Abstract 6709: <i>NF1</i> mutations in lung adenocarcinoma preclinical models and potential targeted therapies: The crucial role of the RAS-MAPK pathway

Targeting tumor suppressor genes, such as NF1, is a major challenge in cancer. Somatic NF1 mutations are found in ∼15% of lung adenocarcinoma (LUAD) cases. Still, the molecular vulnerabilities and cellular adaptations associated with these mutations remain unclear. Therefore, we aimed to study the functional consequences of NF1 loss in LUAD and its impact on the RAS/MAPK pathway, as well as potential therapeutic strategies. We established isogenic NF1-mutated cellular models (mono- and bi-allelic NF1 mutations) using CRISPR-Cas9 technology on the HBE4-E6/E7-C1 human bronchial epithelial cell line. Our studies included transcriptomic, phenotypic, and pharmacological studies, utilizing RAS/MAPK and PI3K-AKT-mTOR pathways inhibitors. Differential expression analysis was performed with the “limma” R-package with a 2 × 2 factorial design. We also computed in silico data from public drug sensitivity databases of LUAD cell lines. We tested pharmacological combinations in a patient-derived xenograft mouse (PDX) obtained from a LUAD tumor with a homozygous nonsense mutation of NF1: c.943C&amp;gt;T, p.(Gln315*) (Variant Allele Frequency ∼94%). We confirmed that NF1 loss-of-function led to the RAS/MAPK pathway activation, while the PI3K-AKT-mTOR pathway was not activated. We observed distinct transcriptomic clusters based on NF1 mutation status (wild-type [WT], heterozygous, and homozygous). Gene Set Enrichment Analysis found significant KRAS signaling down-regulated gene enrichment in NF1-mutated clones (q-value=0.059). Moreover, homozygous NF1-mutated lung cells exhibited more aggressive characteristics in vitro than heterozygous or WT cells: higher proliferation, higher adhesion, and greater migration capacities. In our in vitro pharmacological tests, only homozygous NF1 mutated cells were sensitive to Trametinib (a MEK inhibitor). No sensitivity was observed in these models when treated with the mTOR inhibitor AZD8055 or the PI3K inhibitor Buparlisib alone. Trametinib appeared to modulate the RAS/MAPK pathway more significantly at the transcriptomic level in cells with homozygous NF1 mutations than in NF1 WT. Trametinib and Buparlisib synergistically affected the NF1-/- model. Analysis of public drug sensitivity databases indicated that inhibitors of the RAS/MAPK and PI3K-AKT-mTOR pathways are effective against NF1-mutated LUAD cell lines. We then performed in vivo pharmacological tests on the LUAD PDX: Trametinib alone and in combination with Buparlisib resulted in significant tumor volume reductions of 72% and 84%, respectively. Collectively, these findings establish a promising possible efficacy of MEK inhibitors for LUAD patients with NF1 homozygous mutation. Citation Format: Jean-Stephane Giraud, Doriane Gorret, Manuela Ye, Dominique Lallemand, William C. Reinhold, Didier Decaudin, Ingrid Laurendeau, Eric Pasmant, Camille Tlemsani. NF1 mutations in lung adenocarcinoma preclinical models and potential targeted therapies: The crucial role of the RAS-MAPK pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6709.