Mechanisms of proteasome inhibitor PS-341-induced G(2)-M-phase arrest and apoptosis in human non-small cell lung cancer cell lines.
OBJECTIVE
PS-341 is a novel dipeptide boronic acid proteasome inhibitor with in vitro and in vivo antitumor activity that induces mechanisms of apoptosis by unknown mechanisms.


METHODS
Human non-small cell lung cancer cell lines were used to investigate effects PS-341 on cell proliferation, cell cycle progression, and the induction of apoptosis.


RESULTS
PS-341 was 38-360-fold more cytotoxic against H460 cells when compared with the proteasome inhibitors MG-132 and PSI. Differential PS-341 cytotoxic effects were found with respect to P53 function: H322 cells (p53 mutant) were 6-fold less sensitive as compared with H460 cells (p53 wild type); and H358 cells (p53 null) were 1.6-fold more sensitive as compared with H460 cells (p53 wild type). A concentration- and time-dependent cell cycle blockade at G(2)-M phase was seen for H460 cells without any direct effects on microtubule polymerization or depolymerization. PS-341 exposure in H460 cells led to stabilization of p53, induction of p21(cip/waf-1) and MDM2 expression, an increase in cyclin B and cyclin A, and the activation of cyclin B and cyclin A kinases. MDM2 induction was found only in H460 cells, whereas in H322 and H358 cells, G(2)-M-phase arrest, p21(cip/waf-1) induction, and an increase in cyclin B1 were found. The commitment of G(2)-M-phase cells to apoptosis was verified by the activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase in drug-free medium.


CONCLUSIONS
Our data suggest that the PS-341-induced G(2)-M-phase arrest may be associated with the inhibition of degradation of cell cycle regulators and that the up-regulation of p21(cip/waf-1) expression may be via p53-dependent and/or -independent pathways. The resulting disturbance of cell cycle progression leads either to growth inhibition or to the initiation of apoptotic pathways.
Ling
Yi-He
YH
Department of Oncology, Albert Einstein College of Medicine, 13200 Morris Park Avenue, Bronx, NY 10461, USA.
Liebes
Leonard
L
Jiang
Jian-Dong
JD
Holland
James F
JF
Elliott
Peter J
PJ
Adams
Julian
J
Muggia
Franco M
FM
Perez-Soler
Roman
R
D017209:Apoptosis; D015153:Blotting, Western; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology*; D002453:Cell Cycle; D002455:Cell Division; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D003546:Cysteine Endopeptidases; D004305:Dose-Response Relationship, Drug; D016195:G2 Phase; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000473:pathology*; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D009154:Mutation; D011233:Precipitin Tests; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D011719:Pyrazines / Q000494:pharmacology*; D013997:Time Factors; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation
D001897:Boronic Acids; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D011719:Pyrazines; D016159:Tumor Suppressor Protein p53; D000069286:Bortezomib; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex