RASGRP1 and acute lymphoblastic leukemia: However, RAS signaling cascade upregulation could also arise from mutations or alterations in the activity/expression of key regulatory components of the RAS pathway, including RAS guanine nucleotide-releasing protein 1 (RASGRP1, that is frequently overexpressed in human T-ALL cell lines and primary samples) [75,76], or RAS GTPase-activating proteins (RAS-GAPs), such as neurofibromin 1 or p120 RAS-GAP [77,78].