Figure 1.

BMSCs contribute to erlotinib resistance in lung cancer cells in hypoxia. (a) Erlotinib inhibited the proliferation of A549, H358, H460 cell lines and LLC cells in a dose-dependent manner. (b) Co-culture with BMSCs increased lung cancer cell growth after treatment of erlotinib in hypoxic conditions. (c) Media collected from hypoxic BMSCs increased cancer cell growth after treatment of erlotinib.CCK-8 cell viability assay was performed to evaluate cell viability after treatment of erlotinib. Results are presented as the median of three independent experiments (**p < .01, ***p < .001, Student’s t test). (d) BMSCs promoted erlotinib resistance in syngeneic mouse lung cancer model. LLC cells with or without BMSCs were injected subcutaneously into C57BL/6 mice. When the tumor reached approximately 250–300 mm³, the mice were treated with erlotinib. Tumors excised from the mice are shown. (e) Tumor growth curve presenting in tumor volume. Each bar represents the mean tumor volume with 95% confidence intervals. Tumors were measured every 2 days. Results are presented as the median of three independent experiments (*p < .05, **p < .01, Student’s t test). (f) Immunofluorescence analysis of ki67 in tumors. Upper: tumors from mice receiving co-injection of BMSCs and LLC; lower: tumors from mice receiving injection of LLC alone. Red dots indicate the ki67 positive cells. The amplifications were presented. (g) Scatter plot of the observed expression scores of ki67. Expression was scored semi-quantitatively by positive area.