Abstract B47: Overexpression of TLX3 or HOXA9 in association mutant IL7Rα are sufficient to generate T-ALL in vivo

Abstract

Abstract Background: Mutations of the IL7Rα chain occur in approximately 10% of pediatric T-cell acute lymphoblastic leukemia cases. While we have shown that mutant IL7Rα is sufficient to transform an immortalized thymocyte cell line, mutation of IL7Rα alone was insufficient to cause transformation of primary T cells, suggesting that additional genetic lesions may be present, contributing to initiate leukemia. Studies addressing the combinations of mutant IL7Rα plus TLX3 or HOXA9 overexpression indicate in vitro grow advantage, suggesting these two genes as potential collaborative candidates. Furthermore, patients with mutated IL7Rα were more likely to have TLX3 or HOXA subgroup leukemia. Objective: We sought to determine whether combination of mutant hIL7Rα plus TLX3 or HOXA9 overexpression is sufficient to generate T-cell leukemia in vivo. Methods: Double-negative thymocytes were isolated from C57BL/6J mice and transduced with retroviral vectors containing mutant hIL7Rα plus TLX3 or HOXA9. The same combinations were tested for the hIL7Rα wild-type. Transduced thymocytes were cultured on the OP9-DL4 bone marrow stromal cell line for 7-13 days and accessed for driver oncogenes expression and then injected into sublethally irradiated Rag-/- mice. Mice were euthanized at onset of clinical signs, and cells were immunophenotyped by flow cytometry. Results: Thymocytes transduced with muthIL7Rα-TLX3 showed overexpression of c-Myc and Pim-1. Nonetheless, there was no difference in the protein level expression for these two proteins in either thymocytes transduced with muthIL-7Rα-HOXA9 or in the control wthIL7Rα-TLX3. Mice injected with either muthIL7Ra-TLX3 or muthIL7Rα-HOXA9 cells, but not the controls (wthIL7Rα-TLX3 or wthIL7Rα-HOXA9), developed leukemia approximately 14 days post injection, characterized by GFP-expressing T-cells in blood, spleen, liver, lymph nodes, and bone marrow. Conclusion: Thymocytes transduced with muthIL7Rα-TLX3 showed c-Myc and Pim-1 upregulation. Cells expressing the combination muthIL7Rα-TLX3 or muthIL7Rα-HOXA9 were sufficient to trigger T-cell leukemia in vivo. Citation Format: Gisele O.L. Rodrigues, Julie Hixon, Hila Winer, Wenqing Li, Scott Durum. Overexpression of TLX3 or HOXA9 in association mutant IL7Rα are sufficient to generate T-ALL in vivo [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B47.