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P1.06 - Poster Session 1 - Prognostic and Predictive Biomarkers (ID 161)
- Event: WCLC 2013
- Type: Poster Session
- Track: Biology
- Presentations: 1
- Coordinates: 10/28/2013, 09:30 - 16:30, Exhibit Hall, Ground Level
P1.06-054 - Targeting MCL1 amplification in NSCLC through anthracycline-mediated transcriptional suppression (ID 3213)
09:30 - 16:30 | Author(s): K.J. O’byrne
Targeting oncogene dependency for effective therapy has been one of the most successful strategies for managing metastatic non-small cell lung cancer (NSCLC). Although validating therapeutically tractable oncogenic driver mutations are a major focus, non-driver mutations may also confer dependencies that may also be exploitable. The prosurvival BCL2 protein, MCL1 prevents mitochondrial apoptosis by blocking interaction of proapoptotic BH3 only proteins with their multidomain proapototic counterparts, BAX and BAK. MCL1 is often mutated in cancers, and ranks as one of the most frequently amplified loci at 1q21.2. MCL1 amplified tumours exhibit addiction to this oncogene. Anthracyclines have been shown to transcriptionally suppress MCL1. Phase IIA studies in NSCLC have shown that epirubicin has useful single agent activity in unselected patients, with a significantly greater response rate than that achieved with standard chemotherapy. We therefore set out to evaluate MCL1 addiction in NSCLC, its correlation with anthracyline induced apoptosis and the prevalence of 1q21.2amplification to support a planned 1q21.2 stratified phase II trial in NSCLC, (EORTC-1303-LCG).
RNAi targeting MCL1was conducted in NCI-H460, NCI-H1299, NCI-H28 and NCI-H23 cell lines. Doxorubicin activity was measured by viability assay and apoptosis was assessed by western blot. gDNA from cell lines was obtained by Phenol-Chloroform extraction. The QIAamp DNA FFPE Tissue Kit was used to extract gDNA from FFPE tissues. MCL1 amplification was quantified by real-time PCR with a set of two primers and one probe (minor groove-binding (MGB) hydrolysis probe assay) for the gene of interest MCL1 and the two reference genes CCT3 and H6PD. Tonsil samples were used as a control diploid population.
MCL1 silencing efficiently induced apoptosis in a subset of NSCLC cells, however we identified two cell lines that were resistant to MCL1 knockdown (NCI-H1299 and NCI-H28). Doxorubicin efficiently induced apoptosis in MCL1 addicted cells but exhibited significantly less activity in cells that were not addicted. We developed a genomic DNA based quantitative real time PCR assay to evaluate copy number variation (CNV) at the 1q21.2 locus. A clear correlation r >0.91 was observed for 1q21.2 CNV compared with reference Conan Copy Number Analysis Tool (Cancer genome project, Sanger). Increased 1q21.2 copy number was consistently associated with MCL1addiction; however addiction also occurred in cells lacking 1q21.2 CNV, suggesting that MCL1 amplification represents a subset of MCL1 dependence. The concentration of doxorubicin was titrated against MCL1 protein downregulation into therapeutically sub-micromolar concentration range and we observed that MCL1 downregulation occurred coincidently with cleavage of poly-ADP ribose polymerase. We then screened DNA isolated from 19 adenocarcinomas, and identified 1q21.2 CNVs in 36.8%, with high level amplification (CNV >5) in 1q21.2 in 10.5%.
Targeting MCL1 addiction in 1q21.2 amplified NSCLC induces apoptosis and this dependence can be exploited by anthracyclines at therapeutically relevant concentrations. Given its significant prevalence in NSCLC, our data suggests that 1q21.2 amplification could be a novel non-driver mutation predictive for anthracycline response.