Hypoxia Promotes Synergy between Mitomycin C and Bortezomib through a Coordinated Process of Bcl-xL Phosphorylation and Mitochondrial Translocation of p53.
Colorectal peritoneal carcinomatosis (CPC) exhibits severe tumor hypoxia, leading to drug resistance and disease aggressiveness. This study demonstrates that the combination of the chemotherapeutic agent mitomycin C with the proteasome inhibitor bortezomib induced synergistic cytotoxicity and apoptosis, which was even more effective under hypoxia in colorectal cancer cells. The combination of mitomycin C and bortezomib at sublethal doses induced activation of c-Jun NH2-terminal kinase and p38 mitogen-activated protein kinase and resulted in Bcl-xL phosphorylation at Serine 62, leading to dissociation of Bcl-xL from proapoptotic Bak. Interestingly, the intracellular level of p53 became elevated and p53 translocated to the mitochondria during the combinatorial treatment, in particular under hypoxia. The coordinated action of Bcl-xL phosphorylation and p53 translocation to the mitochondria resulted in conformational activation of Bak oligomerization, facilitating cytochrome c release and apoptosis induction. In addition, the combinatorial treatment with mitomycin C and bortezomib significantly inhibited intraperitoneal tumor growth in LS174T cells and increased apoptosis, especially under hypoxic conditions in vivo. This study provides a preclinical rationale for the use of combination therapies for CPC patients.


CONCLUSIONS
The combination of a chemotherapy agent and proteasome inhibitor at sublethal doses induced synergistic apoptosis, in particular under hypoxia, in vitro and in vivo through coordinated action of Bcl-xL and p53 on Bak activation.
Department of Surgery, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.
Xinxin
X
Song
Department of Surgery, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.
Ashok-Kumar
AK
Dilly
Department of Surgery, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.
Haroon Asif
HA
Choudry
Department of Surgery, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.
David L
DL
Bartlett
Protein Metabolism Medical Research Center and Department of Biomedical Science, College of Medicine, Seoul National University, Seoul, Korea.
Yong Tae
YT
Kwon
Department of Surgery, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania. Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania. leeyj@upmc.edu.
Yong J
YJ
Lee
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000494:pharmacology; D000069286:Bortezomib / Q000008:administration & dosage* / Q000494:pharmacology; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D016685:Mitomycin / Q000008:administration & dosage* / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays; D051020:bcl-X Protein / Q000378:metabolism*
D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein; D016685:Mitomycin; D000069286:Bortezomib