title: Activation of NF-kappaB and upregulation of intracellular anti-apoptotic proteins via the IGF-1/Akt signaling in human multiple myeloma cells: therapeutic implications.
abstract: Interleukin-6 (IL-6) and insulin-like growth factor-1 (IGF-1) promote the proliferation of multiple myeloma (MM) cells and protect them against dexamethasone (Dex)-induced apoptosis. We have previously shown that Apo2 ligand/TNF-Related apoptosis inducing ligand (Apo2L/TRAIL) induces apoptosis of MM cells, including cells either sensitive or resistant to Dex and cytotoxic drugs, and overcomes the growth and survival effect of IL-6; conversely, NF-kappaB transcriptional activity attenuates their Apo2L/TRAIL-sensitivity. In the current study, we demonstrate that IGF-1 stimulates sustained activation of NF-kappaB and Akt; induces phosphorylation of the FKHRL-1 Forkhead transcription factor; upregulates a series of intracellular anti-apoptotic proteins including FLIP, survivin, cIAP-2, A1/Bfl-1, and XIAP; and decreases Apo2L/TRAIL-sensitivity of MM cells. In contrast, IL-6 does not cause sustained NF-kappaB activation, induces less pronounced Akt activation and FKHRL-1 phosphorylation than IGF-1, and increases the expression of only survivin. Forced overexpression of constitutively active Akt in MM-1S cells reduced their sensitivity to Apo2L/TRAIL and to doxorubicin (Doxo). In contrast, the Akt inhibitor IL-6-Hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate induced cell death of both Dex- and Doxo-sensitive and -resistant cells; opposed the protective effect of constitutive Akt activity against Apo2L/TRAIL; and abrogated the NF-kappaB activation, increase of anti-apoptotic proteins and protection against Apo2L/TRAIL induced by IGF-1. These findings therefore define an important role of the Akt pathway in modulating tumor cell responsiveness to Apo2L/TRAIL, delineate molecular mechanisms for the survival effects of IGF-1, and characterize differential pathophysiologic sequelae of IGF-1 vs IL-6 on MM cells. Importantly, they provide the basis for future clinical trials in MM combining conventional or novel agents with strategies designed to neutralize IGF-1.
authors.affiliation: Jerome Lipper Multiple Myeloma Center, Department of Adult Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, MA 02115, USA.
authors.forename: Constantine S
authors.initials: CS
authors.lastname: Mitsiades
authors.forename: Nicholas
authors.initials: N
authors.lastname: Mitsiades
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Poulaki
authors.forename: Robert
authors.initials: R
authors.lastname: Schlossman
authors.forename: Masaharu
authors.initials: M
authors.lastname: Akiyama
authors.forename: Dharminder
authors.initials: D
authors.lastname: Chauhan
authors.forename: Teru
authors.initials: T
authors.lastname: Hideshima
authors.forename: Steven P
authors.initials: SP
authors.lastname: Treon
authors.forename: Nikhil C
authors.initials: NC
authors.lastname: Munshi
authors.forename: Paul G
authors.initials: PG
authors.lastname: Richardson
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Anderson
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D004268:DNA-Binding Proteins / Q000378:metabolism; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D009101:Multiple Myeloma / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D016328:NF-kappa B / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D053221:TNF-Related Apoptosis-Inducing Ligand; D014157:Transcription Factors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D051017:Apoptosis Regulatory Proteins; D004268:DNA-Binding Proteins; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D007334:Insulin-Like Growth Factor I; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D053221:TNF-Related Apoptosis-Inducing Ligand; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C085126:FOXO1 protein, human; C505653:TNFSF10 protein, human; C494918:AKT1 protein, human