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I. El-Hariry
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MO12 - Prognostic and Predictive Biomarkers III (ID 96)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Medical Oncology
- Presentations: 1
- Moderators:B. Han, M. Edelman
- Coordinates: 10/29/2013, 10:30 - 12:00, Parkside Ballroom B, Level 1
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MO12.01 - Novel Mechanisms of Sensitivity and Acquired Resistance to HSP90 inhibition by Ganetespib (ID 2739)
10:30 - 10:35 | Author(s): I. El-Hariry
- Abstract
- Presentation
Background
HSP90 is a promising anti-cancer target. Inhibition by the Hsp90 inhibitor ganetespib has shown promising activity with improved survival in patients with metastatic lung adenocarcinoma, and it is now being evaluated in malignant pleural mesothelioma. However, the mechanisms underlying resistance are currently unknown. The aims of this study were to establish the role for mitochondrial apoptosis in mediating the anti-cancer activity of ganetespib, and to also identify mechanisms of acquired resistance to support personalised therapy.Methods
We conducted a functional genetic screen to determine the role of the proapoptotic BAX/BAK proteins using double knockout mouse embryonic fibroblasts (MEFs) shRNA and siRNA. Focused RNAi targeting BH3-only proteins, Caspase 8 and MCL1 was conducted in MSTO-211H, H460 and H23 cell lines. Apoptosis was measured by a Caspase3 activity assay and data were validated by western blot and SubG1 population analysis. Prosurvival Bcl2 family regulation was evaluated by western blot, and MCL1 transcriptional suppression monitored by real-time quantitative PCR and luciferase reporter assay. MCL1 amplification was quantified by genomic real-time PCR. Ganetespib resistant cells were generated by increasing drug exposure. Hsp90 ATP-binding site and Caspase8 were sequenced in both parental and resistant cell lines.Results
Ganetespib required a functional mitochondrial pathway for induction of apoptosis. Interrogation of pro-apoptotic BH3-only proteins revealed a co-operation between BID, BIK and PUMA. Caspase8 activates BID and, when silenced, protected cells from ganetespib. MCL1 was transcriptionally suppressed by ganetespib, and when Mcl-1 downregulation was achieved by siRNA, it was sufficient to induce BID/BIK-dependent apoptosis in MCL1-dependent cells. We observed that MCL1 addicted cells were also more sensitive to ganetespib than non-addicted. In addition, amplification of MCL1 was detected only in ganetespib sensitive cell lines. Ectopic MCL1 was not sufficient to rescue from ganetespib-induced apoptosis. To better understand mechanisms of resistance, we established ganetespib-resistant cell lines. Resistant cells did not select for HSP90 mutations, and these cells conserved on-target suppression of PI3K/AKT, MAPK signalling, upregulation of HSP70, and MCL1 downregulation. However addiction to MCL1 was lost as was block of Caspase8 activation with consequent cross-resistance to TRAIL. PCR of Caspase8 cDNA revealed an acquired structural alteration in the 3’-untranslated region.Conclusion
Here we show that HSP90 inhibition requires engagement of the mitochondrial apoptosis pathway, and involves cooperation of multiple BH3-only proteins with parallel suppression of MCL1. Interestingly, ganetespib may exploit tumour dependence on MCL1; this may be clinically relevant given that MCL1 (1q21.2) amplification correlates with dependence and its gene copy number alteration is one of the most frequent across cancers. Acquired resistance involves selection for loss of dependence on MCL1, and a block in Caspase8 signalling which lies upstream of BID. Failure of ectopic MCL1 overexpression to rescue is indicative of redundant death signalling by ganetespib. Clinical significance of core apoptosis gene expression will be explored and presented in a correlative analysis of the 9090-06 ganetespib monotherapy clinical trial in NSCLC.Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.
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O03 - NSCLC - Targeted Therapies I (ID 113)
- Event: WCLC 2013
- Type: Oral Abstract Session
- Track: Medical Oncology
- Presentations: 1
- Moderators:J. Ross, J.C. Yang
- Coordinates: 10/28/2013, 10:30 - 12:00, Bayside Auditorium B, Level 1
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O03.01 - GALAXY-1: Randomized phase II study of docetaxel with or without ganetespib in advanced lung adenocarcinoma: Results in biomarker sub-groups and all adenocarcinoma patients. (ID 1715)
10:30 - 10:40 | Author(s): I. El-Hariry
- Abstract
- Presentation
Background
Ganetespib (G) is a highly potent 2[nd]-generation Hsp90 inhibitor showing synergistic activity with docetaxel (D) in NSCLC xenografts. G has a favorable clinical safety profile and has shown single-agent clinical activity in NSCLC patients with tumors harboring EML4-ALK translocations and KRAS mutations (mKRAS).Methods
We conducted a randomized, international open-label Phase 2 study of D with or without G in patients with advanced lung adenocarcinoma, one prior systemic therapy, and ECOG PS 0/1. D was given at 75 mg/m[2] on Day 1 of a three-week cycle in both arms. In the combination arm, G was given at 150 mg/m[2] on Days 1 and 15. The co-primary endpoints were PFS in patients with elevated LDH (eLDH) levels, or tumors harboring KRAS mutation. Key secondary endpoints were OS and PFS in all adenocarcinoma patients. Target enrollment was 240 adenocarcinoma patients, including 120 eLDH and 80 mKRAS patients. The study was initiated in all NSCLC patients and amended to include only those with adenocarcinoma histology.Results
Enrollment of 252 adenocarcinoma patients completed in November 2012; enrollment of eLDH (total N=112) and mKRAS (total N= 86) patients completed in May 2013. In all adenocarcinoma patients (N=252), baseline characteristics were balanced between the two arms (median age 60 years, males 56%, PS 0 41% and never-smokers 25%). Median numbers of cycles delivered were 6 and 4 for D+G and D, respectively. Grade 3/4 adverse events for the D+G and D alone arms were: neutropenia 37% vs. 38%; fatigue 6% vs. 3%; anemia 8% vs. 2%; diarrhea 3% vs. 0; fever with neutropenia 11% vs. 2%. A pre-specified analysis was conducted in May 2013. PFS HR for eLDH population (N=76) was 0.88 (90% CI: 0.57, 1.36, p=0.310); OS HR was 0.63 (90% CI: 0.40, 0.99, p=0.046). PFS HR for mKRAS population (N=63) was 0.83 (90% CI: 0.51, 1.37, p=0.271); and OS HR was 0.85 (90% CI: 0.48, 1.50, p=0.313). OS HR in the all adenocarcinoma population was 0.82 (90% CI: 0.62, 1.09, p=0.082), and the PFS HR was 0.84 (90% CI: 0.65, 1.07, p=0.038). For patients that were enrolled >6 months after diagnosis of advanced NSCLC (N=176), a pre-specified stratification factor, the OS HR was 0.61 (90% CI: 0.43, 0.87, p=0.0093), and the PFS HR was 0.61 (90% CI: 0.45, 0.83, p=0.0041). Final data analysis is expected by end of September 2013. Updated PFS and OS results for all populations will be presented at the meeting.Conclusion
Survival improvement was noted in all adenocarcinoma patients with the addition of ganetespib to docetaxel. The maximal benefit was achieved in patients with eLDH and those diagnosed with advanced NSCLC >6 months prior to study entry.Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.
