An aberrant autocrine activation of the platelet-derived growth factor α-receptor in follicular and papillary thyroid carcinoma cell lines

Platelet-derived growth factor receptor (PDGFR) can bind to its ligand and consequently possess a kinase activity, and which is associated with the carcinogenesis of different cell types, including astrocytomas, oligodendrogliomas, and glioblastoma. In a cDNA microarray analysis, we observe the over-expressed mRNA of both PDGF-A and PDGF-α receptor in thyroid carcinoma cells. And the elevated protein expressions of PDGF-A and PDGF-α receptor in thyroid carcinoma cells were also confirmed by a Western blot analysis. The phosphorylation of PDGF-α receptor evaluated by an antibody against Tyr 720-phosphate was found in thyroid carcinoma cells. The tyrosine kinase activity of PDGF-α receptor was inhibited by tyrphostin AG1295 and showed a dose-dependent inhibition for the proliferation of thyroid carcinoma cells. These findings imply that autocrine activation of PDGF-α receptor plays a crucial role in the carcinogenesis of thyroid cells.