When apoptosis was determined by AnnexinV/7AAD staining, JSI 124 induced apoptosis in NALM 6 cells by 1% to 40%. In addition, although SP600125 treat ment dramatically http://www.selleckchem.com/products/Imatinib(STI571).html reduced c Jun protein levels in these cells, SP600125 had no effect on the selleck chemicals llc apoptosis induced by JSI 124 in NALM 6 cells. Similarly, SP600125 did not influence the thoroughly degree of apoptosis induced in BJAB and I 83 cells by JSI 124. We and others Inhibitors,Modulators,Libraries Inhibitors,Modulators,Libraries have shown that JSI 124 induced apoptosis is dependent on down regulation of XIAP, a member of the IAP family and serine 727 phosphorylation of STAT3 in B cell leukemia cells and primary CLL cells. However, SP600125 had no effect on the reduction in XIAP and serine 727 phosphorylation of STAT3 levels by JSI 124 but did reduce the Inhibitors,Modulators,Libraries effect of JSI 124 on c Jun expression.

Similarly, while cell cycle arrest was observed in all three cell lines following treatment with JSI 124 this was not Inhibitors,Modulators,Libraries influenced by prior treatment Inhibitors,Modulators,Libraries with SP600125. The percentage of BJAB cells in G2/M phase increased from 10% to 22% with JSI 124 treatment Inhibitors,Modulators,Libraries alone and increased to 22% when the cells were pre treated with SP600125. In I 83 cells, the G2/M fraction increased from 9% to 23% by JSI 124 and 22% by the SP600125 and JSI 124 combination. Simi larly, JSI 124 also induced NALM 6 cell accumulation in G2/M phase from 16% to 29% and no protection was observed by SP600125. These results demonstrate that the effects of JSI 124 on cell growth are unrelated Inhibitors,Modulators,Libraries to its effects on the JNK/c Jun pathway.

STAT3 is a transcription factor aberrantly activated in many human solid and hematological cancers and plays a role in oncogenesis.

We have previously demon Inhibitors,Modulators,Libraries Inhibitors,Modulators,Libraries strated that JSI 124 induces cell cycle arrest at Inhibitors,Modulators,Libraries the G2/ M phase through inhibition of STAT3 activity in human B leukemic cells. We evaluated whether Inhibitors,Modulators,Libraries JSI 124 induced c Jun activity is dependent on STAT3 expres sion in the cells. Inhibitors,Modulators,Libraries To this end, STAT3 was knocked down using siRNA before treatment with JSI 124 and the Inhibitors,Modulators,Libraries cell lysates were examined for JSI 124 induction of c Jun by immunoblot analysis in transfected and non transfected cells.

The c Jun protein level in cells trans fected Inhibitors,Modulators,Libraries with siRNA against STAT3 or non targeting con trol siRNA was same as JSI 124 treated cells.

To control for transfection efficiency, the STAT3 level was assessed in transfected and non transfected cells and this confirmed a significant Inhibitors,Modulators,Libraries decrease in STAT3 in siRNA treated cells.

Conversely, selleck chemicals the STAT3 level was unchanged in cells treated with siRNA against c Jun. These data imply that JSI 124 induced activation of c Jun was not dependent on STAT3 expression sellectchem in these cells. To determine whether JSI 124induced cell cycle arrest involves activation of c Jun, I 83 cells were treated with ref 1 siRNA against c Jun following JSI 124 treatment and cells were examined for accumulation at G2/M.