Tumours of mutant p53 Pdx1-Cre; LSL-KrasG12D/+; LSL-Trp53R172H/+ mice are highly metastatic compared to Pdx1-Cre; LSL-KrasG12D/+; Trp53flox/+mice38 that are known to invariantly undergo LOH of p53 and are therefore considered to be p53 null. The gene discussed is TP53; the disease is neoplasm.