Fig. 4.

Topoisomerase inhibitors activate JAK2-STAT1 pathway and JAK2 mediates TI-promoted CXCL1 and cell motility. a Western blot analysis of JAK2 and STAT1 phosphorylation after treatment with VP-16 (20 μM), CPT-11 (80 μg/ml), or ADM (0.2 μg/ml) for 0.5 h. b Validation of the efficiency of JAK2 knockdown after transfection with different siRNAs for 48 h (upper three panels) or siRNA #1 for 24, 48 and 72 h (lower three panels). c Western blot analysis of STAT1 phosphorylation and CXCL1 expression in cells transfected with JAK2-specific siRNA for 48 h. Cells were treated with VP-16 (20 μM) or CPT-11 (80 μg/ml) for 0.5 h before harvest. d Migration assay of cells transfected with JAK2-specific siRNA. 24 h after transfection, cells were subjected to migration assay for 24 h in the presence of VP-16 (20 μM) or CPT-11 (80 μg/ml). e Western blot of JAK2 and STAT1 phosphorylation and CXCL1 expression in cells pretreated with AG490 (40 μM) for 1 h and subsequently treated with VP-16 (20 μM) or CPT-11 (80 μg/ml) for 0.5 h. f Migration assay of cells treated with AG490 (40 μM) plus VP-16 (20 μM) or CPT-11 for 24 h