Fig. 1

Expression and functionality of EGFR in osteosarcoma cell lines. a Western blot analysis of EGFR in 9 membrane protein-enriched fractions prepared from human osteosarcoma cell lines is opposed to an extract from Calu 3, a gefitinib-sensitive NSCLC cell line, used as a positive control. β-actin is shown as loading control. EGFR mRNA expression levels are indicated relatively to Calu 3 set as 1. b Four representative osteosarcoma cell lines with enhanced EGFR expression were either cultured under FCS at 10 % (10 % FCS), serum-starved for 24 h (0 % FCS) or stimulated with EGF (50 ng/ml for 15 min) following serum starvation for 24 h (EGF). The impact on EGFR phosphorylation and downstream activation of MAPK (ERK) and PI3K (AKT, S6, GSK3β) signaling pathways was determined by Western blot analysis. c Bar charts depict densitometric quantification of the Western blots (ImageJ Software) from (b) and data are given as phosphorylation of the indicated proteins relative to serum-starved conditions (0 % FCS)