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Erin L Stewart
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MA27 - Novel Drugs and PDX Models (ID 931)
- Event: WCLC 2018
- Type: Mini Oral Abstract Session
- Track: Targeted Therapy
- Presentations: 2
- Moderators:
- Coordinates: 9/26/2018, 13:30 - 15:00, Room 206 BD
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MA27.01 - Establishment of PDX From Tumors Characterized by EGFR Mutations or ALK Fusion Genes from Resections, Biopsies and Pleural Fluids (ID 12144)
13:30 - 13:35 | Author(s): Erin L Stewart
- Abstract
- Presentation
Background
Patient-derived xenograft (PDX) models allow for cancer tissue expansion, providing an effective method to evaluate tumor biology and mechanisms of response or resistance. Our study aims to establish models in patients enriched for lung adenocarcinoma (LUAD) with EGFR mutations or ALK fusion genes which respond initially to oral targeted therapy, but typically develop resistance and disease relapse within 2 years. The PDXs will be evaluated for their potential to model therapy outcomes, to determine resistance mechanisms and to evaluate novel therapy strategies to overcome resistance.
a9ded1e5ce5d75814730bb4caaf49419 Method
From August 2015 to January 2018, we collected 109 samples from patients with EGFR- or ALK-driven LUAD and from never-smoker LUAD patients with unknown mutation status. Five samples with low tissue viability (i.e. necrotic) or very low tumor content (<100 malignant cells) were excluded. Adequate samples were implanted into the subcutaneous tissue of NOD-SCID mice. At this time, 16 samples have reached the study endpoint (tumor growth ≥1.5cm3) and 60 showed no tumor-growth following implantation (median follow-up: 8m). Results are currently pending for 18 models.
4c3880bb027f159e801041b1021e88e8 Result
Samples were collected from surgical resections (31, 36%), CT-guided biopsies (12, 14%), EBUS (19, 22%) and pleural fluid effusions (24, 28%). Most patients were female (51/86, 59%), never smokers (62/85, 73%), and had stage III or IV cancer (55/79, 70%). Mutations in EGFR and ALK were found in 55/81 (68%) and 12/84 (14%) primary cancers, respectively. Early-passage xenograft engraftment (XG) was observed in only 16 (19%) PDXs, including 9/55 (16%) EGFR- and 1/12 (8%) ALK-mutant cancers. The phenotype and molecular changes (EGFR and ALK) were consistent within the PDX model and its corresponding patient sample. Samples collected from surgical-resection specimens showed a trend towards higher engraftment rates (p=0.084). Conversely, the presence of EGFR or ALK mutations showed a trend towards non-engraftment (noXG, p=0.075). Patient smoking status and tumor stage did not influence engraftment rate. To identify reasons for no tumor-growth, we conducted histological analysis in the subcutaneous fat-pads (nodes in the implant sites) of 28 noXG mice. Interestingly, we identified small non-palpable foci of carcinoma in 8 animals (4 EGFR+ and 2 ALK+).
8eea62084ca7e541d918e823422bd82e Conclusion
Environmental or molecular factors may impair engraftment rates of EGFR+ and ALK+ LUAD samples in PDX models. Nevertheless, these models recapitulate the primary disease and could be useful for population-based drug-screening studies.
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MA27.03 - Multi-Omic Characterization of TKI-Treated Drug-Tolerant Cell Population in an EGFR-Mutated NSCLC Primary-Derived Xenograft (ID 13370)
13:40 - 13:45 | Presenting Author(s): Erin L Stewart
- Abstract
- Presentation
Background
Sixty to eighty percent of advanced stage lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutated tumors respond to first generation EGFR tyrosine kinase inhibitors (TKIs). However, cure is not yet achievable with any EGFR TKI monotherapy, as patients eventually progress due to acquired resistance. In vitro evidence suggests that minor populations of epigenetically modified drug tolerant cells (DTCs) may be important for tumor cells surviving TKI. We hypothesize that molecularly characterizing DTCs in vivo and comparing them to the untreated tumor in a patient-derived xenograft (PDX) model may delineate mechanisms of tolerance that closely mimic those occurring in patients.
a9ded1e5ce5d75814730bb4caaf49419 Method
DTCs were produced via chronic exposure to erlotinib in a lung adenocarcinoma PDX harbouring an exon 19 deletion. Histological, genomic, transcriptomic (including single-cell RNA-seq), and epigenetic characterizations were performed on DTCs and compared to untreated baseline (BL) tumors.
4c3880bb027f159e801041b1021e88e8 Result
Compared to BL, DTCs exhibit decreased levels of proliferation (Ki67 by immunohistochemistry (IHC) and increased expression of senescence/quiescence (p21) and anti-apoptosis (BCL-XL) immunohistochemistry (IHC) markers, while maintaining EGFR pathway signaling (pEGFR, pAKT, pERK, pS6 IHC). Whole exome-sequencing provides evidence that DTCs likely do not represent mutationally distinct subclones from the bulk tumor. Instead, DTCs exhibit a number of differentially expressed genes compared to BL tumors that are involved in cell cycle arrest, senescence/quiescence, differentiation, vesicles, and inflammation. Genes with epigenetic differences (chromatin openness and/or promoter methylation) are involved in similar cellular processes. A minor (<2%) subpopulation of transcriptomically-defined DTC-like cells in the BL tumors are very similar to the DTCs, supporting the hypothesis that DTCs may exist prior to treatment. A number of transcription regulators are found to have differential gene expression and epigenetic regulation as well as DNA-binding motifs found in regions of chromatin uniquely open in DTCs or baseline tumors. These transcription regulators are involved in cell maintenance, proliferation, and differentiation, and may play key roles in promoting DTC phenotype.
8eea62084ca7e541d918e823422bd82e Conclusion
In this specific EGFR mutant PDX model sensitive to first generation TKIs, DTC-like cells are found in the BL untreated tumors, and its resultant phenotype after exposure to TKI appears to be involved in cell cycle, differentiation, senescence/quiescence, proliferation and maintenance. PDX models may provide insights into therapeutic strategies to target DTCs, and further improve the survival of EGFR-mutated NSCLC patients.
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MTE01 - Preclinical Models of Lung Cancer (Ticketed Session) (ID 811)
- Event: WCLC 2018
- Type: Meet the Expert Session
- Track: Biology
- Presentations: 1
- Moderators:
- Coordinates: 9/24/2018, 07:00 - 08:00, Room 206 F
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MTE01.02 - Lung Patient Derived Xenograft and Organoid (ID 11547)
07:30 - 08:00 | Author(s): Erin L Stewart
- Abstract
- Presentation
Abstract not provided
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