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Ref Type Journal Article
PMID (29284706)
Authors Croessmann S, Sheehan JH, Lee KM, Sliwoski G, He J, Nagy R, Riddle D, Mayer IA, Balko JM, Lanman R, Miller VA, Cantley LC, Meiler J, Arteaga CL
Title PIK3CA C2 Domain Deletions Hyperactivate Phosphoinositide 3-kinase (PI3K), Generate Oncogene Dependence, and Are Exquisitely Sensitive to PI3Kα Inhibitors.
Journal Clinical cancer research : an official journal of the American Association for Cancer Research
Vol 24
Issue 6
Date 2018 03 15
URL
Abstract Text Purpose: We describe herein a novel P447_L455 deletion in the C2 domain of PIK3CA in a patient with an ER+ breast cancer with an excellent response to the PI3Kα inhibitor alpelisib. Although PIK3CA deletions are relatively rare, a significant portion of deletions cluster within amino acids 446-460 of the C2 domain, suggesting these residues are critical for p110α function.Experimental Design: A computational structural model of PIK3CAdelP447-L455 in complex with the p85 regulatory subunit and MCF10A cells expressing PIK3CAdelP447-L455 and PIK3CAH450_P458del were used to understand the phenotype of C2 domain deletions.Results: Computational modeling revealed specific favorable inter-residue contacts that would be lost as a result of the deletion, predicting a significant decrease in binding energy. Coimmunoprecipitation experiments showed reduced binding of the C2 deletion mutants with p85 compared with wild-type p110α. The MCF10A cells expressing PIK3CA C2 deletions exhibited growth factor-independent growth, an invasive phenotype, and higher phosphorylation of AKT, ERK, and S6 compared with parental MCF10A cells. All these changes were ablated by alpelisib treatment.Conclusions: C2 domain deletions in PIK3CA generate PI3K dependence and should be considered biomarkers of sensitivity to PI3K inhibitors. Clin Cancer Res; 24(6); 1426-35. ©2017 AACR.

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Molecular Profile Treatment Approach
Gene Name Source Synonyms Protein Domains Gene Description Gene Role
Therapy Name Drugs Efficacy Evidence Clinical Trials
Drug Name Trade Name Synonyms Drug Classes Drug Description
Gene Variant Impact Protein Effect Variant Description Associated with drug Resistance
PIK3CA H450_P458del deletion gain of function PIK3CA H450_P458del results in the deletion of nine amino acids in the C2 PI3K-type domain of the Pik3ca protein from amino acids 450 to 458 (UniProt.org). H450_P458del confers a gain of function to the Pik3ca protein as demonstrated by transformation in culture and activation of the PI3K/Akt/Mtor pathway via increased phosphorylation of Akt, Erk, P70S6K, and P90RSK (PMID: 29284706).
PIK3CA P447_L455del deletion gain of function PIK3CA P447_L455del results in the deletion of nine amino acids in the C2 PI3K-type domain of the Pik3ca protein from amino acids 447 to 455 (UniProt.org). P447_L455del confers a gain of function to the Pik3ca protein as demonstrated by transformation in culture and activation of the PI3K/Akt/Mtor pathway via increased phosphorylation of Akt, Erk, P70S6K, and P90RSK (PMID: 21266528, PMID: 29284706).
Molecular Profile Indication/Tumor Type Response Type Therapy Name Approval Status Evidence Type Efficacy Evidence References
PIK3CA P447_L455del estrogen-receptor positive breast cancer predicted - sensitive Alpelisib + Letrozole Case Reports/Case Series Actionable In a clinical case study, a patient with estrogen-receptor positive breast cancer harboring PIK3CA P447_L455del demonstrated an 11 month sustained response to the combination therapy of Femara (letrozole) and Alpelisib (BYL719) (PMID: 29284706). 29284706
PIK3CA H450_P458del breast cancer sensitive Alpelisib Preclinical - Cell culture Actionable In a preclinical study, transformed breast epithelial cells expressing PIK3CA H450_P458del were sensitive to treatment with Alpelisib (BYL719) in culture, demonstrating growth inhibition and decreased invasiveness of acini (PMID: 29284706). 29284706