title: Proximity ligation assays for isoform-specific Akt activation in breast cancer identify activated Akt1 as a driver of progression.
abstract: The PI3K/Akt signal transduction pathway plays an important role in cancer progression and cell survival. Akt activation is associated with poor outcome in endocrine-treated breast cancer, whereas high levels of cytoplasmic Akt2 are associated with an improved overall survival. Proximity ligation assays (PLAs) were used to determine quantitative expression levels of isoform-specific activation (phosphorylation) of Akt1 and Akt2 in formalin-fixed, paraffin-embedded cell lines and breast cancer tumour tissues in situ. PLAs demonstrated a range of expression in breast cancer samples for total pAkt1 and pAkt2. High levels of pAkt1 were associated with reduced DRFS (HR: 1.45, 95% CI 1.14-1.83, p = 0.002) and OS (HR: 1.42, 95% CI 1.10-1.83, p = 0.007). When PLA results were combined, patients that had high levels of pAkt1 only had a significantly decreased DRFS (HR: 1.92, 95% CI 1.34-2.76, p = 0.005) and OS (HR: 1.94, 95% CI 1.32-2.86, p = 0.008) compared to other patients. Using PLAs to discriminate activation of Akt1 versus Akt2 suggests that Akt1 drives progression in early breast cancers. In cases where both Akt1/Akt2 are activated, Akt2 may act to reverse this effect. Using PLAs, we have measured activation of Akt1 and Akt2 proteins separately in situ in FFPE breast cancer samples.
authors.affiliation: Transformative Pathology, Ontario Institute for Cancer Research, MaRS Centre, South Tower, 101 College St, Suite 800, Toronto, Ontario, Canada M5G 043.
authors.forename: Melanie
authors.initials: M
authors.lastname: Spears
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Cunningham
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Taylor
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Mallon
authors.forename: Jeremy St J
authors.initials: JS
authors.lastname: Thomas
authors.forename: Gillian R
authors.initials: GR
authors.lastname: Kerr
authors.forename: Wilma J L
authors.initials: WJ
authors.lastname: Jack
authors.forename: Ian H
authors.initials: IH
authors.lastname: Kunkler
authors.forename: David A
authors.initials: DA
authors.lastname: Cameron
authors.forename: Udi
authors.initials: U
authors.lastname: Chetty
authors.forename: John M S
authors.initials: JM
authors.lastname: Bartlett
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism* / Q000503:physiopathology; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D010766:Phosphorylation / Q000502:physiology; D011379:Prognosis; D020033:Protein Isoforms / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015203:Reproducibility of Results
chemical_list: D020033:Protein Isoforms; C494918:AKT1 protein, human; C494921:AKT2 protein, human; D051057:Proto-Oncogene Proteins c-akt