Molecular characterization of PS-341 (bortezomib) resistance: implications for overcoming resistance using lysophosphatidic acid acyltransferase (LPAAT)-beta inhibitors.
PS-341 (bortezomib, Velcadetrade mark) is a promising novel agent for treatment of advanced multiple myeloma (MM); however, 65% of patients with relapsed refractory disease in a phase II study do not respond to PS-341. We have previously shown that lysophosphatidic acid acyltransferase (LPAAT)-beta inhibitor CT-32615 triggers caspase-dependent apoptosis, and can overcome resistance to conventional therapeutics (i.e., dexamethasone, doxorubicin, melphalan) in MM cells. In this study, we therefore determined whether CT-32615 could also overcome resistance to PS-341. We first characterized molecular mechanisms of resistance to PS-341 in DHL-4 cells. DHL-4 cells express low levels of caspase-3 and caspase-8; furthermore, no cleavage in caspase-8, caspase-9, caspase-3, poly ADP-ribose polymerase (PARP), or DNA fragmentation factor 45 was triggered by PS-341 treatment. We have previously shown that PS-341 treatment triggers phosphorylation of c-Jun NH(2)-terminal kinase (JNK), which subsequently induces caspase-dependent apoptosis; conversely, JNK inhibition blocks PS-341-induced apoptosis. We here show that phosphorylation of SEK-1, JNK, and c-Jun are not induced by PS-341 treatment, suggesting that PS-341 does not trigger a stress response in DHL-4 cells. Importantly, CT-32615 inhibits growth of DHL-4 cells in a time- and dose-dependent fashion: a transient G2/M cell cycle arrest induced by CT-32615 is mediated via downregulation of cdc25c and cdc2. CT-32615 triggered swelling and lysis of DHL-4 cells, without caspase/PARP cleavage or TUNEL-positivity, suggesting a necrotic response. Our studies therefore demonstrate that LPAAT-beta inhibitor CT-32615 triggers necrosis, even in PS-341-resistant DHL-4 cells, providing the framework for its evaluation to overcome clinical PS-341 resistance and improve patient outcome.
Hideshima
Teru
T
Jerome Lipper Multiple Myeloma Center, Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA.
Chauhan
Dharminder
D
Ishitsuka
Kenji
K
Yasui
Hiroshi
H
Raje
Noopur
N
Kumar
Shaji
S
Podar
Klaus
K
Mitsiades
Constantine
C
Hideshima
Hiromasa
H
Bonham
Lynn
L
Munshi
Nikhil C
NC
Richardson
Paul G
PG
Singer
Jack W
JW
Anderson
Kenneth C
KC
D000217:Acyltransferases / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D016203:CDC2 Protein Kinase / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005434:Flow Cytometry; D016195:G2 Phase; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D009101:Multiple Myeloma / Q000188:drug therapy / Q000378:metabolism; D009336:Necrosis; D010766:Phosphorylation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D011506:Proteins / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology*; D013997:Time Factors; D016896:Treatment Outcome; D020687:cdc25 Phosphatases / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D001897:Boronic Acids; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011506:Proteins; D011719:Pyrazines; C109664:caspase-activated DNase inhibitor; D000069286:Bortezomib; D000255:Adenosine Triphosphate; D000217:Acyltransferases; C018764:2-acylglycerophosphate acyltransferase; D011065:Poly(ADP-ribose) Polymerases; D016203:CDC2 Protein Kinase; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases