Induction of apoptosis by the garlic-derived compound S-allylmercaptocysteine (SAMC) is associated with microtubule depolymerization and c-Jun NH(2)-terminal kinase 1 activation.
Epidemiological and experimental carcinogenesis studies provide evidence that components of garlic (Allium sativum) have anticancer activity. We recently reported that the garlic derivative S-allylmercaptocysteine (SAMC) inhibits growth, arrests cells in G(2)-M, and induces apoptosis in human colon cancer cells (Shirin et al., Cancer Res., 61: 725-731, 2001). Because a fraction of the SAMC-treated cells are specifically arrested in mitosis, we examined the mechanism of this effect in the present study. Immunofluorescent microscopy revealed that the treatment of SW480 cells or NIH3T3 fibroblasts with 150 micro M SAMC (the IC(50) concentration) caused rapid microtubule (MT) depolymerization, MT cytoskeleton disruption, centrosome fragmentation and Golgi dispersion in interphase cells. It also induced the formation of monopolar and multipolar spindles in mitotic cells. In vitro turbidity assays indicated that SAMC acted directly on tubulin to cause MT depolymerization, apparently because it interacts with -SH groups on tubulin. To investigate the signaling pathways involved in SAMC-induced apoptosis, we assayed c-Jun NH(2)-terminal kinase (JNK) activity and found that treatment with SAMC caused a rapid and sustained induction of JNK activity. The selective JNK inhibitor SP600125 inhibited the early phase (24 h) but not the late phase (48 h and later) of apoptosis induced by SAMC. Expression of a dominant-negative mutant of JNK1 in SW480 cells inhibited apoptosis induced by SAMC at 24 h but had no protective effect at 48 h. JNK1(-/-) mouse embryonic fibroblasts were resistant to SAMC-induced apoptosis at 24 h but not at 48 h. On the other hand, the inhibition or abrogation of JNK1 activity did not inhibit the G(2)-M arrest induced by SAMC. SAMC also activated caspase-3. The general caspase inhibitor z-VAD-fmk inhibited both early and late phases of apoptosis induced by SAMC. We conclude that the garlic-derived compound SAMC exerts antiproliferative effects by binding directly to tubulin and disrupting the MT assembly, thus arresting cells in mitosis and triggering JNK1 and caspase-3 signaling pathways that lead to apoptosis.
Xiao
Danhua
D
Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Pinto
John T
JT
Soh
Jae-Won
JW
Deguchi
Atsuko
A
Gundersen
Gregg G
GG
Palazzo
Alexander F
AF
Yoon
Jung-Taek
JT
Shirin
Haim
H
Weinstein
I Bernard
IB
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001665:Binding Sites; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D018385:Centrosome / Q000187:drug effects / Q000502:physiology; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D003545:Cysteine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006056:Golgi Apparatus / Q000187:drug effects / Q000502:physiology; D006801:Humans; D051379:Mice; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects / Q000502:physiology; D041681:NIH 3T3 Cells; D014404:Tubulin / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; C086300:S-allylmercaptocysteine; D014404:Tubulin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D003545:Cysteine