Geranylgeranylation is required for expression of PBK in MDA-MB-231 cells. A, The cells were treated with atorvastatin (AT) or the geranylgeranyltransferase I inhibitor GGTI-298 for 48 hrs. The effects of atorvastatin or GGTI-298 on PBK protein level were detected by immunoblotting. B, MDA-MB-231 or MCF7 cells were treated with DMSO (control) or atorvastatin for 48 hrs. The cells were stained with anti-PBK (green) or DAPI (blue).