pERK levels significantly correlate with Six1 expression in human breast cancer. (A) Tumor arrays containing 72 human breast cancer samples were stained with anti-Six1 (1:100 Atlas antibodies) and anti-pERK (1:100 Phosphosolutions) antibodies. The immunostained arrays were scored in a blinded manner by a pathologist (PJ). Patients whose tumors have high levels of nuclear Six1, also have high levels of pERK, as assessed using the anti-Six1 antibody (nuclear Six1 intensity) and pERK expression (both nuclear and cytoplasmic, intensity times area). Error bars represent mean value +/- SEM. P values represent statistical analysis between no-Six1 expression and high-Six1 expression samples using a two-tailed t test. (B) Representative images of no Six1 and high Six1 expressing tumors, and of pERK staining in the same tumors. pERK, phosphorylated extracellular signal-regulated kinase; SEM, standard error of the mean.