Oligomycin-induced Bioenergetic Adaptation in Cancer Cells with Heterogeneous Bioenergetic Organization

Abstract

Cancer cells constantly adapt to oxidative phosphorylation (OXPHOS) suppression resulting from hypoxia or mitochondria defects. Under the OXPHOS suppression, AMP-activated protein kinase (AMPK) regulates global metabolism adjustments, but its activation has been found to be transient. Whether cells can maintain cellular ATP homeostasis and survive beyond the transient AMPK activation is not known. Here, we study the bioenergetic adaptation to the OXPHOS inhibitor oligomycin in a group of cancer cells. We found that oligomycin at 100 ng/ml completely inhibits OXPHOS activity in 1 h and induces various levels of glycolysis gains by 6 h, from which we calculate the bioenergetic organizations of cancer cells. In glycolysis-dominant cells, oligomycin does not induce much energy stress as measured by glycolysis acceleration, ATP imbalance, AMPK activation, AMPK substrate acetyl-CoA carboxylase phosphorylation at Ser 79 , and cell growth inhibition. In OXPHOS-dependent LKB1 wild type cells, oligomycin induces 5-8% ATP drops and transient AMPK activation during the initial 1-2 h. After AMPK activation is completed, oligomycininduced increase of acetyl-CoA carboxylase phosphorylation at Ser 79 is still detected, and cellular ATP is back at preoligomycin treatment levels by sustained elevation of glycolysis. Cell growth, however, is inhibited without an increase in cell death and alteration in cell cycle distribution. In OXPHOS-dependent LKB1-null cells, no AMPK activation by oligomycin is detected, yet cells still show a similar adaptation. We also demonstrate that the adaptation to oligomycin does not invoke activation of hypoxia-induced factor. Our data suggest that cancer cells may grow and survive persistent OXPHOS suppression through an as yet unidentified regulatory mechanism.The bioenergetic organization, the fraction of cellular ATP produced by glycolysis and mitochondrial OXPHOS, 2 determines the bioenergetic homeostasis in cells. Tumors have a bioenergetic organization distinct from that of normal cells, in which the burden of ATP production increasingly shifts from OXPHOS to glycolysis, the so-called Warburg effect (1). Deregulation of multiple oncogenes and tumor suppressors during tumorigenesis contributes to this distinct neoplastic metabolism alteration because glycolysis is the downstream target of the altered pathways (2, 3). In addition, mitochondrial defects can also drive up the aerobic glycolysis to bioenergetically compensate for the loss of OXPHOS ATP production. The reduction in OXPHOS activity has been identified in widely spread cancer cells (4 -9). The switch of bioenergetic dependence from OXPHOS to glycolysis is proposed for cancer cells to cope with intermittent and chronicle hypoxia microenvironments, reduce mitochondrial-initiated cell death (3, 10), and promote invasion and metastasis (10 -12).Suppression of OXPHOS activity activates master energy stress sensor AMPK that reprograms the global cellular metabolism for the stress adaptation (13,14). In compensating for the loss of OXPHOS ATP...

A Small-Molecule Inhibitor of Glucose Transporter 1 Downregulates Glycolysis, Induces Cell-Cycle Arrest, and Inhibits Cancer Cell Growth In Vitro and In Vivo

“…4F). This result indicates that at 50 nmol/L, an effective mitochondriainhibitory dose (35), oligomycin alone did not change cell proliferation rate but sensitized cancer cells to the inhibitory activity of WZB117 (Fig. 4F).…”

“…4F). Mitochondria inhibition is known to upregulate glycolysis (35). These data suggest that when a Glut1/glycolysis inhibitor, WZB117 in this case, was added to oligomycin-treated cells, these cells were unable to compensate for oligomycin-induced inhibition of mitochondria with upregulating glycolysis.…”

Monitoring the dielectric response of single cells following mitochondrial adenosine triphosphate synthase inhibition by oligomycin using a dielectrophoretic cytometer

“…Monitoring the cell response within the first hours of the treatment with oligomycin reveals important information on the ion regulations and the impact of mitochondrial ATP synthase inhibition while avoiding the impact of cell adaptability, which will affect longer time period studies. 23 …”

The Hypoxia-inducible Factor Renders Cancer Cells More Sensitive to Vitamin C-induced Toxicity

“…Next, we used DCA and oligomycin to show that reduced mitochondrial utilization by VHL-defective RCC10 cells, and the consequent reduced ATP levels, contribute to their enhanced sensitivity to the toxicity of Vc. DCA blocks pyruvate dehydrogenase kinase 1 (50), activating the Krebs cycle, whereas oligomycin impairs energy generation through mitochondria by inhibiting the mitochondrial ATP synthase (51). Pretreatment of VHL-defective cells with DCA reduced Vc-induced toxicity in VHL-defective RCC10 cells (Fig.…”