Date of Award

Fall 2012

Degree Type

Thesis

Degree Name

Master of Science (MSc)

Department

Medical Sciences

Supervisor

Theodoros Tsakiridis

Co-Supervisor

Gurmit Singh

Language

English

Committee Member

Hal Hirte

Abstract

Purpose

To examine the potential of the anti-diabetic agent Metformin (MET) to enhance responses of NSCLC to ionizing radiation (IR).

Experimental Design

Human NSCLC A549, H1299 and SK-MES cells were treated with IR, MET or the mTOR inhibitor rapamycin and subjected to proliferation, clonogenic, immunoblotting, cell cycle and apoptosis assays. A549 and H1299 cells were grafted into flanks of immunosuppressed mice and treated with MET and/or IR. Tumours were analyzed by immunoblotting and immunohistochemistry.

Results

MET(2.5uM-5mM) caused dose-dependent inhibition of proliferation (10-70%)in all lines, inibited clonogenic survival and sensitized cells to IR. In A549 cellsMET caused inhibition of proliferation comparable to rapamycin, stimulated expression and activation of the ATM and AMPK-p53-p21cip1and inhibited the Akt-mTOR-4-EBP1 pathway.MET caused G1 arrest of cell cycle, enhanced apoptosis and induced sustained DNA repair foci of gH2AX. MET and IR alone inhibited xenograft growth and combined treatment enhanced that further. IR and MET induced sustained enhancement of expression and activity of ATM-AMPK-p53-p21cip1and inhibitionof Akt-mTOR-4-EBP1 pathways in tumours also. MET reduced expression of angiogenesis and enhanced expression of apoptosis markers in both control and radiated tumours.

Conclusions

Clinically achievable(uM) doses ofMET inhibit human NSCLC cell and tumour growth and sensitize them to IR.This is accompanied by desirable modulation of molecular signals, inhibition of angiogenesis and induction of apoptosis. Our results suggest that MET could be a clinically useful adjunct to radiotherapy in NSCLC and support clinical investigation of MET in combination with radiotherapy.

McMaster University Library

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