p53 is a major inducer of apoptosis in multiple circumstances, including the exposure of cells to proteasome inhibitors. The figure shows the stabilization of p53 in intestinal adenomas of APC^min/+ mice treated with proteasome inhibitor bortezomib. Coimmunofluorescent staining documented the colocalization of stabilized p53 (red) with the stem/progenitor cell marker Sox9 (blue) and revealed that p53 can be easily stabilized in stem/progenitor-like cells in mouse intestinal adenomas. For details, see article by Xue and colleagues on page 3595.