Background: The aim of the current study was to investigate a putative relationship between (i) growth characteristics (proliferation and tumorigenicity) of nine glioblastoma multiforme (GBM) cell lines under different growth-stimulating conditions in vitro and (ii) their basal expression of a panel of growth factor receptors/autocrine cytokines.
Materials and methods: Basal expressions of the epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor-beta (PDGFR-beta), platelet-derived growth factor-AA (PDGF-AA) and PDGF-BB, tumor growth factor-alpha (TGF-alpha) and TGF-beta as well as tumor necrosis factor-alpha (TNF-alpha) were determined by immunocytochemistry at standard cell culture conditions (10% fetal calf serum [FCS]). Proliferation and tumorigenicity at 10% FCS and relative serum starvation (0.5% FCS) were assessed by using Coulter counting and soft agar cloning, respectively.
Results: The ratio between cell multiplications at 10% and 0.5% FCS over a 10-day period was defined as a measure of growth factor dependence of cellular proliferation. Expression of EGFR (but not of PDGFR-beta) strongly correlated to this ratio (Spearman rank correlation coefficient R = 0.87). No considerable correlations were present among other appropriate pairs of variables with biologically founded putative relationships.
Conclusion: Greater expression of EGFR is associated with increased growth factor dependence of cellular proliferation. Our results strengthen the role of EGFR as a rational molecular target of therapeutic intervention in GBM.