the SDHA (60). SDH inhibitors exhibit potent and selective anti-proliferative activity in multiple cancer cell lines, acting to inhibit mitochondrial electron transport (1,61). Thus, SDH is considered a target for novel anticancer therapies (62).…”