PKC expression and proliferation of breast cancer cell lines. Western blots show expression levels of PKCα, PKCδ, and PKCε in T47D, MCF-7, MDA-MB-231, and MDA-MB-468 breast cancer cells (A). Cell pellets of proliferating cells were immunohistochemically stained with anti-Ki-67. At least 200 cells per cell line were scored for negative-weak or strong staining intensity (B). The viable cell number was measured by WST-1 assay after 24 and 48 hours in culture. Ratio 48 h:24 h was used as an indicator of cell proliferation (C). For all experiments, cells were grown in complete medium. Western blots are representative of three independent experiments. Data in B and C are mean ± SEM, n = 3. Asterisks indicate statistically significant differences (* p < 0.05 and ** p < 0.01) compared to other cell lines (B and C).