Novel NOTCH1-unmutated T-ALL Cell Line With Suppressed Growth by Gamma-secretase Inhibitors

T-cell acute lymphoblastic leukemia (T-ALL) frequently involves the activation of NOTCH1 signaling. However, effective NOTCH-directed therapies remain elusive. We established and characterized a novel T-ALL cell line, TMD11, lacking NOTCH mutations but sensitive to γ-secretase inhibitors (GSIs), providing a tool for discovering novel molecular targeted therapies.

TMD11 cells were established by long-term proliferation of leukemia cells from a patient with T-ALL without adding growth factors. Immunoblotting, whole-exome sequencing, and RNA sequencing were used to assess the NOTCH receptors, ligands, and targets (HES1 and MYC). Proliferation was measured using the water-soluble tetrazolium 8 assay after exposure to recombinant NOTCH ligands (JAGGED1 and DLL1) or GSIs (DAPT and Compound E). Morphology was examined using Wright staining. The comparative GSI sensitivity was evaluated using NOTCH1-mutated T-ALL cell lines (KOPT-K1 and Jurkat) and acute myeloid leukemia (AML) cell lines (TMD7 and THP-1).

The TMD11 cells had a normal karyotype. No pathogenic mutations were detected in the NOTCH genes. NOTCH ligands (JAGGED1, DLL1, and DLL4) were undetectable using immunoblotting. RNA sequencing showed the absence of ligand gene transcripts, except for faint JAGGED1. Cleaved NOTCH1 (active form) was not detected, although HES1 and MYC were expressed. Treatment with recombinant JAGGED1 and DLL1 induced cleaved NOTCH1 but did not enhance proliferation or upregulate HES1 and MYC expression. In contrast, DAPT and Compound E dose-dependently suppressed TMD11 cell growth and reduced HES1 and MYC expression. TMD11 exhibited stronger GSI sensitivity than KOPT-K1, Jurkat, and the two AML cell lines.

Alternative mechanisms link GSIs to the regulation of HES1 and MYC. TMD11 provides a unique model for probing NOTCH-independent GSI actions and screening novel targeted therapeutics in NOTCH-unmutated T-ALL.