title: CCL2 is a negative regulator of AMP-activated protein kinase to sustain mTOR complex-1 activation, survivin expression, and cell survival in human prostate cancer PC3 cells.
abstract: CCL2 is a cytokine prevalent in the prostate cancer tumor microenvironment. Recently, we reported that CCL2 induces the mammalian target of rapamycin (mTOR) pathway to promote prostate cancer PC3 cell survival; however, the mechanism used by CCL2 to maintain mTOR complex-1 (mTORC1) activation requires clarification. This study demonstrates that upon serum starvation, CCL2 functions as a negative regulator of AMP-activated protein kinase (AMPK) by decreasing phosphorylation at its major regulatory site (Thr(172)) in PC3, DU145, and C4-2B prostate cancer cells. The CCL2-mediated AMPK regulation decreased raptor phosphorylation (Ser(792)) resulting in hyperactivation of mTORC1. D942, a pharmacological activator of AMPK, stunted CCL2-induced mTORC1 activity, survivin expression, and cell survival without significantly affecting Akt activity. CCL2, however, conferred some resistance to the lethal effect of D942 compared with untreated cells. By using Akt-specific inhibitor X, it was shown that Akt inactivation did not cause an increase in AMPK phosphorylation in CCL2-stimulated cells, suggesting that CCL2-mediated negative regulation of AMPK is independent of Akt. Furthermore, bisindolylmaleimide-V, a specific inhibitor of p70(S6K), stunted survivin expression and induced cell death in CCL2-treated PC3. Altogether, these findings suggest that CCL2 hyperactivates mTORC1 through simultaneous regulation of both AMPK and Akt pathways and reveals a new network that promotes prostate cancer: CCL2-AMPK-mTORC1-survivin.
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI 48109, USA. rocach@umich.edu
authors.forename: Hernan
authors.initials: H
authors.lastname: Roca
authors.forename: Zachary S
authors.initials: ZS
authors.lastname: Varsos
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Pienta
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D015153:Blotting, Western; D002264:Carboxylic Acids / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D018932:Chemokine CCL2 / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005663:Furans / Q000494:pharmacology; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology; D011506:Proteins; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000077022:Survivin; D058570:TOR Serine-Threonine Kinases; D013912:Threonine / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C107489:BIRC5 protein, human; D002264:Carboxylic Acids; D018932:Chemokine CCL2; C517023:D942 compound; D005663:Furans; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D011506:Proteins; D000077022:Survivin; D014157:Transcription Factors; D013912:Threonine; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases