Briefly, fresh ST samples were fragmented and digested with collagenase and DNase for 1 hour at 37°C. After removing tissue debris, ST cell suspensions in culture medium (RPMI 1640 medium; Life Technologies, Gaithersburg, MD, USA) supplemented with 25 mM HEPES (2 mM L-glutamine, 2% nonessential amino acids, 100 IU/ml penicillin, and 100 mg/ml streptomycin; Life Technologies) with 10% heat-inactivated FCS (Life Technologies) were incubated at 37°C in six-well plates (Coster, Cambridge, MA, USA) for 45 min.