CDK4 and breast cancer: We discovered several cell cycle-associated proteins (e.g. CDK1, CDK4-pThr172), luminal epithelial cell markers (e.g. E-Cadherin, CK8/18), the microtubule-forming protein Tubulin (acetylated Tubulin, Tubulin beta-chain), the Ras-inhibitor NF1 (Neurofibromin), c-Met-pTyr1003 and beta-Catenin-pSer55, whose expression affected BC-PDMs sensitivity to PTX treatment.