Vimentin is required for lung adenocarcinoma metastasis via heterotypic tumor cell-cancer-associated fibroblast interactions during collective invasion

Purpose: Vimentin is an epithelial to mesenchymal transition (EMT) biomarker and intermediate filament protein that functions during cell migration to maintain structure and motility. Despite the abundance of clinical data linking vimentin to poor patient outcome, it is unclear if vimentin is required for metastasis or is a correlative biomarker. We developed a novel genetically engineered mouse model (GEMM) to probe vimentin in lung adenocarcinoma metastasis. Experimental Design: We used the LSL-Kras G12D/Lkb1 fl/fl/Vim-/-model (KLV-/-), which incorporates a whole-body knockout of vimentin and is derived from the Cre-dependent LSL-Kras G12D/Lkb1 fl/fl model (KLV+/+). We compared the metastatic phenotypes of the GEMMs and analyzed primary tumors from the KLV models and lung adenocarcinoma patients to assess vimentin expression and function. Results: Characterization of KLV^+/+ and KLV-/- mice, show that vimentin is not required for primary lung tumor growth but is required for metastasis and vimentin loss generates lower grade primary tumors. Interestingly, in the KLV+/+ mice, vimentin was not expressed in tumor cells but in cancer-associated fibroblasts (CAFs) surrounding collective invasion packs (CIPs) of epithelial tumor cells, with significantly less CIPs in KLV-/- mice. CIPs correlate with tumor grade, and are vimentin-negative and E-cadherin-positive, indicating a lack of cancer cell EMT. Similar heterotypic staining pattern was observed in human lung adenocarcinoma samples. In vitro studies show that vimentin is required for CAF-led tumor cell invasion, supporting a vimentin-dependent model of collective invasion. Conclusions: These data show that vimentin is required for lung adenocarcinoma metastasis by maintaining heterotypic tumor cell-CAF interactions during collective invasion.

http://ift.tt/2AurI1F