Fluoxetine mediates G0/G1 arrest by inducing functional inhibition of cyclin dependent kinase subunit (CKS)1.
Fluoxetine, a well-known antidepressant used clinically for mental depression has gained attention in cancer research owing to its chemosensitizing potential in drug resistant cell lines. Some preliminary reports, however, suggested its independent cytotoxic potential which is not yet well characterized. Our aim in this study was to characterize its antiproliferative activity in tumor cells and to further elucidate the mechanism. We found that fluoxetine sensitized the effect of cyclophosphamide even in drug sensitive MDA MB 231 and SiHa cells. IC(50) values of 28 and 32 microM were obtained for fluoxetine mediated antiproliferative response in these cells. Further, PARP and caspase 3 cleavage analyses confirmed fluoxetine mediated apoptosis at molecular level. Cell cycle analysis showed that fluoxetine arrested cells at G0/G1 phase in a time dependent manner. The application of bioinformatics tools at this juncture predicted CKS1 as one of the possible targets of fluoxetine, which is of relevance to cell cycle biology. Fluoxetine showed the potential to disrupt skp2-CKS1 assembly required for ubiquitination and proteasomal degradation of p27 and p21. Our in vitro results were in agreement with the predictions made in silico. We found that fluoxetine treatment could accumulate p27 and p21, an immediate outcome characteristic of functional inhibition of CKS1. This was accompanied by the accumulation of cyclin E, another possible target of CKS1. We observed CKS1 downregulation also upon prolonged fluoxetine treatment. Fluoxetine had downregulated cyclin A which confirmed G0/G1 arrest at the molecular level. We conclude that fluoxetine induced cell cycle arrest is CKS1 dependent.
Krishnan
Anand
A
Translational Cancer Research Laboratory, Department of Molecular Medicine, Rajiv Gandhi Centre for Biotechnology, Trivandrum, Kerala 695014, India. krisanandin@yahoo.com
Hariharan
Ramkumar
R
Nair
S Asha
SA
Pillai
M Radhakrishna
MR
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D042846:CDC2-CDC28 Kinases; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D003520:Cyclophosphamide / Q000494:pharmacology; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000473:pathology; D005473:Fluoxetine / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects*; D006801:Humans; D012333:RNA, Messenger / Q000378:metabolism; D016192:Resting Phase, Cell Cycle / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000378:metabolism / Q000473:pathology
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; C093090:CKS1B protein, human; D002352:Carrier Proteins; D019925:Cyclin A; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D012333:RNA, Messenger; D005473:Fluoxetine; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003520:Cyclophosphamide; D042846:CDC2-CDC28 Kinases; D018844:Cyclin-Dependent Kinases