PI3K/AKT/mTOR signaling is critical for the cancer initiation and progression. Aberrant PI3K/AKT/mTOR hyperactivation has been documented in a large proportion of breast cancer patients. However, PI3K/AKT inhibitors have shown limited efficacy in the clinic, due to dose-limiting toxicities and emergence of resistance. Thus, identification of aberrant mechanisms of upstream regulation of AKT and identification of downstream mechanisms of PI3K/AKT signal relay to phenotypes associated with malignancy, remains critical. Epigenetic regulation plays an important role in tumorigenesis, and inhibitors targeting epigenetic factors are in clinical trials. Methylation of histones as well as non-histone proteins has been shown to play a functionally pivotal role in human cancers, including breast cancer. However, whether oncogenic signaling pathways, including PI3K/AKT/mTOR, are subject to methylation-dependent regulation has not been explored. Our preliminary data show that AKT undergoes lysyl methylation, a novel mode of regulation that contributes to protein kinase activation in breast cancer. Depletion of the histone methyltransferase SETDB1 reduces AKT activity, suggesting that SETDB1 could be a novel therapeutic target for PI3K/AKT-driven breast cancers. Therefore, in Aim 1 we propose that aberrant expression of SETDB1 in breast cancer contributes to hyperactivation of AKT in a methylation-dependent manner. We will define mechanistically how SETDB1 functions as a novel upstream regulatory mechanism that promotes AKT activation. We will further examine whether genetic ablation of SETDB1 suppresses proliferation in vitro and in vivo. Gene transcription, protein translation and metabolic reprogramming are known to mediate PI3K/AKT/mTOR signaling in cancer. Our preliminary studies have uncovered a previously unrecognized mechanism, whereby the N-glycosyl transferase ALG3 (asparagine-linked glycosylation 3 homolog), is co- amplified with PIK3CA in breast tumors, tightly correlates with a proliferative gene signature in breast cancers and is phosphorylated downstream of PI3K/AKT/mTOR. Deregulation of ALG3 induces ER stress leading to activation of the unfolded protein response (UPR). Thus, in Aim 2, we propose that ALG3 is a functional target of PI3K/AKT/mTOR/S6K1 signaling, and that hyperactivation of this pathway is required to meet the demands of increased protein translation, thereby reducing ER stress. We will determine the mechanism by which PI3K/mTOR signaling regulates ALG3 function and perform functional glycomics in vitro and in vivo. We will determine the contribution of ALG3 to growth in pathway-mutant cells and use combination therapy approaches with PI3K/AKT/mTOR inhibitors and drugs that block ER stress/UPR. The proposed studies will provide the molecular basis and rationale for developing more effective targeted therapies by suppressing the PI3K/AKT pathway based on individual patients? signaling signatures to achieve better treatment outcome.

Public Health Relevance

This project focuses on elucidating the underlying molecular mechanism(s) that govern upstream PI3K/AKT activation and downstream function in breast cancer. We hypothesize that aberrant activation of AKT is mediated through lysyl methylation of AKT mediated by the SETDB1 methylase and that this confers kinase activation, and downstream signaling. We further hypothesize that in PI3K/AKT/mTOR hyperactive cancers, the N-glycosyl mannosyl transferase ALG3 is an S6K1 substrate that is also co-amplified with PIK3CA in breast cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA177910-07
Application #
9930050
Study Section
Molecular Oncogenesis Study Section (MONC)
Program Officer
Xu, Wanping
Project Start
2013-07-16
Project End
2024-04-30
Budget Start
2020-05-01
Budget End
2021-04-30
Support Year
7
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Beth Israel Deaconess Medical Center
Department
Type
DUNS #
071723621
City
Boston
State
MA
Country
United States
Zip Code
02215
Cheng, Ji; North, Brian J; Zhang, Tao et al. (2018) The emerging roles of protein homeostasis-governing pathways in Alzheimer's disease. Aging Cell 17:e12801
Zhang, Jinfang; Bu, Xia; Wang, Haizhen et al. (2018) Cyclin D-CDK4 kinase destabilizes PD-L1 via cullin 3-SPOP to control cancer immune surveillance. Nature 553:91-95
Shimizu, Kouhei; Nihira, Naoe Taira; Inuzuka, Hiroyuki et al. (2018) Physiological functions of FBW7 in cancer and metabolism. Cell Signal 46:15-22
Zhang, Jinfang; Dang, Fabin; Ren, Junming et al. (2018) Biochemical Aspects of PD-L1 Regulation in Cancer Immunotherapy. Trends Biochem Sci 43:1014-1032
Clement, Emilie; Inuzuka, Hiroyuki; Nihira, Naoe T et al. (2018) Skp2-dependent reactivation of AKT drives resistance to PI3K inhibitors. Sci Signal 11:
Huang, Li-Yu; Zhao, Junjie; Chen, Hao et al. (2018) SCFFBW7-mediated degradation of Brg1 suppresses gastric cancer metastasis. Nat Commun 9:3569
Wan, Lixin; Xu, Kexin; Wei, Yongkun et al. (2018) Phosphorylation of EZH2 by AMPK Suppresses PRC2 Methyltransferase Activity and Oncogenic Function. Mol Cell 69:279-291.e5
Thomas, Clémence; Henry, Whitney; Cuiffo, Benjamin G et al. (2017) Pentraxin-3 is a PI3K signaling target that promotes stem cell-like traits in basal-like breast cancers. Sci Signal 10:
Zhang, Linli; Peng, Shan; Dai, Xiangpeng et al. (2017) Tumor suppressor SPOP ubiquitinates and degrades EglN2 to compromise growth of prostate cancer cells. Cancer Lett 390:11-20
Lien, Evan C; Dibble, Christian C; Toker, Alex (2017) PI3K signaling in cancer: beyond AKT. Curr Opin Cell Biol 45:62-71

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