... requires cyclin D-CDK4/6 and cyclin E-CDK2, whichphosphorylate the retinoblastoma protein [26]. CDK inhibitors(CKIs) are the negative regulators and are grouped into twofamilies [27]. The INK4 family ... level of cyclin-dependent kinase inhibitors (CKIs) (p21, p2 7) compared to the control, while treatments with inhibitors (c, d) diminished c-Myc and upregu-lated p21 and p27. In contrast, p15 ... Osaka, Japan),containing 10% fetal bovine serum (FBS; Gibco Invitrogen),100 U/mL penicillin (Gibco Invitrogen) and 100 g/mL strep-tomycin (Gibco Invitrogen), at 37°C in 5% CO2 humidifiedatmosphere....