TP53 and neoplasm: While several studies have shown a positive effect of p53 on late gene expression and cytopathic effect in tumor cell lines (29, 30), a recent study in two types of normal human cells concluded that Ad5 late gene expression occurs as efficiently in p53-depleted cells as in control cells (32), and in one of these cell types, virus yield was also shown to be unaffected; these authors argued that any positive role for p53 found previously was an artifact of working in tumor cell lines and/or of making comparisons between cells of differing p53 status that were in other respects not well matched.