Figure 3. Establishment of osimertinib-resistant H1975 cell lines. (A) CCK-8 assay was conducted by treating H1975 cells with different concentrations of osimertinib. (B) Relative expression of lncRNA MSTRG.292666.16 and MSTRG.292667.12 in H1975 sensitive (H1975S) cells and H1975 resistant (H1975R) cells. (C) Representative TEM image of exosomes isolated from H1975S cells (left) and H1975R cells (right). Scale bar: 100 nm; (D) Nanoparticle tracking analysis of the size of exosomes isolated from H1975S cells (left) and H1975R cells (right). (E) Western blot analysis of exosomal marker CD9, CD63 and CD81. GAPDH and Calnexin were used as negative control. (F) Relative expression of lncRNA MSTRG.292666.16 in exosomes isolated from H1975S cells (H1975S-exo) and H1975R (H1975R-exo) cells. (G) The uptake of the PKH67 labelled osimertinib-resistant exosomes was evident in H1975 cells after 12 h of incubation. Cytoskeleton was dyed with actin-red, exosomes were dyed with PKH67. Scale bar, 10 μm.