SUMOylation plays a role in gemcitabine- and bortezomib-induced cytotoxicity in human oropharyngeal carcinoma KB gemcitabine-resistant clone.
Bortezomib, a novel dipeptide boronic acid proteasome inhibitor, has been shown in previous studies to be synergistic with gemcitabine; however, the molecular mechanisms are not fully understood. Because post-translational modification of proteins, such as ubiquitination and SUMOylation, plays a critical role in governing cellular homeostasis, we explored this further by treating human oropharyngeal carcinoma KB wild-type (KBwt) and gemcitabine-resistant (KBGem) cells with gemcitabine and bortezomib in a time-dependent and sequence-dependent manner. Treatment with bortezomib at 4 to 8 hours post-gemcitabine significantly induced cell death in KBwt cell lines. However, in KBGem cells, bortezomib alone was just as cytotoxic. Using reporter assays, nuclear factor-kappaB (NF-kappaB) activity was found to be 5-fold higher in KBGem cells than that in KBwt cells, and the combination treatment decreased NF-kappaB activity by 44% in KBwt cells and 28% in KBGem cells, respectively. By Western blot analyses, treatment with gemcitabine and bortezomib resulted in a cleavage of NF-kappaB in KBwt but not in KBGem cells. SUMOylation capacity was modulated by transducing KBwt and KBGem cells with lenti-SUMO-1 or the unconjugatable lenti-SUMO-1aa followed by drug treatment. The expression of cyclins A, D1, and E was differentially regulated by SUMOylation capacity in KBGem but not in KBwt cells. We report herein that the activation of NF-kappaB signaling plays a critical role in eliciting KBwt cell survival against gemcitabine, whereas the role of SUMOylation in modulating the steady-state levels of key cell cycle regulator proteins seems more significant in KBGem cells.
Department of Medical Oncology and Therapeutic Research, City of Hope National Medical Center, 1500 East Duarte Road, Duarte, CA 91010, USA.
Vincent
V
Chung
Bingsen
B
Zhou
Xiyong
X
Liu
Lijun
L
Zhu
Lee M
LM
Boo
Ha-Van
HV
Nguyen
David K
DK
Ann
Jing
J
Song
Yuan
Y
Chen
Yun
Y
Yen
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D001897:Boronic Acids / Q000627:therapeutic use*; D000069286:Bortezomib; D002277:Carcinoma / Q000188:drug therapy*; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D009959:Oropharyngeal Neoplasms / Q000188:drug therapy*; D011719:Pyrazines / Q000627:therapeutic use*; D025842:SUMO-1 Protein / Q000378:metabolism*; D000093542:Gemcitabine
D001897:Boronic Acids; D018797:Cell Cycle Proteins; D016328:NF-kappa B; D011719:Pyrazines; D025842:SUMO-1 Protein; D003841:Deoxycytidine; D000069286:Bortezomib; D000093542:Gemcitabine