EFNA1 and breast cancer: To investigate the interrelationship between ephrin signaling and TGF-β, we generated a metaEphrin index consisting of the top 30 genes most highly correlated with EFNA1 mRNA in normal human tissues, and we showed that this index was strongly positively correlated with the TSTSS in ER+ breast cancer datasets (see Figure 8B for the TCGA cohort; similar results were also seen for the GSE6532 and NKI cohorts in Additional file 13).