Figure 3.

Leptin mediated erlotinib resistance in lung cancer cells. (a) Treatment of leptin increased erlotinib resistance in lung cancer cell A549, H358 and H460. Betulinic acid which inhibits lipogenesis reverses the erlotinib resistance mediated by leptin.(b) Leptin increased cancer cell growth in a dose-dependent manner 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 < .05, **p < .01, Student’s t test). (c) Treatment of leptin increased clonogenic potential after treatment of erlotinib. (d) Transfection of leptin-siRNAs which block the expression of leptin in BMSCs or addition of leptin neutralizing antibody before treatment of hypoxia enhanced erlotinib-induced cytotoxicity in lung cancer cells. Results are presented as the median of three independent experiments (*p < .05, **p < .01, Student’s t test).(e) Leptin promoted erlotinib resistance in syngeneic mouse lung cancer model. The tumor-bearing mice with co-injection of LLC and BMSCs were treated with erlotinib with or without leptin antibody. The inhibition of leptin with neutralizing antibody sensitized lung cancer cells to erlotinib. Tumors excised from the mice are shown. (f) 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).