Selective amino acid restriction targets mitochondria to induce apoptosis of androgen‐independent prostate cancer cells

Abstract

Relative specific amino acid dependency is one of the metabolic abnormalities of cancer cells, and restriction of specific amino acids induces apoptosis of prostate cancer cells. This study shows that restriction of tyrosine and phenylalanine (Tyr/Phe), glutamine (Gln), or methionine (Met), modulates Raf and Akt survival pathways and affects the function of mitochondria in DU145 and PC3, in vitro. These three restrictions inhibit energy production (ATP synthesis) and induce generation of reactive oxygen species (ROS). Restriction of Tyr/Phe or Met in DU145 and Met in PC3 reduces mitochondrial membrane potential (DeltaPsim) and induces caspase-dependent and -independent apoptosis. In DU145, Tyr/Phe or Met restriction reduces activity of Akt, mitochondrial distribution of phosphorylated Raf and apoptosis inducing factor (AIF), and increases mitochondrial distribution of Bak. Mitochondrial Bcl-XL is increased in Tyr/Phe-restricted but decreased in Met-restricted cells. Under Tyr/Phe or Met restriction, reduced mitochondrial Raf does not inactivate the pro-apoptotic function of Bak. Tyr/Phe restriction also inhibits Bcl-2 and Met restriction inhibits Bcl-XL in mitochondria. These comprehensive actions damage the integrity of the mitochondria and induce apoptosis of DU145. In PC3, apoptosis induced by Met restriction was not associated with alterations in intracellular distribution of Raf, Bcl-2 family proteins, or AIF. All of the amino acid restrictions inhibited Akt activity in this cell line. We conclude that specific amino acid restriction differentially interferes with homeostasis/balance between the Raf and Akt survival pathways and with the interaction of Raf and Bcl-2 family proteins in mitochondria to induce apoptosis of DU145 and PC3 cells.

Amino Acid Deprivation Decreases Intracellular Levels of Reactive Oxygen Species in Hepatic Stellate Cells

“…Studies performed in animal models for methionine restriction, describe a decrease in mitochondrial ROS levels and oxidative damage to mitochondrial DNA that could be responsible for the well-documented beneficial effects of caloric or protein restriction in the aging process [17,18]. Although these results suggest a protective antioxidant action for amino acid restriction, there are also data both in yeast [19] and mammalian cells [9,10] indicating that amino acid deprivation can also cause a pro-oxidant effect.…”

“…A key mediator of amino acid deficiency is GCN2 (general control nonderepresible 2) kinase, an enzyme that undergoes activation by direct binding of uncharged tRNA through a histidine-tRNA synthetase homologous domain [5,6]. Regulation of other enzymes such as ERK, JNK, p38 MAPK, Akt and mTOR [7][8][9][10] has also been described in different cell lines cultured in the absence of an essential amino acid.…”

Methionine Restriction and Modification of Epithelial Tight Junction Barrier Function and Permeability

“…In prostate cancer cells, MR not only induced apoptosis, but also reduced the invasiveness of two different prostate cell lines [16]. This effect seemed to be via a FAK/extracellular-regulated kinase (ERK)-dependent pathway [16] and Raf/Akt survival pathway [17]. MR also modulates g-protein activity and the relative abundance and phosphorylation of the motility proteins cofilin and profilin [14].…”

Taxol-induced alteration of intracellular amino-acid profile related to human cervical carcinoma HeLa cell death

“…Specific amino-acid dependency is one of the metabolic abnormalities of cancer cells. Restriction of tyrosine and phenylalanine (Tyr/Phe) or glutamine (Gln) can induce apoptosis of prostate cancer cells (Fu et al 2006). Amino-acid deprivation by substitution of the cell culture medium with Earle's balanced salt solution leads to apoptosis in murine C2C12 muscle cells (Martinet et al 2005).…”