SphK1 and Androgen Signaling Figure 7. The increase in SphK1 activity during NED is cyclic AMP- dependent. A, SphK1 activity was determined in LNCaP and C4-2B cells treated for 3 days in absence or in presence of 10 mM Fsk/10 mM IBMX or 10 mM Epi. B, intracellular concentrations of cAMP were quantified in LNCaP and C4-2B cells treated for 3 days with 5% FBS or 10 mM Fsk/10 mM IBMX in absence or in presence of 5 mM SKI-2. C, chromogranin A (CgA) content was evalated by immunoblotting in LNCaP and C4-2B cell extracts incubated for 3 days with or without 5 mM SKI-2 in presence of 5% FBS, 10 mM Fsk/10 mM IBMX or 10 mM Epi. Similar results were obtained in three independent experiments. D, intracellular concentrations of cAMP were quantified in LNCaP and C4-2B cells before or 14 days after treatment or not with 5 mM SKI-2 under charcoal stripped conditions. Columns, mean of three independent experiments; bars, SD. The two-tailed P values between the means are as follow: ***, P,0.001; *, P,0.05; or ns, non significant. doi:10.1371/journal.pone.0008048.g007 PLoS ONE | www.plosone.org 9 November 2009 | Volume 4 | Issue 11 | e8048