Akt/mTOR Activation in Lung Cancer Tumorigenic Regulators and Their Potential Value as Biomarkers

Abstract

The high incidence and modest therapeutic outcomes of lung cancer have prompted the identification of cell molecular targets/biomarkers within the complex networks of interactions involved in cell malignancy. Most of the EMT-related regulatory mediators underline patients’ biologic variations, therapeutic refractory events, and tumor cell heterogeneity. Patient stratification based on the understanding of the relevant pathways, such as the PI3K/Akt axis crucial in EMT initiation, could favorably alter disease management. Significant clinical advantage could be expected when overexpressed Akt tyrosine kinase (Akt2) is addressed as a malignant biomarker to guide clinical management decisions, improving prognosis in lung cancer patients. Moreover, one should not miss the opportunity of using it as a druggable target aiming at the inhibition of the downstream complexity that underlies cell proliferation and survival, expression of stemness markers and drug resistance. The value of mTOR, as a downstream target of Akt, and the further activation of EMT transcription factors Twist, Snail and Zeb1 are revisited in this review. An in-depth state-of-the-art assessment provides evidence of its role in the mechanistic inhibition of epithelial markers, such as E-cadherin and miR-200, while inducing the expression of the mesenchymal ones, such as vimentin, N-cadherin, and miR-21. Lastly, evidence suggesting another transcription factor, FOXM1, as the link between the PI3K/Akt and Wnt/β-catenin pathways, prompting cell metabolism through the regulation of p70S6K, is analyzed. A more realistic approach is advised to address unmet clinical needs and support decision making at a clinical level. Taking into consideration several complex intracellular interactions might further improve patient stratification and result in better outcomes.