Marine alkaloid polycarpine and its synthetic derivative dimethylpolycarpine induce apoptosis in JB6 cells through p53- and caspase 3-dependent pathways.
OBJECTIVE
Polycarpine from ascidian Polycarpa aurata was previously found to be active against different human tumor cells. In this study, we investigated the antitumor mechanisms of polycarpine and its synthetic derivative, desmethoxyethoxy-polycarpine (dimethylpolycarpine), through the induction of apoptosis. This new knowledge regarding the proapoptotic action of polycarpine and dimethylpolycarpine should lead to a better understanding of their effects and development of a new class of anticancer drugs.


METHODS
Apoptosis was clearly observed by flow cytometry and Western blotting using an antibody against cleaved caspase-3 as an apoptotic marker.


RESULTS
Polycarpines differentially activated p38 kinase, JNKs, and ERKs in JB6 Cl 41 cells. The polycarpines-induced apoptosis was decreased in cells expressing a dominant-negative mutant of JNK. Both compounds stimulated p53-dependent transcriptional activity and phosphorylation. Induction of p53-phosphorylation at serine 15 was suppressed in JNKI and JNK2 knockout cells. Furthermore, polycarpines were unable to induce apoptosis in p53-deficient MEFs in contrast to a strong induction of apoptosis in wild type MEFs, suggesting that p53 is involved in apoptosis induced by polycarpines. The p53 phosphorylation in turn was mediated by activated JNKs.


CONCLUSIONS
These results indicate that all three MAPK signaling pathways are involved in the response of JB6 cells to treatment with polycarpines. Evidence also supports a proapoptotic role of the JNKs signaling pathway in vivo and clearly indicates that JNKs are required for phosphorylation of c-Jun, activation of p53, and subsequent apoptosis induced by polycarpines.
Fedorov
Sergey N
SN
Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA.
Bode
Ann M
AM
Stonik
Valentin A
VA
Gorshkova
Irina A
IA
Schmid
Patricia C
PC
Radchenko
Oleg S
OS
Berdyshev
Evgueni V
EV
Dong
Zigang
Z
D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D007093:Imidazoles / Q000138:chemical synthesis* / Q000494:pharmacology*; D051379:Mice; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis*; D014561:Urochordata
D000470:Alkaloids; D007093:Imidazoles; D016159:Tumor Suppressor Protein p53; C475052:polycarpine; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases