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

William L. Blalock, Marianne Pearce, Linda S. Steelman, Richard A. Franklin, Sean A. McCarthy, Holly Cherwinski, Martin McMahon, James A. McCubrey

Research output: Contribution to journalArticlepeer-review


The Raf/MEK/MAP kinase cascade plays a critical role in transducing growth signals from activated cell surface receptors. Using ΔMEK1: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 ΔMEK1: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 ΔMEK1:ER activation than those that remained cytokine-dependent. ΔME-K1:ER-responsive cells could be maintained long-term in the presence of β-estradiol as well as the estrogen-receptor antagonist 4-Hydroxy-Tamoxifen and the antiestrogen 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 growth in a manner similar to that observed when cytokine is withdrawn from the parental cells.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 ΔMEK1:ER-responsive cells with a specific and selective inhibitor, PD98059, prevented growth in response to β-estradiol. GM-CSF mRNA transcripts were detected in the MEK1-responsive cells indicating that the activated ΔMEK1: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.

Original languageEnglish
Pages (from-to)526-536
Number of pages11
Issue number4
Publication statusPublished - Jan 27 2000


  • Cytokines
  • MEK1
  • Oncogenes
  • Signal transduction

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research
  • Genetics


Dive into the research topics of 'A conditionally-active form of MEK1 results in autocrine transformation of human and mouse hematopoietic cells'. Together they form a unique fingerprint.

Cite this