小中大谢谢，已经搞定。
U937 were obtained from ATCC (American Type Culture Collection,
Manassas, USA). The cells were cultivated in RPMI–1640
cell culture medium (Invitrogen, Karlsruhe, Germany), supplemented
with 10% FCS (PAN Biotech GmbH, Aidenbach, Germany)
and 1% penicillin/streptomycin (Invitrogen) at 37 ◦C at 5% CO2 in
160ml cell culture flasks (Nunc, Wiesbaden, Germany). For differentiation,
the cells were cultivated in 24-well plates (Nunc)
at a density of 5×104 cells/ml/well and stimulated with PMA
(Sigma–Aldrich, Seelze, Germany) at a concentration of 0.1ug/ml
for 2 days (days −2 to day 0).
