Gene Expression Meta-Analysis Identifies VDAC1 as a Predictor of Poor Outcome in Early Stage Non-Small Cell Lung Cancer

Background: The bioenergetic status of non-small cell lung cancer correlates with tumour aggressiveness. The voltage dependent anion channel type 1 (VDAC1) is a component of the mitochondrial permeability transition pore, regulates mitochondrial ATP/ADP exchange suggesting that its over-expression could be associated with energy dependent processes including increased proliferation and invasiveness. To test this hypothesis, we conducted an in vivo gene-expression meta-analysis of surgically resected non-small cell lung cancer (NSCLC) using 602 individual expression profiles, to examine the impact of VDAC1 on survival.

18F-fluorodeoxyglucose positron emission tomography/computed tomography-based radiotherapy target volume definition in non-small-cell lung cancer: delineation by radiation oncologists vs. joint outlining with a PET radiologist?

Purpose: F-18-Fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) has benefits in target volume (TV) definition in radiotherapy treatment planning (RTP) for non small-cell lung cancer (NSCLC); however, an optimal protocol for TV delineation has not been determined. We investigate volumetric and positional variation in gross tumor volume (GTV) delineation using a planning PET/CT among three radiation oncologists and a PET radiologist.

Procaspase 8 overexpression in non-small-cell lung cancer promotes apoptosis induced by FLIP silencing

We found that procaspase 8 was overexpressed in non-small-cell lung cancers (NSCLCs) compared with matched normal tissues. The caspase 8 inhibitor FLICE-inhibitory protein (FLIP) was also overexpressed in the majority of NSCLCs. Silencing FLIP induced caspase 8 activation and apoptosis in NSCLC cell lines, but not in normal lung cell lines. Apoptosis induced by FLIP silencing was mediated by the TRAIL death receptors DR4 and DR5, but was not dependent on ligation of the receptors by TRAIL. Furthermore, the apoptosis induced by FLIP silencing was dependent on the overexpression of procaspase 8 in NSCLC cells. Moreover, in NSCLC cells, but not in normal cells, FLIP silencing induced co-localization of DR5 and ceramide, and disruption of this co-localization abrogated apoptosis. FLIP silencing supra-additively increased TRAIL-induced apoptosis of NSCLC cells; however, normal lung cells were resistant to TRAIL, even when FLIP was silenced. Importantly, FLIP silencing sensitized NSCLC cells but not normal cells to chemotherapy in vitro, and silencing FLIP in vivo retarded NSCLC xenograft growth and enhanced the anti-tumour effects of cisplatin. Collectively, our results suggest that due to frequent procaspase 8 overexpression, NSCLCs may be particularly sensitive to FLIP-targeted therapies.

PARP inhibition induces BAX/BAK-independent synthetic lethality of BRCA1-deficient non-small cell lung cancer

Evasion of apoptosis contributes to both tumourigenesis and drug resistance in non-small cell lung carcinoma (NSCLC). The pro-apoptotic BCL-2 family proteins BAX and BAK are critical regulators of mitochondrial apoptosis. New strategies for targeting NSCLC in a mitochondria-independent manner should bypass this common mechanism of apoptosis block. BRCA1 mutation frequency in lung cancer is low; however, decreased BRCA1 mRNA and protein expression levels have been reported in a significant proportion of lung adenocarcinomas. BRCA1 mutation/deficiency confers a defect in homologous recombination DNA repair that has been exploited by synthetic lethality through inhibition of PARP (PARPi) in breast and ovarian cells; however, it is not known whether this same synthetic lethal mechanism exists in NSCLC cells. Additionally, it is unknown whether the mitochondrial apoptotic pathway is required for BRCA1/PARPi-mediated synthetic lethality. Here we demonstrate that silencing of BRCA1 expression by RNA interference sensitizes NSCLC cells to PARP inhibition. Importantly, this sensitivity was not attenuated in cells harbouring mitochondrial apoptosis block induced by co-depletion of BAX and BAK. Furthermore, we demonstrate that BRCA1 inhibition cannot override platinum resistance, which is often mediated by loss of mitochondrial apoptosis signalling, but can still sensitize to PARP inhibition. Finally we demonstrate the existence of a BRCA1-deficient subgroup (11-19%) of NSCLC patients by analysing BRCA1 protein levels using immunohistochemistry in two independent primary NSCLC cohorts. Taken together, the existence of BRCA1-immunodeficient NSCLC suggests that this molecular subgroup could be effectively targeted by PARP inhibitors in the clinic and that PARP inhibitors could be used for the treatment of BRCA1-immunodeficient, platinum-resistant tumours. Copyright (C) 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Conventional 3D staging PET/CT in CT simulation for lung cancer: impact of rigid and deformable target volume alignments for radiotherapy treatment planning

Objective: Positron emission tomography (PET)/CT scans can improve target definition in radiotherapy for non-small cell lung cancer (NSCLC). As staging PET/CT scans are increasingly available, we evaluated different methods for co-registration of staging PET/CT data to radiotherapy simulation (RTP) scans.

Methods: 10 patients underwent staging PET/CT followed by RTP PET/CT. On both scans, gross tumour volumes (GTVs) were delineated using CT (GTVCT) and PET display settings. Four PET-based contours (manual delineation, two threshold methods and a source-to-background ratio method) were delineated. The CT component of the staging scan was co-registered using both rigid and deformable techniques to the CT component of RTP PET/CT. Subsequently rigid registration and deformation warps were used to transfer PET and CT contours from the staging scan to the RTP scan. Dice’s similarity coefficient (DSC) was used to assess the registration accuracy of staging-based GTVs following both registration methods with the GTVs delineated on the RTP PET/CT scan.

Results: When the GTVCT delineated on the staging scan after both rigid registration and deformation was compared with the GTVCT on the RTP scan, a significant improvement in overlap (registration) using deformation was observed (mean DSC 0.66 for rigid registration and 0.82 for deformable registration, p50.008). A similar comparison for PET contours revealed no significant improvement in overlap with the use of deformable registration.

Conclusions: No consistent improvements in similarity measures were observed when deformable registration was used for transferring PET-based contours from a staging PET/CT. This suggests that currently the use of rigid registration remains the most appropriate method for RTP in NSCLC.