DEOXYRIBONUCLEIC-ACID TRIPLEX FORMATION INHIBITS GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR GENE-EXPRESSION AND SUPPRESSES GROWTH IN JUVENILE MYELOMONOCYTIC LEUKEMIC-CELLS

Juvenile myelomonocytic leukemia (JMML) ia a severe childhood malignan cy. The autocrine production of GM-CSF is believed to be responsible f or the spontaneous proliferation of JMML cells. A nuclear factor-kappa -B (NF-kappa-B)/Rel binding site within the GM-CSF gene promoter, term ed the kappa-B element, plays an important role in the controlling tra nscription from the GM-CSF gene. We investigated the effect of an olig onucleotide GM3, directed to form a DNA triple helix across the kappa- B element, on growth and GM-CSF production by JMML cells. Treatment of these cells, either unstimulated or induced by TNF-alpha, with GM3 le d to a significant and specific triplex-mediated inhibition of gene tr anscription with a functional outcome; i.e., cell growth. We observed the constitutive presence of NF-kappa-B/Rel proteins in the nucleus of JMML cells. The constitutive and TNF-alpha-induced NF-kappa-B/Rel com plexes were identical and were composed mainly of p50 and c-Rel protei ns. Treatment of the cells with a neutralizing anit-TNF-alpha monoclon al antibody completely abrogated constitutive nuclear expression of NF -kappa-B/Rel proteins. These results indicate that the aberrant, const itutive GM-CSF gene activation in JMML is maintained by TNF-alpha-medi ated activation of NF-kappa-B/Rel proteins. Our findings identify the molecular basis for the autocrine TNF-alpha activation of the GM-CSF g ene in JMML and suggest potential novel and specific approaches for th e treatment of this aggressive childhood leukemia.