Inhibition of CaMKII-mediated c-FLIP expression sensitizes malignant melanoma cells to TRAIL-induced apoptosis.
TRAIL can induce apoptosis in melanoma cells and thus may offer new hope for melanoma therapy. However, many melanoma cells are resistant to TRAIL. To examine molecular mechanisms in cell resistance, we analyzed TRAIL-induced DISC in TRAIL-sensitive melanoma cells and showed that apoptosis-initiating caspase-8 and caspase-10 were recruited to the DISC where they became activated through autocatalytical cleavage, leading to apoptosis through cleavage of downstream substrates such as caspase-3 and DFF45. In TRAIL-resistant melanoma cells, however, c-FLIP proteins were recruited to the DISC, resulting in the inhibition of caspase-8 and caspase-10 cleavage in the DISC. Both calmodulin-dependent protein kinase II (CaMKII) protein and enzymatic activity were upregulated in resistant cells and CaMKII inhibitor KN-93 downregulated expression of c-FLIP proteins, thus sensitizing resistant cells to TRAIL-induced apoptosis. Transfection of CaMKII cDNA in sensitive melanoma cells resulted in cell resistance to TRAIL, where transfection of CaMKII dominant-negative cDNA in resistant cells restored TRAIL sensitivity in cells. These results indicate that the CaMKII-mediated pathway for c-FLIP upregulation protects melanoma cells from TRAIL-induced apoptosis and targeting this pathway may provide novel therapeutic strategies in treatment of melanomas.
Xiao
Chang
C
Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada T6G 2S2.
Yang
Bao Feng
BF
Song
Jin H
JH
Schulman
Howard
H
Li
Liang
L
Hao
Chunhai
C
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008545:Melanoma / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases