We aim to understand differences in cell cycle transition genes and oncogenic signalling between cell cycle phases in breast cancer subtypes as well assessing the impact of the TME on cell cycle activity and the response to anti-oestrogen treatment. These aims will be achieved through hypothesis-driven data analysis, the application of innovative methodology and by combining the diverse expertise of an experienced research team. A total of 3 projects are proposed: - Study 1. Applying metro traffic management models to cell cycle phase data in order to better understand oncogenic pathway signalling dynamics. - Study 2. Assessing how the tumour microenvironment impacts cell cycle activity - Study 3. Assessing how cell proliferation and the tumour microenvironment impact response to tamoxifen treatment.