Modulation of leukotriene signaling inhibiting cell growth in chronic myeloid leukemia

Abstract

Although tyrosine kinase inhibitors (TKIs) have dramatically improved clinical outcome in chronic myeloid leukemia (CML), cure rarely occurs. This may be due to BCR-ABL-independent, aberrant signaling pathways, one of which leads to leukotriene (LT) formation. Well-recognized as inflammatory mediators, LT can also affect oncogenic mechanisms of several tumors. We have previously discovered elevated LT-synthesis and up-regulated cysteinyl-LT-inducing enzyme in CML. Here we report on dose-dependent inhibition of CML cell growth exerted by specific blockers of LT-signaling. Thus, the cysteinyl-LT1-receptor-antagonist montelukast significantly reduced the growth of K562, KCL22, and KU812 cells, as well as primary CD34 blood cells from two CML patients. Adding montelukast to the TKI imatinib caused combined inhibition. No effect was seen on normal bone marrow cells. Similarly, growth inhibition was also observed with the 5-lipoxygenase (LO)-inhibitor BWA4C, the 5-LO-activating-protein-(FLAP)-inhibitor licofelone and the LTB(BLT1)-receptor-antagonist LY293111. Thus, blocking of aberrant LT-signaling may provide an additional, novel therapeutic possibility in CML.

Montelukast, a cysteinyl leukotriene receptor antagonist, inhibits the growth of chronic myeloid leukemia cells through apoptosis

“…Our group has previously described that human CML cells have a high capacity to synthesize bioactive LTs and that LTs are capable of stimulating normal myeloid progenitor cell growth (21,22). Recently, we also showed that physiological concentrations of the CysLT1R antagonist montelukast, alone or together with imatinib, induced a clear and dose-dependent inhibition of the growth of human CML cells, while normal bone marrow cells and fibroblasts were unaffected (23). Herein, we further analyzed the mechanisms underlying the cytotoxic activity exerted by montelukast on CML cells by assessing its relation to receptor expression and induction of key proteins linked to apoptotic events.…”

“…Proliferation assay. Cell proliferation of JURL-MK1 cells was measured using the MTT cell proliferation assay according to the manufacturer's instructions as previously described (23). Cells were seeded in triplicate in flat-bottomed 96-well plates at 30,000 cells/well and treated for 72 h in the presence of 1 µM montelukast and/or 0.1 imatinib µM.…”

“…In order to ascertain whether cell death induced by montelukast is caspase-dependent, we treated cells with Z-vAD with or without montelukast. Cells were pretreated with 50 µM Z-vAD for 30 min and then montelukast (2 µM) was added and treated for additional 72 h. Cell viability was measured using the MTT cell proliferation assay, as previously described (23).…”

“…To assess apoptosis induction, K562 and JURL-MK1 cells were treated with 2, 3 or 5 µM montelukast for 8 h. Alterations in Wnt/β-catenin signaling were examined in K562 cells treated with 30 nM montelukast for 15, 60, 90 and 180 min. Whole-cell lysates were prepared in RIPA buffer (50 mM Tris-HCl, pH 7.4, 150 mM NaCl, 0.5% Igepal, 5 mM EDTA and 0.1% SDS) and western blot analysis was performed as previously described (23). The following primary antibodies were used: CysLT1R (120500; Cayman Chemicals, Ann Arbor, MI, USA); PARP1 (H250; sc-7150; Santa Cruz Biotechnology); Bax (2772), β-catenin (9582), phospho-β-catenin (9561), βTrCP (4394; all from Cell Signaling Technology); c-myc (ab56; Abcam, Cambridge, UK).…”

“…We previously showed clear expression of CysLT1R in K562, KU812 and KCL22 CML cells (23). To show the importance of CysLT1R for the growth of CML cells, the receptor was knocked down using siRNA in K562 cells.…”