CDK4 and neoplasm: Our in vivo study demonstrated that safranal delays the re-growth of quiescent PCa and inhibits tumor progression via the downregulation of Skp2, E2F1, NF-κB p65, p-IκBα (Ser32), c-MYC, p-Rb (Ser807), CDK4, CDK6, and CDK2 expression and elevation of p21 and p27 levels in tumor tissues, concordant with our in vitro findings.