AICAR inhibits cancer cell growth and triggers cell-type distinct effects on OXPHOS biogenesis, oxidative stress and Akt activation

Abstract

The AMP-activated protein kinase agonist AICAR mimics a low intracellular energy state and inhibits the proliferation of cancer cells by different mechanisms, which may depend on the bioenergetic signature of these cells. AICAR can also stimulate mitochondrial biogenesis in myoblasts, neurons and HeLa cells. Yet, whether the reactivation of oxidative phosphorylation biogenesis by AICAR contributes to the growth arrest of cancer cells remains undetermined. To investigate this possibility, we looked at the impact of 24- and 48-hour treatments with 750 μM AICAR on human cancer cell lines (HeLa, DU145, and HEPG2), non-cancer cells (EM64, FM14, and HLF), embryonic cells (MRC5) and Rho(0) cells. We determined the bioenergetic profile of these cells and assessed the effect of AICAR on oxidative phosphorylation biogeneis, cell viability and cell proliferation, ROS generation, mitochondrial membrane potential and apoptosis induction. We also followed possible changes in metabolic regulators such as Akt and Hif1-α stabilization which might participate to the anti-proliferative effect of AICAR. Our results demonstrated a strong and cancer-specific anti-growth effect of AICAR that may be explained by three different modes according to cell type: the first mode included stimulation of the mitochondrial apoptotic pathway however with compensatory activation of Akt and upregulation of oxidative phosphorylation. In the second mode of action of AICAR Akt phosphorylation was reduced. In the third mode of action, apoptosis was activated by different pathways. The sensitivity to AICAR was higher in cells with a low steady-state ATP content and a high proliferation rate.

Activation of AMP-kinase by AICAR induces apoptosis of DU-145 prostate cancer cells through generation of reactive oxygen species and activation of c-Jun N-terminal kinase

“…In contrast ROS elevation and induction of apoptosis were observed in several cancer cell lines including E47 hepatoma cells (13) and glioma (14) as well as in pancreatic β-cells (15). Thus, AICAR may trigger opposite responses in different cells, as previously discussed (18). To investigate the impact of ROS generation in AMPK, JNK and caspase-3 activation, cells were incubated either in the presence of JNK inhibitor II, the free radical scavenger NMPG or Comp C. In the presence of ROS scavenger, AMPK and JNK phosphorylation as well as caspase-3 activation were completely abolished which clearly indicates that ROS are regulating the signaling cascade leading to cell apoptosis.…”

“…Treatment of several cancer cell lines with AICAR has been shown to cause apoptosis (18). However, it is not yet known by which signaling pathways apoptosis induction occurs.…”

Regulation and Quantification of Cellular Mitochondrial Morphology and Content

“…[25,40]). Similarly, analysis of individual enzyme activities under non-substrate limiting (Vmax) conditions generally reflects the levels of mitochondrial OXPHOS proteins (e.g.…”

AMPK—friend or foe for targeted therapy?

“…In DU145 cells, an androgen receptor (AR) negative human PC line with activated Akt and upregulated glycolysis, 5-aminoimidazole-4-carboxamide riboside (AICAR)-mediated AMPK activation has been reported to suppress proliferation without evidence of increased apoptosis. 4 Our recent comparative analysis of the paired PC3 and PC3M cells as models of progressively invasive (androgen-independent) PC also supported the notion of tumor suppressing effects upon activation of AMPK (Fig. 1).…”