Leptin upregulates the CSL gene in mammary cancer cells.

<p>Leptin transcriptional activation of CBF (or CSL) promoter is linked to several leptin-induced signaling pathways. (A) 4T1 cells were transiently transfected with a CBF-Luc reporter construct and incubated with leptin (0 and 1.2 nM) alone or plus siRNA oligonucleotides (SignalSilence control-siRNA and STAT3, MEK1, AKT1, mTOR, JNK, p38-siRNA). (B) Protein levels of kinases after siRNA treatment were determined by WB analysis using β-actin as loading control. (C) 4T1 cells transfected with CBF-Luc reporter were incubated with leptin alone or plus pharmacological inhibitors of JAK2/STAT3 (AG490, 30 µM), MEK/MAPK/ERK1/2 (PD98059, 30 µΜ), PI-3K/AKT1 (Wortmannin, 50 nM), PKC-Ca dependant (Gö6976, 30 µΜ), p38 kinase (SB203580, 2 µΜ), JNK (SP600125, 30 µM) and mTOR (Rapamycin, 20 nM) signaling pathways for 24 h. Luciferase activity was determined as described (see M &M) and expressed as a percent of basal or leptin-treated cells. (a) <i>P<0.05</i> when comparing levels of luciferase activity to control (basal) or leptin-treated cells. Data (mean ± standard error) representative results derived from a minimum of 3 independent experiments.