TP53 and gastric cancer: A screen of an additional 94 gastric cancer/normal pairs confirmed the frequency of PAPPA mutations as being 6% among all GC samples (Table S12 in Additional file 5) and 20% among TP53 wild-type GCs (with mutations in key functional domains; Figures S13 and S14 in Additional file 1), highlighting it as a potential driver gene in this subtype.