Northern blot analysis of p53, Bcl-2, Bcl-xl, and Bax mRNA from 22 ALL cell lines. Total RNA was extracted with the GITC-cesium chloride centrifugation method. Total RNA (10 μg per lane) was electrophoresed on a 1% agarose/6% formaldehyde gel. The p53, Bcl-2, Bcl-xl, and Bax probes were prepared by ³²P randomized labeling using cDNAs. Hybridization and wash were performed as described in the Materials and Methods. Membranes were rehybridized with a β-actin probe as a control for equal RNA loading and RNA integrity.