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Evidence for a biphasic apoptotic pathway induced by melatonin in MCF‐7 breast cancer cells
Author(s) -
Cucina Alessandra,
Proietti Sara,
D’Anselmi Fabrizio,
Coluccia Pierpaolo,
Dinicola Simona,
Frati Luigi,
Bizzarri Mariano
Publication year - 2009
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.2008.00645.x
Subject(s) - melatonin , apoptosis , poly adp ribose polymerase , mcf 7 , biology , caspase , fas ligand , programmed cell death , endocrinology , cancer research , medicine , cancer cell , cancer , biochemistry , polymerase , human breast , gene
Previous investigations demonstrated that melatonin exerts an oncostatic action on estrogen‐responsive breast cancer, both in vitro and in vivo. Nevertheless, the pro‐apoptotic effect of melatonin is still a matter of debate. An experimental study was undertaken to focus on melatonin‐related apoptosis and to identify the apoptotic pathways involved. Whole cell‐count, flow‐cytometry analysis and proteins involved in apoptotic pathways [p53, p73, murine double minute 2 (MDM2), caspases‐9,‐7,‐6, cleaved‐poly ADP ribose polymerase (PARP), Bcl‐2, Bax and apoptotic inducing factor (AIF)] were investigated in human MCF‐7 breast cancer cells treated with physiological (1 nM) concentration of melatonin. Melatonin exerts a significant growth‐inhibitory effect on MCF‐7 cells, becoming evident after 72 hr and thereafter increasing linearly up to 144 hr. In this model, the growth‐inhibition is transforming growth factor beta 1 (TGFβ1)‐dependent and it might be reversed by adding an anti‐TGFβ1 antibody. Melatonin induces a significant rise in apoptotic rate, at both 24 and 96 hr. The anti‐TGFβ1 antibody almost completely suppresses melatonin‐related late apoptosis; however, early apoptosis is unaffected. Early programmed cell death is associated with a significant increase in the p53/MDM2 ratio and in AIF release, without modifications in caspase activity or cleaved‐PARP levels. Activated caspases‐9 and ‐7 and cleaved‐PARP increased significantly at 96 hr, concomitantly with a down‐regulation of the Bcl‐2/Bax ratio. These data suggest that two distinct apoptotic processes are triggered by melatonin in MCF‐7 cells: an early, TGFβ1 and caspase‐independent response, and a late apoptotic TGFβ1‐dependent process in which activated‐caspase‐7 is likely to be the terminal effector.