Activating E17K mutation in the gene encoding the protein kinase AKT in a subset of squamous cell carcinoma of the lung

Abstract

Somatic mutation (E17K) that constitutively activates the protein kinase AKT1 has been found in human cancer patients. We determined the role of the E17K mutation of AKT1 in lung cancer, through sequencing of AKT1 exon 4 in 105 resected, clinically annotated non-small cell lung cancer specimens. We detected a missense mutations G→A transition at nucleotide 49 (that results in the E17K substitution) in two squamous cell carcinoma (2/36) but not in adenocarcinoma (0/53). The activity of the endogenous kinase carrying the E17K mutation immunoprecipitated by tumour tissue was significantly higher compared with the wildtype kinase immunoprecipitated by the adjacent normal tissue as determined both by in vitro kinase assay using a consensus peptide as substrate and by in vivo analysis of the phosphorylation status of AKT1 itself (pT308, pS473) or of known downstream substrates such as GSK3 (pS9/S22) and p27 (T198). Immunostaining or immunoblot analysis on membrane-enriched extracts indicated that the enhanced membrane localization exhibited by the endogenous E17K-AKT1 may account for the observed increased activity of mutant E17K kinase in comparison with the wild-type AKT1 from adjacent normal tissue. In conclusion, this is the first report of AKT1 mutation in lung cancer. Our data provide evidence that, although AKT1 mutations are apparently rare in lung cancer (1.9%), the oncogenic properties of E17K-AKT1 may contribute to the development of a fraction of lung carcinoma with squamous histotype (5.5%).

AKT1E17K in human solid tumours

“…The observation appears to hold true in lung cancer were the AKT1 mutation was detected only once in squamous cell and not in adenocarcinoma samples. This is in accordance with a previous report (Malanga et al, 2008).…”

“…The AKT1 E17K mutation alters the electrostatic interactions of the pocket, activates AKT1 in a PI3K-independent manner, transforms rodent cells in vitro and can induce leukaemia in mice (Carpten et al, 2007). Until now AKT1 mutations have been reported in breast, colon, ovarian and lung cancer (Carpten et al, 2007;Malanga et al, 2008). Interestingly, in all the cases examined only one change (E17K) was detected.…”

“…Interestingly, in all the cases examined only one change (E17K) was detected. The tumour datasets analysed until now have been relatively small and the reported frequencies are generally low (5/61 breast, 3/51 colon, 1/50 ovarian and 3/105 lung) (Carpten et al, 2007;Malanga et al, 2008). The status of the AKT1 E17K mutation in larger tumour sets and in additional cancer types remains to be determined (Brugge et al, 2007).…”

Oncogenic E17K mutation in the pleckstrin homology domain of AKT1 promotes v-Abl-mediated pre-B-cell transformation and survival of Pim-deficient cells

“…Furthermore, recent evidence indicates that the molecular mechanism underlying activation of AKT1(E17K) is a broadened target lipid selectivity that allows high-affinity binding to PI(4,5)P2 (Landgraf et al, 2008). AKT1(E17K) mutation has been reported in various human cancers, including breast cancers, colorectal cancers, ovarian cancers, squamous cell carcinoma of the lung, endometrial carcinomas, urothelial carcinoma and bladder cancer, but not in other multiple human malignancies, including acute leukemias and liver cancers (Carpten et al, 2007;Kim et al, 2008;Mahmoud et al, 2008;Malanga et al, 2008;Mohamedali et al, 2008;Riener et al, 2008;Shoji et al, 2009;Zilberman et al, 2009;Askham et al, 2010). These studies suggested that AKT1(E17K) mutation occurs at a low frequency and in a tissue-specific manner.…”

Targetable “Driver” Mutations in Non Small Cell Lung Cancer

“…The frequency of AKT1 mutations is only 1% reported in NSCLC but they have been identified only in squamous cell carcinomas [66,67].…”