The analysis reveals that Egfr is expressed in cancer cells, is not detected in tumor endothelial cells or infiltrating immune cells, but, surprisingly, is highly enriched in PDGFR-β positive cells that predominantly comprise endothelium-associated perivascular cells in the PNET tumors of RT2 mice.38Hb-egf is highly enriched in tumor endothelial cells and perivascular cells and, to a lesser extent in cancer cells, whereas Tgf-α appears exclusively enriched in the unlabeled cancer cell fraction (Fig. 6A). The gene discussed is EGF; the disease is cancer.