A novel regulatory circuit of ATG4B and SESN3 promotes T cell leukemogenesis.

[BACKGROUND] T cell acute lymphoblastic leukemia is a fatal hematological malignancy. Despite the treatment progress, no targeted therapy is available currently, which urges to deepen the understanding of the underlying mechanism of T-ALL cell growth/survival. Autophagy is a conserved cellular process, which plays a dual role in human cancers. Nevertheless, many aspects of the involvement of autophagy in T-ALL are not fully understood.

[METHODS] T-ALL patient cells and normal control cells were subjected to RT‒qPCR analysis. Gene silence and overexpression was used to study the function of ATG4B and sestrin 3 (SESN3) in T-ALL cells. Atg4b deficient mice were used to study the role of Atg4b in normal hematopoietic cells and T cell development. The efficacy of S130, an ATG4B inhibitor to suppress T-ALL cell growth was evaluated in xenograft models.

[RESULTS] The results showed that the expression of several autophagy-related genes (especially ATG4B) was significantly higher in T-ALL patient cells than control cells. ATG4B ablation decreased autophagic flux and inhibited T-ALL cell growth. In contrast, Atg4b depletion had mild effects on normal hematopoiesis and T cell development. RNA-seq data and subsequent studies revealed a novel regulatory circuit of ATG4B and SESN3, and the results indicated that SESN3 hampered T-ALL cell growth via the inhibition of both mTOR/S6K/protein synthesis pathway and autophagy. Importantly, S130 exhibited anti-leukemia activity in xenograft models.

[CONCLUSIONS] The present study demonstrates that a novel ATG4B-SESN3 regulatory circuit plays a crucial role in T cell leukemogenesis, which suggests that targeting ATG4B is a promising strategy for T-ALL treatment.