Abstract 7032: The role of general control nonderepressible 2 (GCN2) kinase in leukemogenesis and therapeutic response to L-asparaginase

Abstract Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, affecting the lymphoid cells of both B and T lineages. Most ALL cells are auxotrophic for asparagine, a nonessential amino acid for protein synthesis, due to the low expression of asparagine synthetase (ASNS), a rate-limiting enzyme for de novo biosynthesis of asparagine. Standard ALL treatment takes advantage of this vulnerability by giving patients L-asparaginase, a bacterial enzyme that depletes the circulating asparagine. However, previous work from our lab and others has shown that some ALL cells become resistant to L-asparaginase treatment through the induction of ASNS expression. Mechanistically, amino acid starvation activates the general control of nonderepressible 2 (GCN2) kinase, leading to the accumulation of the ATF4 transcriptional factor. ATF4, in turn, is recruited to the promoter of the ASNS gene to activate its transcription. However, the role of GCN2 kinase in the process of leukemogenesis under nutrient limiting environment has not been established. Here, we found that, in a mouse T-ALL model driven by a KRas(G12D) mutation, ATF4 and ASNS expression were strongly elevated in leukemic tissues. However, germline deletion of the Gcn2 did not delay leukemogenesis in primary T-ALL and secondary T-ALL generated by transplanting the pre-leukemic bone marrow cells into Gcn2 wildtype recipient mice. Although GCN2 inactivation does not affect leukemogenesis, it sensitizes T-ALL cells to L-asparaginase treatment in vitro and in vivo. In addition, a small molecule inhibitor of GCN2, GCN2iB, synergistically inhibits leukemic growth and survival in the mouse T-ALL model and human T-ALL lines where the basal expression of ASNS is low. Finally, we tested a newly developed inhibitor of ASNS (ASX-173), which selectively killed leukemic cells in the absence of exogenous asparagine even though their basal level expression of ASNS is high. Taken together, our results suggest that targeting GCN2 or ASNS will have therapeutic implications in ALL patients who become resistant to L-asparaginase treatment. Citation Format: Rodney Claude, Sankalp Srivastava, Minghua Zhong, Can Chen, Sandeep Batra, Utpal Dave, Chi Zhang, Yue Fang, Kirk Staschke, Ronald A. Wek, Ji Zhang. The role of general control nonderepressible 2 (GCN2) kinase in leukemogenesis and therapeutic response to L-asparaginase [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7032.