8-Amino-adenosine induces loss of phosphorylation of p38 mitogen-activated protein kinase, extracellular signal-regulated kinase 1/2, and Akt kinase: role in induction of apoptosis in multiple myeloma.
Multiple myeloma is a slowly proliferating B-cell malignancy that accumulates apoptosis-resistant and replication-quiescent cell populations, posing a challenge for current chemotherapeutics that target rapidly replicating cells. Multiple myeloma remains an incurable disease in need of new therapeutic approaches. The purine nucleoside analogue, 8-amino-adenosine (8-NH2-Ado), exhibits potent activity in preclinical studies, inducing apoptosis in several multiple myeloma cell lines. This cytotoxic effect requires phosphorylation of 8-NH2-Ado to its triphosphate form, 8-amino-ATP, and results in a concomitant loss of endogenous ATP levels. Here, we show the novel effect of 8-NH2-Ado on the phosphorylation status of key cellular signaling molecules. Multiple myeloma cells treated with 8-NH2-Ado exhibit a dramatic loss of phosphorylation of several important signaling proteins, including extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and Akt kinase. Cells depleted of ATP independent of 8-NH2-Ado do not exhibit the same decrease in phosphorylation of vital cellular proteins. Therefore, the significant shifts in endogenous ATP pools caused by 8-NH2-Ado treatment cannot account for the changes in phosphorylation levels. Instead, 8-NH2-Ado may influence the activity of select regulatory protein kinases and/or phosphatases, with preliminary data suggesting that protein phophatase 2A activity is affected by 8-NH2-Ado. The distinctive effect of 8-NH2-Ado on the phosphorylation status of cellular proteins is a novel phenomenon for a nucleoside analogue drug and is unique to 8-NH2-Ado among this class of drugs. The kinetics of 8-NH2-Ado-mediated changes in phosphorylation levels of critical prosurvival and apoptosis-regulating proteins suggests that the modulation of these proteins by dephosphorylation at early time points may be an important mechanistic step in 8-NH2-Ado-induced apoptosis.
Ghias
Kulsoom
K
Robert H. Lurie Comprehensive Cancer Center, Department of Medicine, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Olson 8340, Chicago, Illinois 60611, USA. n-
Ma
Chunguang
C
Gandhi
Varsha
V
Platanias
Leonidas C
LC
Krett
Nancy L
NL
Rosen
Steven T
ST
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000737:chemistry; D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007700:Kinetics; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009101:Multiple Myeloma / Q000473:pathology*; D009705:Nucleosides / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011687:Purines / Q000737:chemistry; D015398:Signal Transduction; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D009705:Nucleosides; D011518:Proto-Oncogene Proteins; D011687:Purines; C010533:8-aminoadenosine; D000255:Adenosine Triphosphate; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D010744:Phosphoric Monoester Hydrolases; D000241:Adenosine