Analyses of PLK1 interactive proteins and their expression levels following PLK1 downregulation. (a) IPA analyses demonstrate a protein-protein interaction network featuring PLK1 at the center. This network shows some of the direct interactions that take place with PLK1 and which proteins act as intermediates between PLK1 and the drugs used to generate the therapy-resistant cell lines. (b) Represents a nonquantitative RT-PCR result for the expression of PLK1 in GRL MCL cells following 24 hours of treatment with BI2536. (c) Quantitative RT-PCR results showing expression of selected PLK1-associated genes from IPA analyses in therapy-resistant and parental MCL cells following downregulation with BI2536. Expression of each gene was analyzed from Ct value obtained from real-time PCR. Fold change of genes expression was calculated with respect to vehicle- (DMSO-) treated control cells and normalized to GAPDH.