Increased Tumor Growth Rate and Mesenchymal Properties of NSCLC-Patient-Derived Xenograft Models during Serial Transplantation

SIMPLE SUMMARY: Advances have been made in the study of NSCLC tumors using in vivo models, such as patient-derived xenografts (PDXs). However, the number of PDX models that can represent the heterogeneity of NSCLC between different individuals is still limited. We successfully established nine PDX mice, from which lung adenocarcinoma tumors bearing the KRAS-G12C mutation were the most frequently grafted. We show that the most aggressive tumors have a greater implantation capacity, and the success of their implantation is indicative of a poor prognosis. By using H-score to quantify cell proliferation and mesenchymal markers, we show that PDX tumors evolved towards a more proliferative and mesenchymal phenotype associated with higher protein levels of Ki67, vimentin, and ezrin, suggesting that the evaluation of their combined expression could be used as a prognostic marker to study disease progression. These PDX models provide a valuable platform for NSCLC translational research. ABSTRACT: Non-small-cell lung cancer (NSCLC) is the leading cause of cancer death worldwide. The high mortality is very often a consequence of its late diagnosis when the cancer is already locally advanced or has disseminated. Advances in the study of NSCLC tumors have been achieved by using in vivo models, such as patient-derived xenografts. Apart from drug screening, this approach may also be useful for study of the biology of the tumors. In the present study, surgically resected primary lung cancer samples (n = 33) were implanted in immunodeficient mice, and nine were engrafted successfully, including seven adenocarcinomas, one squamous-cell carcinoma, and one large-cell carcinoma. ADC tumors bearing the KRAS-G12C mutation were the most frequently engrafted in our PDX collection. Protein expression of vimentin, ezrin, and Ki67 were evaluated in NSCLC primary tumors and during serial transplantation by immunohistochemistry, using H-score. Our data indicated a more suitable environment for solid adenocarcinoma, compared to other lung tumor subtypes, to grow and preserve its architecture in mice, and a correlation between higher vimentin and ezrin expression in solid adenocarcinomas. A correlation between high vimentin expression and lung adenocarcinoma tumors bearing KRAS-G12C mutation was also observed. In addition, tumor evolution towards more proliferative and mesenchymal phenotypes was already observed in early PDX tumor passages. These PDX models provide a valuable platform for biomarker discovery and drug screening against tumor growth and EMT for lung cancer translational research.