Proximity ligation assays for isoform-specific Akt activation in breast cancer identify activated Akt1 as a driver of progression

• Published in: The Journal of pathology Vol. 227; no. 4; pp. 481 - 489
• Main Authors: Spears, Melanie, Cunningham, Carrie A, Taylor, Karen J, Mallon, Elizabeth A, Thomas, Jeremy St J, Kerr, Gillian R, Jack, Wilma JL, Kunkler, Ian H, Cameron, David A, Chetty, Udi, Bartlett, John MS
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.08.2012; Wiley
• Subjects: Akt; Biological and medical sciences; breast cancer; Breast Neoplasms - metabolism; Breast Neoplasms - physiopathology; Cohort Studies; Disease Progression; Female; Gynecology. Andrology. Obstetrics; Humans; Investigative techniques, diagnostic techniques (general aspects); Mammary gland diseases; Medical sciences; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Phosphorylation - physiology; Prognosis; Protein Isoforms - metabolism; Proto-Oncogene Proteins c-akt - metabolism; proximity ligation assay; Reproducibility of Results; Tumors; Molecular form; Breast disease; Proximity; Akt protein kinase; Activation; Breast cancer; Malignant tumor; Akt; proximity ligation assay; Assay; Mammary gland diseases; Anatomic pathology; Ligature; Cancer
• DOI: 10.1002/path.4022
• ISSN: 0022-3417

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. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.