Dihydroartemisinin Triggers Ferroptosis in Multidrug-Resistant Leukemia Cells.

The molecular mechanisms and role of ferroptosis in tumor drug resistance remain unclear. In this study, we found that multidrug-resistant (MDR) K562/adriamycin (ADM) leukemia cells possessed higher glutathione (GSH) levels and iron-regulatory protein 2 (IRP2), transferrin receptor, ferritin heavy chain 1 (FTH1), and peroxidase-4 (GPX4) expression than parental drug-sensitive K562 leukemia cells. These elevations might have increased the antioxidant ability of K562/ADM cells and granted them increased buffering capacity against iron disorder, protecting them from ferroptosis and favoring drug resistance. However, dihydroartemisinin (DHA) restrained MDR K562/ADM cell viability and enhanced the sensitivity to ADM by strengthening ferroptosis induced by downregulation of GSH levels and GPX4, IRP2, and FTH expression, upregulation of reactive oxygen species (ROS) levels, and the consequent suppression of total serine/threonine kinase (AKT), total mammalian target of rapamycin (t-mTOR), phosphorylated mTOR (p-mTOR), and p-mTOR/t-mTOR levels. Moreover, compared with K562 cells, MDR K562/ADM cells exhibited greater ROS increases, GSH decreases, and viability rescue after ferroptosis inhibitor treatment owing to further suppression of FTH1, GPX4, p-mTOR, and p-mTOR/t-mTOR. Collectively, the increase in oxidative damage and the blockade of antioxidant defence shaped DHA-induced ferroptosis, which was responsible for the sensitivity of MDR leukemia cells to DHA. Regulating iron homeostasis/ROS/AKT/mTOR might be a potential chemotherapeutic strategy for sensitizing drug-resistant leukemia.

Targeting glycometabolic reprogramming to restore the sensitivity of leukemia drug-resistant K562/ADM cells to adriamycin.

AIMS: Mounting studies have confirmed that cancer cells reprogram their metabolism during early carcinogenesis to develop many other hallmarks, and demonstrated a relationship between aerobic glycolysis and the occurrence of drug resistance. However, the molecular mechanisms and role in tumor drug resistance of aerobic glycolysis remain unclear. MAIN METHODS: We analyzed differentially expressed genes (DEGs) at the RNA level between the multi-drug resistance (MDR) leukemia cell line K562/adriamycin (ADM) and its parental, drug-sensitive K562 cell line. Clustering and enrichment analysis of DEGs was performed. Oxamate, a lactic dehydrogenase inhibitor were used to assess the effect of glycolysis inhibition on ADM susceptibility and the expression of the enriched DEGs in K562/ADM cells. KEY FINDINGS: A total of 1742 DEGs were detected between the K562/ADM and K562 cell lines. The differential expression of unigenes encoding enzymes involved in glycometabolism signifies that there was a greater aerobic glycolysis flux in K562/ADM cells. The PI3K-AKT signaling pathway, which is related to glucose metabolism, showed representative differential enrichment and up-regulation in K562/ADM cells. Oxamate improved and re-sensitized the therapeutic effect of ADM in ADM-resistant cells by inhibiting aerobic glycolysis either directly or indirectly by down-regulation of the AKT-mTOR pathway. SIGNIFICANCE: Our findings suggest that ADM resistance mediated by the increase of aerobic glycolysis, which related to the over-activation of the AKT-mTOR-c-Myc pathway in MDR leukemia cells. Inhibition of aerobic glycolysis and down-regulation of signaling pathways involved in aerobic glycolysis represent a potential chemotherapeutic strategy for sensitizing leukemic cells and thereby overcoming MDR.

Glycometabolic adaptation mediates the insensitivity of drug-resistant K562/ADM leukaemia cells to adriamycin via the AKT-mTOR/c-Myc signalling pathway.

In human leukaemia, resistance to chemotherapy leads to treatment ineffectiveness or failure. Previous studies have indicated that cancers with increased levels of aerobic glycolysis are insensitive to numerous forms of chemotherapy and respond poorly to radiotherapy. Whether glycolysis serves a key role in drug resistance of leukaemia cells remains unclear. The present study systematically investigated aerobic glycolytic alterations and regulation in K562/adriamycin (ADM) multidrug­resistant (MDR) and ADM­sensitive K562 leukaemia cells in normoxia, and the association between drug resistance and improper glycometabolism. The cell proliferating activity was assessed with an MTT colorimetric assay, glycolysis, including glucose consumption, lactate export and key­enzyme activity was determined by corresponding commercial testing kits. The expression levels of hexokinase­II (HK­II), lactate dehydrogenase A (LDHA), glucose transporter­4 (GLUT­4), AKT, p­AKT473/308, mammalian target of rapamycin (mTOR), p­mTOR, c­Myc and hypoxia­inducible factor­1α (HIF­1α) were analyzed by western blot or reverse transcription­quantitative polymerase chain reaction (RT­qPCR). K562/ADM cells exhibited increased glucose consumption and lactate accumulation, increased lactate dehydrogenase, hexokinase and pyruvate kinase activities, and reduced phosphofructokinase activity. In addition, K562/ADM cells expressed significantly more HK­II and GLUT­4. Notably, inhibition of glycolysis effectively killed sensitive and resistant leukaemia cells and potently restored the sensitivity of MDR cells to the anticancer agent ADM. The AKT serine/threonine kinase (AKT)/mechanistic target of rapamycin (mTOR) signalling pathway, a crucial regulator of glycometabolic homeostasis, mediated over­activation and upregulation of c­Myc expression levels in K562/ADM cells, which directly stimulated glucose consumption and enhanced glycolysis. In conclusion, the present study demonstrated that MDR leukaemia cells exhibit increased aerobic glycolytic activity and that this may be responsible for resistance to chemotherapeutics in leukaemia MDR cells via activation of the AKT­mTOR­c­Myc signalling pathway. Therefore, inhibition of aerobic glycolysis may be a potential therapeutic strategy to efficiently treat multidrug resistance in relapsed or refractory leukaemia and cancers.

Differential expression and response to arsenic stress of MRPs and ASAN1 determine sensitivity of classical multidrug-resistant leukemia cells to arsenic trioxide.

There is no cross-resistance between arsenic trioxide and conventional chemotherapeutics. Classical multi-drug resistant (MDR) cells remain sensitive to arsenic trioxide, which may even reverse the drug resistance. Arsenic trioxide is also effective in leukemias/tumors that persist despite conventional cytotoxic or targeted drugs. We obtained a highly arsenic-resistant MDR leukemic cell line, HL-60/RS, by exposing leukemic HL-60 cells to adriamycin selection. We compared the arsenic sensitivity, and the expression and responses to arsenic of the arsenic-related transporters, MRP1, MRP2, and ASNA1, in paired parent/arsenic-resistant HL-60/RS/HL-60 and arsenic-sensitive/parental K562/ADM/K562 cells. Expression levels of MRP1, MRP2, and ASNA1 were negatively correlated with cell sensitivities to arsenic trioxide, and ASNA1 expression notably was highest in HL-60/RS cells and lowest in K562/ADM cells. Expression levels of MRP1, MRP2, and ASNA1 were significantly enhanced in HL-60/RS cells and inhibited in K562/ADM cells by arsenic trioxide treatment, compared with their parental sensitive cells, in accord with the high-resistance of HL-60/RS cells and high-sensitivity of K562/ADM cells. In conclusion, the cross-resistance of conventional chemotherapeutics-resistant leukemic cells to arsenic trioxide is determined by both levels of MRP1, MRP2, and ASNA1, and also by the responses of these transporters to arsenic stress.