PROM1 and neoplasm: Immunohistochemical and immunofluorescence assays of both proteins strongly correlated with the gene expression results (Figure 2): MMP7 showed strong staining in ∼80% (9 out of 11) of the ER-negative tumours but in none of the ER-positive tumours (0 out of 4), and CD133 showed strong staining in 90% of the ER-negative tumours (10 out of 11) but was completely absent from the four ER-positive tumours (P-values=0.011 and 0.004, respectively).