SKP2 and cancer: To establish molecular circuits of cell cycle control for mathematical modeling, we used QIAGEN's Ingenuity® Pathway Analysis (IPA®, QIAGEN Redwood City, https://www.qiagenbioinformatics.com//ingenuity) to generate a 14-protein network, which involve key proteins in regulating cell cycle and with extremely high relevance in human cancers including cyclin proteins (CCND1, CCNE1, and CCN), CDKs (CDK1, 2, 4, and 6), SKP2, CDKN1B, p53, and CDH1.