Targeting cancer metabolism as a novel therapeutic strategy for breast cancers with PI3K/ Akt activation.

Our hypothesis is that breast cancers with constitutive activation of the PI3K/Akt pathway conferred by loss of PTEN or activating PIK3CA mutations have a number of metabolic Achilles heels that can be targeted directly by drugs inhibiting critical metabolic regulators such as MCT1/4, GLS and/or indirectly through inhibition of co-dependent pathways such as DNA repair, and PI3K/Akt. Mechanistic exploration of their metabolic restructurings can assist with the development of novel targets for drug development and the identification of combinatorial drug regimens. This together with parallel efforts to identify robust molecular diagnostic assays that could predict BCs with PI3K/Akt activation based on their metabolic signatures will be the cornerstone of designing clinical trials capable of treating a substantial fraction of BC patients.

This project is part of the CRUK Grand Challenge Award funded program that aims to map the entire molecular make-up of tumours using the latest technologies in high-throughput mass spectrometry imaging. The first objective of this study will be to identify specific metabolite profiles associated with the activation of the PI3K/Akt pathway driven by oncogenic mutations in PIK3CA (E545K and H1047R) and/or loss of PTEN. This will be achieved by performing mass-spec metabolomics profiling of human primary breast cancers followed by extensive genomic profiling of the metabolically distinct sub-regions e.g. by next generation sequencing (NGS) and expression microarrays with the focus to unveil novel gene alterations-metabolic phenotype interactions that are associated with the activation of the PI3K/Akt pathway.

This analysis will be further expanded in breast tumours obtained from mice with mammary-specific mutations in PIK3CA or deletion of PTEN. In parallel, we will aim to generate a collection of breast cancer patient-derived xenografts (PDXs) and derive matched organoid models, aiming at recovering distinct metabolic phenotypes in pre-clinical models for genetic and pharmacological inhibition screening. The comparison of GEMMS with organoids/PDXs and clinical samples will allow us to make an assessment on model stability and heterogeneity and establish appropriate models for understanding the therapy sensitivity pattern of PI3K/Akt activated breast cancers in vivo.

The second aim of this project is to identify metabolic vulnerabilities of breast cancers with PI3K/Akt activation and is based on the mechanistic exploration of key metabolic properties identified in these tumours and whether they are dictated by lipid phosphatase/kinase and Akt-dependent and independent functions. In relevant organoid and cell line models we will test if unique metabolic signatures can be rescued by targeting various nodes of the PI3K/Akt signalling pathway e.g. BKM120 (Pan-PI3K inhibitor), GDC0941 (PI3Kα/δ inhibitor), BYL719 (PI3Kα inhibitor), AZD6482 and TGX22 (PI3Kβ inhibitors), MK2206 and GSK690693 (Pan-Akt inhibitors), and mTOR inhibitors (Rapamycin and Torin). To further explore the mechanistic basis behind the observed changes in the context of PTEN, we will investigate the metabolic signatures of PTEN null MCF10A cells expressing GFP, WT PTEN, catalytically inert C124S, lipid (G129E) and protein phosphatase (Y138L) mutants of PTEN. This work will uncover and biochemically dissect the signalling nodes that contribute in the metabolic restructurings of PI3K/Akt activated cancers and identify novel metabolic vulnerabilities both in terms of genetically/pharmacologically manipulating key metabolic enzymes and/or modifying tumour diet. Such therapeutic interventions will be tested across all available PDO and representative PDX models with or without PTEN loss or oncogenic PIK3CA mutations alone and/or in combination with inhibition of co-dependent pathways.

This project will deliver insight into major questions that are applicable across cancer research. We will establish the broader metabolic wiring of breast cancers and better determine the plasticity of the tumour metabolism across a variety of pre-clinical models. We will identify the metabolic vulnerabilities conferred by the activation of the PI3K/Akt pathway and elucidate the metabolic biomarkers that govern the response to known therapeutic regimes. In doing so we will establish the pivotal metabolic features (tumour or microenvironment dependencies – and whether they can be targeted therapeutically). These results will prove invaluable information for drug target identification and repurposing into clinical trials.