The results show differential PKC activation/inactivation in chemoresistant breast cancer cells, in which especially the phosphorylations of pPKCαβII (Thr638/641) (Figure 3a, 3b) and pPKD/PKCμ (Ser744/748) (Figure 4a-4d) is significantly up-regulated, whereas the phosphorylation of atypical pPKCδθ (Ser643/676) (Figure 3i, 3j) is significantly and substantially reduced. The gene discussed is PRKD1; the disease is breast cancer.