PI3K regulates TAZ/YAP and mTORC1 axes that can be synergistically targeted

Sarcomas are a heterogeneous group of cancers with few shared therapeutic targets. We show that PI3K signaling is frequently activated in sarcomas due to PTEN loss (in 30-60%), representing a common therapeutic target. The PI3K pathway has lacked a downstream oncogenic transcription factor. We show TAZ and YAP are transcriptional co-activators regulated by PI3K and drive a transcriptome necessary for tumor growth in a PI3K-driven sarcoma mouse model. This PI3K-TAZ/YAP axis exists in parallel to the known PI3K-Akt-mTORC1 axis providing a rationale for combination therapy targeting the TAZ/YAP-TEAD interaction and mTORC1. Combination therapy using IK-930 (TEAD inhibitor) and everolimus (mTORC1 inhibitor) synergistically diminished proliferation and anchorage dependent growth of PI3K-activated sarcoma cell lines at low, physiologically achievable doses. Furthermore, this combination therapy showed a synergistic effect in vivo , suggesting that an integrated view of PI3K and Hippo signaling can be leveraged therapeutically in PI3K activated sarcomas.