SUP-B15

YAP1 Knockdown Attenuates the Hippo Pathway in SUP-B15 Cells

Despite the clinical progress in chemotherapy and stem cell transplantation, relapse and chemoresistance of childhood acute lymphoblastic leukemia (cALL) are still serious problems, which calls for novel targets for cALL treatment. Jiang's group set out to explore the Hippo pathway and its role in cALL by detecting the protein expression levels of YAP1, TAZ, and Cyr61. They downregulated YAP1 in SUP-B15 cells by transfecting shRNA to test the effect of YAP1 on cALL development. The YAP1 mRNA and protein levels were reduced in the sh-YAP1 group compared to the sh-NC group, while they were increased in the YAP1 group compared to the Vehicle group (Fig. 1a-c), which verified the transfection effect. The protein level of p-YAP1 was elevated and TAZ and Cyr61 levels were reduced when YAP1 was knocked down. The protein level of p-YAP1 was increased, while TAZ and Cyr61 levels were decreased in the YAP1 group compared to the Vehicle group (Fig. 1b and c). The data shows that YAP1 knockdown inhibits the Hippo pathway in SUP-B15 cells.

Fig. 1. YAP1 knockdown attenuates the Hippo pathway in SUP-B15 cells (Jiang H, Zhang R B, et al., 2024).

Combination of Azacitidine and Flumatinib Induces Apoptosis in Sup-B15 Cells by Blocking the Cell Cycle through the MDM2-P53 Signaling Pathway

Adult acute lymphoblastic leukemia (ALL) is a life-threatening malignancy characterized by the Philadelphia (Ph) chromosome and the BCR-ABL fusion protein. Flumatinib (FLU), a tyrosine kinase inhibitor (TKI), could induce cell cycle arrest and apoptosis in Ph+ALL. Azacitidine (AZA) can target aberrant DNA methylation commonly occurring in Ph+ALL. However, the combinatorial effects and mechanisms of AZA and FLU remain unknown. Zhang et al. aimed to elucidate the synergistic effects of TKI FLU combined with the methyltransferase inhibitor AZA in Ph+ALL cells and the possible underlying mechanism.

A dose- and time-dependent effect on the cell proliferation arrest was found in SUP-B15 cells with treatment of AZA or FLU alone. The IC₅₀ of AZA and FLU were 5.6 μM and 0.9 μM, respectively (Fig. 2A). Combination of AZA and FLU significantly enhanced the cell proliferation arrest compared with FLU alone (Fig. 2B). The CompuSyn analysis showed a synergistic effect of AZA and FLU (Fig. 2C). Combination treatment significantly induced G1 phase arrest (Fig. 2D) and apoptosis (Fig. 2E) more strongly than single treatment. qPCR assay showed an upregulation of BAX and P21 mRNA and a downregulation of BCL2 and CyclinE mRNA with combination treatment (Fig. 2F). Moreover, TP53 was upregulated and MDM2 was downregulated at both mRNA (Fig. 2F) and protein levels (Fig. 2H). MDM2 was significantly overexpressed in Ph+ALL patient cohort in the GEO database (Fig. 2G). The synergistic mechanism was summarized in (Fig. 2I). The above results indicated that the combination of AZA and FLU showed a synergistic anti-leukemia effect on cell proliferation arrest and apoptosis in Ph+ALL cells.

Fig. 2. The combination of AZA and FLU has a synergistic anti-leukemia effect on cell proliferation arrest and apoptosis in Ph+ALL cells (Zhang L Y, Ge Z, et al., 2023).