Fig. 1.

Identification of SFRP4 as the gene most correlated with invasion. cDNA array expression data was generated for 65 tumours of known T-stage. a K means clustering was performed based on depth of invasion (T stage). Overall patterns of gene expression (y-axis) using depth of invasion as a continuous variable (x-axis) visualising all 7383 genes were generated. SFRP4 (black line) was identified as the gene most correlated with invasion in this dataset. Findings were then validated over independent platforms and datasets. b SFRP4 expression in gastric tissues. 146 gastric tissues were profiled using Affymetrix U133 plus 2 arrays and stratified according to tissue type. Histologically normal gastric tissues [NN (n = 7)] exhibited significantly lower SFRP4 expression than other benign tissues [chronic gastritis (CG (n = 22); p = 0.0077)] and intestinal metaplasia [IM (n = 23; p = 0.0031)]. Highest levels of SFRP4 expression were observed in gastric tumour samples (n = 99; p < 0.0001). Further analysis of the 2 histological subtypes showed SFRP4 expression to be highest in diffuse GC (n = 39) compared to intestinal gastric cancer (n = 50; p = 0.0004). Mann–Whitney test was used for analysis. SFRP4 expression based on T-stage was determined in (c) an updated Australian data set of 99 tumours (p = 0.003; Kruskal–Wallis test) and the (d) Singapore dataset (n = 178; p = 0.009 Kruskal–Wallis test) were run on Affymetrix Human U133 plus 2 arrays. Each panel represents an individual probe for SFRP4 on the array. e The data was also validated using the TCGA RNASeq data set (n = 255; p = 2 × 10^–5 Kruskal–Wallis test) (f) SFRP4 protein expression was determined by IHC on a TMA. Staining was quantitated using a semi-quantitative scale from 0 (no staining; white bar), 1 + (blue bar), 2 + (red bar) and 3 + (black bar) (h) representative images showing staining of normal gastric mucosa and an intestinal type GC (IGC). Images × 10 and magnified × 40