1. HER2 and PI3K-targeted therapies result in FOXO3a-mediated feedback upregulation of HER3 and IGF1R and provide an escape from PI3K pathway inhibition.
HER2 and PI3K-targeted therapies result in FOXO3a-mediated feedback upregulation of HER3 and IGF1R and provide an escape from PI3K pathway inhibition. A, in the basal state, AKT-mediated FOXO3a phosphorylation inhibits translocation of FOXO3a to the nucleus and provides a basal inhibition of RTK synthesis. B, in the presence of PI3K inhibition, via either upstream RTK blockade or small molecule inhibitors, decreased AKT activity allows FOXO3a to translocate to the nucleus and effect transcription of FOXO3a target genes, including HER3 and IGF1R. The increased RTK expression mediates resistance to PI3K inhibition by increasing input into the PI3K pathway and alternate growth pathways, including MAPK. Dotted lines represent multiple steps not shown graphically; line strength represents relative activation. HER2, human epidermal growth factor receptor 2; HER3, human epidermal growth factor receptor 3; FOXO3a, forkhead box O3a.
Samuel J. Klempner et al. Cancer Discovery 2013;3:
©2013 by American Association for Cancer Research