CDK4/6 inhibitor, Palbociclib, has shown a high success in breast cancer subtypes however it is often accompanied by a dependency on mutation status of cell lines. Consequently, there has been speculation on the breast cancer subtypes which should be offered treatment with specific CDK4/6 inhibitors and the response that can be expected. A common observation has been the induction of a cell programme known as "senescence" whereby cells experience a complete halt in mitosis, however, remaining metabolically active. Therapy-induced senescence markers and its effect on the tumour microenvironment as well as the diversity of this cell state remain unappreciated. In the following proteomics, phosphoproteomics and secretome datasets we focus on MDA-MB-231 cells, a triple negative cell line, to better understand the senescence-like cell state which arises after treatment. Ultimately, the dataset encompasses the population that arises upon Palbociclib treatment and highlights potential signatures and biomarkers of the cell state which could provide information on the use of CDK4/6 inhibitors in triple negative breast cancer subtypes.