SKP2 and cancer: The STAT3 factor has been found to be aberrantly expressed in cancer stem cells (CSC) of breast tumors, being important in formation, self-renewal, and differentiation [27], promoting oncogenes such as c-MYC, S-phase associated protein kinase 2 (SKP2), and cyclin D1, as well as anti-apoptotic proteins such as Bcl-2, Bcl-xL, Mcl-1, and survivin [30].