2.4. Assessment of cell viability and apoptosis

Cell viability was determined using the MTT assay. Briefly, after transient transfection, K562 cells were seeded into a 96‐well plate at a concentration of 1.5 × 10⁴ cells/100 μl. At 24, 48, and 72 hr after transfection, respectively, 10 μl of MTT labeling reagent provided by the Cell Proliferation Kit 1 (Roche, Mannheim, Germany) was added to each well according to the procedures recommended by the manufacturer. Measurement of the soluble formazan product in each well was carried out by photometric reading at 570/690 nm on a Synergy H1 Hybrid Multi‐Mode Microplate Reader (BioTek, Winooski, VT). The experiments were repeated three times for each transfection.

Apoptosis resistance was assessed with an Annexin V‐FITC Apoptosis Detection Kit 1 (BD Biosciences, San Diego, CA) according to the manufacturer's protocol.

Forty‐eight hours after transfection, cells were treated for 16 hr with low and high doses of cisplatin (10 and 20 μM) to induce apoptosis and were analyzed using an Accuri C6 flow cytometer (BD Biosciences, San Jose, CA) and BD ACCURI C‐Flow software.