Objective To explore the effect of Flavokawain B on the proliferation and apoptosis of acute T lymphoblastic leukemia(T -ALL)cells and its preliminary mechanism.Methods After the T -ALL cell lines CEM-C7(sensitive to glucocorticoids)and MOLT -4(resistant to glucocorticoids)cells were treated with different concentrations of Flavokawain B,the influence of Flavokawain B on the growth rate and doubling time of CEM-C7 and MOLT -4 cells was observed by 3 -(4,5 -dimethylthiazol -2 -yl)-5 -(3 -carboxymethoxyphenyl)-2 -(4 -sulfophenyl)-2H -tetrazolium(MTS)assay,and apoptosis was analyzed by using flow cytometry.Furthermore,Wes-tern blot assay was used to detect the expressions of Bim,Bcl -2 and cleaved Caspase -9.At last,the expressions of Bim and Bcl -2 in clinical T -ALL patient samples were also detected by using Western blot assay.Results MTS as-say showed that Flavokawain B significantly inhibited the cellular proliferation of T -ALL cell lines in a dose and time dependent manner(P <0.01 ).Flow cytometry findings revealed that Flavokawain B significantly induced the apoptosis of T -ALL cells in a dose -dependent manner(P <0.001 ).Western blot results indicated that Flavokawain B in-creased the expression of Bim and cleaved Caspase -9,and decreased the expression of Bcl -2 in T -ALL cell lines, which increased Bim and decreased Bcl -2 in clinical T -ALL patients samples,both in a dose -dependent manner. Conclusions Flavokawain B can inhibit the proliferation and induce the apoptosis of T -ALL cells by up -regulating the expression of Bim and down -regulating the expression of Bcl -2 and activating Caspase -9,whether resistant to glu-cocorticoids or not.

Objective:Endoplasmic reticulum stress(ERS)was used as the research emphasis to further investigate the mechanisms of apoptosis of FLT3-ITD-mutated leukemia cells and decreased expression of FLT3-ITD mutated protein induced by all-trans retinoic acid(ATRA).Methods:FLT3-ITD-mutated leukemia cell lines(MV4-11 and MOLM13)were treated with ATRA. Flow cytometry was conducted to assess cell apoptosis. Real-time fluorescent quantitative PCR(RT-qPCR)and Western blot were used to detect the expression of ERS-related and autophagy-related genes and protein, respectively.Results:A low-dose ATRA further increased FLT3-ITD cells and ERS levels. ATRA acted on the ERS-related PERK/eif2ɑ signaling pathway and continued to increase the ERS of FLT3-ITD cells, resulting in an upregulation of apoptotic gene CHOP expression. After the treatment with ATRA, FLT3-ITD protein in FLT3-ITD cells was decreased. Of the two main ERS-related protein degradation pathways, ER-associated degradation(ERAD)and ER-activated autophagy(ERAA), the expression of ERAD-related protein ATF6 in FLT3-ITD cells was not significantly changed on ATRA, whereas the expression of ERAA-related proteins Atg7 and Atg5 were significantly increased.Conclusions:ATRA further raises the ERS level of FLT3-ITD cells continuously by activating the ERS-related PERK/eif2ɑ signal pathway and induces FLT3-ITD protein autophagy degradation through ERAA pathway, which induces apoptosis of FLT3-ITD-mutated leukemia cells. These results provide preliminary evidence on the use of ATRA in the treatment of refractory leukemia with FLT3-ITD.