Assessing the temporal role of miR-200 loss in murine models of NSCLC

Lung cancer is the leading cause of cancer related deaths in the United States, with non-small cell lung cancer (NSCLC) making up a majority of new diagnoses. Metastasis is the big killer in NSCLC and is driven by epithelial-mesenchymal transition (EMT) and immune evasion. The microRNA 200 family is a master regulator of EMT and is implicated in immune regulation. In this study we have developed a novel genetically engineered mouse model (GEMM) and derived primary cell lines from them to explore the role of microRNA-200 in early EMT and immune changes. Our model combines conditional activation of KrasG12D, Trp53R172H, and deletion of miR-200141/c autochthonously in mouse lungs, creating models with distinct metastatic potentials. Mice with loss of miR-200 had detectable distant metastases earlier than their cohorts where miR-200 was left intact. Based on survival and metastatic data, a time point of 16 weeks was chosen to examine early changes occurring in the tumors and lung microenvironment. In this study, we found that in the lungs of GEMMs harboring loss of miR-200 tumors, there was a shift in the immune microenvironment favoring pro-tumor activity. We saw these changes ahead of detectable epithelial-mesenchymal transition in the primary lesions, as IHC showed highly epithelial tumors with an increased CD8+ T cell infiltration. Similar stains done on GEMMs at late-stage time points show a more complete EMT and CD8+ T cell exclusion. Characterizing the primary cell lines derived from late stage GEMM tumors, revealed many cell lines are highly mesenchymal, metastatic, and able to exclude CD8+ T cells. In this study, we show the role early loss of miR-200 has on preparing the immune microenvironment to allow for tumor progression and metastasis.