KDR and breast cancer: To assess this, we compared the expression and phosphorylation status of cyclins and cyclin-dependent kinases (CDKs) in endothelial cells and MCF-7 breast cancer epithelial cells treated with either JK-31, nocodazole (a cell synchronization agent), bohemine (a control CDK1 inhibitor) or sunitinib (a control VEGFR inhibitor) (Figure 5C and 5D).