PIK3CA and cancer: Specifically, HSP90 functions as a molecular chaperone stabilizing multiple oncogenic proteins; IGF1R and PIK3CA are central components of growth and survival signalling pathways frequently dysregulated in these cancer cells; CDK6 regulates cell cycle progression; and HDAC2 and HDAC8 modulate epigenetic regulation and gene expression linked to tumour proliferation and apoptosis [51,52,53,54,55,56,57].