Syk expression protects MDA-MB-231 cells from oxidative stress-induced apoptosis and degradation of Bcl-x L 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 H 2 O 2 for the indicated times. Cell lysates were analyzed by RT-PCR to measure the levels of Bcl-x L and Bcl-x S mRNA (top) or by Western blotting to detect expressed Syk-EGFP (bottom). (B) Comparison of relative levels of Bcl-x L mRNA to Bcl-x S 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