Figure 5
PID1 protein is differentially regulated by etoposide and cisplatin. SDS-PAGE and western blotting of tumor cell lysates for PID1 protein. (A,B) PID1 protein is increased by etoposide and vincristine but decreased by cisplatin: LN229 (A) or U87 (B) GBM cells were plated overnight in 6-well plates (4 × 105 cells/well). Cells were then treated with vehicle, cisplatin (5 µg/ml; CDDP), etoposide (10 µg/ml; ETOP), or vincristine (50 ng/ml; VCR) for 24 hrs. (C) Etoposide-induced increase in PID1 protein is inhibited by the NFκB inhibitor, Bay117085: U87 cells were pre-treated with Bay117085 (2 µM) prior to exposure to etoposide (10 µg/ml) for 24 hr. Shown is one of two experiments with similar results. (D) Cisplatin decreases PID1 protein: U87 cells were treated with cisplatin (5 µg/ml) for the times indicated. (E,F) Bortezomib prevents the cisplatin-induced decrease in PID1 protein: Bortezomib was added to LN229 (E) and U87 (F) GBM cells 1 hr prior to start of a 24 hr incubation with cisplatin (5 µg/ml). (G) ERK and GAPDH protein levels are not decreased by cisplatin while PID1 is: Bortezomib (2 nM) or vehicle were added to U87 cells 1 hr before they began 24 hr incubation with cisplatin (5 µM). Densitometry normalized to controls in left lane is listed under the blot.
