FIG 2.
Syk expression protects MDA-MB-231 cells from oxidative stress-induced apoptosis and degradation of Bcl-xL mRNA. (A) MDA-MB-231-TR (TR) cells lacking Syk or MDA-MB-231-TRS (TRS) cells either induced (+) or not induced (−) with doxycycline (Tet) to express Syk-EGFP were treated with 5 mM H2O2 for the indicated times. Cell lysates were analyzed by RT-PCR to measure the levels of Bcl-xL and Bcl-xS mRNA (top) or by Western blotting to detect expressed Syk-EGFP (bottom). (B) Comparison of relative levels of Bcl-xL mRNA to Bcl-xS mRNA. Ratios were normalized to a value of 1.0 for Syk-deficient cells at time zero. Bars represent means ± SEMs from three replicate experiments. *, P < 0.05; **, P < 0.01. (C) MDA-MB-231-TR cells (−) or doxycycline-induced MDA-MB-231-TRS cells (+) were treated with 5 mM H2O2 for the indicated times. Cell lysates were analyzed by SDS-PAGE and Western blotting (WB) with antibodies against Bcl-xL (top) and Syk-EGFP (bottom). (D) MDA-MB-231-TR cells lacking Syk (−) or MDA-MB-231-TRS cells induced with doxycycline to express Syk-EGFP (+) were treated with 5 mM H2O2 for the indicated times. Cell lysates were analyzed by SDS-PAGE and Western blotting with antibodies against PARP. The cleaved form of PARP is indicated by the arrow.