- Activation of the PI3K signaling pathway is a common event in human breast cancer and is most commonly due to PI3K alpha mutation, HER2 amplification, or PTEN inactivation. Activation of the pathway plays an important role in oncogenesis and tumors with these lesions are dependent on pathway function, whereas tumors in which the pathway is not deregulated are not. While inhibitors of the PI3K pathway effectively suppress growth in vivo, they tend not to induce regression. Our proposal is based on the idea that physiologic adaptation to PI3K pathway inhibitors attenuates the antitumor effects of these drugs and that inhibition of the adaptation will markedly enhance their therapeutic effects. We have shown that constitutive activation of mitogenic signaling by oncoproteins is accompanied by exaggerated feedback inhibition throughout the signaling network. These high levels of feedback play important roles in the biology of transformation and in the response of tumor cells to targeted therapies. High signaling output causes profound inhibition of normal signaling pathways and this causes the cell to be hyperdependent on the oncoprotein dependent pathway. This is responsible in part for the initial sensitivity of these tumors to pharmacologic inhibition of this pathway. But while the tumor is initially sensitive to inhibitors of the activated pathway, inhibition relieves feedback, reactivates upstream signaling and this, we believe, attenuates the antitumor effects of these drugs. Our previous data shows that inhibitors of different nodes in the PI3K pathway (PI3K, AKT, mTOR) all relieve feedback and that combined inhibition of PI3K signaling and adaptive receptor reactivation has enhanced therapeutic activity and causes tumor regression. We now propose in Aim 1 to characterize the relief of feedback responses to selective inhibition of PI3K, AKT or mTOR.
In Aim 2 we will use genetic and pharmacologic modalities to determine which adaptations are most responsible for maintaining the survival of the tumor in which the oncogenic pathway has been inhibited.
In Aim 3, the data will be used to identify combination therapies based on this concept and test and optimize their antitumor effects in vivo

Public Health Relevance

- Breast cancer is the leading cause of cancer among women in the United States. Activation of the PI3K pathway is characteristic of the majority of breast tumors. Drugs targeting this pathway universally relieve feedback inhibition of receptors and result in activation of physiologic signaling pathways. These adaptations limit the antitumor efficacy of the drugs. This proposal seeks to identify and characterize these feedback adaptations and develop therapeutic strategies to overcome them.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Program Projects (P01)
Project #
Application #
Study Section
Special Emphasis Panel (ZCA1-GDB-8 (M1))
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Sloan-Kettering Institute for Cancer Research
New York
United States
Zip Code
Er, Ekrem Emrah; Valiente, Manuel; Ganesh, Karuna et al. (2018) Pericyte-like spreading by disseminated cancer cells activates YAP and MRTF for metastatic colonization. Nat Cell Biol 20:966-978
Chen, Chun-Chin; Kass, Elizabeth M; Yen, Wei-Feng et al. (2017) ATM loss leads to synthetic lethality in BRCA1 BRCT mutant mice associated with exacerbated defects in homology-directed repair. Proc Natl Acad Sci U S A 114:7665-7670
Gao, Hua; Chakraborty, Goutam; Zhang, Zhanguo et al. (2016) Multi-organ Site Metastatic Reactivation Mediated by Non-canonical Discoidin Domain Receptor 1 Signaling. Cell 166:47-62
Ebbesen, Saya H; Scaltriti, Maurizio; Bialucha, Carl U et al. (2016) Pten loss promotes MAPK pathway dependency in HER2/neu breast carcinomas. Proc Natl Acad Sci U S A 113:3030-5
Malladi, Srinivas; Macalinao, Danilo G; Jin, Xin et al. (2016) Metastatic Latency and Immune Evasion through Autocrine Inhibition of WNT. Cell 165:45-60
Rodrik-Outmezguine, Vanessa S; Okaniwa, Masanori; Yao, Zhan et al. (2016) Overcoming mTOR resistance mutations with a new-generation mTOR inhibitor. Nature 534:272-6
Chen, Qing; Boire, Adrienne; Jin, Xin et al. (2016) Carcinoma-astrocyte gap junctions promote brain metastasis by cGAMP transfer. Nature 533:493-498
Kass, Elizabeth M; Lim, Pei Xin; Helgadottir, Hildur R et al. (2016) Robust homology-directed repair within mouse mammary tissue is not specifically affected by Brca2 mutation. Nat Commun 7:13241
She, Qing-Bai; Gruvberger-Saal, Sofia K; Maurer, Matthew et al. (2016) Integrated molecular pathway analysis informs a synergistic combination therapy targeting PTEN/PI3K and EGFR pathways for basal-like breast cancer. BMC Cancer 16:587
Yang, C; Li, Z; Bhatt, T et al. (2016) Acquired CDK6 amplification promotes breast cancer resistance to CDK4/6 inhibitors and loss of ER signaling and dependence. Oncogene :

Showing the most recent 10 out of 97 publications