Repression of JNK3 protein kinase enhances PTX toxicity. (A) Northern Blot hybridization analysis of mRNA in normal epithelial cells (EP1 and EP2) and HNSCC cells (UKHN-2 and UKHN-3) using a JNK3 gene specific cDNA probe. GAPDH specific probe was used as a control for equal loading. (B) Human normal nasal epithelial cells were treated with JNK3 protein kinase selective inhibitor at concentrations ranging from 20 nM to 100 nM for 3 hours. Cells of the same origin were then treated under exactly the same conditions, and were subsequently exposed to 6 ng/ml of PTX for 24 hours. Cell survival was determined using the crystal violet assay as demonstrated in Figure1/H. Percent survival of JNK3 inhibitor-treated cells and those treated with both JNK3 inhibitor and PTX are shown. Data are representative of four independent experiments represent mean ±SD.