Genetic Alterations in the PI3K/AKT Pathway and Baseline AKT Activity Define AKT Inhibitor Sensitivity in Breast Cancer Patient-derived Xenografts

Albert Gris-Oliver, Marta Palafox, Laia Monserrat, Fara Braso-Maristany, Andreu Odena, Monica Sanchez-Guixe, Yasir H. Ibrahim, Guillermo Villacampa, Judit Grueso, Mireia Pares, Marta Guzman, Olga Rodríguez, Alejandra Bruna, Caroline S. Hirst, Alan Barnicle, Elza C. de Bruin, Avinash Reddy, Gaia Schiavon, Joaquín Arribas, Gordon B. MillsCarlos Caldas, Rodrigo Dienstmann, Aleix Prat, Paolo Nuciforo, Pedram Razavi, Maurizio Scaltriti, Nicholas C. Turner, Cristina Saura, Barry R. Davies, Mafalda Oliveira, Violeta Serra

    Research output: Contribution to journalArticlepeer-review

    2 Scopus citations

    Abstract

    Purpose: AZD5363/capivasertib is a pan-AKT catalytic inhibitor with promising activity in combination with paclitaxel in triple-negative metastatic breast cancer harboring PI3K/AKT-pathway alterations and in estrogen receptor–positive breast cancer in combination with fulvestrant. Here, we aimed to identify response biomarkers and uncover mechanisms of resistance to AZD5363 and its combination with paclitaxel. Experimental Design: Genetic and proteomic markers were analyzed in 28 HER2-negative patient-derived xenografts (PDXs) and in patient samples, and correlated to AZD5363 sensitivity as single agent and in combination with paclitaxel. Results: Four PDX were derived from patients receiving AZD5363 in the clinic which exhibited concordant treatment response. Mutations in PIK3CA/AKT1 and absence of mTOR complex 1 (mTORC1)-activating alterations, for example, in MTOR or TSC1, were associated with sensitivity to AZD5363 monotherapy. Interestingly, excluding PTEN from the composite biomarker increased its accuracy from 64% to 89%. Moreover, resistant PDXs exhibited low baseline pAKT S473 and residual pS6 S235 upon treatment, suggesting that parallel pathways bypass AKT/ S6K1 signaling in these models. We identified two mechanisms of acquired resistance to AZD5363: cyclin D1 overexpression and loss of AKT1 p.E17K. Conclusions: This study provides insight into putative predictive biomarkers of response and acquired resistance to AZD5363 in HER2-negative metastatic breast cancer.

    Original languageEnglish (US)
    Pages (from-to)3720-3731
    Number of pages12
    JournalClinical Cancer Research
    Volume26
    Issue number14
    DOIs
    StatePublished - Jul 15 2020

    ASJC Scopus subject areas

    • Oncology
    • Cancer Research

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