CDK4 and breast cancer: Furthermore, neither in the spontaneously immortalized, non-tumorigeneic MCF-10A nor in the two breast cancer cell lines DU4475 and MDA-MB-468 was a detectable increase in any of the proliferation markers (CDK4, cyclin D1/2, PCNA) or EMT/invadopodia markers (MMP14, phospho-vimentin (Ser56) and PARP) observed (Figures 1 and 3).