Select microtubule inhibitors increase lysosome acidity and promote lysosomal disruption in acute myeloid leukemia (AML) cells

Abstract

To identify new biological vulnerabilities in acute myeloid leukemia, we screened a library of natural products for compounds cytotoxic to TEX leukemia cells. This screen identified the novel small molecule Deoxysappanone B 7,4' dimethyl ether (Deox B 7,4), which possessed nanomolar anti-leukemic activity. To determine the anti-leukemic mechanism of action of Deox B 7,4, we conducted a genome-wide screen in Saccharomyces cerevisiae and identified enrichment of genes related to mitotic cell cycle as well as vacuolar acidification, therefore pointing to microtubules and vacuolar (V)-ATPase as potential drug targets. Further investigations into the mechanisms of action of Deox B 7,4 and a related analogue revealed that these compounds were reversible microtubule inhibitors that bound near the colchicine site. In addition, Deox B 7,4 and its analogue increased lysosomal V-ATPase activity and lysosome acidity. The effects on microtubules and lysosomes were functionally important for the anti-leukemic effects of these drugs. The lysosomal effects were characteristic of select microtubule inhibitors as only the Deox compounds and nocodazole, but not colchicine, vinca alkaloids or paclitaxel, altered lysosome acidity and induced lysosomal disruption. Thus, our data highlight a new mechanism of action of select microtubule inhibitors on lysosomal function.

<p>In vivo Screening of Natural Products Against Angiogenesis and Mechanisms of Anti-Angiogenic Activity of Deoxysappanone B 7,4ʹ-Dimethyl Ether</p>

“…Deox B 7,4 is a compound with anti-leukemic activity. 31 In the present study, we found that Deox B 7,4 can also function as an anti-angiogenic agent to inhibit the vessel growth of the zebrafish. The Tg (fli1a:EGFP) y1 embryos at 24 hpf were exposed to 1, 2.5, and 5 μM of Deox B 7,4, respectively, for 24 h, the number of complete ISVs formed in the zebrafish embryos at 48 hpf was observed under a fluorescence microscope.…”

The Function of V-ATPases in Cancer

“…It is therefore not surprising that prolonged inhibition of V-ATPase activity is lethal to cells. However, there is evidence that cancer cells are particularly reliant on the V-ATPase for survival, exhibiting greater sensitivity to V-ATPase inhibition than nontransformed cells (12,129,135,174).…”

“…V-ATPase activity is important for excretion of excess acid into the extracellular environment, thus maintaining a neutral cytosolic pH (24,117,134). To aid this, V-ATPase expression on the whole may be upregulated (12), or the pump may be localized to the plasma membrane through the expression of specific V-ATPase subunit a isoforms known to direct the pump to the cell surface (21,63). This activity contributes to reversal of the normal cellular pH gradient across the plasma membrane, specifically alkalinization of the cytosol and acidification of the extracellular space in tumor cells (181,214).…”

Deoxynivalenol induces structural alterations in epidermoid carcinoma cells A431 and impairs the response to biomechanical stimulation

“…Lysosomes are acidic organelles that play a crucial role in the turnover of cellular components and autophagic degradation 34 , 35 . Proper cellular function of these organelles is tightly related to their spatial localization and their interaction with tubulin microtubules 36 – 39 . Recent studies connected the importance of autophagic processes to biomechanical responses 40 , 41 .…”