Naive T cells express full-length Notch receptors; however, T cells isolated from tumour-bearing mice have decreased expression of Notches 1–4 and a reduction in Notch target genes (Deltex1, Hey1 and Hes1) together suggesting T cells from tumours have repressed Notch signalling and decreased effector function [117,118,119]. This evidence concerns the gene HEY1 and neoplasm.