Introduction
T-cell lymphoma patient outcome remains largely unsatisfactory. To identify active therapies, we screened 474 compounds as single agents and in combination with the pan-HDAC inhibitor belinostat in four TCL cell lines.
Methods
Cells were exposed to 0.5µM library compound, belinostat alone (half IC50 concentration), or library compound + belinostat for 3 days, followed by MTT assay. Kinetic proliferation assays were performed in an Incucyte. Synergism was determined using Chou-Talalay, ZIP, Loewe, Bliss and HSA models. In-house RNA-Seq data were used to compare NAMPT and NAPRT expression.
Results
The nicotinamide phosphoribosyltransferase (NAMPT) inhibitor STF-31 combined beneficially with belinostat, demonstrating synergism in all cell lines in validation experiments. NAMPT inhibitors (NAMPTi) STF-31, padnarsertib, and OT-82 were all highly active in H9 (IC50: 59nM, 0.69nM, 458 nM, respectively) and MAC1 (101nM, 0.6nM, 243nM) but showed poorer activity in HH (24μM, 12μM, 7.8μM) and FE-PD (93μM, 13.5μM, N/A). Belinostat/padnarsertib and belinostat/OT-82 combination treatments were beneficial: belinostat/padnarsertib, was synergistic in H9, HH, and FE-PD for ≥3 of 5 synergy models, 2/5 models in MAC1; belinostat/OT-82, was synergistic in ≥3 of 5 models for all four cell lines. Kinetic proliferation assays in resistant FE-PD and HH indicated higher sensitivity to NAMPTi after prolonged treatment. Higher levels of NAMPT than NAPRT transcripts in H9 and MAC1 suggested a skewed dependence on NAMPT in these cell lines. Cell cycle analysis confirmed the delayed anti-proliferation effect of padnarsertib in FE-PD.
Conclusions
NAMPTi are relatively unexplored in TCL. These data support further preclinical and clinical investigations of NAMPTi as a single agent and combined with belinostat for the treatment of TCL.
