Function Of ASS1 In The Development Of T-ALL

BackgroundAcute T-lymphoblastic leukemia（T-ALL）is a type of hematologic tumor with malignant proliferation of hematopoietic progenitor cells.Global case statistics show that more than 40,000 adults and 50,000 children are diagnosed with leukemia every year,these patients have a high risk of relapse and poor prognosis even when treated early in the disease.At present,the chemotherapy and targeted drugs used in the treatment of T-ALL cause great damage to normal cells,and new therapeutic methods are urgently needed.The urea cycle is the only source of endogenous arginine.ASS1,a rate-limiting enzyme in the urea cycle,is silenced in many tumor cells,which forcing tumor cells to rely on arginine uptake from the environment.Tumors with ASS1 silencing can be treated with arginine deprivation agents.MethodsIn this study,flow cytometry,molecular cell assay and mouse experiment were used to explore the feasibility of targeted ASS1 therapy for T-ALL.RNA-seq,Western Blot and other techniques were used to explore the mechanism,which provided a theoretical basis for the research and development of ASS1 targeted drugs.ResultsAnalysis of GEO and TRAGET databases showed that the expression level of ASS1 in T-ALL was significantly higher than that in normal bone marrow,and the survival of T-ALL patients with high expression of ASS1 was shorter.After cell experiments in vitro,we found that knockdown ASS1 could inhibit the proliferation of T-ALL,and then we wanted to know the mechanism of this inhibition.Based on high-throughput sequencing analysis,we found that the expression of c-Myc was significantly down-regulated after ASS1 knockdown,and GSEA results showed that Myc-related pathways were enriched.In addition,ASS1 can regulate c-Myc,as shown by Western Blot,and then we tried to find the dependent signaling pathway.Through molecular experiments,we found that the inhibition of T-ALL proliferation was due to the inhibition of PI3K/AKT-mTOR signaling pathway,and finally determined that the down-regulation of c-Myc was the most important factor leading to the inhibition of tumor cell proliferation.These results suggest that ASS1 is an important upstream protein in the development of T-ALL.Finally,we construct Cdh5-Cre⁺;Ass1^{lox P/lox P};Pten^{lox P/lox P}bi-specific homozygous knockout mice found that ASS1knockout effectively delayed tumor progression in mouse primary T-ALL.Moreover,PDX model was constructed to prove that knockdown ASS1 can also play a beneficial role in human T-ALL.ConclusionWe propose that ASS1 is a potential target for the treatment of T-ALL,and the mechanism involved is that ASS1 regulates c-Myc through the PI3K/AKT-mTOR pathway,ultimately affecting the progression of tumor cells.In this paper,we have shown that both in vivo and in vitro experiments have beneficial effects,providing a new idea for the development of T-ALL targeted drugs.