In the present study, we investigated the effects of STAT3 and related mechanisms on everolimus mediated cell growth inhibition in human epidermal keratinocyte cell lines. Our findings suggest that STAT3 activity in keratinocytes may be a biomarker of everolimus induced dermatological events. Materials and methods Chemicals Everolimus, a derivative of sirolimus and an mTOR inhibitor, was purchased from Sigma Aldrich Chemical, Co. Stattic, a small molecule inhibitor of STAT3 activation, was purchased from Enzo Life Sciences, Inc. STA 21, a STAT3 inhibitor, was purchased from Santa Cruz Biotechnology. Z3, an inhibitor of the autophosphorylation of Janus kinase 2, was obtained from Calbiochem.

SB203580, a specific blocker of p38 mitogen activated protein kinase activity, and SP600125, a kinase inhibitor CORM-3 selective and reversible inhibitor of the c Jun N terminal kinase 1, JNK2, and JNK3, were obtained from Cayman Chemical Company. U0126, a selective inhibitor of mitogen induced extracel lular kinase 1 and MEK2, was purchase from Cell Signaling Technology, Inc. Antibodies Rabbit anti phosphorylated STAT3 at tyrosine 705 and serine 727, mouse anti STAT3 antibodies, rabbit anti phospho extracellular signal regulated kinase 1 2, rabbit anti Erk 1 2 antibodies, rabbit anti phospho p38 MAPK, rabbit anti p38 antibodies, anti phospho S6 kinase and anti p70 S6 kinase antibodies were purchased from Cell Signaling Technology. Mouse anti phospho JNK and rabbit anti JNK antibodies, as well as anti mouse HRP conjugated IgG, anti rabbit HRP conjugated IgG, and anti rabbit FITC conjugate IgG, were purchased from Santa Cruz Biotechnology.

selleck chemical A rabbit anti B actin antibody was obtained from Sigma Aldrich. Cells and cell culture HaCaT cells, the human immortalized keratinocyte cell lines, were kindly provided by Professor Norbert Fusenig. HepG2 cells, the human hepatocarcinoma cell lines, were purchased from JCRB. HaCaT and HepG2 cells were maintained in Dulbeccos Modified Eagles Medium supplemented with 10% heat inactivated fetal bovine serum, 100 units mL of penicillin, and 100 ug mL streptomycin. Caki 1 cells, the human renal cell carcinoma cell lines, were purchased from JCRB. Caki 1 cells were maintained in Eagles Minimum Essential Medium supplemented with 10% heat inactivated fetal bovine serum, 100 units mL of penicillin, and 100 ug mL streptomycin, similar to the HaCaT culture medium.

Each cell line was seeded into culture flasks, grown in a humidified atmosphere of 5% CO2 and 95% air at 37 C, and subcultured with 0. 05% trypsin 0. 02% EDTA. WST 8 colorimetric assay The effects of various signal transduction inhibitors and transfection with expression plasmids on the everolimus mediated cell growth inhibition in HaCaT cells were evalu ated via the WST 8 assay using the Cell Counting Kit 8 as described previously.