Proteasome inhibition activates epidermal growth factor receptor (EGFR) and EGFR-independent mitogenic kinase signaling pathways in pancreatic cancer cells.
OBJECTIVE
In the current study, we investigate the activation of antiapoptotic signaling pathways in response to proteasome inhibitor treatment in pancreatic cancer and evaluate the use of concomitant inhibition of these pathways to augment proteasome inhibitor treatment responses.


METHODS
Pancreatic cancer cell lines and mouse flank xenografts were treated with proteasome inhibitor alone or in combination with chemotherapeutic compounds (gemcitabine, erlotinib, and bevacizumab), induction of apoptosis and effects on tumor growth were assessed. The effect of bortezomib (a first-generation proteasome inhibitor) and NPI-0052 (a second-generation proteasome inhibitor) treatment on key pancreatic mitogenic and antiapoptotic pathways [epidermal growth factor receptor, extracellular signal-regulated kinase, and phosphoinositide-3-kinase (PI3K)/AKT] was determined and the ability of inhibitors of these pathways to enhance the effects of proteasome inhibition was assessed in vitro and in vivo.


RESULTS
Our data showed that proteasome inhibitor treatment activates antiapoptotic and mitogenic signaling pathways (epidermal growth factor receptor, extracellular signal-regulated kinase, c-Jun-NH2-kinase, and PI3K/AKT) in pancreatic cancer. Additionally, we found that activation of these pathways impairs tumor response to proteasome inhibitor treatment and inhibition of the c-Jun-NH2-kinase and PI3K/AKT pathways increases the antitumor effects of proteasome inhibitor treatment.


CONCLUSIONS
These preclinical studies suggest that targeting proteasome inhibitor-induced antiapoptotic signaling pathways in combination with proteasome inhibition may augment treatment response in highly resistant solid organ malignancies. Further evaluation of these novel treatment combinations in clinical trials is warranted.
Sloss
Callum M
CM
Division of Surgical Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts, USA.
Wang
Fang
F
Liu
Rong
R
Xia
Lijun
L
Houston
Michael
M
Ljungman
David
D
Palladino
Michael A
MA
Cusack
James C
JC
D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D061067:Antibodies, Monoclonal, Humanized; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D000068258:Bevacizumab; D015153:Blotting, Western; D001897:Boronic Acids / Q000008:administration & dosage; D000069286:Bortezomib; D045744:Cell Line, Tumor; D000068818:Cetuximab; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D066246:ErbB Receptors / Q000187:drug effects* / Q000378:metabolism; D000069347:Erlotinib Hydrochloride; D005260:Female; D006801:Humans; D007783:Lactones / Q000008:administration & dosage; D051379:Mice; D008819:Mice, Nude; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D011480:Protease Inhibitors / Q000627:therapeutic use*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000008:administration & dosage; D011758:Pyrroles / Q000008:administration & dosage; D011799:Quinazolines / Q000008:administration & dosage; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D001897:Boronic Acids; D007783:Lactones; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D011758:Pyrroles; D011799:Quinazolines; D003841:Deoxycytidine; D000068258:Bevacizumab; D000069286:Bortezomib; C475865:marizomib; D000069347:Erlotinib Hydrochloride; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D000068818:Cetuximab; D000093542:Gemcitabine