We have studied the PI3K protein complex over the last several years using LC-MS/MS and protein binding can vary across cancer cell lines due to differences in biological activity, sticky proteins, etc. In order to address the PI3K core complex and its function, drosophila S2R+ cells32 were used as a model system to identify PI3K interactions that were conserved through evolution from common human cancers back to flies and to help sort out non-specific binding proteins from biological interactions. The gene discussed is PIK3CA; the disease is cancer.