In order to study the effect of enhanced p53 activity on the TME independently of its effect on p53-mutant tumor cells, we implanted B16 melanoma cells that have a functional Trp53 gene in C57BL/6J mice and treated these mice daily with APR-246 or vehicle control (PBS) starting 1 week after implantation (Figure 1A). Here, TP53 is linked to melanoma.