The knockdown of PKD1 increases cell invasion. (a) MCF-7 cells were stably transduced with lentivirus coding for two different human shRNA sequences for protein kinase D (PKD) 1 (PKD1-RNAi Seq.1 and Seq.2) or for a non-target sequence which served as control. Cells were lysed and analysed for PKD1 expression by western blotting. Immunostaining for PKD2 and actin expression served as controls. (b) MCF-7 control and PKD1-RNAi clones were subjected to a cell proliferation assay using the CyQuant cell proliferation assay kit. (c) MCF-7 control and PKD1-RNAi clones were seeded on Matrigel-coated Transwell filters and Transwell invasion assays were performed over a time period of 16 hours. (d) MCF-7 cells stably-transfected with control RNAi or PKD1-RNAi were grown in 3D/Matrigel cell culture over a period of 60 days. Cells were photographed at day 60. Bars indicate the size of the spheroids. For experiments shown in b and c, error bars represent standard deviation. P values were acquired with the student's t-test using Graph Pad software. All P values indicate statistical significance.