Multiplex PEA results of proteins measured in GC tissues and serum specimen. (A) Venn diagram showing the number of proteins detectable or undetectable in serum and in tissue specimen. (B) Comparison of subcellular location between proteins detectable in serum but not in tissue and proteins detectable in tissue but not in serum by the FunRich software. The 13 proteins detectable in GC tissue but not in serum are AGR3, ARTN, CAMKK1, IL1A, IL20RA, IL22RA1, IL24, IL33, JUN, LIF, NCLN, NRTN, PAK4. The 14 proteins detectable in GC serum but not in tissue are CRX, DKKL1, FAM19A5, FCRLB, FGF23, IL10, IL10RA, IL2, LYPD1, OPTC, SEZ6L, SLITRK2, TCL1B, WNT9A. (C) Principal component analysis (PCA) plot illustrating the sample distribution of 100 gastric tumour tissues (T, blue) and matched adjacent noncancerous tissues (N, red), based on 245 proteins levels. Each dot represents an individual sample. (D) Volcano plot showing the 245 proteins levels in GC tissues compared to matched non-tumour tissues. The dashed line represents the cutoff line with indicated significance criteria. Points having absolute log fold-change ≥2 and FDR adjusted p-value <0·05 are shown in red, with absolute log fold-change <2 and p-value ≥0·05 are in gray, and the rest are in black. (E) PCA plot illustrating the distribution of 50 serum samples from controls (Ctrl, red), 100 GC preoperative serum samples (Pre, green) and matched 100 postoperative samples (Post, blue), based on 316 proteins levels. (F—H) Volcano plots showing the 316 protein levels in preoperative GC serum samples versus controls (F), between preoperative and postoperative ones (G), and between postoperative samples and controls (H). Points having absolute log fold-change ≥0·5 and FDR adjusted p-value <0·05 are shown in red, with absolute log fold-change <0·5 and p-value <0·05 are in black, with absolute log fold-change <0·5 and p-value ≥0·05 are in gray, and the rest are in orange. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)