Inhibition of glycolysis modulates prednisolone resistance in acute lymphoblastic leukemia cells

Treatment failure in pediatric acute lymphoblastic leukemia (ALL) is related to cellular resistance to glucocorticoids (eg, prednisolone). Recently, we demonstrated that genes associated with glucose metabolism are differentially expressed between prednisolone-sensitive and prednisolone-resistant precursor B-lineage leukemic patients. Here, we show that prednisolone resistance is associated with increased glucose consumption and that inhibition of glycolysis sensitizes prednisolone-resistant ALL cell lines to glucocorticoids. Treatment of prednisolone-resistant Jurkat and Molt4 cells with 2-deoxy-D-glucose (2-DG), lonidamine (LND), or3-bromopyruvate (3-BrPA) increased the in vitro sensitivity to glucocorticoids, while treatment of the prednisolone-sensitive cell lines Tom-1 and RS4; 11 did not influence drug cyto-toxicity. This sensitizing effect of the glycolysis inhibitors in glucocorticoid-resistant ALL cells was not found for other classes of antileukemic drugs (ie, vincris-tine and daunorubicin). Moreover, down-regulation of the expression of GAPDH by RNA interference also sensitized to prednisolone, comparable with treatment with glycolytic inhibitors. Importantly, the ability of 2-DG to reverse glucocorticoid resistance was not limited to cell lines, but was also observed in isolated primary ALL cells from patients. Together, these findings indicate the importance of the glycolytic pathway in glucocorticoid resistance in ALL and suggest that targeting glycolysis is a viable strategy for modulating prednisolone resistance in ALL

Asparagine synthetase expression is linked with L-asparaginase resistance in TEL-AML1-negative but not TEL-AML1-positive pediatric acute lymphoblastic leukemia

Resistance to L-asparaginase in leukemic cells may be caused by an elevated cellular expression of asparagine synthetase (AS). Previously, we reported that high AS expression did not correlate to L-asparaginase resistance in TEL-AML1-positive B-lineage acute lymphoblastic leukemia (ALL). In the present study we confirmed this finding in TEL-AML1-positive patients (n = 28) using microarrays. In contrast, 35 L-asparaginase-resistant TEL-AML1-negative B-lineage ALL patients had a significant 3.5-fold higher AS expression than 43 sensitive patients (P < .001). Using real-time quantitative polymerase chain reaction (RTQ-PCR), this finding was confirmed in an independent group of 39 TEL-AML1-negative B-lineage ALL patients (P = .03). High expression of AS was associated with poor prognosis (4-year probability of disease-free survival [pDFS] 58% +/- 11%) compared with low expression (4-year pDFS 83% +/- 7%; P = .009). We conclude that resistance to l-asparaginase and relapse risk are associated with high expression of AS in TEL-AML1-negative but not TEL-AML1-positive B-lineage ALL

The synergism of MCL1 and glycolysis on pediatric acute lymphoblastic leukemia cell survival and prednisolone resistance

In vitro and in vivo resistance to prednisolone are predictive for an adverse prognosis in pediatric precursor B-acute lymphoblastic leukemia. Causes of resistance are still poorly understood. In this study, we observed that prednisolone exposure of prednisolone-sensitive patients' leukemic cells decreased anti-apoptotic MCL1 protein levels by 2.9-fold, while MCL1 protein expression in prednisolone-resistant leukemic patients' cells was unaffected (P<0.01). Locked nucleic acid oligonucleotides directed against MCL1 reduced MCL1 protein levels by 82±16% (P<0.05) in leukemic cells, decreased proliferation by 9-fold and sensitized to prednisolone up to 80.8-fold, compared to a non-silencing-control locked nucleic acid (P<0.05). Remarkably, we discovered that MCL1-silencing up-regulated the glucose consumption of leukemic cells by 2.5-fold (P<0.05), suggesting a potential rescue mechanism mediated by glycolysis. Targeting glycolysis by 2-deoxyglucose synergistically inhibited leukemic survival by 23.2-fold in MCL1-silenced cells (P<0.05). Moreover, 2-deoxyglucose and MCL1 locked nucleic acid concomitantly sensitized leukemic cells to prednisolone compared to MCL1 locked nucleic acid or 2-deoxyglucose alone (P<0.05). In conclusion, these results indicate the need to target both MCL1 and glycolysis simultaneously to inhibit leukemic survival and sensitize acute leukemia patients towards prednisolone