Absence of E17K mutation in the pleckstrin homology domain of AKT1 in gastrointestinal and liver cancers in the Korean population

Differential effects of AKT1(p.E17K) expression on human mammary luminal epithelial and myoepithelial cells

Recently, we identified a somatic mutation in AKT1, which results in a glutamic acid to lysine substitution (p.Glu17Lys or E17K). E17K mutations appear almost exclusively in breast cancers of luminal origin. Cellular models involving cell lines such as human mammary epithelial and MCF10 are model systems that upon transformation lead to rare forms of human breast cancer. Hence, we studied the effects of E17K using a clinically pertinent luminal cell line model while providing evidence to explain why E17K mutations do not occur in the mammary myoepithelium. Thus the purpose of our study was to perform a functional and differential proteomics study to assess the role of AKT1(E17K) in the development of breast cancer. We used a set of genetically matched nontumorigenic and tumorigenic mammary luminal and myoepithelial cells. We demonstrated that in myoepithelial cells, expression of E17K inhibited growth, migration, and protein synthesis compared with wild-type AKT1. In luminal cells, E17K enhanced cell survival and migration, possibly offering a selective advantage in this type of cell. However, antineoplastic effects of E17K in luminal cells, such as inhibition of growth and protein synthesis, may ultimately be associated with favorable prognosis. Our study illustrates the importance of cellular context in determining phenotypic effects of putative oncogenic mutations.

The oncogenic mutation in the pleckstrin homology domain of AKT1 in endometrial carcinomas

Background:

The phosphatidylinositol 3′-kinase (PI3K)–AKT pathway is activated in many human cancers and plays a key role in cell proliferation and survival. A mutation (E17K) in the pleckstrin homology domain of the AKT1 results in constitutive AKT1 activation by means of localisation to the plasma membrane. The AKT1 (E17K) mutation has been reported in some tumour types (breast, colorectal, ovarian and lung cancers), and it is of interest which tumour types other than those possess the E17K mutation.

Methods:

We analysed the presence of the AKT1 (E17K) mutation in 89 endometrial cancer tissue specimens and in 12 endometrial cancer cell lines by PCR and direct sequencing.

Results:

We detected two AKT1 (E17K) mutations in the tissue samples (2 out of 89) and no mutations in the cell lines. These two AKT1 mutant tumours do not possess any mutations in PIK3CA, PTEN and K-Ras.

Interpretation:

Our results and earlier reports suggest that AKT1 mutations might be mutually exclusive with other PI3K–AKT-activating alterations, although PIK3CA mutations frequently coexist with other alterations (such as HER2, K-Ras and PTEN) in several types of tumours.