Abstract 911: Ablation of rare tumor propagating cells during early lung adenocarcinoma development abrogates tumor growth and progression
Authors: Marini Kieren D. , Champion Emma C. , Dinh Phuong T. , Hwang Elizabeth E. , Sayles Leanne C. , Sweet-Cordero E. Alejandro 
Published: June 2022

Abstract
Lung cancer is the leading cause of cancer-related death worldwide. Non-small lung cancer accounts for 85% of diagnoses and the predominant subtype is lung adenocarcinoma (LUAD). Previously, we identified a population of Tumor Propagating Cells (TPCs) in the Kras; TP53 GEM model of LUAD. We demonstrated that TPCs have a greater capacity for secondary tumor formation and are enriched after treatment. The TPC population is defined by the expression of CD24, ITGB4 and Notch, with further functional validation showing that Notch3 contributes to this propagation phenotype in a non-redundant fashion. To investigate the biology of these TPCs, we have produced a KrasFSFG12D; Tp53FRT/FRT; Notch3CreERT2; RFP; inducible Diphtheria toxin receptor mouse (KPFFNRiDTR) for lineage tracing and ablation of Notch3 expressing tumor cells to get a granular understanding of the cell types/progeny generated by Notch3 expressing cells and the effects of removing these cells on the tumor microenvironment.In this model, adenovirus expressing FLP is delivered intra-tracheally resulting in expression of an oncogenic form of Kras and deletion of TP53, initiating LUAD tumors. Upon administration of Tamoxifen, Notch3 expressing cells are labelled by induced expression of RFP and DTR, then these cells can be ablated by subsequent dosing with Diphtheria toxin. By labelling/ablating cells at different disease progressions we can infer the importance of Notch signaling at key timepoints and assess the contribution of Notch3 expressing cells to the tumor microenvironment and tumor progression. We have found that Notch3 is expressed in the epithelial progenitors during early embryogenesis up to ~p5 and then gets turned off in the epithelial compartment of distal lung during alveologenesis, and in adults Notch3 is only expressed in the lung pericytes. Thus, the cell of origin for LUAD does not express Notch3, even if the TPC does, and we see the acquisition of Notch3 expression during early tumorigenesis. If we ablate Notch3 positive cells during this state we effectively prevent further growth of the tumors, however we still see similar tumor numbers at endpoint, suggesting that all lesions that will progress are already present when we ablate the TPCs. Considering that the total number of Notch3 cells in the tumor is approximated 1%, this is a profound effect on the overall growth of the tumor and suggests that the TPCs are fundamentally required for lung adenocarcinoma progression and may be a viable target for treatment.
Citation Format: Kieren D. Marini, Emma C. Champion, Phuong T. Dinh, Elizabeth E. Hwang, Leanne C. Sayles, E. Alejandro Sweet-Cordero. Ablation of rare tumor propagating cells during early lung adenocarcinoma development abrogates tumor growth and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 911.