Akt2 knock-down reveals its contribution to human lung cancer cell proliferation, growth, motility, invasion and endothelial cell tube formation.

Samir Attoub,Nasseredine Kamel Hammadi,Jan Mester,Anne-Marie Gaben,Kholoud Arafat

doi:10.1038/srep12759

Abstract

The Akt/PKB serine/threonine protein kinase consists of three isoforms: Akt-1, −2 and −3. Their overexpression has been detected in human cancers, but their roles in cancer progression are unclear. We investigated the impact of specific silencing of Akt1 and Akt2 on human lung cancer cell proliferation, colony growth, motility, and invasion in vitro as well as tumor growth in vivo using human Non-Small Cell Lung Cancer cells LNM35, and on the vascular tube formation using HUVEC cells. Although silencing of Akt1 decreased cellular invasion at least in part via COX-2 inhibition, it had almost no effect on cell motility, proliferation, colony formation, and angiogenesis. Transient as well as stable silencing of Akt2 resulted in a strong inhibition of Rb phosphorylation associated with a decrease in cellular proliferation and colony formation, leading to the inhibition of tumor growth in the xenograft model. Silencing of Akt2 also reduced cellular motility and invasion in vitro, presumably via COX-2 inhibition. Moreover, silencing of Akt2 in the HUVEC cells resulted in the inhibition of their spontaneous angiogenic phenotype. Altogether, these results indicate that Akt2 plays an important role in lung cancer progression and can be a promising target for lung cancer therapy.

Highlights

Radiotherapy[8,9]
We observed a strong expression of Akt[1] and Akt[2] in these cells whereas the Akt[3] signal was weak in all cells and barely detectable in LNM35 and Human Umbilical Vein Endothelial Cells (HUVECs) cells
We decided to use the highly tumorigenic and metastatic lung cancer cells LNM35 to investigate the impact of specific silencing of the Akt[1] and Akt[2] isoforms on human lung cancer progression

Summary

Introduction

Radiotherapy[8,9]. Besides, accumulating evidence implicates the PI3K-Akt pathway in the regulation of cancer cell motility, tumor invasion and metastasis[10,11]. The anticancer activity of several humanized function-blocking antibodies and tyrosine kinase inhibitors such as Herceptin and Gleevec, respectively targeting ErbB2/HER2 and abl/c-kit, rely at least in part on their impact on the PI3K-Akt pathways In line with this proposition, Akt overexpression and constitutive activation have been demonstrated in premalignant and malignant human bronchial epithelial cells[9,13,14]. Using RNA interference selectively targeting Akt[1] and -2 isoform, we explored their respective roles in the human lung cancer cells’ proliferation and colony growth in vitro and in tumor growth in vivo as well as its role in cell motility and invasion. Their role in angiogenesis was explored in vitro using human umbilical vein endothelial cells

Methods

Results

Conclusion