Vascular mimicry is a potential mechanism of resistance to tyrosine kinase inhibitors in lung cancer cell lines with EGFR mutations

Background: Resistance to tyrosine kinase inhibitors is a significant obstacle for the treatment of non-small cell lung cancers with epidermal growth factor receptor mutations. Emerging evidence suggests that vascular mimicry, in which tumor cells form vascular-like structures, may contribute to tumor aggressiveness and therapeutic resistance. Therefore, we aim to establish an in vitro model of epidermal growth factor receptor-mutant non-small cell lung cancer cells to investigate vasculogenic mimicry as a potential mechanism of resistance to tyrosine kinase inhibitors. Methods: On a layer of Geltrex, H1975, PC9, H1650, HCC827 and A549 cells form tube-like structures that have been quantified under the microscope. Upregulation of endothelial and downregulation of epidermal markers were evaluated using RT-qPCR. Proliferative assays were performed in two- and three-dimensional conditions using gefitinib and osimertinib. Vasculogenic mimicry was assessed in vivo through PAS/CD31 immunohistochemistry in H1975 xenografts that were sensitive and resistant to osimertinib. Results: Under three-dimensional conditions, epidermal growth factor receptor-mutant non-small cell lung cancer cell lines reorganize into vascular-like loops in the absence of endothelial cells, indicating vascular mimicry. Gene expression analysis showed increased levels of CDH5 (VE-cadherin), KDR (VEGFR2), SLUG, and ZEB1, with some variation in epidermal markers like CDH1. H1975 and PC9 exhibited a vascular mimicry signature, while HCC827 and H1650 showed an intermediate phenotype with partial endothelial-like transition. Drug-sensitivity tests revealed that PC9 and H1975 cells acquired resistance to gefitinib and osimertinib when grown on Geltrex, whereas HCC827 cells remained sensitive. Xenografts of H1975 made resistant to osimertinib showed more PAS⁺/CD31⁻ vascular mimicry structures than parental H1975 cells (p = 0.036). Conclusions: Our findings identify vascular mimicry as a possible resistance mechanism to tyrosine kinase inhibitors targeting the epidermal growth factor receptor in non-small cell lung cancer cell lines. Tumor cells can reprogram themselves and form three-dimensional endothelial-like networks, highlighting the tumor microenvironment's role in drug response. Targeting vascular mimicry may help to overcome drug resistance in oncogene addicted lung cancers.