In vitro activity: CC-401, a small molecule that is a specific inhibitor of all three JNK isoforms. CC-401 competitively binds the ATP binding site in JNK, resulting in inhibition of the phosphorylation of the N-terminal activation domain of the transcription factor c-Jun. The specificity of this inhibitor is tested in vitro using osmotic stress of the HK-2 human tubular epithelial cell line.

Kinase Assay: CC-401 is a potent, specific, second generation and ATP-competitive anthrapyrazolone c-Jun N terminal kinase (JNK) inhibitor with potential antineoplastic activity. It is a potent inhibitor of all three forms of JNK with Ki of ranging from 25 to 50 nM. It inhibits sorbitol-induced phosphorylation of c-Jun in a dosage-dependent manner. However, CC-401 does not prevent sorbitol-induced phosphorylation of JNK, p38, or ERK. The specific JNK inhibitor, CC-401, was synthesized by Celgene Corporation as a competitive inhibitor of the ATP binding site in the active, phosphorylated form of JNK. CC-401 has at least 40-fold selectivity for JNK compared with other related kinases.

Cell Assay:Human HK-2 proximal tubular epithelial cells are cultured in DMEM/F12 media supplemented with 10% FCS, 10 ng/mL EGF, and 10 μg/mL bovine pituitary extract. For Western blot studies, cells are seeded into six-well plates and allowed to adhere overnight, and medium is changed to DMEM/F12 supplemented with only 0.5% FCS for 24 h, by which time cells are confluent. CC-401 is prepared in citric acid (pH 5.5) and added to the confluent cells 1 h before the addition of 300 mM sorbitol, and cells are harvested 30 min later using urea-RIPA buffer. Three experiments are performed, each with two replicates per condition. For ELISA experiments, HK-2 cells are seeded into 24-well plates, allowed to adhere overnight, cultured in DMEM/F12 with 0.5% FCS for 24 h, and then incubated with CC-401 or vehicle for 60 min before stimulation with 1 μM Angiotensin II (AngII).