AMPK-independent down-regulation of cFLIP and sensitization to TRAIL-induced apoptosis by AMPK activators.
The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a TNF superfamily member that is being considered as a new strategy in anticancer therapy because of its ability to induce apoptosis, alone or in combination with other stimuli, in many cancer cells. AMP-activated protein kinase (AMPK) is an evolutionarily conserved key regulator of cellular energy homeostasis that protects the cell from energy depletion and stress by activating several biochemical pathways that lead to the conservation, as well as generation, of ATP. Here we report that a number of AMPK activators, including the small molecule activator A-769662, markedly sensitize TRAIL-resistant breast cancer cells to TRAIL-induced apoptosis. However, silencing AMPKalpha1 expression with siRNA or over-expression of DN-AMPKalpha1 does not inhibit AICAR, glucose deprivation, phenformin or A-769662-induced sensitization to TRAIL. Furthermore, the expression of constitutively active AMPK subunits does not sensitize resistant breast cancer cells to TRAIL-induced apoptosis. The cellular FLICE-inhibitory proteins (cFLIP(L) and cFLIP(S)) were significantly down-regulated following exposure to AMPK activators through an AMPK-independent mechanism. Furthermore, in cells over-expressing cFLIP(L), sensitization to TRAIL by AMPK activators was markedly reduced. In summary, our results indicate that AMPK activators facilitate the activation by TRAIL of an apoptotic cell death program through a mechanism independent of AMPK and dependent on the down-regulation of cFLIP levels.
García-García
Celina
C
Centro Andaluz de Biología Molecular y Medicina Regenerativa, Consejo Superior de Investigaciones Científicas, Avenida Américo Vespucio s/n, 41092 Sevilla, Spain. celina.garcia@cabimer.es
Fumarola
Claudia
C
Navaratnam
Naveenan
N
Carling
David
D
López-Rivas
Abelardo
A
D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D000263:Adenylate Kinase / Q000378:metabolism*; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D020536:Enzyme Activators / Q000494:pharmacology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D020868:Gene Silencing; D006801:Humans; D021122:Protein Subunits; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D020536:Enzyme Activators; D021122:Protein Subunits; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D055372:AMP-Activated Protein Kinases; C526180:PRKAA1 protein, human; D000263:Adenylate Kinase