Lw-218, a New Flavonoid Compound, Exerts Anti-T-Cell Malignancies Effects Via Autophagy-Mediated Apoptosis

Background:T-cell malignancies are characterized by the excessive proliferation of hematopoietic precursor cells of T-cell lineage lymphocytes in bone marrow. T-cell malignancies consist of T-cell lymphoblastic leukemia (T-ALL) and T-cell non-Hodgkin lymphoma (T-NHL). Effective therapeutic options are limited for T-cell malignancies patients. Apoptosis is one of the most important means to cure cancer. Autophagy, a conserved process that sequesters and targets cellular components for lysosomal degradation, also plays highly context-specific roles in mediating cell death. Our research found that LW-218, a new synthetic flavonoid compound, exerted anti-T-cell malignancies cell lines effects by autophagy-mediated apoptosis induction.

Methods:In vitrostudy, T-ALL cell lines (Jurkat, Molt4) and T-NHL cell lines (Hut102, Hut78) were used to investigated LW-218-induced apoptosis effects by survival assays (Flow cytometry, Annexin V/PI). A series of experiment were used to assess the autophagy flux triggered by LW-218, by using mCherry-GFP-LC3 construct, Lysotracker Red staining, and determining the expression ratio of LC3-II/LC3-I. Western blot assay, RT-qPCR, transfection with siRNA, and immunofluorescence were used to investigate the underlying mechanism. In vivostudies, the anti-tumor effects of LW-218 were evaluate in T-ALL xenografts which established by subcutaneous injection of Jurkat cells.

Results:Mechanistic studies demonstrated that LW-218-induced cell apoptosis in T-cell malignancies cell lines was correlated with activation of caspase 8, caspase 3 and caspases 9, and the substrate PARP1. In addition, LW-218 induced autophagy flux in T-cell malignancies, as increased ratios of LC3B-II/LC3B-I and reductions of P62 expression. The increased numbers of GFP-mCherry puncta and fluorescent intensity also indicated the increase in autolysosomes. The autophagy-mediated cell death must strictly follow the criteria that the inhibition of autophagy, through either genetic or chemical means, prevents cell death. LW-218-induced cell apoptosis and the activation of caspases3/8/9 could be prevented when the autophagy flux was blocked by autophagy inhibitors. mTOR is a master regulator of cellular metabolism and governs the programmed cell death pathways of apoptosis and autophagy. The results showed that LW-218 inhibited the expression of p-mTOR (Ser2448). And the restored activation of mTOR correlated with the inhibition of autophagy flux, which indicated mTOR might be involved in LW-218-induced autophagy. LW-218 also induced cleavage of Bid, the substrate of caspases 8, which indicated that the apoptosis mediated by autophagy might via caspases 8 and Bid activation. Thein vivostudies also verified that LW-218 inhibited the growth of tumors.

Conclusions:Our study provides a new insight into the mechanism of LW-218-induced autophagy-mediated apoptosis, suggesting the potency of LW-218 to be a promising agent against T-cell malignancies.