NSC114792 inhibits IL-2-induced JAK3/STAT5 but not PRL- or IL-3-induced JAK2/STAT5 signaling. Effects of NSC114792 on JAK2/STAT5 and JAK3/STAT5 signaling induced by PRL (prolactin) (A) and IL-2 (B), respectively, in the rat pre-T lymphoma cell line Nb2. Effects of NSC114792 on JAK2/STAT5 and JAK3/STAT5 signaling induced by IL-3 (C) and IL-2 (D), respectively, in the murine myeloid progenitor cell line 32D stably expressing IL-2Rβ (32D/IL-2Rβ). These cells were starved for 16 hours in the presence of either vehicle (DMSO) alone, NSC114792 at different concentrations, or the pan-JAK inhibitor AG490 (100 μmol/L). Nb2 cells and 32D/IL-2Rβ cells were subsequently stimulated by PRL (100 ng/mL) or IL-2 (100 ng/mL) for 10 minutes, and IL-3 (5 ng/mL) or IL-2 (100 ng/mL) for 30 minutes, respectively. In Nb2 cells, NSC114792 decreased IL-2-induced phospho-JAK3 and -STAT5 levels in a dose-dependent manner, but failed to decrease PRL-induced phospho-JAK2 and -STAT5 levels. Similarly, in 32D/IL-2Rβ cells, this compound blocked IL-2-induced phospho-JAK3 and -STAT5, but was defective in inhibiting IL-3 induced phospho-JAK2 and -STAT5. AG490, a pan-JAK inhibitor, non-selectively blocked both phospho-JAK2 and -JAK3 in all cells.