TY - GEN A1 - Verbrugge, Sue Ellen A1 - Al, Marjon A1 - Assaraf, Yehuda G. A1 - Kammerer, Sarah A1 - Chandrupatla, Durga A1 - Honeywell, Richard A1 - Musters, Rene A1 - Giovannetti, Elisa A1 - O`Toole, Tom A1 - Scheffer, George L. A1 - Krige, David A1 - Gruijl, Tanja de A1 - Niessen, Hans W.M. A1 - Lems, Willem F. A1 - Kramer, Pieternella A. A1 - Scheper, Rik J. A1 - Cloos, Jacqueline A1 - Ossenkoppele, Gert A1 - Peters, Godefridus J. A1 - Jansen, Gerrit T1 - Multifactorial resistance to aminopeptidase inhibitor prodrug CHR2863 in myeloid leukemia cells: Down-regulation of carboxylesterase 1, drug sequestration in lipid droplets and pro-survival activation ERK/Akt/mTOR T2 - OncoTarget : open access impact journal N2 - Aminopeptidase inhibitors are receiving attention as combination chemotherapeutic agents for the treatment of refractory acute myeloid leukemia. However, the factors determining therapeutic efficacy remain elusive. Here we identified the molecular basis of acquired resistance to CHR2863, an orally available hydrophobic aminopeptidase inhibitor prodrug with an esterase-sensitive motif, in myeloid leukemia cells. CHR2863 enters cells by diffusion and is retained therein upon esterase activity-mediated conversion to its hydrophilic active metabolite drug CHR6768, thereby exerting amino acid depletion. Carboxylesterases (CES) serve as candidate prodrug activating enzymes given CES1 expression in acute myeloid leukemia specimens. We established two novel myeloid leukemia sublines U937/CHR2863(200) and U937/CHR2863(5uM), with low (14-fold) and high level (270-fold) CHR2863 resistance. The latter drug resistant cells displayed: (i) complete loss of CES1-mediated drug activation associated with down-regulation of CES1 mRNA and protein, (ii) marked retention/sequestration of the prodrug, (iii) a substantial increase in intracellular lipid droplets, and (iv) a dominant activation of the pro-survival Akt/mTOR pathway. Remarkably, the latter feature coincided with a gain of sensitivity to the mTOR inhibitor rapamycin. These finding delineate the molecular basis of CHR2863 resistance and offer a novel modality to overcome this drug resistance in myeloid leukemia cells. Y1 - 2015 U6 - https://doi.org/10.18632/oncotarget.6169 SN - 1949-2553 VL - 7 IS - 5 SP - 5240 EP - 5257 ER - TY - GEN A1 - Jansen, Gerrit A1 - Al, Marjon A1 - Assaraf, Yehuda G. A1 - Kammerer, Sarah A1 - van Meerloo, Johan A1 - Ossenkoppele, Gert J. A1 - Cloos, Jacqueline A1 - Peters, Godefridus J. T1 - Statins markedly potentiate aminopeptidase inhibitor activity against (drug-resistant) human acute myeloid leukemia cells T2 - Cancer drug resistance N2 - Aim: This study aimed to decipher the molecular mechanism underlying the synergistic effect of inhibitors of the mevalonate-cholesterol pathway (i.e., statins) and aminopeptidase inhibitors (APis) on APi-sensitive and -resistant acute myeloid leukemia (AML) cells. Methods: U937 cells and their sublines with low and high levels of acquired resistance to (6S)-[(R)-2-((S)-Hydroxy-hydroxycarbamoyl-methoxy-methyl)-4-methyl-pentanoylamino]-3,3 dimethyl-butyric acid cyclopentyl ester (CHR2863), an APi prodrug, served as main AML cell line models. Drug combination effects were assessed with CHR2863 and in vitro non-toxic concentrations of various statins upon cell growth inhibition, cell cycle effects, and apoptosis induction. Mechanistic studies involved analysis of Rheb prenylation required for mTOR activation. Results: A strong synergy of CHR2863 with the statins simvastatin, fluvastatin, lovastatin, and pravastatin was demonstrated in U937 cells and two CHR2863-resistant sublines. This potent synergy between simvastatin and CHR2863 was also observed with a series of other human AML cell lines (e.g., THP1, MV4-11, and KG1), but not with acute lymphocytic leukemia or multiple solid tumor cell lines. This synergistic activity was: (i) specific for APis (e.g., CHR2863 and Bestatin), rather than for other cytotoxic agents; and (ii) corroborated by enhanced induction of apoptosis and cell cycle arrest which increased the sub-G1 fraction. Consistently, statin potentiation of CHR2863 activity was abrogated by co-administration of mevalonate and/or farnesyl pyrophosphate, suggesting the involvement of protein prenylation; this was experimentally confirmed by impaired Rheb prenylation by simvastatin. Conclusion: These novel findings suggest that the combined inhibitory effect of impaired Rheb prenylation and CHR2863-dependent mTOR inhibition instigates a potent synergistic inhibition of statins and APis on human AML cells. KW - Aminopeptidase KW - Statins KW - Mevalonate pathway KW - Carboxyl esterase KW - Rheb KW - mTOR Y1 - 2023 U6 - https://doi.org/10.20517/cdr.2023.20 SN - 2578-532X VL - 6 IS - 2 SP - 430 EP - 446 PB - OAE Publishing Inc. ER -