N. Leonard

In pursuit of synergy: An investigation of the PI3K/mTOR/MEK co-targeted inhibition strategy in NSCLC.

Clinical PI3K inhibition has been somewhat disappointing, due to both inadequate patient stratification and compensatory cell signalling through bypass mechanisms. As such, investigation of PI3K-MEK co-targeted inhibition has been recommended. With high mortality rates and a clear need for new therapeutic intervention strategies, non-small cell lung cancer (NSCLC) is an important setting to investigate the effectiveness of this approach. Here, 174 NSCLC tumours were screened for 150 mutations by Fluidigm technology, with 15 patients being profiled for phosphoprotein expression. The effects of GDC-0941 (a pan PI3K inhibitor), GDC-0980 (a dual PI3K/mTOR inhibitor) and GDC-0973 (a MEK inhibitor) alone and in combination were assessed in 3 NSCLC cell lines. PIK3CA was mutated in 5.17% of NSCLC patients. GDC-0941 and GDC-0980 treatment induced anti-proliferative and pro-apoptotic responses across all NSCLC cell lines, while GDC-0973 treatment induced only anti-proliferative responses. GDC-0980 and GDC-0973 combined treatment led to significant increases in apoptosis and synergistic reductions in proliferation across the panel of cell lines. This study found that the PI3K/MEK co-targeted inhibition strategy is synergistic in all 3 molecular subtypes of NSCLC investigated. Consequently, we would advocate clinical trials for NSCLC patients combining GDC-0980 and GDC-0973, each of which are separately under clinical investigation currently.

Big applications for a microRNA signature: the diagnostic, prognostic and predictive biomarker potential of a novel 5-miR signature associated with cisplatin resistant NSCLC

MicroRNAs are a class of small non-coding RNAs that range in size from 19–25 nucleotides. They have been shown to regulate a number of processes within tumour biology, including metastasis, invasion and angiogenesis. More recently, miRNAs have been linked to chemoresistance in solid tumours, including lung cancer. Their role in cisplatin resistance and their potential as biomarkers has yet to be determined.

In with the old! Repurposing disulfiram to target cancer stem cells (CSCs) and the root of cisplatin resistance

Cisplatin remains the cornerstone of NSCLC management. Despite initial sensitivity tumours develop resistance, undermining the cytotoxic effect of cisplatin. Numerous mechanisms have been investigated in terms of cisplatin resistance and its development, however, the clinical issue of resistance remains. An avenue of interest is the CSC hypothesis, in which the survival and expansion of highly resistant CSCs during chemotherapy are thought to be a contributing factor of resistance. Specific inhibition of key CSC markers in combination with chemotherapy may subvert the inherent resistance of the CSCs thereby restoring therapeutic effeciency. One such CSC marker is aldehyde dehydrogenase 1 (ALDH1). We hypothesise that inhibition of the ALDH1-positive CSCs within cispaltin resistant NSCLC will resensitise the cells to cisplatin.

6 Cisplatin induces the emergence and expansion of a distinct cancer stem cell (CSC) population in NSCLC

line expression of the miRNAs, the miR-30 family members and miR34a-5p were up-regulated in the CisR xenograft FFPE tissue relative to PT. Conclusion: A novel miRNA signature associated with cisplatin resistance was identified in vitro, genetic manipulation of which enhanced the cytotoxic effects of cisplatin. The 5-miR signature shows both diagnostic and prognostic biomarker potential across a number of biological mediums. Disclosure: All authors have declared no conflicts of interest.

4 Identification and targeting of the DNA repair gene, XRCC6BP1, in cisplatin resistant NSCLC

A. Pender1, S. Rana1, E. Izquierdo Delgado2, P. Proszek2, I. GarciaMurillas3, J. Bhosle4, M. O’Brien4, J.F. Palma5, N.C. Turner6, S. Popat6, J. Downward1, D. Gonzalez2. 1Lung Cancer Group, The Institute of Cancer Research, London, United Kingdom; 2The Centre for Molecular Pathology, The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom; 3Molecular Oncology Group, The Institute of Cancer Research, London, United Kingdom; 4Department of Medicine, The Royal Marsden NHS Foundation Trust, London, United Kingdom; 5Genomics & Oncology, Roche Molecular Systems, Inc, Pleasanton, AL, United States of America; 6Medicine, Royal Marsden Hospital, London, United Kingdom

80P XRCC6BP1: A key DNA repair gene in platinum-resistant NSCLC

Background In the absence of specific treatable mutations, platinum-based doublet chemotherapy remains the gold standard treatment for NSCLC patients. However, its clinical efficacy is hindered in many patients due to both intrinsic and acquired resistance to these agents, in particular, cisplatin. Alterations in the DNA repair capacity of damaged cells is now recognised as an important factor in mediating this phenomenon. Methods DNA Repair Pathway RT2 Profiler Arrays were used to elucidate key DNA repair genes in H460 cisplatin resistant (CisR) and corresponding parental (PT) NSCLC cell lines previously generated in our laboratory. DNA repair genes significantly altered in CisR cells were validated using RT-PCR and western blot analysis, respectively. Loss of function studies were carried out using siRNA technology. The effect of gene knockdown on apoptosis was assessed by Annexin V/propidium iodide (PI) staining using the Cytell® Imaging System. DNA damage and repair in response to cisplatin following gene knockdown was investigated using the γH2AX foci formation assay. The translational relevance of these genes was examined in a cohort of chemo-naive matched normal and tumour lung tissues (n = 20). Results We identified a number of important DNA repair genes differentially regulated between H460 PT and CisR NSCLC cells. These included XRCC6BP1, TOP3A, XPA, PMS1 and hSSB1. XRCC6BP1 mRNA was significantly increased (19.4-fold) in H460 CisR cells relative to their PT counterparts. Gene silencing of XRCC6BP1 re-sensitized CisR lung cancer cells to the pro-apoptotic effects of cisplatin and significantly reduced the DNA repair capacity of these cells. Relative to matched normal lung tissues, XRCC6BP1 mRNA was significantly increased in adenocarcinoma tissues (AD), while hSSB1 mRNA was significantly increased in both AD and squamous cell carcinoma (SCC) tissues. Conclusions We have identified XRCC6BP1, in addition to hSSB1, as key DNA repair genes implicated in cisplatin resistant NSCLC. Our data highlights the potential of targeting XRCC6BP1, at least in part, in re-sensitizing chemoresistant lung cancer cells to the cytotoxic effects of cisplatin chemotherapy.