• TEM
• therapy resistance
• H1975
• Osimertinib
• EGFR
• NSCLC
• cancer stem cells
• BMI-1

EGFR-mutated Non-Small Cell Lung Cancer patients are currently treated with Osimertinib, a third-generation EGFR-Tyrosine Kinase Inhibitor. Unfortunately, they experience relapse to such treatment, thus requiring further research. We investigated aggressiveness mechanisms in Osimertinib-resistant EGFR-mutant lung cancer cells with high levels of the cancer stem cell gene BMI-1.
We used two lung adenocarcinoma cell lines: H1975 cells, responsive to Osimertinib, and the H1975 Osimertinib-resistant line (H1975R). According to our Western Blot and RNAseq data, H1975R cells show increased BMI-1 expression than the parental ones. Since invasiveness is typical of highly aggressive cells, we asked whether H1975R cells display higher migratory capacity than H1975 cells. For this reason, we performed in vitro wound healing assays to predict in vivo cellular migration. Statistically significant results showed higher in vitro migratory ability of H1975R cells than the parental line, at all time-points analyzed.
Subsequently, we decided to test our hypothesis in vivo by using a zebrafish xenograft model as initial animal system. We run several tests to optimize the protocol. No statistically significant differences in their migratory ability emerged from these preliminary results.
Since alterations of important cellular structures have been proposed to be involved in lung cancer progression and drug resistance, we observed both H1975 and H1975R cells through electron microscopy to assess the presence of possible structural differences between them. Increased numbers of extracellular vesicles and altered nuclear numbers as well as abnormal nuclear and mitochondrial morphologies resulted in H1975R cells compared to H1975 cells.