GSTM1 and neoplasm: We ascribe the activation of two distinct pools of Egfr in PNET tumors (the first in cancer cells and the second in tumor-associated pericytes) to 2 EGF family ligands, Tgf-α and Hb-egf, which respectively mediate the antiapoptotic and proangiogenic activities of Egfr, revealing dual roles for Egfr signaling in this tumorigenesis pathway.