iMSC#3 secretes PGE
, which can be inhibited by Indomethacin. iMSC#3 cells were grown to confluency, and growth medium was changed from MEMα to RPMI with or without Indomethacin as indicated. After 24 h, primary BCP-ALL cells were added as indicated and cocultures incubated for an additional 24 h. Supernatants were subsequently subjected to analysis of prostaglandin E2 levels by EIA as described in Materials and Methods. The results are presented as scatter plots with horizontal bars representing median values. *P < 0.05 by Wilcoxon matched pairs signed rank test.