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.
Chung
Vincent
V
Department of Medical Oncology and Therapeutic Research, City of Hope National Medical Center, 1500 East Duarte Road, Duarte, CA 91010, USA.
Zhou
Bingsen
B
Liu
Xiyong
X
Zhu
Lijun
L
Boo
Lee M
LM
Nguyen
Ha-Van
HV
Ann
David K
DK
Song
Jing
J
Chen
Yuan
Y
Yen
Yun
Y
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