The dynamic ability of tumor cells to adapt to a variety of stresses, including ischemia and cytotoxic chemotherapies, ultimately leads to more aggressive tumor growth and chemoresistance. 14-3-3?, an oncogenic phospho-binding protein, is known to play a central role in this process, yet a fundamental gap exists in our understanding of 1) how 14-3-3? responds to stress to promote cell survival/adaptation; and 2) how 14-3-3? can be targeted to sensitize tumor cells to stress. Until this gap is filled, the therapeutic targeing of 14-3-3? to improve cancer outcomes will be unattainable. The long-term goal is to develop strategies to overcome chemoresistance in cancer and improve patient outcomes. The overall objective of this proposal is to understand a recently discovered 14-3-3?- mediated mechanism of autophagy control and develop strategies to inhibit 14-3-3? in breast cancer. The central hypothesis is that ischemia rearranges the 14-3-3? interactome to promote a ULK1- and AMPK-governed 14-3-3? interaction with phosphorylated Atg9A, which, in turn, promotes autophagy- mediated anthracycline resistance in triple negative breast cancer (TNBC). Additionally, from a therapeutic perspective, it is posited that inhibition of HDAC6, which deacetylates 14-3-3? at critical lysine residues, offers a novel strategy to broadly disrupt 14-3-3? interactions in breas tumors. Guided by strong preliminary data, this hypothesis will be tested in the following specific aims: 1) Determine the mechanism by which ULK1 and AMPK govern Atg9A activity and whether disrupting Atg9A phosphorylation overrides chemoresistance in TNBC; and 2) Target the mechanism of 14-3-3? acetylation to suppress 14-3-3? binding activity in vivo. In the first aim, a combination of proteomics, molecular and microscopy approaches will be used to determine the interplay between AMPK and ULK1 in the regulation of Atg9A phosphorylation and 14-3-3? binding. Additionally, a 14-3-3?-binding defective phosphomutant of Atg9A, which we have already established, will be used to determine whether abrogation of this mechanism blocks anthracycline resistance in TNBC.
In aim 2, a clinically approved HDAC6 inhibitor will be tested for its ability to induce 14-3-3? acetylation and disrupt 14-3- 3?-mediated survival pathways in a series of patient derived TNBC xenografts. The approach is innovative because it has utilized 14-3-3? interactomics as a tool to understand adaptive mechanisms of cell survival. Moreover, the approach in aim 2 employs a completely novel strategy to block 14-3-3? in a patient-derived TNBC mouse model. The proposed research is significant because it will contribute fundamentally to our understanding of autophagy, an emerging mechanism of chemoresistance, and could ultimately yield 14-3-3?-targeted strategies to improve clinical outcomes in a patient population (triple negative breast cancer) with limited treatment options.
The research proposed here is relevant to public health because an understanding of 14-3-3? regulation and survival pathways will enhance our ability to rationally target the pro-tumor effects of 14-3-3? in human cancer and thereby improve outcomes for cancer patients. This work is pertinent to the NCI's goal of elucidating the basic mechanisms of cancer biology in order to ultimately eliminate suffering and death due to cancer.
| Banks, Courtney J; Rodriguez, Nathan W; Gashler, Kyle R et al. (2017) Acylation of Superoxide Dismutase 1 (SOD1) at K122 Governs SOD1-Mediated Inhibition of Mitochondrial Respiration. Mol Cell Biol 37: |
