An Azaindole-Based Small Molecule Hzx-02-059 Induces Methuosis in B-Cell Acute Lymphoblastic Leukemia through the PI3K/AKT Axis

Methuosis is a newly defined nonapoptotic cell death characterized by the accumulation of large liquid-filled vacuoles in cytoplasm, which is distinct from necrosis, autophagy and apoptosis. A novel azaindole-based methuosis inducer, named HZX-02-059, displays cytotoxic effects to a series of cancer cellular models via blocking the role of PIKfyve. The discovery of HZX-02-059 sheds light on a novel therapeutic option for refractory cancer patients who have limited effective treatments. Despite significant advances in treatments, over 50% of adult patients with B-cell acute lymphoblastic leukemia (B-ALL) fail to achieve durable responses with current intensive chemotherapies, which highlight an urgent need of new therapeutic regimens for this patient population. Here, we applied HZX-02-059 to B-ALL cell lines and mice models to uncover its potential role and underlying mechanism.

Morphology changes of HZX-02-059-treated B-ALL cells were observed under the light microscope, and these treated cells were to certain extent collapsed into debris. Of note, higher concentration of this compound induced the accumulation of substantial larger vacuoles in cytoplasm. To assess the cytotoxicity of this compound, we performed cell counting kit-8 (CCK-8) and colony forming unit (CFU) assays. As expected, HZX-02-059 significantly inhibited cancer cell proliferation and reduced the capability of cell colony forming in a dose-dependent manner. Next, we carried out an EdU assay to determine the influence of HZX-02-059 on cell cycle distribution. As a result, B-ALL cells treated with HZX-02-059 were mainly blocked at G2/M phase. Western blotting was conducted to investigate the underlying molecular basis of HZX-02-059 in B-ALL. To the end, we found that HZX-02-059 negatively regulated the proteins involved in the PI3K/AKT pathway. Also, this drug decreased the expression of the pathway downstream transcription factors NF-ǐB and c-Myc, suggesting that the dysregulation of the PI3K/AKT axis is a potential mechanism of action of HZX-02-059 against B-ALL.

To further evaluate itsin vivotherapeutic effect, B-ALL patient-derived xenograft (PDX) mice were established and administrated with HZX-02-059. The result revealed a survival benefit of the treatment as compared with the control, which grants this molecule great potential for clinical usage. Thus, our results suggest that HZX-02-059 is a potent anti-BALL reagent in preclinical models that warrant further investigation of this drug as an alternative therapeutic strategy for B-ALL patients who are resistant to conventional therapies.