RT Journal Article
SR Electronic
T1 Inhibition of c-Myc Down-Regulation by Sustained Extracellular Signal-Regulated Kinase Activation Prevents the Antimetabolite Methotrexate- and Gemcitabine-Induced Differentiation in Non-Small-Cell Lung Cancer Cells
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1679
OP 1687
DO 10.1124/mol.107.043372
VO 73
IS 6
A1 Serra, Jordi M.
A1 Gutiérrez, Antonio
A1 Alemany, Regina
A1 Navarro, María
A1 Ros, Teresa
A1 Saus, Carlos
A1 Ginés, Jordi
A1 Sampol, Antonia
A1 Amat, Juan Carlos
A1 Serra-Moisés, Lorenzo
A1 Martín, Javier
A1 Galmés, Antonio
A1 Vögler, Oliver
A1 Besalduch, Joan
YR 2008
UL http://molpharm.aspetjournals.org/content/73/6/1679.abstract
AB Non-small-cell lung cancer (NSCLC) is characterized by severe resistance to chemotherapy. Here, we demonstrate that A549 adenocarcinoma cells permanently differentiate with the antimetabolites methotrexate (MTX) and gemcitabine (GE) when blocking the resistance mechanism that normally counteracts this process. MTX (1-10 μM) and GE (1 μM) induced growth arrest accompanied by sustained extracellular signal-regulated kinase (ERK1/2) phosphorylation and moderate reduction of c-Myc levels after 96 h, whereas only a low percentage of the cells differentiated. Combination with the mitogen-activated protein kinase kinase (MEK) inhibitor 1,4-diamino-2,3-dicyano-1,4-bis-(methylthio)butadiene (U0126) reduced MTX- or GE-induced ERK1/2 over-phosphorylation, nearly abolished c-Myc expression, and provoked radical morphological changes in all cells. Besides the appearance of multilamellar bodies and intracellular cytokeratin reorganization, modulation of molecular markers occurred in a manner consistent with differentiation (gelsolin, +300%; surfactant protein A and C, -70%). Similar to U0126, c-Myc inactivation with specific small interfering RNA initiated differentiation only in the presence of MTX, demonstrating that inhibition of the mitogen-activated protein kinase/ERK pathway alone or down-regulation of c-Myc is not sufficient to induce this process. It is noteworthy that withdrawal of antitumoral drugs and U0126 neither reversed differentiation nor reactivated proliferation. Our results reveal that maintenance of a certain threshold of c-Myc expression through sustained ERK1/2 activation represents a molecular mechanism that confers resistance to antimetabolite-induced differentiation in A549 cells, and provide a novel molecular basis for therapeutic strategies based on irreversible differentiation of cancer cells using conventional chemotherapeutic antimetabolites in combination with inhibitors of the MEK/ERK pathway or c-Myc. The American Society for Pharmacology and Experimental Therapeutics