**2. Materials and methods**

The chemical and reagents used in the study were; MTT (3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) (PhytoTechnology Laboratories, USA), DMSO (dimethylsulfoxide) (Fisher Scientific, UK), Dulbecco's Modified Eagle's Medium (DMEM) and Roswell Park Memorial Institute medium (RPMI 1640) powders with L-glutamine (GIBCO, New Zealand), fetal bovine serum (FBS), horse serum, trypsin–EDTA, phosphate-buffered saline (PBS) tablets and penicillin (10,000 U/mL)–streptomycin (10 mg/mL) (Sigma-Aldrich, USA), acridine orange (AO) and propidium iodide (PI), annexin V-FITC (BD Pharmingen), and gel red nucleic acid stain and apoptotic DNA ladder detection kit (Abcam, USA).
