Nitrosylcobalamin potentiates the anti-neoplastic effects of chemotherapeutic agents via suppression of survival signaling.
Nitrosylcobalamin (NO-Cbl) is a chemotherapeutic pro-drug derived from vitamin B12 that preferentially delivers nitric oxide (NO) to tumor cells, based upon increased receptor expression. NO-Cbl induces Apo2L/TRAIL-mediated apoptosis and inhibits survival signaling in a variety of malignant cell lines. Chemotherapeutic agents often simultaneously induce an apoptotic signal and activation of NF-kappaB, which has the undesired effect of promoting cell survival. The specific aims of this study were to 1) measure the anti-tumor effects of NO-Cbl alone and in combination with conventional chemotherapeutic agents, and to 2) examine the mechanism of action of NO-Cbl as a single agent and in combination therapy.



Using anti-proliferative assays, electrophoretic mobility shift assay (EMSA), immunoblot analysis and kinase assays, we demonstrate an increase in the effectiveness of chemotherapeutic agents in combination with NO-Cbl as a result of suppressed NF-kappaB activation.



Eighteen chemotherapeutic agents were tested in combination with NO-Cbl, in thirteen malignant cell lines, resulting in a synergistic anti-proliferative effect in 78% of the combinations tested. NO-Cbl pre-treatment resulted in decreased NF-kappaB DNA binding activity, inhibition of IkappaB kinase (IKK) enzymatic activity, decreased AKT activation, increased caspase-8 and PARP cleavage, and decreased cellular XIAP protein levels.



The use of NO-Cbl to inhibit survival signaling may enhance drug efficacy by preventing concomitant activation of NF-kappaB or AKT.
Bauer
Joseph A
JA
Taussig Cancer Center, Center for Hematology and Oncology Molecular Therapeutics, The Cleveland Clinic Foundation, Cleveland, Ohio, United States of America. bauerj@ccf.org <bauerj@ccf.org>
Lupica
Joseph A
JA
Szugye
Heidi
H
Morrison
Bei H
BH
Haney
Rebecca M
RM
Masci
Rhonda K
RK
Lee
Rebecca M
RM
Didonato
Joseph A
JA
Lindner
Daniel J
DJ
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001053:Apolipoproteins / Q000502:physiology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009603:Nitroso Compounds / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000494:pharmacology; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
D000970:Antineoplastic Agents; D001053:Apolipoproteins; D016328:NF-kappa B; D009603:Nitroso Compounds; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C113298:nitrosylcobalamin; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; D014805:Vitamin B 12