Cells were grown in RPMI 1640 supplemented with 10% heat-inactivated fetal bovine serum (FBS), penicillin (10 U/ml), streptomycin (10 μg/ml) and 0.2 mM sodium pyruvate. Cultures were incubated in the presence of 5% CO2 at 37 °C and 100% relative humidified atmosphere.