Screen of Small Molecule ONC201/TIC10 Identifies Single Agent Activity and Combinatorial Efficacy with Bortezomib, Rituximab or Dexamethasone in Killing of Acute Lymphoblastic Leukemia Cells

The antitumor protein recombinant tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potential anticancer therapy although it has notable shortcomings that have limited its clinical development. Our lab previously identified a novel use for TRAIL-inducing compound 10 (ONC201/TIC10) as an efficacious antitumor therapeutic that induces TRAIL pathway activation through dual blockade of Akt and ERK that releases Foxo3a to transcriptionally activate the TRAIL and its death receptor DR5 genes. ONC201/TIC10 is being developed by Oncoceutics for the clinical therapy of cancer. Acute lymphoblastic leukemia (ALL) is a heterogeneous disease with an increasing rate of refractory/relapsed population of patients, making it a challenging disease to treat. Therefore, new therapeutic options as single dose or combinational treatments are required. Therapeutic agonist TRAIL antibodies have been investigated as a therapy for solid tumors; however, the biologic agents have not been explored extensively as a potential single or combinational therapy for the treatment of ALL. The aim of this study was to begin to characterize ONC201/TIC10 as a single agent for ALL therapy and in combination with bortezomib to increase induction of tumor cell death.

Single agent ONC201/TIC10 decreased ALL cell viability at IC50 values ranging from 2.5-5 µM after a 48 hour treatment. ONC201/TIC10 was combined with various accepted clinical treatments of ALL to determine if a synergistic or additive effect exists. Treatments of compounds at doses below their IC50, including the proteasome inhibitor bortezomib and monoclonal antibody-based rituximab therapy, showed synergistic or additive anti-leukemic effects when treated mutually with ONC201/TIC10 in ALL and T-cell ALL. TRAIL and Foxo3a expression was monitored by western blot analysis and apoptosis was indicated by both subG1 and caspase activity to investigate the effect of these combination treatments.

Bortezomib-ONC201/TIC10 combinational treatments decreased cell viability by approximately 30% in MALT-4 cells and 20% in Jurkat compared to single dose bortezomib treatments. Rituximab and the steroid compound dexamethasone were administered both below their IC50 in combination with ONC201/TIC10 and exhibited 20-40% cell viability decrease in ALL in vitro beyond the monoagent effects. Pharmacological enhancement by the addition of ONC201/TIC10 increased apoptotic efficacy and significantly decreased cell viability during combination treatments as compared to single agent therapy. The formation of the TRAIL death-inducing signaling complex could provide a rationale for further investigation into ONC201/TIC10 combinational treatment in ALL. These preclinical results suggest that there may be a clinical therapeutic advantage to modifying current ALL patient therapies to include the addition of ONC201/TIC10.