Curcumin selectively induces apoptosis in deregulated cyclin D1-expressed cells at G2 phase of cell cycle in a p53-dependent manner.
Curcumin (diferuloylmethane) is known to induce apoptosis in tumor cells. In asynchronous cultures, with time-lapse video-micrography in combination with quantitative fluorescence microscopy, we have demonstrated that curcumin induces apoptosis at G(2) phase of cell cycle in deregulated cyclin D1-expressed mammary epithelial carcinoma cells, leaving its normal counterpart unaffected. In our search toward delineating the molecular mechanisms behind such differential activities of curcumin, we found that it selectively increases p53 expression at G(2) phase of carcinoma cells and releases cytochrome c from mitochondria, which is an essential requirement for apoptosis. Further experiments using p53-null as well as dominant-negative and wild-type p53-transfected cells have established that curcumin induces apoptosis in carcinoma cells via a p53-dependent pathway. On the other hand, curcumin reversibly inhibits normal mammary epithelial cell cycle progression by down-regulating cyclin D1 expression and blocking its association with Cdk4/Cdk6 as well as by inhibiting phosphorylation and inactivation of retinoblastoma protein. In addition, curcumin significantly up-regulates cell cycle inhibitory protein (p21Waf-1) in normal cells and arrests them in G(0) phase of cell cycle. Therefore, these cells escape from curcumin-induced apoptosis at G(2) phase. Interestingly, these processes remain unaffected by curcumin in carcinoma cells where cyclin D1 expression is high. Similarly, in ectopically overexpressed system, curcumin cannot down-regulate cyclin D1 and thus block cell cycle progression. Hence, these cells progress into G(2) phase and undergo apoptosis. These observations together suggest that curcumin may have a possible therapeutic potential in breast cancer patients.
Choudhuri
Tathagata
T
Bose Institute, P-1/12 Calcutta Improvement Trust Scheme VII M, Kolkata, India.
Pal
Suman
S
Das
Tanya
T
Sa
Gaurisankar
G
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001940:Breast / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D003474:Curcumin / Q000494:pharmacology*; D019938:Cyclin D1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005260:Female; D016195:G2 Phase / Q000187:drug effects*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D041681:NIH 3T3 Cells; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53; D019938:Cyclin D1; D003474:Curcumin