TP53 and cancer: Similar observations were made with our mutant mice, where Pik3caH1047R expression did not lead to spontaneous cancer within the time frame analyzed, but accelerated the onset of cancer upon concomitant heterozygous loss of the Apc tumour suppressor gene; as shown previously25, or in the presence of other oncogenic lesions, such as loss of p53 or PTEN9,40,41.