Analyses of 41 independent breast cancer expression profile studies, such as van de Vijver study, demonstrate that PBX1 and ERα are also co-expressed in primary breast tumors (p = 2.72e-13 for the van De Vijver study and p≤1e-4 for all other studies) (Figure 1E) [42]. This evidence concerns the gene ESR1 and breast neoplasm.