This project looks at the effect a chemical modulator targeting PI3Kα has on the phosphoproteome of PI3Kα-WT and PI3Kα-KO MEFs. PI3K signalling is a critical regulator of numerous cellular processes such as proliferation, apoptosis, migration, invasion, metabolism, cell growth and autophagy. The PI3K pathway is frequently hyperactivated in cancer, commonly due to activating mutations or via loss of the lipid phosphatases that negatively regulate the pathway. We have recently identified a new small molecule modulator of the PI3K pathway and have used an unbiased phosphoproteomics approach to examine the impact of this compound on signalling pathways in cells that are wild-type and knockout for PI3K. Immortalised mouse embryonic fibroblasts (MEFs) isolated from PI3Kα-WT and PI3Kα-KO embryos were treated with and without the modulator (5 µM), exploring early (15 min) and late (4 h) time points. Insulin is a well-characterised activator of PI3K. Therefore, PI3Kα-WT MEFs were also treated with insulin (100 nM) as a positive control to compare with the PI3K modulator.