TP53 and neoplasm: Here we show that unlike the mouse, the porcine TP53 locus contains internal Pint and P2 promoters equivalent to those found in human, resulting in expression of Δ152p53α isoform and its circular counterpart circTP53. Both are involved in the development of OS and others tumours in the flTP53R167H pigs and the detection of Δ152p53α isoform in serum is indicative of tumorigenesis.