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MINI 14 - Pre-Clinical Therapy (ID 119)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:L. Fernandez-Cuesta, A.F. Gazdar
- Coordinates: 9/08/2015, 10:45 - 12:15, Mile High Ballroom 2c-3c
MINI14.01 - EGFR-Mutated PDX in NSCLC: Molecular Fidelity and Correlation of PDX and Patient Response to EGFR Inhibition (ID 2191)
10:45 - 12:15 | Author(s): J.G. Keck
Inevitable emergence of resistance to tyrosine kinase inhibitor (TKI) therapy in EGFR-mutated NSCLC warrants development of pro-active therapeutic strategies to delay or circumvent this evolution. To model such approaches, we are employing a clinically and genomically annotated patient derived xenotransplant (PDX) resource designed to duplicate relevant known mechanisms of resistance to TKI therapy. This analysis examines molecular fidelity and correlates response between patient and PDX in EGFR-mutant NSCLC.
Six EGFR-mutated NSCLC, 1 EGFR-TKI naïve and 5 after progressive disease on erlotinib, were implanted subcutaneously into the flank of NOD.Cg-Prkdc[scid] Il2rg[tm1Wjl]/SzJ (NSG) mice as previously described (DR Gandara, Clin Lung Cancer 2015). Models were considered established when PDX growth was confirmed in passage 1 (P1); tumor growth studies were conducted in P3-P5. The donor patient tumor (PT) and the resultant PDX were analyzed for driver mutations (Response Genetics Inc., and Illumina TSCAP), copy number variants (CNV) and global RNA expression (Affymetrix arrays). Informed consent was obtained from all patients. EGFR-mutant PDX treatments included: erlotinib, afatinib, cetuximab, and afatinib+cetuximab. Patient response was graded by RECIST 1.1 and measured in PDX by tumor shrinkage from pre-treatment baseline. In select models, pharmacodynamic studies (kinase arrays; immunoblotting) were also performed.
The EGFR mutation subtypes identified in the donor PT were preserved in all PDX models (4 EGFR E19del and 2 EGFR L858R). Corresponding putative mechanisms of resistance were identical in both PT and PDX in 3 cases: EGFR T790M (2 of 5) and MET amplification (1 of 5). Of 5 post-erlotinib progression PDX models, 3 had progressive disease (PD) and 2 had transient tumor shrinkage to erlotinib. The PDX derived from an erlotinib-naïve patient (EGFR E19del) demonstrated sustained tumor shrinkage to erlotinib. Patient-PDX treatment correlations were possible in 3 post erlotinib-progression models. Two of these patients received afatinib-cetuximab: 1 with partial response (PR) and 1 with PD. The two models corresponding to these patients, when treated with afatinib-cetuximab, underwent complete regression of tumor (CR) and PD, respectively. Pharmacodynamic assessment of the responding model at 24h showed near complete diminishment of pEGFR following afatinib-cetuximab, concomitant with decreased pHer2, pERK, pAKT and p38. Erlotinib showed transient inhibition on signaling in this model at 6h, returning to baseline by 24h. In contrast, the non-responding model showed minimal effects on target inhibition and signal transduction following treatment with any EGFR inhibitor.
Genomic fidelity was preserved in EGFR-mutant PDX, including putative mechanisms of resistance in the post-erlotinib progression models. The majority (3/5) of the EGFR-mutant PDXs created after erlotinib resistance demonstrated PD. In the other post-erlotinib progression models transient tumor shrinkage was noted, which may reflect PDX passaging in the absence of selective pressure of EGFR-inhibition or pharmacokinetic considerations. Overall, the PDX response to treatment reflected the corresponding patient’s clinical course. Pharmacodynamic studies of select models informed PDX response to treatment.
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