Salicylate activates AMPK and synergizes with metformin to reduce the survival of prostate and lung cancer cells ex vivo through inhibition of de novo lipogenesis.

Aspirin, the pro-drug of salicylate, is associated with reduced incidence of death from cancers of the colon, lung and prostate and is commonly prescribed in combination with metformin in individuals with type 2 diabetes. Salicylate activates the AMP-activated protein kinase (AMPK) by binding at the A-769662 drug binding site on the AMPK β1-subunit, a mechanism that is distinct from metformin which disrupts the adenylate charge of the cell. A hallmark of many cancers is high rates of fatty acid synthesis and AMPK inhibits this pathway through phosphorylation of acetyl-CoA carboxylase (ACC). It is currently unknown whether targeting the AMPK-ACC-lipogenic pathway using salicylate and/or metformin may be effective for inhibiting cancer cell survival. Salicylate suppresses clonogenic survival of prostate and lung cancer cells at therapeutic concentrations achievable following the ingestion of aspirin (<1.0 mM); effects not observed in prostate (PNT1A) and lung (MRC-5) epithelial cell lines. Salicylate concentrations of 1 mM increased the phosphorylation of ACC and suppressed de novo lipogenesis and these effects were enhanced with the addition of clinical concentrations of metformin (100 μM) and eliminated in mouse embryonic fibroblasts (MEFs) deficient in AMPK β1. Supplementation of media with fatty acids and/or cholesterol reverses the suppressive effects of salicylate and metformin on cell survival indicating the inhibition of de novo lipogenesis is probably important. Pre-clinical studies evaluating the use of salicylate based drugs alone and in combination with metformin to inhibit de novo lipogenesis and the survival of prostate and lung cancers are warranted.

O'Brien AJ ，Villani LA ，Broadfield LA ，Houde VP ，Galic S ，Blandino G ，Kemp BE ，Tsakiridis T ，Muti P ，Steinberg GR ... -  《-》

Metformin and salicylate synergistically activate liver AMPK, inhibit lipogenesis and improve insulin sensitivity.

Ford RJ ，Fullerton MD ，Pinkosky SL ，Day EA ，Scott JW ，Oakhill JS ，Bujak AL ，Smith BK ，Crane JD ，Blümer RM ，Marcinko K ，Kemp BE ，Gerstein HC ，Steinberg GR ... -  《-》

Metformin enhances cisplatin cytotoxicity by suppressing signal transducer and activator of transcription-3 activity independently of the liver kinase B1-AMP-activated protein kinase pathway.

Lin CC ，Yeh HH ，Huang WL ，Yan JJ ，Lai WW ，Su WP ，Chen HH ，Su WC ... -  《-》

Activation of AMP-activated Protein Kinase by Metformin Induces Protein Acetylation in Prostate and Ovarian Cancer Cells.

AMP-activated protein kinase (AMPK) is an energy sensor and master regulator of metabolism. AMPK functions as a fuel gauge monitoring systemic and cellular energy status. Activation of AMPK occurs when the intracellular AMP/ATP ratio increases and leads to a metabolic switch from anabolism to catabolism. AMPK phosphorylates and inhibits acetyl-CoA carboxylase (ACC), which catalyzes carboxylation of acetyl-CoA to malonyl-CoA, the first and rate-limiting reaction in de novo synthesis of fatty acids. AMPK thus regulates homeostasis of acetyl-CoA, a key metabolite at the crossroads of metabolism, signaling, chromatin structure, and transcription. Nucleocytosolic concentration of acetyl-CoA affects histone acetylation and links metabolism and chromatin structure. Here we show that activation of AMPK with the widely used antidiabetic drug metformin or with the AMP mimetic 5-aminoimidazole-4-carboxamide ribonucleotide increases the inhibitory phosphorylation of ACC and decreases the conversion of acetyl-CoA to malonyl-CoA, leading to increased protein acetylation and altered gene expression in prostate and ovarian cancer cells. Direct inhibition of ACC with allosteric inhibitor 5-(tetradecyloxy)-2-furoic acid also increases acetylation of histones and non-histone proteins. Because AMPK activation requires liver kinase B1, metformin does not induce protein acetylation in liver kinase B1-deficient cells. Together, our data indicate that AMPK regulates the availability of nucleocytosolic acetyl-CoA for protein acetylation and that AMPK activators, such as metformin, have the capacity to increase protein acetylation and alter patterns of gene expression, further expanding the plethora of metformin's physiological effects.

Galdieri L ，Gatla H ，Vancurova I ，Vancura A ... -  《-》

Salicylate enhances the response of prostate cancer to radiotherapy.

Radiotherapy (RT) is a key therapeutic modality for prostate cancer (PrCa), but RT resistance necessitates dose-escalation, often causing bladder and rectal toxicity. Aspirin, a prodrug of salicylate (SAL), has been associated with improved RT response in clinical PrCa cases, but the potential mechanism mediating this effect is unknown. SAL activates the metabolic stress sensor AMP-activated protein kinase (AMPK), which inhibits de novo lipogenesis, and protein synthesis via inhibition of Acetyl-CoA Carboxylase (ACC), and the mammalian Target of Rapamycin (mTOR), respectively. RT also activates AMPK through a mechanism distinctly different from SAL. Therefore, combining these two therapies may have synergistic effects on suppressing PrCa. Here, we examined the potential of SAL to enhance the response of human PrCa cells and tumors to RT. Androgen-insensitive (PC3) and -sensitive (LNCaP) PrCa cells were subjected to proliferation and clonogenic survival assays after treatment with clinically relevant doses of SAL and RT. Balb/c nude mice with PC3 xenografts were fed standard chow diet or chow diet supplemented with 2.5 g/kg salsalate (SAL pro-drug dimer) one week prior to a single dose of 0 or 10 Gy RT. Immunoblotting analysis of signaling events in the DNA repair and AMPK-mTOR pathways and lipogenesis were assessed in cells treated with SAL and RT. SAL inhibited proliferation and clonogenic survival in PrCa cells and enhanced the inhibition mediated by RT. Salsalate, added to diet, enhanced the anti-tumor effects of RT in PC3 tumor xenografts. RT activated genotoxic stress markers and the activity of mTOR pathway and AMPK and mediated inhibitory phosphorylation of ACC. Interestingly, SAL enhanced the effects of RT on AMPK and ACC but blocked markers of mTOR activation. Our results show that SAL can enhance RT responses in PrCa. Salsalate is a promising agent to investigate this concept in prospective clinical trials of PrCa in combination with RT.

Broadfield LA ，Marcinko K ，Tsakiridis E ，Zacharidis PG ，Villani L ，Lally JSV ，Menjolian G ，Maharaj D ，Mathurin T ，Smoke M ，Farrell T ，Muti P ，Steinberg GR ，Tsakiridis T ... -  《-》