NOTCH1 and neoplasm: To determine the role of NOTCH1 in driving proliferation of R26PR-derived T-ALLs, we cultured a tumor cell line derived from these animals in the presence of the γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), which inhibits the release of NICD from the cell membrane.