Sulforaphane potentiates oxaliplatin-induced cell growth inhibition in colorectal cancer cells via induction of different modes of cell death
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The objective of this study was to investigate, whether the plant-derived isothiocyanate Sulforaphane (SFN) enhances the antitumor activities of the chemotherapeutic agent oxaliplatin (Ox) in a cell culture model of colorectal cancer. Caco-2 cells were cultured under standard conditions and treated with increasing concentrations of SFN [1–20 μM] and/or Ox [100 nM–10 μM]. For co-incubation, cells were pre-treated with SFN for 24 h. Cell growth was determined by BrdU incorporation. Drug interactions were assessed using the combination-index method (CI) (Cl < 1 indicates synergism). Apoptotic events were characterized by different ELISA techniques. Protein levels were examined by Western blot analysis. Annexin V- and propidium iodide (PI) staining followed by FACS analysis was used to differentiate between apoptotic and necrotic events. SFN and Ox alone inhibited cell growth of Caco-2 cells in a dose-dependent manner, an effect, which could be synergistically enhanced, when cells were incubated with the combination of both agents. Co-treated cells further displayed distinctive morphological changes that occurred during the apoptotic process, such as cell surface exposure of phosphatidylserine, membrane blebbing as well as the occurence of cytoplasmic histone-associated DNA fragments. Further observations thereby pointed toward simultaneous activation of both extrinsic and intrinsic apoptotic pathways. With increasing concentrations and treatment duration, a shift from apoptotic to necrotic cell death could be observed. In conclusion, the data suggest that the isothiocyanate SFN sensitizes colon cancer cells to Ox-induced cell growth inhibition via induction of different modes of cell death.
KeywordsSulforaphane Oxaliplatin Colorectal cancer Cell growth Apoptosis
Half maximal inhibitory concentration
Fetal calf serum
Dulbecco’s modified Eagle’s medium
TNF-related apoptosis-inducing ligand
Poly [ADP-ribose] polymerase
This work was supported by a graduate scholarship grant from the DFG to Bettina M. Kaminski. Bettina M. Kaminski is a member of the Frankfurt International Research Graduate School for Translational Biomedicine (FIRST), Frankfurt am Main.
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