“…One of the important factors that consist of this phenomenon is the autocrine signalling of growth factors (Vassbotn et al, 1993). The coexpression of platelet-derived growth factor (PDGF) and its receptor (PDGFR) is frequently detected in a variety of tumours including malignant glioma (Maxwell et al, 1990;Hermanson et al, 1992;Guha et al, 1995), lung cancer (Antoniades et al, 1992), and sarcoma (Smits et al, 1992), suggesting the existence of PDGF autocrine loop. Platelet-derived growth factor, a potent mitogen for glial cells, vascular smooth muscle cells, and fibroblasts, exists as disulphide-linked dimers of four homologous polypeptide chains, PDGF-A and -B, and the recently identified PDGF-C and PDGF-D (Ross et al, 1986;Deuel, 1987;Li et al, 2000;Bergsten et al, 2001;Gilbertson et al, 2001;LaRochelle et al, 2001).…”