Furthermore, both PTEN (rs = −0.502; p = 0.005) (Figure 3A, 3B) and PDCD4 (rs = −0.426; p = 0.019) (Figure 3C, 3D) protein expression significantly and inversely correlated with the expression of miR-21 in HER2-positive breast cancer patients. Here, ERBB2 is linked to breast cancer.