A conditionally-active form of MEK1 results in autocrine transformation of human and mouse hematopoietic cells

• Published in: Oncogene Vol. 19; no. 4; pp. 526 - 536
• Main Authors: BLALOCK, W. L, PEARCE, M, STEELMAN, L. S, FRANKLIN, R. A, MCCARTHY, S. A, CHERWINSKI, H, MCMAHON, M, MCCUBREY, J. A
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing 27.01.2000; Nature Publishing Group
• Subjects: Biological and medical sciences; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Fundamental and applied biological sciences. Psychology; MEK1 protein; Molecular and cellular biology; Human; Cell proliferation; Enzyme; Transferases; Rodentia; Cytokine; Hematopoietic cell; Gene expression; Cell transformation; Carcinogenesis; Signal transduction; Vertebrata; Regulation(control); Mammalia; Cell line; Mouse; Protein kinase; Onc gene; Biological receptor
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/sj.onc.1203337

The Raf/MEK/MAP kinase cascade plays a critical role in transducing growth signals from activated cell surface receptors. Using deltaMEK1:ER, a conditionally-active form of MEK1, we demonstrate the ability of this dual specificity protein kinase to abrogate the cytokine-dependency of the human and murine hematopoietic cells lines TF-1, FDC-P1 and FL5.12. Cytokine-independent cells were obtained from TF-1, FDC-P1 and FL5.12 cells at frequencies of 2.5 x 10(-3), 5 x 10(-5) and 10(-7) respectively, indicating that not all cells expressing deltaMEK1:ER were factor-independent. In general, cells that were converted to a cytokine-independent phenotype displayed a higher level of MAP kinase activity in response to deltaMEK1:ER activation than those that remained cytokine-dependent. deltaME-K1:ER-responsive cells could be maintained long-term in the presence of beta-estradiol as well as the estrogen-receptor antagonist 4-Hydroxy-Tamoxifen and the anti-estrogen ICI 164383. Removal of hormone led to the rapid cessation of cell growth in a manner similar to that observed when cytokine is withdrawn from the parental cells. Treatment of deltaMEKI:ER-responsive cells with a specific and selective inhibitor, PD98059, prevented growth in response to beta-estradiol. GM-CSF mRNA transcripts were detected in the MEK1-responsive cells indicating that the activated deltaMEK1:ER may induce a pathway leading to autocrine proliferation. Treatment of MEK1-responsive cells with an anti-GM-CSF antibody, but not a control antibody, suppressed cell growth. The cell lines described here will be useful for elaborating the ability of the MAP kinase pathway to regulate cell proliferation in hematopoietic cells.