TP53 and neoplasm: The incidence of mammary tumours and their growth rate was significantly lower and tumour onset was delayed in CQ-pre-treated rats after being subjected to mammary adenocarcinoma induction using N-methyl-N-nitrosourea (NMU), as shown by Loehberg et al. In wild-type BALB/c mice transplanted with mammary ducts of BALB/c p53-null mice, CQ pre-treatment did not affect tumour incidence [23].