We also included differentially expressed genes identified by microarray studies for TGF–β responsive genes in the GEO microarray database, which includes TGF–β regulated genes in acute myelogenous leukemia cells (GSE1805 in the GEO database)[22], in lung carcinoma (A549) (GSE7436 in the GEO database), in immortalized lung epithelial (HPL1D) cells [23], in MDA-MB-468 Smad4 positive/negative clones treated with TGF–β (GSE2567), in human HP75 pituitary cell line [24], in breast cancer cells (GSE5265) [25] and in two glioma cell lines U373MG and U87MG [26]. Here, SMAD4 is linked to central nervous system cancer.