Ing 20 ml of MEF medium, in which DMEM was supplemented with 10 FBS, 1 penicillin/ streptomycin, 1 NEAA and 1 glutamine.Proliferation assay30 ?103 MEFs were seeded in triplicate in 6-well plates and incubated in serum-free medium overnight. The medium was then replaced with medium containing 10 serum and the cells were trypsinized and counted at 1, 2, 3 and 4 days of observation. Results of t