Cyclin D is regulated by the downstream pathway of mitogen receptors via the Ras/MAP kinase and the β-catenin-Tcf/LEF pathways [17] and PI3K.[18] The MAP kinase ERK activates the downstream transcription factors Myc, AP-1 [7] and Fos[19] which in turn activate the transcription of the Cdk4, Cdk6 and cyclin D genes, and increase ribosome biogenesis. Rho family GTPases,[20] integrin linked kinase[21] and focal adhesion kinase (FAK) activate cyclin D gene in response to integrin.[22]