Independent confirmation for the notion that chemoresistance of breast cancer cultures is associated with activation of PKC was obtained from experiments in which we directly assessed both PKC expression and phosphorylation of different PKC isoforms including PKCα, pPKCαβII, pPKC pan-βII, PKD/PKCμ, pPKD/PKCμ, PKCζ, PKCδ, pPKCδθ as well as total PKC (Figure 3). Here, PRKD1 is linked to breast cancer.