TP53 and cancer: A recent study has demonstrated semi-heritable cell-to-cell heterogeneity in gene expression in mammalian cells, which is associated with drug resistance in cancer [11] and time-lapse fluorescence microscopy has shown that cell-to-cell variability in the expression of some genes, such as p53 and p21, is associated with cell-to-cell variability in proliferation and survival [1,12].