A BAX/BAK/CypD-Independent Intrinsic Death Pathway Figure 4. BAX and BAK-independent cells death induced by ER stress and serum withdrawal is not affected by BCL-XL overexpression or by BH3-only proteins. (A) WT and BAX/BAK DKO MEFs were stably transduced with retroviruses expressing human BCL-XL or empty vector (Mock) and the expression levels of BCL-XL was evaluated by Western blot analysis. As loading control, HSP90 levels were determined. (B) Then the susceptibility of cells presented in (A) to cell death was assessed after treatments with 10 mg/ml Tm in cells pretreated in cell culture media containing 0.5% serum for 2 h or grown with regular cell culture media. Cell death was monitored by PI staining and FACS analysis at 16, 20 and 24 h. Mean and standard deviation is presented of three independent experiments. Two-way ANOVA was used to analyze statistical significance PLoS ONE | www.plosone.org 8 June 2012 | Volume 7 | Issue 6 | e37782