Glycogen Synthase Kinase 3 Protein Kinase Activity Is Frequently Elevated in Human Non-Small Cell Lung Carcinoma and Supports Tumour Cell Proliferation

Emma E Vincent,Piotr Dzien,Margaret T May,Linda O′Flaherty,Joya Pawade,Martin R Hetzel,Lois Phillips,Olivier E Pardo,Carys Morgan,Michael J Seckl,Jeremy M Tavaré,Douglas J E Elder,Muhammad Sohail,Jun Li

doi:10.1371/journal.pone.0114725

Emma E Vincent, Piotr Dzien + Show 12 more

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https://doi.org/10.1371/journal.pone.0114725

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Abstract

BackgroundGlycogen synthase kinase 3 (GSK3) is a central regulator of cellular metabolism, development and growth. GSK3 activity was thought to oppose tumourigenesis, yet recent studies indicate that it may support tumour growth in some cancer types including in non-small cell lung carcinoma (NSCLC). We examined the undefined role of GSK3 protein kinase activity in tissue from human NSCLC.MethodsThe expression and protein kinase activity of GSK3 was determined in 29 fresh frozen samples of human NSCLC and patient-matched normal lung tissue by quantitative immunoassay and western blotting for the phosphorylation of three distinct GSK3 substrates in situ (glycogen synthase, RelA and CRMP-2). The proliferation and sensitivity to the small-molecule GSK3 inhibitor; CHIR99021, of NSCLC cell lines (Hcc193, H1975, PC9 and A549) and non-neoplastic type II pneumocytes was further assessed in adherent culture.ResultsExpression and protein kinase activity of GSK3 was elevated in 41% of human NSCLC samples when compared to patient-matched control tissue. Phosphorylation of GSK3α/β at the inhibitory S21/9 residue was a poor biomarker for activity in tumour samples. The GSK3 inhibitor, CHIR99021 dose-dependently reduced the proliferation of three NSCLC cell lines yet was ineffective against type II pneumocytes.ConclusionNSCLC tumours with elevated GSK3 protein kinase activity may have evolved dependence on the kinase for sustained growth. Our results provide further important rationale for exploring the use of GSK3 inhibitors in treating NSCLC.

Highlights

Lung cancer is the leading cause of cancer death worldwide and non-small cell lung carcinoma (NSCLC) accounts for 85–90% of all cases
We show that Glycogen synthase kinase 3 (GSK3) expression and protein kinase activity is elevated in 41% of NSCLC tumours and that GSK3 protein kinase activity supports the proliferation of NSCLC cell lines, but not of immortalised pneumocytes
This study provides the first evidence that GSK3 protein kinase activity is elevated in early stage NSCLC and that this may contribute to the cancer cell phenotype

Summary

Introduction

Lung cancer is the leading cause of cancer death worldwide and non-small cell lung carcinoma (NSCLC) accounts for 85–90% of all cases. We explored the role of GSK3 in NSCLC by examining its expression and protein kinase activity in freshly isolated NSCLC tissue compared to patient-matched control tissue, and the sensitivity of NSCLC cell lines to inhibition of GSK3 using a small molecule inhibitor. We show that GSK3 expression and protein kinase activity is elevated in 41% of NSCLC tumours and that GSK3 protein kinase activity supports the proliferation of NSCLC cell lines, but not of immortalised pneumocytes These data suggest the potential for a subset of patients with NSCLC to benefit from the therapeutic use of GSK3 inhibitors previously developed for other human diseases

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