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 - Li, Chouyang A1 - Rezania, Simin A1 - Kammerer, Sarah A1 - Sokolowski, Armin Andreas A1 - Devaney, Trevor Thomas Joseph A1 - Gorischek, Astrid A1 - Jahn, Stephan Wenzel A1 - Hackl, Hubert A1 - Groschner, Klaus A1 - Windpassinger, Christian A1 - Malle, Ernst A1 - Bauernhofer, Thomas A1 - Schreibmayer, Wolfgang T1 - Piezo1 forms mechanosensitive ion channels in the human MCF-7 breast cancer cell line T2 - Scientific Reports N2 - Mechanical interaction between cells - specifically distortion of tensional homeostasis-emerged as an important aspect of breast cancer genesis and progression. We investigated the biophysical characteristics of mechanosensitive ion channels (MSCs) in the malignant MCF-7 breast cancer cell line. MSCs turned out to be the most abundant ion channel species and could be activated by negative pressure at the outer side of the cell membrane in a saturable manner. Assessing single channel conductance (GΛ) for different monovalent cations revealed an increase in the succession: Li⁺ < Na⁺ < K⁺ ≈Rb⁺ ≈ Cs⁺. Divalent cations permeated also with the order: Ca²⁺ < Ba²⁺. Comparison of biophysical properties enabled us to identify MSCs in MCF-7 as ion channels formed by the Piezo1 protein. Using patch clamp technique no functional MSCs were observed in the benign MCF-10A mammary epithelial cell line. Blocking of MSCs by GsMTx-4 resulted in decreased motility of MCF-7, but not of MCF-10A cells, underscoring a possible role of Piezo1 in invasion and metastatic propagation. The role of Piezo1 in biology and progression of breast cancer is further substantiated by markedly reduced overall survival in patients with increased Piezo1 mRNA levels in the primary tumor. Y1 - 2015 U6 - https://doi.org/10.1038/srep08364 SN - 2045-2322 VL - 5 ER -