PCNA and breast cancer: Ge et al. [18] identified 131 mRNAs in 36 types of normal tissues whose expression correlated r > 0.65 with expression of PCNA. Expression patterns of these 131 genes were collapsed into a median value (called PCNA “metagene”) by Venet et al., who removed the proliferation effect by performing multivariate analysis of expression profiles published by 47 breast cancer (survival) studies [16].