Fig. 2

Gene expression profile of HCT116-derived tumorspheres investigated through RNAseq analysis indicated that PDGFA and STAT3 were significant. (a) In total, 688 genes increased and 1788 genes decreased in the HCT116-derived tumorspheres compared with the parental HCT116 cells. (b) Numbers of significant genes upregulated and downregulated in the HCT116-derived tumorspheres according to q value (p < 0.005 with > 1 fold change by log2) were 654 and 840, respectively. (c) Upregulated genes in the HCT116-derived tumorspheres were classified according to their molecular functions using PANTHER software (http://pantherdb.org/) and shown in Additional file 2: Figure S1. Upregulated genes with a > 3-fold change (log2) (Table 1) and genes associated with EGF, FGF, and insulin (Table 2) were analyzed using NetworkAnalyst (http://www.networkanalyst.ca/) for identifying the relevant signaling pathways based on the KEGG database. Genes associated with the cancer pathway are indicated by blue spots, revealing the overexpression of PDGFA and STAT3, indicated by arrows. (d) Through qPCR, the growth factor inducing PDGFA levels was identified. Thus, 20 ng/mL of EGF significantly induced PDGFA levels. (e) PDGF-AA was consequently demonstrated to be capable of inducing LGR5 levels and (f) leading to β-catenin expression. *p < 0.05. **p < 0.01