Curcumin induces apoptosis-independent death in oesophageal cancer cells.
BACKGROUND
Oesophageal cancer incidence is increasing and survival rates remain extremely poor. Natural agents with potential for chemoprevention include the phytochemical curcumin (diferuloylmethane). We have examined the effects of curcumin on a panel of oesophageal cancer cell lines.


METHODS
MTT (3-(4,5-dimethyldiazol-2-yl)-2,5 diphenyl tetrazolium bromide) assays and propidium iodide staining were used to assess viability and DNA content, respectively. Mitotic catastrophe (MC), apoptosis and autophagy were defined by both morphological criteria and markers such as MPM-2, caspase 3 cleavage and monodansylcadaverine (MDC) staining. Cyclin B and poly-ubiquitinated proteins were assessed by western blotting.


RESULTS
Curcumin treatment reduces viability of all cell lines within 24 h of treatment in a 5-50 muM range. Cytotoxicity is associated with accumulation in G2/M cell-cycle phases and distinct chromatin morphology, consistent with MC. Caspase-3 activation was detected in two out of four cell lines, but was a minor event. The addition of a caspase inhibitor zVAD had a marginal or no effect on cell viability, indicating predominance of a non-apoptotic form of cell death. In two cell lines, features of both MC and autophagy were apparent. Curcumin-responsive cells were found to accumulate poly-ubiquitinated proteins and cyclin B, consistent with a disturbance of the ubiquitin-proteasome system. This effect on a key cell-cycle checkpoint regulator may be responsible for the mitotic disturbances and consequent cytotoxicity of this drug.


CONCLUSIONS
Curcumin can induce cell death by a mechanism that is not reliant on apoptosis induction, and thus represents a promising anticancer agent for prevention and treatment of oesophageal cancer.
O'Sullivan-Coyne
G
G
Leslie C. Quick Laboratory, Cork Cancer Research Centre, BioSciences Institute, University College Cork and Mercy University Hospital, Cork, Ireland.
O'Sullivan
G C
GC
O'Donovan
T R
TR
Piwocka
K
K
McKenna
S L
SL
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003474:Curcumin / Q000494:pharmacology*; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D004938:Esophageal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D008940:Mitotic Index; D046988:Proteasome Endopeptidase Complex / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism
D000970:Antineoplastic Agents; C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D025801:Ubiquitin; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex; D003474:Curcumin