@misc{VerbruggeAlAssarafetal., author = {Verbrugge, Sue Ellen and Al, Marjon and Assaraf, Yehuda G. and Kammerer, Sarah and Chandrupatla, Durga and Honeywell, Richard and Musters, Rene and Giovannetti, Elisa and O`Toole, Tom and Scheffer, George L. and Krige, David and Gruijl, Tanja de and Niessen, Hans W.M. and Lems, Willem F. and Kramer, Pieternella A. and Scheper, Rik J. and Cloos, Jacqueline and Ossenkoppele, Gert and Peters, Godefridus J. and Jansen, Gerrit}, title = {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}, series = {OncoTarget : open access impact journal}, volume = {7}, journal = {OncoTarget : open access impact journal}, number = {5}, issn = {1949-2553}, doi = {10.18632/oncotarget.6169}, pages = {5240 -- 5257}, abstract = {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.}, language = {en} } @misc{LiRezaniaKammereretal., author = {Li, Chouyang and Rezania, Simin and Kammerer, Sarah and Sokolowski, Armin Andreas and Devaney, Trevor Thomas Joseph and Gorischek, Astrid and Jahn, Stephan Wenzel and Hackl, Hubert and Groschner, Klaus and Windpassinger, Christian and Malle, Ernst and Bauernhofer, Thomas and Schreibmayer, Wolfgang}, title = {Piezo1 forms mechanosensitive ion channels in the human MCF-7 breast cancer cell line}, series = {Scientific Reports}, volume = {5}, journal = {Scientific Reports}, issn = {2045-2322}, doi = {10.1038/srep08364}, pages = {9}, abstract = {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.}, language = {en} }