Effects of the proteasome inhibitor bortezomib alone and in combination with chemotherapy in the A549 non-small-cell lung cancer cell line.
BACKGROUND
Non-small-cell lung cancer (NSCLC) has a poor prognosis. Despite advances in therapy, survival has improved only slightly. The 26S proteasome regulates multiple cellular processes through degradation of ubiquitin-tagged proteins. The proteasome inhibitor, bortezomib (Velcade, formerly PS-341), has been shown to be an active anticancer agent both in vitro and in vivo in multiple tumor types.


OBJECTIVE
To determine the molecular and cellular effects of the proteasome inhibitor in NSCLC as well as to evaluate the effectiveness of sequential treatment with bortezomib and gemcitabine/carboplatin (G/C) chemotherapy both in vitro and in vivo.


METHODS
All experiments were performed in the A549 NSCLC cell line. MTT assays were used to evaluate cytotoxicity. Western blotting evaluated protein levels. Measures of apoptosis included FACS analysis, DAPI staining and caspase-3 cleavage. Long-term cell viability was determined using an anchorage-dependent clonogenic assay. Sequential studies were performed in vitro and in vivo.


RESULTS
Bortezomib increased p21(waf1/cip1), induced G(2)/M arrest, and triggered a small amount of apoptosis. The apoptotic effect of G/C chemotherapy was eliminated when bortezomib was administered prior to the chemotherapy; however, it was accentuated when the bortezomib was given simultaneously or after the chemotherapy.


CONCLUSIONS
Bortezomib improves efficacy in combination with gemcitabine and carboplatin in NSCLC, but sequential effects are important and must be considered when developing therapeutic regimens.
Mortenson
Melinda M
MM
Department of Surgery, University of California Davis Medical Center, 4501 X Street, Sacramento, CA 95817, USA.
Schlieman
Michael G
MG
Virudachalam
Subbulakshmi
S
Bold
Richard J
RJ
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use*; D001897:Boronic Acids / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D000069286:Bortezomib; D016190:Carboplatin / Q000008:administration & dosage; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy*; D002470:Cell Survival / Q000187:drug effects; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011480:Protease Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011719:Pyrazines / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D000093542:Gemcitabine
D001897:Boronic Acids; D011480:Protease Inhibitors; D011719:Pyrazines; D003841:Deoxycytidine; D000069286:Bortezomib; D016190:Carboplatin; D000093542:Gemcitabine